A PHYLOGENETIC ANALYSIS OF THE ISOPODA WITH SOME CLASSIFICATORY RECOMMENDATIONS

RICHARD C. BRUSCA AND GEORGE D.F. WILSON

Brusca, R.C. and Wilson, G.D.F. 1991 09 01: A phylogenetic analysis of the Isopoda with some classificatory recommendations. Memoirs of the Queensland Museum 31: 143-204. Brisbane. ISSN 0079-8835.

The phylogenetic relationships of the isopod crustacean suborders are assessed using cladistic methodology. The monophyly of the Flabellifera was tested by including all 15 component families separately in the analysis. Four other peracarid orders (Mysidacea, Amphipoda, Mictacea, and Tanaidacea) were used as multiple out-groups to root our phylogenetic estimates within the Isopoda. A broad range of possible characters for use in assessing isopod relationships is discussed and a final data (character) matrix was selected. This data matrix, comprising 29 taxa and 92 characters, was subjected to computer-assisted analysis using four different phylogenetic programs: HENNIG86, PAUP, PHYLIP, and MacClade. Phylogenetic hypotheses from the literature (particularly Wagele, 1989a) are discussed and compared with our own conclusions. The following hypotheses are suggested by our analysis. The Isopoda constitutes a monophyletic group. The Phreatoicidea is the earliest derived group of living isopods, followed by an Asellota-Microcerberidea line, and next the Oniscidea. Above the Onis- cidea is a large clade of 'long-tailed' isopod taxa (Valvifera, Anthuridea, Flabellifera, Epicaridea, Gnathiidea). The Microcerberidea is the sister group of the Asellota, but probably should not be included in the Asellota. The Oniscidea constitutes a monophyletic group. The monotypic taxon Calabozoidea is either a primitive oniscidean, or is a sister group of the Oniscidea (Calabozoa is not an asellotan). Our cladistic analysis suggests that the primitive isopod body plan was one in which well-developed lateral coxal plates were lacking, the pleopods were multiarticulate, the uropods arose on the posterior margin of the pleotelson, the telsonic region was not elongate, and the mandibular molar process was a broad flat grinding structure. Extant taxa with this body plan (Phreatoicidea, Asellota, Microcerberidea) occur primarily in relictual habitats. Oniscidea conform to this body plan except in possessing lateral coxal plates. The long-tailed isopod morphology (broad flat uropods, an elongate telsonic region, and well-developed lateral coxal plates) appears to be a derived condition within the Isopoda. Suborders and families with this body plan appear to be most speciose, or to have had their origin, in the Southern Hemisphere. The 'caridoid'-like pleonal morphology of many long-tailed isopods (Flabellifera, Gnathiidea, Anthuridea) is thus secondarily derived and convergent to the condition seen in the mysidaceans and other true caridoid crustaceans. The broad, elongate tailfan of the long-tailed isopod taxa is not used for a caridoid-like tail locomotory behaviour (e.g. the 'caridoid escape reaction'), but rather as a steering/stabil­ ising plane. The emergence of the long-tailed body plan seems to have coincided with a shift in isopod habits from infaunal to more active, swimming, epifaunal lifestyles. Accompanying this transition was enlargement of the lateral coxal plates (perhaps to increase hydrodynamic streamlining of the body) and a shift to active carnivory and predation, and eventually parasitism in several groups. The Suborder Flabellifera (as it is currently recognised) is not a monophyletic taxon. Three taxa usually ranked at the subordinal level (Anthuridea, Gnathiidea and Epicaridea) have their phylogenetic origins within the lineage of families that currently constitutes the Flabellifera. The Protognathiidae is not closely related to the Gnathiidea. Protognathiidae is probably closely related to Anuropidae and is part of a clade culminating in the parasitic family Cymothoidae. Wagele's (1989a) recently proposed new classification of the Isopoda, including his new suborders Sphaeromatidea and Cymothoida (sic), is not corroborated by our phylogenetic analysis. Unambiguous sister group relationships cannot be hypothesised for the long-tailed isopod taxa with the current data base. A new formal classification of the order Isopoda must await better resolution of the phy logeny based upon an expanded data set. • Isopoda, phytogeny, classification, morphology, biogeography. 144 MEMOIRS OF THE QUEENSLAND MUSEUM

Richard C. Brusca, San Diego Natural History Museum, P.O. Box 1390, San Diego, California 92112, USA.; George D.F. Wilson, Australian Museum, 6—8 College St., Sydney South, New South Wales 2000, Australia; 29 March, 1991.

'Amidst this prudent love of obscurity, the (1905) considered it a synonym of her 'Flabel­ one feature of moral character which they lifera' (following Sars to include the Aegidae, possess in common is strong evidence that Anthuridae, Cirolanidae, Corallanidae, Cymot- all of them must have sprang from a common hoidae, Excorallanidae, Gnathiidae, Limnorii- origin.' dae, Serolidae, and Sphaeromidae). Menzies The Reverend T.R.R. Stebbing (1893), Speak­ (1962) considered the Cirolanoidea to be a sub- ing of isopods. tribe of his tribe Flabellifera, synonymous to the Most of the isopod suborders were described Cymothoidea of some previous authors (includ­ and delineated in the early part of the nineteenth ing the Anuropidae, Cirolanidae, Limnoriidae, century, but for the past 150 years classification Sphaeromidae). Wagele (1989a) used Leach's of these suborders and their families has been (1814) spelling of 'Cymothoida', for his newly unsettled. Until fairly recently many workers proposed suborder (for the Aegidae, Anuropi­ included the Tanaidacea within the Isopoda and dae, Bopyridae [=Epicaridea], Cirolanidae, included either (or both) the Gnathiidea and An­ Corallanidae, Cymothoidae, Gnathiidae, Phora- thuridea within the Flabellifera (or 'Cy- topodidae, Protognathiidae, and Tridentellidae). mothoidea') (Bate and Westwood, 1863-68; In 1983 Van Lieshout erected a new mono- Stebbing, 1893; Sars, 1897; Richardson, 1905; typic suborder (Calabozoidea) for Calabozoa Smith and Weldon, 1923; Hale, 1929; Nierstrasz pellucida, a ground-water isopod from Venezue­ and Schuurmans-Stekhovan, 1930; Menzies, lan wells, and discussed its possible affinities to 1962; Nay lor, 1972). Hansen (1916) and Monod both the Oniscidea and the Asellota. Wagele (1922) recognised the necessity of separating the (1989a) argued for placing the Calabozoidea tanaidaceans from the isopods, and also removed near the Asellota, depicting these two suborders the gnathiids and anthurideans from the Flabel­ as sister groups on his phylogenetic tree. lifera. Some authorities sought to establish a Recent summaries by Bowman and Abele fundamental split between the gnathiids and the (1982), Brusca and Iverson (1985), Schram remaining Isopoda. Monod (1922) called the (1986), and Brusca and Brusca (1990) took the gnathiids Decempedes ('10-footed'), and all conservative approach in recognizing 9 subor­ other isopods the Quatuordecempedes ('14- ders (Table 1, Figs 1-3), maintaining separate footed'). Following Latreille (1804), Menzies subordinal status for the Microcereridea, An­ (1962) used the name Tetracera for the non- thuridea, Gnathiidea, and Epicaridea. gnathiid isopods. Menzies (1962) chose to retain An examination of previously published stud­ the anthurideans within the Flabellifera, but later ies concerning isopod phylogeny reveals a fairly removed them (Menzies and Glynn, 1968). broad range of ideas (Fig. 4 ). Beginning with Karaman (1933) alliedMicrocerberus with the Hansen (1905), however, two taxa have domi­ Anthuridea, and many subsequent workers ac­ nated the literature as contenders for the title of cepted this placement (Remane and Siewing, 'most primitive living isopods', the Flabellifera 1953; Chappuis and Delamare, 1954; Lang, and the Asellota. Schultz (1969,1979) deviated 1960; Schultz, 1979; Kussakin, 1973). However, markedly from this pattern, and his phylogeny Lang (1961) created a new suborder for this depicted the Gnathiidea as the most primitive genus, the Microcerberidea, and Wagele (1982b, living isopod group. Schram (1974) appears to 1983b) argued against any relationship between have been the only person to have previously the microcerberids and anthurideans, instead specifically espoused the Phreatoicidea to be the suggesting that the former were highly special­ earliest derived isopod suborder. ized asellotans. Supporters of the 'Asellota-are-primitive' hy­ The name 'Cirolanoidea' has been used in potheses have included Hansen (1925), Monod different ways by different workers. Richardson (1922), Birstein (1951), Zenkevich and Birstein FIG. 1. Examples of 'short-tailed' isopod suborders. A, Phreatoicidea (Mesamphisopus depressus, after Nicholls, 1943). B, Asellota (laniropsis montereyensis, after Menzies, 1952). C, Microcerberidea (Micro­ cerberus sp., after Argano, 1988). D, Calabozoidea (Calabozoa pellucida, after Van Lieshout, 1983). E, Oniscidea (Armadillidium vulgare, after Sutton, 1972). PHYLOGENETIC ANALYSIS OF THE ISOPODA 145 146 MEMOIRS OF THE QUEENSLAND MUSEUM

TABLE 1. Taxa analysed in the present study. potheses have included Racovitza (1912), Sternberg (1972), Kussakin (1973, 1979), OUT-GROUPS Bruce (1981), and Wagele (1989a). Among the Flabellifera, the Cirolanidae (especially Bathy- Order MYSIDACEA nomus) is usually chosen as the model for the Order MICTACEA Order TANAIDACEA archtypical ancestral isopod. Kussakin (1979) Order AMPHIPODA refined his earlier views to present a phylogeny IN-GROUPS in which a 'cirolanid-like ancestor' (but that was not yet a 'true' flabelliferan) gave rise to an Order ISOPODA Anthuridea/Microcerberidea line as the most Suborder Phreatoicidea primitive living isopod group, followed by the Suborder Asellota Oniscidea and Valvifera, with the extant Flabel­ Suborder Microcerberidea lifera, Phreatoicidea, and Asellota being the Suborder Oniscidea most highly derived taxa. Kussakin (1979) came Infraorder Tylomorpha to this conclusion despite his contention that the Infraorder Ligiamorpha most primitive arrangement of pereopodal coxae Suborder Calabozoidea occurs in the Asellota, a group in which he noted, Suborder Valvifera 'the coxopodite still looks like a normal seg­ Suborder Epicaridea ment'. Within the flabelliferan line, Kussakin Suborder Gnathiidea hypothesized three lineages. One lineage lead to Suborder Anthuridea predacious/parasitic lifestyles (Cirolanidae, Suborder Flabellifera Aegidae, Cymothoidae, and ultimately the Epi­ Family Aegidae caridea); the other two lines were said to have Family Anuropidae given rise to benthic herbivores and detritivores, Family Bathynataliidae such as the Serolidae and Sphaeromatidae. He Family Cirolanidae allied the Anuropidae with the Valvifera and Family Corallanidae Family Cymothoidae Oniscidea, rather than with the Flabellifera. Family Keuphyliidae Kussakin described (but did not depict on his Family Limnoriidae phylogenetic tree) the Asellota arising from a Family Lynseiidae hypothetical ancestral cirolanid stem group, via Family Phoratopodidae the Phreatoicidea. Bruce (1981) supported Kus- Family Plakarthriidae sakin's (1979) views, and further hypothesised Family Protognathiidae the Phoratopodidae to be the sister group of the Family Serolidae Valvifera. Nicholls (1943, 1944), Dahl (1954), Family Sphaeromatidae and Stromberg (1972) also argued that the Phrea­ Family Tridentellidae toicidea originated from an ancient Flabelliferan stock close to the modern Cirolanidae. (1961), Belyaev (1966), and most recently Schmalfuss (1989). Although Schmalfuss' tree Wagele (1981) claimed that 'general agree­ has the appearance of a cladogram, it appears to ment exists among isopod workers that the an­ be an intuitive tree based on ad hoc assumptions cestral isopod body shape and external features were certain to have been similar to those of of ancestry. It used 4 specific synapomorphies to living Cirolanidae (though perhaps lacking define 8 isopod suborders. Schmalfuss did not coxal plates),' but later stated that the Cirolani­ describe his method of tree construction, tree dae could not possibly be considered as primitive selection, character analysis, or character polar­ isopods and that they were the probable sister ity assessment; did not calculate tree lengths or group of the Anthuridea. Still later Wagele homoplasy values; did not describethe charac­ (1989a) claimed that the (hypothetical) ancestor ters he utilised; and, rooted his tree based on of the Isopoda was cirolanid-like, even though ambiguous statements regarding ad hoc hy­ his 'Hennigian' phylogenetic analysis con­ pothetical morphotypes rather than on methods firmed that the Cirolanidae was a highly derived such as out-group or ontological analysis. It group (Fig. 4D). should be noted that for 8 taxa there exist Stromberg (1972) counted the number of hy­ 660,032 possible tree topologies (Felsenstein, pothesised plesiomorphic features occurring in 1978). each of the isopod suborders, concluding on this Supporters of 'Flabellifera-are-primitive' hy­ basis that the Flabellifera (notably the Cirolani- PHYLOGENETIC ANALYSIS OF THE ISOPODA 147

dae) were the most primitive living group and the number of possible trees quickly becomes stem group from which all other isopod sub­ astronomical. An analysis of the 10 nominate orders were derived. He presented an argument isopod suborders alone requires assessment of for close alliance between the Flabellifera, the 282 million possible trees, 34.5 million of which Epicaridea, and the Gnathiidea. are bifurcating trees (Felsenstein, 1978). The present study analyses 29 taxa, for which there All of the above hypotheses, except Wagele 36 (1989a), consisted of ad hoc tree construction are 8.7 X 10 possible bifurcating trees. Hence, and evolutionary narratives in the traditional, or to select a single shortest tree with the highest orthodox, sense. Each was based on a small set degree of parsimony and the lowest level of of selected characters that held sway over all homoplasy by 'eyeballing the data' is difficult, others. Most relied on a mix of both primitive if not impossible. Nevertheless, Wagele's and derived features to infer relationships. None (1989a) analysis was a very important step for­ was based on a large data set of empirically ward in isopod phylogenetics, and was the first evaluated characters, and none used any strict published study at the subordinal level to use a analytical methodology. Most, if not all, relied relatively large data set and provide lists of upon the (stated or unstated) ad hoc selection of general synapomorphies that define putative an extant group of isopods to represent a primi­ monophyletic lines. For these reasons, we com­ tive ancestral morphotype. From these a priori- pare our analysis closely to that of Wagele in the selected hypothetical ancestors, evolutionary discussion section at the end of this paper. scenarios were inferred, and trees were con­ structed based upon these scenarios. Because the METHODS phylogenetic scenarios cited above were not derived from empirical analyses of the data, nor OUT-GROUPS utilized any repeatable methodology, it would be The questions of peracarid monophyly and the unfair (and difficult) to compare them directly to phylogenetic sequence of appearance of the per­ the present study. It is interesting to note that, acarid orders have long been favorite subjects of despite the fact that the Phreatoicidea have the debate among carcinologists. Nearly every im­ oldest known fossil record (Pennsylvanian; aginable topology of phylogenetic relationships Schram, 1970, 1974), none of the above pro­ among the In 1981 peracarida has been proposed posals hypothesised this group (or a phreatoicid- at one time or another. There is no need to review like morphology) to represent the ancestral this debate here (Dahl, 1977; Watling, 1981, isopod type. 1983; Schram, 1981, 1986; Dahl and Hessler, The only previous attempt to undertake a phy­ 1982; Hessler, 1983; Brusca, 1984). However, logenetic analysis of the Isopoda based on a large most published ideas over the years have sug­ data set and a specific methodology was gested that the sister group of the Isopoda is Wagele's (1989a) recent study (Fig. 4D). either the Amphipoda or the Tanaidacea. The Wagele proposed a sweeping reorganisation of recently described Mictacea may also be closely isopod classification. Some of the many changes related to the isopods (Schram, 1986). Because he proposed included the complete elimination of this uncertainty, we use four out-groups in our of the Suborder Flabellifera, and the reduction to analysis: Mysidacea, Amphipoda, Mictacea, and family status of the suborders Gnathiidea and Tanaidacea. The increased accuracy of character Epicaridea (reducing the families of the latter to polarity assessment and tree resolution that can subfamilies and eliminating the name Epicaridea be achieved by use of the multiple out-group altogether). However, even though Wagele's method has been explained by Maddison et al. study was based on a larger set of characters than (1984) and others, the basic premise being that any previous analysis, it was still based on an ad cladograms should be globally parsimonious. hoc hypothetical ancestral morphotype, the phy­ logenetic tree was computed by hand, and no IN-GROUPS attempt was made to achieve either global or Our in-group includes all 10 nominate isopod in-group parsimony or utilise any strict criteria suborders (Table 1), plus the 15 nominate flabel- of tree construction or tree selection. Wagele's liferan families. The relationships of the families classification scheme was not strictly cladistic in included within the Flabellifera have been con­ that it did not recognise the sister group arrange­ troversial, and it has been frequently suggested ments of his cladogram. that the Flabellifera is a non-monophyletic In data sets with more than a few taxa, the (axon. Kussakin (1979), Bruce (1981), and 148 MEMOIRS OF THE QUEENSLAND MUSEUM

FIG. 2. Examples of various 'long-tailed' isopod suborders. A, Epicaridea (Argeia pugettensis). B-C, Gnathiidea (B, Gnathia tridens female; C, Gnathia tridens male). D, Valvifera, Idoteidae {Idotea metallica). E, Valvifera, Arcturidae {Idarcturus hedgpethi). F, Anthundea, Anthuridae (Haliophasma geminata male). G, Anthuridea, Paranthuridae (Paranthura elegans). PHYLOGENETIC ANALYSIS OF THE ISOPODA 149

Wagele (1989a) depicted this group paraphyleti- study we argue that protognathiids share no cally on their trees of the Isopoda. Wagele unique synapomorphies with gnathiids, although (1989a) recommended a reorganisation of the some superficial similarities are present. Wagele Isopoda that would eliminate three currently rec­ (1983b, 1989a) has argued that the Microcer- ognized suborders, the Flabellifera, Epicaridea, beridea are members of the asellote superfamily and Gnathiidea. Although Wagele's tree and Aselloidea. Although the microcerberids have classification are not corroborated by the present several features typically viewed as asellotan study, the Flabellifera as it is currently recog­ (6-articulate antennular peduncle; pleonites 3-5 nized is almost certainly not a monophyletic fused with the pleotelson; females lacking first taxon. Wagele reorganized the above suborders pair of pleopods; male second pleopod with en- into two new groups, which he called the Cy- dopod transformed into a complex gonopod), mothoida (sic) and the Sphaeromatoidea, sub­ they lack other features generally also regarded suming the Gnathiidea, Epicaridea, and several as definitive synapomorphies of the Asellota flabelliferan families into the former. (Note that (e.g. antennal peduncle with a scale; female Wagele's Cymothoida is not the equivalent of pleopod 2 uniramous; exopods of male second Cymothoidea of Richardson, 1905, and others). pleopods modified to work with the elongate In the present study, we test the monophyly of geniculate endopods in sperm transfer; and, possibly, the unique asellotan spermathecal the Flabellifera by including all of its component duct). For these reasons we treat the Asellota and families in the analysis with the other suborders Microcerberidea as separate groups (OTU's) in of the Isopoda. We recognize the following nom­ our analysis. inate families of Flabellifera: Aegidae Dana, 1853; Anuropidae Stebbing, 1893; Bathy- nataliidae Kensley, 1978; Cirolanidae Dana, DATA SOURCES 1853; Corallanidae Hansen, 1890; Cymothoidae Specimens were examined for all taxa treated Leach, 1818; Keuphyliidae Bruce, 1980; Lim- except Protognathiidae. Material was examined noriidae White 1850; Lynseiidae Poore, 1987; on loan from a variety of institutions, and during Phoratopodidae Hale, 1925; Plakarthriidae Ri­ visits to the U.S. National Museum of Natural chardson, 1904; Protognathiidae Wagele and History, Smithsonian Institution (USNM), Los Brandt, 1988; Serolidae Dana, 1853; Sphaero- Angeles County Museum of Natural History matidae Burmeister, 1834; and, Tridentellidae (LACM), Zoologisch Museum, Amsterdam Bruce, 1984. (ZMA), Australian Museum, Sydney (AM), The two infraorders of Oniscidea Latreille, Queensland Museum, Brisbane (QM), Victoria 1803 (Tylomorpha Vandel, 1943 and Ligiamor- Museum, Melbourne (VM), San Diego Natural pha Vandel, 1943; see Holdich et ai, 1984) are History Museum (SDNHM), and Scripps Insti­ also analysed separately because opinion has tution of Oceanography (SIO). In addition to been divided on whether or not the Tylidae are examining specimens, the original literature was true oniscideans (Kussakin, 1979; Holdich et ai, extensively perused. 1984; Wagele, 1989a; Schmalfuss, 1989). Three taxa that are included in our analysis SCORING OF CHARACTERS require brief comment. The Calabozoidea is a One of the advantages of the available com­ monotypic ground-water (freshwater) taxon so puter-assisted numerical techniques (see below) far known only from Venezuela. In her original is that they treat each character independently. description, Van Lieshout (1983) suggested Thus, if the state of a particular character is possible affinities of Calabozoa to both the Asel­ unknown, inapplicable, or we have simply been lota and the Oniscidea. We have examined speci­ unable to resolve it to our satisfaction, we have mens of Calabozoa and found Van Lieshout's scored it as 'missing data' (indicated by a '?' in illustrations and description misleading; new il­ the data matrix). In preliminary analyses, char­ lustrations of the male pleopods 1 and 2 are acters for which no clear polarity could be estab­ provided in Fig. 10. Calabozoa appears to lished were not coded in any primitive-derived possess no asellotan synapomorphies. Wagele sequence, but were left to change in any direction and Brandt (1988) created the Protognathiidae such that simple parsimony (fewest changes) based upon their examination of a single, ap­ was the arbiter. These unpolarised (nonadditive parently manca-stage, individual. Wagele or unordered) characters are indicated in the (1989a) concluded that this new family was the character discussions below. These analyses sister group of the Gnathiidea. In the present proved useful in assessing character homoplasy. 150 MEMOIRS OF THE QUEENSLAND MUSEUM PHYLOGENETIC ANALYSIS OF THE ISOPODA 151

FIG. 4. Some evolutionary trees from previous studies, by Kussakin (1979), Bruce (1981), Schmalfuss (1989), and Wagele (1989a). For the final analyses, however, we decided to phic for that character, but is scored plesiomor­ analyse the data with all characters left un­ phic. Initially polarized characters were scored ordered (nonadditive). as indicated in the ordering of the character state If a character state judged to be plesiomorphic numbers: 0 = plesiomorphic, 1 = apomorphic, 2 is present for only some members of the taxon in = more apomorphic than 1, etc. Homology deci­ question, e.g. 'accessory flagellum on antennule sions were made on the basis of ontogenetic data in most gammaridean amphipods', it is scored and comparative morphology (positional data present in the data matrix for the entire taxon and anatomical similarity). unless otherwise stated, i.e. the derived condition is presumed to define a subset within the taxon. PHYLOGENETIC ANALYSIS Conversely, of course, if an apomorphic state is The character state data were analysed with present in only some members of the taxon in four numerical cladistic analysis packages: question, the entire taxon is not scored apomor­ HENNIG86 (version 1.5), PHYLIP (version FIG. 3. Examples of various isopod families and genera of the suborder Flabellifera. A, Cirolanidae (Metacirolana joanneae, SDNHM). B, Tridentellidae (Tridentella glutacantha, from Delaney and Brusca, 1985). C, Aegidae (Aega plebeia, from Brusca, 1983). D, Cymothoidae (Ceratothoa gilberti, from Brusca, 1981). E, Limnoriidae (Limnoria quadripunctata). F, Serolidae (Serolis carinata, SDNHM A.0114). G, Anuropidae (Anuropus bathypelagicus). H, Sphaeromatidae (Gnorimosphaeroma insulare). I, Sphaero- matidae (Exosphaeroma amplicauda). J, Sphaeromatidae {Bathycopea dallonae). K, Sphaeromatidae (Par- aleptosphaeroma glynni). 152 MEMOIRS OF THE QUEENSLAND MUSEUM

3.2), PAUP (version 3.0), and MacClade (ver­ suborder or family (Appendix III). However, sion 2.1). HENNIG86 is advantageous because because we were concerned in this study with of its speed, successive weighting algorithm, identifying sister group relationships within the ability to depict polytomous tree branches, and Isopoda, we did not make an effort to identify all ability to store many equal-length trees in of the unique synapomorphies that define only memory. The successive weighting program individual taxa (suborders or families). Some (Farris, 1969, 1989) is useful in reducing the characters that proved to define only terminal impact of homoplasous characters on tree to­ taxa in our final trees were early-on suspected to pology. Despite Platnick's (1989) recommenda­ be useful in distinguishing larger sister groups. tion of HENNIG86 as the program of choice, These may be viewed as 'uninformative' charac­ PAUP, MacClade, and the PHYLIP program ters in the final trees by some workers. However, package remain useful for comparative and ana­ they were important in comparative analyses and lytical purposes (Sanderson, 1990). PAUP is by tree testing, and as additional taxa and data are far the most user-friendly, is useful to check described some of these characters may no different character optimisations (a feature cur­ longer remain unique to a single terminal taxon. rently absent from HENNIG86) on the final For these reasons, we felt it was important to trees, and to obtain detailed computations of C.I. leave them in the data matrix, thus allowing (consistency index), character changes, and others to use our data set as a starting point for OTU apomorphy lists. The program MacClade further tree testing. The data set is available on 3.0 was used (on a Macintosh Computer) to diskette on request. branch swap on the final set of trees, in order to evaluate changes in tree length, homoplasy DISCUSSION OF CHARACTERS levels, and character placement on selected al­ ternative trees, including those of Schmalfuss (1989), Wagele (1989a), and others. MacClade STALKED EYES and PAUP are extremely useful in their user- Mysidaceans and mictaceans have compound friendly ability to generate graphic repre­ eyes set on short, movable eyestalks (although sentations of character traces on trees, although eyestalks are absent in the mictacean Hirsutia). In amphipods, a 'rudimentary eyestalk' has been MacClade is seriously hindered by its inability reported from ingolfiellids. Dahl (1977) and to depict multifurcations. Lowry and Poore (1989) have argued that this The principal statistics used in tree evaluation small process in ingolfiellids is not a true eye- were overall tree length (step length) and con­ stalk, but rather is a cuticular process or scale. sistency index (C.I.). Consistency and retention Lowry and Poore's argument hinged on the ob­ indices for each individual character were also servation that unequivocal eye stalks in other computed and used to evaluate their overall ho­ peracarids have 'an attitude and position very moplasy levels. different' than seen in the ingolfiellids. Dahl's Carpenter (1988) recently argued that consen­ argument was based on the absence of 'dioptric sus trees should not be used to construct clado- and nervous elements' in this structure. The first grams. However, we agree with Anderberg and argument is not particularly strong because the Tehler (1990) that strict consensus trees are both position and attitude of peracarid eye stalks vary useful and informative because they reduce the greatly. A positional change in the ingolfiellids conclusions to only those components which all could have been caused by a lateral rotation of equal-length shortest trees have in common. In the entire eye-antennular-antennal complex. fact, they are probably a necessity when high Dahl's argument is stronger, although it relies on levels of homoplasy invest a data set. Even if reductions rather than homologies. Among tan- successive weighting (i.e. the successive ap­ aidaceans, articulated eye-lobes occur in some proximations character weighting method of Apseudomorpha and Tanaidomorpha, including Fanis, 1969) is used, multiple equally parsi­ those with eyes in a variety of positions ranging monious trees may derive from a data set high in from that seen in the Mictacea to that seen in the homoplasy. Thus, we believe that when numer­ ingolfiellids. In amphipods and isopods the eyes ous equally parsimonious trees exist, a strict are entirely sessile, although they may be ele­ consensus tree should be presented. vated on lobes of varying sizes in some species In order to distinguish between some closely of Phreatoicidea, Gnathiidea, Valvifera, and related taxa, we included some characters that Asellota. At the level of the Peracarida most are cunently known to be unique to a given workers might regard motile stalked eyes as the PHYLOGENETIC ANALYSIS OF THE ISOPODA 153

ancestral condition, and sessile eyes (and loss of (1). Character 5 is: branchial structures cephalo- eyes) as derived conditions. However, as Bow­ thoracic (0) vs branchial structures abdominal man (1984) has noted, the primitive condition in (1). Only isopods are scored apomorphic for Crustacea is still unknown. Thus we left this char­ these two characters. acter unordered in all analyses. Character No. 1 is: eyes stalked and basally articulated (0), vs eye BODY SHAPE stalks reduced, lobe-like, but sometimes with basal Living mysidaceans are laterally compressed. articulation (1), vs eyes sessile (2). Most isopods have dorsoventrally flattened bo­ dies. Although the bodies of amphipods (gam- CARAPACE marideans) and phreatoicideans superficially Character 2 describes the development of the appear laterally compressed, their bodies are ac­ carapace. In mysidaceans the carapace generally tually more cylindrical or tubular (semicircular covers all 8 thoracomeres and laterally covers in cross-section). The apparent lateral compres­ the bases of the maxillae and maxillipeds (state sion in these two groups is an illusion created by 0). In all other peracarids, the carapace is either the large, ventrally expanded, pereonal coxal reduced or absent. In tanaidaceans and mic- plates and pleonal epimeres in amphipods, and taceans, lateral carapace folds still cover the the large pleonal epimeres of most phreatoi­ bases of the maxillae and maxillipeds (state 1). cideans. Some phreatoicideans also have lateral In amphipods and isopods a carapace is absent expansions of the pereonal tergites (i.e. true (or exists only as a head shield) and there are no epimeres, or 'pleura') that hang down to give the lateral carapace folds (state 2). Because of con­ body an amphipod-like appearance. The cylin­ troversy regarding the origin (and convergent drical nature of the phreatoicidean body was reductions) of the crustacean carapace, character recognised long ago (Nicholls, 1943, 1944) al­ 2 was left unordered in initial analyses. though not all authors have acknowledged it (Wagele, 1989a). In mictaceans, and in an- MOULTING thuridean and microcerberid isopods (as well as Isopods are apparently unique among many arcturid Valvifera and some Asellota) the crustaceans in that the moulting is Diphasic, the body is also cylindrical, or semicircular in cross- posterior exoskeleton being shed earlier than the section. Subcylindrical bodies also may occur in anterior exoskeleton (George and Sheard, 1954; the Lynseiidae. Given the variety of body shapes Price and Holdich, 1980a, b). The break between that occur in the isopods and other peracarid the two halves occurs at the junction of per- orders, we can make no judgment on which eonites 4 and 5, and the two halves are out of shape is primitive and which is derived. Body synchrony throughout the moult cycle. Charac­ form is probably strongly selective and based ter 3 is: monophasic moulting (0) vs biphasic largely on a group's behaviour and preferred moulting (1). habitat, and therefore any real phylogenetic sig­ nal we may seek has a high probability of being obscured. For example, we could identify 'nar­ HEART AND BRANCHIAL STRUCTURES Mysidaceans, tanaidaceans, and mictaceans row and elongate' as a potentially homologous utilise thin-walled vascularised regions on the feature, but in fact this would introduce obvious carapace for respiratory exchange (pereopodal homoplasy because the groups that would be so gills are absent). However, loss of free carapace classified, the Anthuridea and the Microcer- folds in the Amphipoda and Isopoda necessitated beridea, are probably narrow for entirely differ­ the transfer of respiratory functions to other ent reasons; the former are tubiculous and the areas of the body (Grindley and Hessler, 1971). latter are interstitial. Consequently, we have Amphipods have unique medial percopodal been cautious regarding use of body form in our epipodites ('coxal gills') presumed to function in analysis. respiratory exchange. Whether the medial Some isopods carry the flattened (depressed) epipods of amphipods are homologous to the body form to an extreme. Several flabelliferan lateral epipods of other crustaceans is not known. families (Bathynataliidae, Keuphyliidae, Plakar- In non-isopod peracarids, the heart is positioned thriidae, and Serolidae) have extremely broad and in the thorax. The isopod heart is located in flattened bodies, with broad coxal plates and the thoracomeres 7/8 and the pleon, and they utilize cephalon encompassed by the first pereonite or at the pleopods for respiration. Character 4 is: heart least surrounded by the first pereonite coxal region entirely thoracic (0) vs heart thoraco-abdominal (character 7) (Serolis, Fig. 3F). The Sphaero- 154 MEMOIRS OF THE QUEENSLAND MUSEUM

matidae also includes a number of genera with tirely ectodermally derived, without a true extremely flattened bodies (Amphoroidella, midgut region (1). Chitonopsis, Naesicopea, Paracasidina,Playt- nympha, Platysphaera, Paraleptosphaeroma, STRIATED MUSCLES Platycerceis), as does the Idoteidae (Moplisa) Nylund (1986), Nylund et al. (1987), and and Cirolanidae (Hansenolana). However, these Tjonneland et al. (1987) have described a pattern cases are uncommon and are assumed to repre­ of membrane systems in the heart myofibers of sent derived conditions in these three families. isopods that they claim is unique within the They also differ from the above taxa in that the Malacostraca. We do not find the reasoning cephalon is not entirely encompassed by per- given by Nylund et al. (1987) for placement of eonite I and the lateral coxal plates are not free. the isopods as a sister group to all other Illustrations of the dorsal aspect of phora- eumalacostracans to be logical, because it relies topodids tend to depict these animals as on differences between groups rather than on markedly flat and broad. However, the body of similarities among them, to define relationships. phoratopodids is actually dorsally arched and Nevertheless, ultrastructure of the heart myo- straight-sided, reminiscent of the cirolanid genus fibres appears to be a unique synapomorphy for Politolana and many sphaeromatids (Bruce, isopods. Character 9 is: striated muscles of typi­ 1981, pers. obs.). cal malacostracan type (0) vs striated muscles In the Anuropidae the body is greatly inflated with unique myofibril ultrastructure (1). and globular (character 89), reminiscent of cer­ tain hyperiid amphipods. Anuropids are ap­ SECOND THORACOMERE parently all parasites on gelatinous zooplankton, Mysidaceans, mictaceans, amphipods, and a feature also shared with most, if not all, hy­ most isopods have a free second thoracomere periid amphipods (character 90). (thus one pair of maxillipeds), although the fossil In two flabelliferan families, Limnoriidae and pygoccphalomorphans have two sets of maxil­ Lynseiidae, the orientation of the head on the lipeds. In gnathiid isopods, the second thoracom­ pereon differs from that seen in all other isopods. ere is partly or wholly fused to the cephalon, and In these two groups, the head is set off from the the second thoracopods form a second pair of first pereonite (second thoracomere) and is maxillipeds (called pylopods). In the praniza capable of left-right rotation (character 40); in all stage these appendages are prehensile and used other isopods the head fits snugly against the first for attachment to the host; in adults they are more pereonite and is usually somewhat immersed in typically maxilliped-like. Gnathiids are the only it, restricting head movement to a flexion in the isopods in which the second thoracomere and its dorso-ventral plane. appendages are entirely integrated into the head. In the family Serolidae, the tergite of the Dorsal, medial-only fusion of the second seventh pereomere (and sometimes also the thoracomere with the cephalon occurs in several sixth) is reduced and fused with the adjacent genera in various other isopod suborders and anterior tergite, rendering it indistinguishable families (Bathynataliidae, Serolidae, several dorsally (character 69). sphaeromatid genera [Ancinus, Bathycopea], some Valvifera [Lyidotea, Arcturidae], some GUT TUBE Asellota [Stenasellus], some Microcerberidea The gut tube of mysidaceans and amphipods [Microcerberusmexicanus], and some Phreatoi- has an endodermally derived midgut region (a cidca), but these cases arc not full fusion and do 'true midgut'). It has long been known, however, not incorporate the first pereopods into the that isopods lack an endodermally derived mouth field, as in gnathiids. Complete fusion of midgut (see recent reviews by Bettica et al., the second thoracomere to the cephalon may 1984, Forgarty and Witkus, 1989, and Hames occur in several deep-sea Asellota genera (Ha- and Hopkin, 1989). The entire gut tube of an plomesus) but, again, the first pereopods are not isopod is ectodermally derived; the only cn- modified as maxillipeds or appendages of the dodermally-derived structure is the 'hepatopan- buccal field. These represent derived conditions found within the Asellota and occur only in creas' (the digestive caeca). According to Scholl certain deep-sea forms. Character 10 is: second (1963) the gut of tanaidaceans may also be en­ thoracomere free, not fused to cephalon (0) vs tirely ectodermal. The condition in mictaccans second thoracomere entirely fused to cephalon, is not known. Character 8 is: gut tube with en­ with its appendages (the pylopods) functioning dodermally derived midgut (0) vs gut tube en­ PHYLOGENETIC ANALYSIS OF THE ISOPODA 155

with the cephalic appendages and serving as a dorsally, (Weygoldt, 1958; Stromberg, 1972). second pair of maxillipeds. Gnathiidea is the Eucarids in general tend to have ventral flexure only taxon scored apomorphic for character 10. of the embryos. Character 51 is: embryos curve ventrally (mysidaceans and amphipods) (0), vs embryos curve dorsally (all other peracarids) (1). THORACIC EXOPODS Character 12 is: hatching stage not a manca (0) In mysidaceans and mictaceans, all the thora­ vs hatching stage a manca (1). Character 13 is: copods (primitively) bear exopods. In tan- without a praniza stage (0) vs with a praniza stage aidaceans, only the anterior thoracopods have (1). Characters 12 and 51 were left unordered in exopods. In amphipods and isopods, no thora­ the initial analyses. copods have exopods. Character 11 is: at least some thoracopods with exopods (0); exopods absent from all thoracopods (1). BODY SYMMETRY Only in the isopod Suborder Epicaridea does loss of body symmetry typically occur in adult EMBRYOGENY AND HATCHING STAGES females. Some species of Cymothoidae may be­ All Peracarida have direct development, and in come twisted to one side or the other, but this is all orders except Mysidacea and Amphipoda the not regarded as true asymmetry in the sense of young leave the marsupium as mancas, resem­ loss of, or gross modification of, appendages on bling small adults but with the last (seventh) pair one side of the body, as in the epicarideans. Some of pereopods not yet developed. However, in epicarideans (most Cryptoniscidae and En- some hyperiid amphipods the young do emerge toniscidae) may be so modified as to resemble as virtual mancas, with the seventh legs un­ little more than large egg sacs. Character 14 is: developed or as little more than a limb bud (Bate, adult females bilaterally symmetrical (0) vs adult 1861; Laval, 1980). Brusca (1984) suggested females with loss of symmetry (1). that the mancoid stage in peracarids may be the product of variations in timing in embryogeny and hatching. Its absence in mysidaceans and PARASITISM amphipods may be tied to a more rapid embryo- Adult female epicarideans are obligate para­ logical development (or to delayed postembry- sites on other crustaceans; the miniature males onic hatching) in these taxa (Steele and Steele, live in close association with the female, usually 1975). Manca-like hatching stages also occur in buried among the female's pleopods. Character bathynellaceans (which may hatch with several 15 is: adults not parasitic on other crustaceans (0) posterior thoracopods undeveloped). Moreover, vs adults obligate parasites on other crustaceans some thermosbaenaceans and bathynellaceans (1); only Epicaridea is scored apomorphic for never develop posterior legs even as adults. In this character. Adult Cymothoidae are obligate gnathiids, the young leave the marsupium as a and permanent hematophagic parasites on fresh­ morphologically very distinct mancoid stage water and marine fishes. Character 66 is: adults called the praniza 'larva' (Wagele, 1988). obligate and permanent parasites of fishes. Only the Cymothoidae are scored apomorphic for this Mysidaceans and amphipods also differ from character. Members of the Aegidae, Coral- other peracarids by possession of ventral flexure lanidae, and Tridentellidae — which are often of the embryo within the embryonic membrane, referred to as 'parasites' — do not attach per­ all other peracarids having a dorsal embryonic manently to their prey, nor do corallanids restrict flexure. The embryos of mysidaceans and am­ their diet to fishes. Species in these families can phipods develop a ventral (=caudal) furrow that be considered as micropredators or temporary separates the caudal papilla from the ventral part parasites. of the rest of the embryo. This is presumably linked to the presence of ventrally curved em­ bryos, completion of cleavage in the early stages, CUTICULAR SENSILLA and early appearance of the egg-nauplius stage Holdich (1984) has described two types of in these groups rapid early holoblastic cleavage. cuticular sensilla that he regards as unique to the In all other peracarids that have been studied Oniscidea. The first (character 16) is the cuticu­ (except perhaps thermosbaenaceans), develop­ lar tricorn sensillum, which he adequately docu- ment is slower, the naupliar and metanaupliar ments for the Oniscidae (Oniscus) and somites appear nearly simultaneously, body Porcellionidae {Porcellio, Porcellionid.es), somites begin proliferating before the the dorsal somewhat less convincingly for the Armadillidi- (=caudal) furrow forms, and the embryos curve idae (Armadillidium) and Armadillidae (Venez- 156 MEMOIRS OF THE QUEENSLAND MUSEUM

Hid), and even less convincingly for the Ligiidae biphasic molt boundary between pereonites 4 (Ligia, Ligidium), Philosciidae (Philoscia), Tyl- and 5. idae (Tylos), Platyarthridae {Platyarthrus), Tri- Nevertheless, most other isopods show a clear choniscidae (Androniscus, Trichoniscus), and 3:4 tagmosis. The 3:4 condition prevails in all Scyphacidae (Alloniscus, Deto). Powell and Hal- families of flabelliferans, as well as the An- crow (1982) document tricorns on Oniscus asel- thuridea, Gnathiidea, Epicaridea, and the genus lus, but not on Ligia baudiniana or any Hadromastax (currently placed in the family non-oniscidean species they studied. Modified Limnoriidae, but being elevated to separate tricorns similar to those of the aquatic genus family status by Bruce and Muller). The preda­ Haloniscus can been seen on SEM photographs tory and parasitic isopods (Anthuridea, of the uropods of Calabozoa (Van Lieshout, Anuropidae, Cirolanidae, Corallanidae, Cy- 1983, fig. 5d-e). We have scored both onis- mothoidae, Protognathiidae, Tridentellidae, Epi­ cidean infraorders (Tylomorpha and Ligiamor- caridea) have 3 pairs of raptorial or grasping pha) and the Calabozoidea apomorphic (1) for anterior limbs, while the 4 pairs of posterior this character. The second kind of sensillum is limbs are dedicated more for locomotion. In the the 'antennal and uropodal spikes' (character strictly parasitic Cymothoidae and Epicaridea, 17), which are complex compound sensillar all 7 pairs of legs are strongly prehensile. How­ structures at the tips of the antennae and uropo­ ever, the limbs of cymothoids and epicarideans dal rami. We have scored both oniscidean in­ appear fundamentally different. In epicarideans, fraorders apomorphic (1) for this character. the dactyl is a short acute hook that folds against a greatly enlarged or swollen propodus, which in turn usually articulates on a small triangular PEREON AND PEREOPODS carpus. In cymothoids, the dactyl is greatly elon­ In Isopoda and other peracarid taxa, the per­ gated and articulates on an elongate propodus; eopods tend to form two functional groups: an the carpus is not reduced or triangular shaped, anterior set of legs that are directed forwards and it usually has an indentation to receive the (antero-ventrally), and a posterior set of legs that tip of the dactyl. We believe that Wagele's are directed backwards (postero-ventrally). (1989a) homologisation of these two kinds of Often this grouping allows the anterior legs to legs is probably in error. have a somewhat (or extremely) different role in locomotion or feeding than the posterior legs. The Plakarthriidae seems unique in its posses­ In Phreatoicidea, Asellota, and Microcer- sion of a 1:6 arrangement of the legs; the basis beridea, the legs are grouped 4:3 (four pairs of of pereopod 1 is directed posteriorly, whereas in anterior pereopods directed forwards and three the rest of the legs the bases are directed anteri­ pairs of posterior pereopods directed back­ orly. However, this may be a secondary effect of wards). This seems to be the case with the ter­ the overall body form and orientation of the restrial isopods and the Calabozoidea as well, pereonites, so we have scored this character with although the strong isopody in these taxa tends a '?' for this family. Although the Gnathiidea to decrease the difference between the anterior have a more highly derived body tagmosis, their and posterior groups. The 4:3 grouping may be anterior 3 pereopods are still directed anterior- a natural tagmosis for the isopods owing to the wards, and the remaining limbs are directed post- FIG. 5. Examples of isopod antennules. A, Flabellifera, Aegidae (Aega longicornis, type). B, Flabellifera, Cymothoidae (Nerocila acuminata, from Brusca, 1978). C, Flabellifera, Cirolanidae (Parabalhynomus natalensis, USNM 170251); note sensilla (insert figure to right). D, Flabellifera, Cirolanidae (Bathynomus giganteus, SDNHM). E-F, Flabellifera, Cirolanidae (Bathynomus doderleini, USNM 39321): E, ventral view, F, dorsal view; note 'scale' (insert figure to right of E). G, Oniscidea (Ligia exotica, USNM 43352). H, Oniscidea (Ligidium ungicaudatum, USNM 83070). I, Anthuridea (Cyathura guaroensis, from Brusca and Iverson, 1985). J, Anthuridea (Calathura sp., USNM 99253). K, Anthuridea (Malacanthura caribbica, USNM 173521). L, Phreatoicidea (Phreatomerus latipes, USNM 60659). M, Gnathiidea (Bathygnathia curvirostris, USNM 10580). N, Flabellifera, Bathynataliidae (Bathynatalia gilchristi, USNM 170549). O, Serolidae (Serolis albida, USNM 123900). P, Serolidae (Serolis bromleyana, USNM 123911). Q, Flabel­ lifera, Anuropidae (Anuropus antarcticus, USNM 112260). R, Valvifera, Idoteidae (Synidotea francesae, from Brusca, 1983). S, Flabellifera, Plakarthriidae (Plakarthrium punctatissium, USNM 32500). T, Epi­ caridea (Scalpelloniscus penicillatus, after Grygier,1981). U, Epicaridea (Pseudasmmetrione markhami, after Adkinson and Heard, 1980). V, Flabellifera, Limnoriidae (Limnoria kautensis, after Cookson and Cragg, 1988). LSI VdOdOSI 3H1 dO SISAIVNV DU3Na001AHd 158 MEMOIRS OF THE QUEENSLAND MUSEUM

FIG. 6. Scanning electron micrographs of the antennular scale of Bathynomus giganteus (Flabellifera, Cirolanidae). Images show 4 different magnifications. criorwards; this is most easily seen in the active in Hirsutia is less clear, but it appears to be the praniza stage. same. Mysidaccans have no distinct functional In the Valvifcra, both the 3:4 and 4:3 condition grouping of the pcrcopods, i.e. all legs arise more occurs; Arcturidae and Amcsopodidae have the or less straight out, ventrolateral^ from the 4:3 condition, whereas Chaetiliidae, Holog- body. nathidac, Idoteidae and Xenarcturidae have the Hence, four pereopodal conditions, or 'states' 3:4 condition. In the Pseudidotheidae the fourth exist for character 18: 2:5, 3:4, 4:3, and no leg is directed straight out to the side, and species functional grouping. The relative polarity or in this family may appear to be 3:4 or 4:3, or even direction of evolutionary change(s) associated one condition on the left side and the other with this character is unknown, and this charac­ condition on the right. Because the 3:4 condition ter was initially left unordered in the data set. The is considered primitive in this suborder (Brusca, states of character 18 are assigned the following 1984: 104) Valvifera are scored for that state. codes in the data matrix: 0 = no functional group­ The out-group taxa show a variety of func­ ing (mysidaccans); 1 = 3:4; 2 = 4:3; 3 = 2:5. tional groupings, which may or may not be ho­ In adult Gnathiidca, the seventh pereonite is mologous with the situation seen in the lsopoda. reduced and without pereopods (character 19). The tanaidaceans and gammaridean amphipods Although the seventh pereonite may be lacking have a 4:3 grouping, similar to the Phrcatoicidea. in some anthuridcan genera (Colanthura, In mictaceans, the grouping appears to be 2:5. At Cruregens, etc.; Poore, 1984) and in a few deep- least this is the case in Mictocaris; the condition sea Asellota (Wilson, 1976; 1989),thiscondition PHYLOGENETIC ANALYSIS OF THE ISOPODA 159

is not regarded as primitive in these suborders. It Flabellifera, Anthuridea, and Epicaridea. These is probable that genera of isopods in which sexu­ matters are briefly reviewed below. In the fol­ ally mature adults lack the seventh pereonites lowing discussion, the 'peduncle' of the anten- evolved by way of neotenic events. nule is defined as the enlarged, basal region of In the Phoratopodidae, the posterior pereopods the antennule that bears intrinsic musculature. form sculling 'oars', and the dactyls are reduced The flagella of isopod antennules lack intrinsic or lost (character 88). Flattened posterior swim­ musculature (i.e. no muscles have their origin in ming pereopods also occur in some Munnop- the flagellum); flagella arise from the distal-most sidae (Asellota) and, to a limited extent, some peduncular article. Cirolanidae (Natatolana), but it is not the primi­ As in so many other instances, Caiman (1909) tive condition for these two families. appears to have been the first to comment on the True chelipeds do not occur in isopods, except possible generality and significance of scales on for a few rare cases such as the unusual genera the antennules of isopods, noting their presence Carpias (Asellota) and Chelanthura (An- in two groups, the genus Bathynomus thuridea) although various subchelate and pre­ (Cirolanidae) and 'cryptoniscan larvae of certain hensile conditions do occur. In three groups, epicarideans.' Caiman did not indicate which Aegidae, Cymothoidae, and Epicaridea, the per­ epicarideans he was referring to, nor did he pro­ eopods are prehensile. In aegids, pereopods 1-3 vide figures of these structures. However, he only are prehensile; in cymothoids and epicarids referred to them as 'minute vestiges of the inner all 7 pairs of pereopods are prehensile. We define flagellum', and was presumably referring to spe­ a prehensile pereopod as one in which the dactyl cies of Bopyridae sensu lato. Hansen (1925) is as long or longer than the propodus, acute, and repeated Caiman's remarks, as have many sub­ recurved. Although the pereopods of most epi- sequent workers. Wagele (1983a) used Cai­ carideans are prehensile and used for clinging to man's comment as a basis for 'homologisation their host (crustaceans), they differ fundamen­ of this (scale-bearing) article with the last tally from the legs of aegids and cymothoids, as peduncular segment of other Malacostraca,' on noted above, with which they may not be ho­ the apparent assumption that the antennular mologous. At least some of the anterior per­ peduncle of isopods is homologous to the pro- eopods of serolids, phoratopodids, certain topod of the other segmental body appendages. Sphaeromatidae (Bathycopea, Tecticeps), and Menzies (1957) added an overtone of generality astacillid valviferans are subchelate, but we do with a passing comment in his widely cited lim- not regard these conditions as homologous to the noriid monograph, which reads: 'The conspicu­ prehensile pereopods of cymothoids, aegids or ous scale attached to the first antenna of epicarideans. Character 65 is: pereopods not pre­ Paralimnoria is also characteristic of the genus hensile (except at most pereopod 1) (0); per­ Limnoria and, as Caiman remarks, of the genus eopods 1-3 prehensile (Aegidae, Cymothoidae, Bathynomus (Cirolanidae) and cryptoniscids Epicaridea) (1). (suborder Bopyroidea). It has since been found on Mesanthura (Suborder Anthuridea, Miller ANTENNULES and Menzies, 1952, p. 8) and the young of The antennules of mysidaceans, mictaceans, Cirolana (unpubl. data) and it is possibly char­ and amphipods are biramous. In these groups the acteristic of isopods in general' (51c). Menzies flagella arise from the third peduncular article, (1957) provided an illustration of this structure as in other Peracarida and Eumalacostraca. The for Paralimnoria andrewsi. antennules of tanaidaceans may be either In Bathynomus (B. giganteus, B. doederleni,B. biramous, with the flagella arising from the kapala) the 'antennular scale' takes the form of fourth article (Apseudomorpha) or uniramous a large, cuticularized, volcano-like process with (Neotanaidomorpha, Tanaidomorpha). The a deep pit at the terminus from which arise antennules of nearly all isopods are uniramous numerous long setae (Fig. 6). Under light micro­ (see Figs. 5 and 6 for examples of isopod anten­ scopy this scale resembles a large complex sen- nules). However, the literature contains many sillum. However, SEM examination reveals the allusions to taxa that allegedly possess antennu- scale to be covered with a cuticle bearing the lar scales, or other structures said to represent same type of cuticular surface structure seen on vestigial flagella or remnants of the missing the rest of the body, and to be encircled basally antennular ramus (presumably the exopod). by what may be an articular membrane. Thus, we These various taxa belong to three suborders: tentatively interpret this structure as a true scale, 160 MEMOIRS OF THE QUEENSLAND MUSEUM

i.e. vestigial second ramus. However, in the sim­ In limnoriids, most species do possess an ilar appearing Parabathynomus a scale does not antennular scale on the distal margin of the third exist, although a sensory pit is present in the peduncular article. In some species, this 'scale' same position on the peduncle, and arising from resembles little more than a large, simple seta it is the same kind of setal cluster seen in Bathy- {Paralimnoriaandrewsi Caiman). In most, how­ nomus. The two kinds of sensory structures are ever, it is a small, one-piece, articulating, setae- precisely in the same place, and look very similar bearing structure not unlike that of young in all respects, except that in Parabathynomus bopyrids. The antennular scales of limnoriids are the sensory pit sits on the cuticular surface, rather very small and difficult to observe without the than at the end of a scale. In another very similar use of a scanning electron microscope (for good genus, Booralana, a cluster of sensory setae illustrations and SEM photographs see: Kus- arises from a very shallow depression at this sakin and Malytina, 1989, fig. 3; Cookson and same location on the third peduncular article, but Cragg, 1988, figs. 3d, 4d; Cookson, 1989, PhD there is neither a 'scale' or a distinct pit. Diss.). L.J. Cookson (pers. coram.) feels that the As for the antennular 'scale' of the cryptonis­ Keuphyliidae (Keuphylia nodosa) possesses a cus stage, Caiman appears to have been relying scale similar to that of limnoriids but we have not on Bonnier (1900) and Giard and Bonnier observed this scale ourselves nor was it il­ (1887), who stated that the antennules of epi- lustrated by Bruce (1980). carideans 'are often biramous, with numerous In the case of the Anthuridea, 'scales' or ves­ sensory filaments.' The cryptoniscus stage of the tigial flagellar processes almost certainly do not family Bopyridae sensu lato possesses complex exist. We have examined dozens of anthuridean antennules of uncertain homologisation. The species and failed to find anything resembling a first article, and often the second, typically bear scale or vestigial ramus. We are aware of two toothed 'gnathobasic margins' that are of impor­ reports of such structures in anthurideans. The tance in species-level taxonomy. One to three first was by K.H. Barnard (1925) who claimed lobes may arise from the third article, each an antennular scale was present on Xenanthura highly invested with bundles of long setae. It is brevitelson. Kensley (1980), using SEM tech­ these sensory lobes that Bonnier and Caiman niques, showed this structure to merely be a large presumably interpreted as scales, or vestigial sensillum. The other claim was that of Miller and rami or flagella. When several of these sensory Menzies (1952), who noted an antennular scale lobes are present, only one (usually the largest) in a single female specimen of Mesanthura bears aesthetascs, the others are much smaller hieroglyphica (from Hawaii). Miller and Men­ and bear only 'simple' sensory setae. Thus, the zies stated, 'An antennal scale here observed on large lobe could reasonably be homologised to a the first antenna of a female specimen has not, to reduced antennular flagellum, but the other one our knowledge, been reported previously in the or two lobes appear to be large, complex sensilla, Anthuridae. Because of its minute size and its or possibly one of these represents a true anten­ position, it is not readily seen, hence may have nular scale. Nielson and Stromberg (1973) de­ been overlooked in other species in the family. scribed these lobes in an unidentified bopyrid as It was not found, however, in the other Hawaiian being 'heavily equipped with sensory hairs, anthurids described in this paper' (sic). Their densely crowded together...', and noted that the 'scale' appears identical to the sensory seta antennule is 'apparently an effective sensory shown by Kensley for X. brevitelson. organ as well as an accessory adhesive one.' The The final group said to possess antennular lobes have been clearly figured by Nielson and scales, 'the young of Cirolana', was cited by Stromberg (1965), Bourdon (1968), Grygier Menzies (1957) as, '...(unpubl. data)...'. To our (1981), and others. Grygier (1981) described the knowledge, Menzies never published these antennular peduncles of Scalpelloniscuspenicil­ 'data', nor has anyone else shown antennular latus and S. binoculis as 3-articulate, noting that scales in this genus. One of us (RCB) has ex­ the third article bears a 'pair of 1-merous rami amined hundreds of young Cirolanidae, in and a large, ventrolateral bulb completely Cirolana and many other genera, and has never covered with brush-like bundle of capillary aes­ seen antennular scales in any genus of this family thetascs...'. Kensley (1979) has described the other than Bathynomus. antennules of the cryptoniscus stage of In summary, we conclude that only Bathy­ Zonophryxus trilobus (Dajidae) also as bearing nomus, limnoriids, the cryptoniscus stages of a trilobed second article. bopyrids, and perhaps keuphyliids may possess PHYLOGENET1C ANALYSIS OF THE ISOPODA 161

structures on the antennules that might be rea­ Our examination of the antennule of Balhy­ sonably interpreted as scales. Although we are nomus giganteus (cuticle cleared with xylene) not entirely convinced that these minute, uniar- indicates that the 4th article lacks intrinsic ticulate structures are anything more than com­ musculature, thus conforming to our definition plex sensilla, we have entered this character into of the flagellar article. Several other authors that the data matrix anyway. For character 20, all four have alluded to a 4-jointed antennular peduncle out-groups are scored as possessing a biramous in Balhynomus may have been misinterpreting antennule (or a scale), and among the isopods the the first (proximal) article for two articles, due to epicarideans and limnoriids are scored the same the presence of a strong ridge on the medial (0); Cirolanidae is scored '?' because apparently surface of that joint, such that it could be easily only the genus Balhynomus (of a total of approx. mistaken for two pieces (Fig. 5 C-F). The fourth 45 genera) has a scale; Keuphyliidae is also peduncular article of Bathynataliidae noted by scored '?' because we are uncertain whether a Kensley (1978) and Bruce (1986) corresponds to scale is actually present in this group. All other the small first flagellar article of other flabel- isopods are scored 1 — lacking antennular liferan families. scales. A 4-articulate antennular peduncle un­ Mysidaceans, mictaceans, amphipods, and questionably does occur in two flabelliferan other Eumalacostraca (except tanaidaceans) ap­ groups, Phoratopodidae and Serolidae. But, in pear to primitively possess a 3-articulate anten­ both of these cases the 'extra' fourth article is nular peduncle. It seems reasonable to neither basal nor does it appear to be ho­ homologise these articles to the 3-articulate pro- mologous to the short fourth article noted above topod of other crustacean appendages. Neverthe­ in other isopods, but rather appears to be the less, this is not a certain homologisation because result of a subdivision of the third article into two in all crustacean nauplii this appendage is uni- large equi-width joints with continuous marginal ramous. Moreover, the Apseudomorpha tan­ contours. In the Serolidae we have examined, the aidaceans have the accessory flagellum on the fourth and fifth articles contain no intrinsic fourth article of the antennule, arguing for a musculature. Van Lieshout's (1983) description four-articulate protopod in this group. of Calabozoidea states Calabozoa pellucida has Most isopod workers have regarded the anten­ a 3-articulate peduncle, but her figure 2C gives nular peduncle of the Isopoda to be 3-articulatc. the appearance of a 4-articulate peduncle, However, Bruce (1981, 1986) felt that isopods possibly with a sensillum on the fourth article. 'primitively' have 4-articulate antennular Our observations of Calabozoa indicate that the peduncles because he interpreted the small antennule comprises only 4 articles, presumably fourth article that occurs in many groups (that a 3-articulate peduncle and uniarticulate flagel­ most other workers view as the first flagellar lum (the terminal article bears one aesthetasc and article) as the last, or fourth, peduncular article. one large seta). The antennules of oniscids are so Due to this different interpretation of the fourth reduced that we score them as undecided ('?') article of Cirolanidae (and other non-asel- for this character. Character 21 is: antennular lote/non-phreatoicidean groups), Bruce (1981, peduncle 3-articulate with an undivided third 1986) and Wagele (1983a) were at odds over article (0) vs 4-articulate, presumably by way of whether the 'primitive' isopod antennular subdivision of the third article (1). Only phora- peduncle was 3-articulate (Wiigclc) or 4-articu­ topodids and scrolids are scored apomorphic for late (Bruce). Wagele's opinion is based on the this character. third article of Balhynomus bearing the scale, Reduction of the antennules probably occurs which he homologises with a vestigial second in at least some species in every isopod suborder, flagellum, and at this time we arc inclined to and may occur in various conditions within a accept this homology argument, especially given single suborder or family. When the antennules that the primitive eumalacostracan condition is arc reduced, a corresponding reduction of the almost certainly a 3-articulate antennular deutocercbrum and its olfactory lobes also usu­ peduncle. We see no reason not to accept that the ally occurs (where it has been studied). The small fourth article of Balhynomus is ho­ mode of reduction in the various suborders mologous with the short fourth article of most clearly differs. Reduction typically accompanies other Cirolanidae, Anthuridea, Bathynataliidae, exploitation of parasitic or interstitial habitats. Gnathiidea, and other taxa (Fig. 5), but do not Valviferans have a 3-articulate peduncle, with consider this article to be part of the peduncle. the flagellum often reduced to one or a few 162 MEMOIRS OF THE QUEENSLAND MUSEUM

vestigial articles. Although antennular reduction articles. In Lynseiidae and Keuphyliidae, all 3 is rare in gnathiids, some species also have a peduncular articles are present and the flagellum 2-articulate peduncle and the flagellum reduced is reduced to 3 very short articles. The antennules to a few articles. In the interstitial Microcer- are very short in the Cymothoidae and the dis­ beridea, reduction is such that the peduncle can­ tinction between the peduncle and flagellum is not be distinguished from the flagellum. A indiscernible, the entire structure usually being similar reduction takes place in the parasitic reduced to 7 or 8 short articles (Fig. 5). Reduced Cymothoidae and Epicaridea. Epicarideans have antennular flagella are common in various spe­ highly reduced antennules, usually of 2-3 arti­ cies in many genera of Cirolanidae, wherein a cles; a 3-articulate peduncle is generally ap­ 3-articulate peduncle bears a flagellum reduced parent during larval stages, but reduced in adults. either by loss or fusion (or both) of the flagellar In oniscideans reduction results in very small, 1 -, articles (some Eurydice, Metacirolana, 2-, or 3-articulate antennules, which in some Cirolana, etc.). cases are not even mobile (although Holdich, In examining these various antennular reduc­ 1984: figs 24, 53, shows 4-articulate antennules tions, it is obvious that they are not all ho­ in Porcellio and Deto). Sctation on the second mologous. In fact, reduction in most, or even and/or third article suggests that loss of both each, group could have been by entirely separate peduncular and flagellar articles has probably evolutionary events. Some may be homologous occurred in the Oniscidea. Oniscidean anten­ reductions, but until detailed ultrastructural and nules also differ in arising directly between the anatomical studies have been accomplished a antennae, instead of antero-medially to them, as judgment in this regard cannot be made. For this in most other isopods (character 22). Some an- reason, we have not used antennular reduction as thuridean species also have small, 3-articulate a character in the data set. antennules, with setation again suggesting loss of one of the peduncular articles as well as most ANTENNAE of the flagellar articles. A review of the literature suggests that confu­ Among the Flabellifera, all manner of antcn- sion exists regarding the number of articles in the nule reduction occurs. In many cases, it appears antennal peduncle of peracarids (Fig. 7). Much that the two basal-most articles have fused, as in of this confusion'seems to have derived from many Cirolanidae (C. tuberculoid, Delaney, viewing the number of peduncular articles as a 1986; C. triloba, C. furcata, C. similis, and C. single feature, when in fact it should probably be victoriae, Bruce, 1981; Neocirolana bicrista, examined as at least two separate features (the Holdich et al., 1981); many Corallana and Ex- number of articles in the protopod; and, the num­ corallana (Delaney, 1982, 1984), and perhaps ber of proximal articles of the ramus that com­ Plakarthrium. In Anuropus, only two antennular bines with the protopod to form a functional unit articles remain, and their homology is uncertain. recognized as the peduncle). We define peduncle However, the second (distal) article in Anuropus as the enlarged basal articles of the antenna that is unique in being enormously expanded and bear intrinsic musculature. The flagella of isopod scalloped (character 23). In most limnoriids, the antennae lack intrinsic musculature, i.e. no peduncle appears to have lost one article, and the muscles have their origin in the flagellum. flagellum is also reduced to only a few articles, The antenna of mysidaceans has a 3-articulate although mancas tend to have all 3 peduncular protopod (at least primitively, e.g. M/sis), which

FIG. 7. Examples of isopod antennae. A, Flabellifera, Cirolanidae (Bathynomus giganteus, SDNHM), dorsal aspect showing arliculation with head, base of antennule, and floating cuticular piece on articulating membrane. B, Flabellifera, Cirolanidae {Bathynomus doderleini, USNM 39321, dorsal aspect). C, Phreatoi- cidea (Phreatomerus latipes, USNM 60659). D, Flabellifera, Cirolanidae (Eurydice caudaia). E, Flabel­ lifera, Aegidae (Aega longicornis, holotype). F, Gnathiidea (Bathygnathia curvirostris, USNM 10580), note fusion of distal articles (3 and 4, or 4 and 5). G, Valvifera, Idoteidae (Synisoma sp.). H, Valvifera, Idoteidae (Synidotea francesae, holotype). I, Anthuridea (Malacathura caribbica, USNM 173521). J, Anthuridea (Calaihura sp., USNM 99253). K, Flabellifera, Cirolanidae (Politolana wickstenae, holotype). F, Flabel­ lifera, Cymothoidae (Nerocila acuminata). M, Flabellifera, Anuropidae (Anuropus anlarcticus, USNM 112260). N-P, Valvifera, Pseudidotheidae (Pseudidothea miersii, USNM 139139): N, entire antenna, with 4-articulate peduncle and 2-articulate flagellum; O-P, first two peduncular articles, seen from both sides. Q, Oniscidea, Ligiamorpha (Ligia baudiniana, SDNHM). R, Oniscidea, Ligiamorpha (Ligia exotica, USNM 43252). S, Oniscidea, Ligiamorpha {Ligia occidentalis, SDNHM). PHYLOGENETIC ANALYSIS OF THE ISOPODA 163 164 MEMOIRS OF THE QUEENSLAND MUSEUM

combines with the first two or three flagellar third article bears a movable scale, or 'squama', articles to form a 5- or 6-articulate peduncle, representing the vestigial exopod. although the protopod articles are fused into 1 or Caiman (1909) agreed with Hansen's conclu­ 2 pieces in most living species. A large lamellar sions, noting that the antennal peduncle of scale (the scaphocerite) arises from the third isopods normally comprises 5 articles, but that protopodal article in mysidaceans. Mictaceans in the Asellota, Bathynomus, and Cirolana it is and amphipods have 2-articulate protopods, that 6-articulate, and in some Asellota with 6-articu­ combine with the first 3 flagellar articles to form late peduncles a scale occurs on the third article. 5-articulate peduncles (although this is reduced Wagele (1983a; referring to the protopod as the in some amphipods). Mictaceans, and perhaps 'basipodite') agreed with Hansen's conclusions some apseudomorph tanaidaceans, have a scale that a 6-articulate peduncle is the primitive on the second article, suggesting that it could be isopod condition. Wagele used figures taken homologous with the third protopodal article of from Hurley (1957) and Vandel (1960) to il­ mysidaceans. Amphipods lack an antennal scale. lustrate 6-articulate peduncles in an asellote The antennal peduncle of most isopods also (lathrippa longicauda) and a ligiid (Ligia ital- comprises 5 articles, although in some taxa it is ica), following Hansen in his claim that in the reduced to 4 or fewer articles, and in the Asellota Asellota and Ligiidae a small exopodite (scale) and Microcerberidea (and possibly some Ciro- occurs on the third peduncular article. Wagele lanidae) a 6-articulate peduncle occurs. A review (1983b) also argued that a 6-articulate antennal of these conditions in isopods is given below. peduncle is characteristic of the Microcer­ Milne Edwards and Bouvier (1902) described beridea. Other authors have agreed or disagreed the antennal peduncle of Bathynomus with Hansen's opinion regarding the occurrence (Cirolanidae) as 6-articulate. However, they ap­ of a 6-articulate peduncle in isopods. parently mistook the large articulating mem­ The literature thus contains references to 6-ar­ brane between articles 1 and 2 for an extra article ticulate antennal peduncles occurring in at least (as noted by Bruce, 1986). Hansen (1903) also some genera in four groups: Asellota, Microcer­ described the antennal peduncle of Bathynomus beridea, Oniscidea (Ligiidae), and Cirolanidae. as 6-articulate, but Hansen was focusing on a The contention of a 6-articulate peduncle in the minute strip of sclerotised cuticle at the base of Isopoda is tied to Hansen's and Caiman's homol- the antennal peduncle, at the edge of the articu­ ogisation of isopod antennae with a 'primitive' lating membrane, that he considered to be the crustacean somite appendage with a 3-articulate vestige of a proximal antennal article, or pre- protopod comprising a precoxa, coxa and basis, coxa. Hansen's conclusion that this cuticular with the paired rami arising from the latter. How­ fragment is homologous to a precoxal article was ever, it is of considerable interest to note that, based on the observation that it moved ('articu­ among the Malacostraca, an antennal precoxa lated') within the antennal socket when the (and hence a 3-articulate protopod) unquestion­ antenna was moved. Hansen (1903) also claimed ably occurs only in the groups described above to have found 6-articulate antennal peduncles in — the mysidaceans and certain isopods. In all several species of Cirolana, and in the asellote other malacostracans the protopod comprises genera Eurycope and Asellus. Hansen (1905a, only 2 articles, and the rami (or scale) arises from 1916) later added Conilera (Cirolanidae) and the second article. This suggests the possibility Ligia (Oniscidea) to the list of taxa with 6-articu­ that the primitive state in Crustacea is a 2-articu­ late antennal peduncles, and in his 1925 review late antennal protopod. added Janira maculosa (another asellote), con­ We have examined the cuticular piece noted cluding that the 6-articulate condition was primi­ by Hansen on the articulation membrane of the tive in isopods, and loss of the precoxa was a antenna of B. giganteus and also found it to move derived condition. when the antenna is moved. However, this piece In Hansen's view, then, the primitive isopod does not articulate with any other article, or with antenna was similar to that of mysidaceans, with the head, but simply floats free upon the mem­ a 6-articulate peduncle composed of a 3-articu- brane. A similar free-floating cuticular piece oc­ Iate protopod (comprising the precoxa, coxa, and curs in many genera of Cirolanidae (as noted basis) plus the first three articles of the en- above), although it has rarely been noticed due dopodite; the rest of the endopodite forming the to its small size and failure to be removed with flagellum. Hansen also noted that in most Asel­ the antenna upon dissection. Bruce (1986) com­ lota and in Ligia with a 6-articulate peduncle, the mented on these structures, noting their presence PHYLOGENETIC ANALYSIS OF THE ISOPODA 165

in at least 12 Australian genera of Cirolanidae Thylakogaster, Abyssaranea); Desmosomatidae and illustrating them for three species (Bathy- (Balbidocolon, Eugerda, Chelator, Mirabil- nomus immanis, Cirolana cranchii, and Nata- icoxa, Momedossa, Prochelator, Torwolia, tolana rossi). Homologisation of this piece with Whoia, Thaumastosoma); Nannoniscidae a true basal, or 'precoxal' article seems a rea­ (Hebefustis, Exiliniscus, Panetela, Rapaniscus, sonable hypothesis, although in our opinion still Regabellator); Munnopsidae (Eurycope); Janir- very much open to testing. Moreover, we know idae (Jaera, laniropsis); Pleurocopidae (Pleuro- of no flabelliferan isopod that has an antennal cope); and Munnidae (Munna). Antennal scales scale. occur on the third peduncular article in many of In Ligiidae, the antennal peduncle is usually these same asellote taxa, and also on the third 5-articulate, or occasionally 4-articulate. In this article of some species with fewer than 6 articles family, both the first and second article may be in the peduncle, such that one would interpret the split by 'fracture lines' (often subcuticular) on antenna as retaining the 3-articulate sympod, but one side, so that an observation from only one withonly 1 or2articlesof theendopod contribut­ side of the appendage might give the illusion of ing to the peduncles. there being more than one article present — a Wagele (1982b, 1983b) illustrated a 5-articu­ situation somewhat analogous to that noted late antennal peduncle for Microcerberus mira- above for the antennule of Bathynomus. We have bilis, although he stated that a 6-articulate examined Ligidium ungicaudatum, Ligia oc- antennal peduncle is diagnostic for the Microcer- cidentalis, L. baudiniana, and L. exotica and can beridea. Wagele (1983b) clearly shows a 'pre­ find no trace of a precoxal article. Richardson coxal article' on the antenna of Microcerberus (1905), Van Name (1936), Sutton (1972), Kens- tabai. Baldari and Argano (1984) figured a 5-ar­ ley and Schotte (1989), and others have also ticulate peduncle in Microcerberus redangensis, noted that the antennal peduncle of Ligiidae is but stated that it was 4-articulate. Pennak (1958) no more than 5-articulate. Fragmentation, split­ claimed M. mexicanus had a 5-articulate ting, ridges, etc. occur on the proximal articles peduncle. Messana et al. (1978) clearly showed of the antennal peduncles in many groups, in­ and stated that Microcerberus anfindicus has a cluding Ligiidae, Anthuridea, Phreatoicidea, and 6-articled peduncle. Perhaps both the 5-articu­ others. This splitting may have led some authors late and 6-articulate conditions occur within the to mistakenly interpret one of the pieces as a Microcerberidea but, since the 6-articulate con­ small precoxal article (and thus describe a '6-ar- dition definitely does occur we regard it as the ticulate' peduncle). The first mention of an primitive state. 'extra' article at the base of the antenna in ligiids Nicholls (1943, 1944) noted that the antennal was apparently Hansen (1916) who stated, '...in peduncle of phreatoicids was 5-articulate, but Ligia oceanica we found not only six joints in that a ridge (or groove) lines the lower boundary the peduncle, but even an exopod or squama on of the antennal socket that might suggest the the third joint...'. Hansen's illustration shows ex istence of a former proximal (precoxal) article what appears to us to be a 5-articulate peduncle, that had been incorporated into the head. How­ with the first and second articles fragmented; his ever, such a ridge occurs in many isopods, in­ 'precoxal remnant' appears to be a fragmented cluding Bathynomus, and Milne Edwards and plate of the first article, and his 'scale' appears Bouvier (1902) and Hansen (1903) regarded it as to be the protruding edge of a fragment on the simply part of the head skeleton. second article. The inner margin of the second An antennal scale probably does not exist in article is often slightly elevated, to form a low the Anthuridea. In some species, such as lobe-like ridge, that has perhaps been mistaken Malacanthura caribbica, a minute, simple, un- for a 'scale' in Ligia. Wagele's (1983a) illustra­ jointed, non-articulating structure exists on the tion of Ligia italica (after Vandel, 1960), show­ 5th peduncular article; it appears to be a superfi­ ing a 6-articulate peduncle and a scale, is cial cuticular structure, perhaps a sensillum of probably such a misinterpretation. some kind. We have seen no such structure, or In the Asellota, 6-articulate antennal anything resembling a scale, in species ofCala- peduncles do occur in numerous genera of many thura or Mesanthura that we have examined. families (Fresi, 1972; Gruner, 1965; Hessler, Kensley (pers. comm.) has taken SEM photo­ 1970; Siebenaller and Hessler, 1977; Wilson, graphs of many anthuridean species, including 1976; 1980a, 1986a; Wilson and Hessler, 1981): species that Menzies and K.H. Barnard claimed e.g. Haplomunnidae (Haplomunna, Munella, had antennal scales, and failed to find anything 166 MEMOIRS OF THE QUEENSLAND MUSEUM

other than various, small, superficial, cuticular structures reduces their usefulness in phylo- structures (spines and setae). genetic analysis at the subordinal level. In valviferans, the first two articles of the The isopod mandibular palp, like that of other antennal peduncle are more-or-less fused and peracarids, is primitively 3-articulate. Kussakin operate as a single unit, although the cuticle of (1979:26) illustrated a 4-articulate mandibular these two articles often appears to be 'frag­ palp for Caecocassidlas patagonica (Sphaero- mented' into several pieces. Bruce (1980) de­ matidae) and for Cyathura polita (Anthuridea), scribed Keuphylia nodosa (Keuphyliidae) as even though he described the Isopoda as having having a 5-articulate antennal peduncle with a mandibular palps of 3 or fewer articles. Kus- scale on the second article. We have examined sakin's figures of 4-articulate mandibular palps this species and consider this structure is not a are almost certainly in error. Like Hansen (1890) true 'scale'; it appears to be a cuticular fold or a and Bruce (1983, 1988) for several species of one-piece sensory lobe, and it is on the second Aegidae, Kussakin probably mistook a fold at (not the third) peduncular article. the base of the proximal palp article for an artic­ Character 24 is: antennal peduncle 6-articulate ulation. (0) vs antennal peduncle 5-articulate (1). My- Reduction of the mandibular palp (to one or sidaceans, tanaidaceans, microcerberids and two articles) has occurred in several taxa, and asellotes are scored (0); all other taxa in the data complete loss of the palp has occurred in many matrix are scored (1). In Cirolanidae both condi­ groups (Oniscidea, Calabozoidea, Keuphyli­ tions might exist (given the hypothesis that the idae, Lynseiidae, Gnathiidea, Epicaridea, some small cuticular pieces on the articulating mem­ Anthuridea, some Cirolanidae, many genera of brane in some species represents a vestigial basal Asellota, and all non-Holognathidae Valvifera). article), and the condition in limnoriids and pro- In gnathiids (praniza) and epicarideans, the tognathiids is uncertain; hence these three taxa mandibles are modified as small scythe-like are scored (?). Character 24 was left unordered pointed stylets with serrate cutting edges. in initial analyses. There are two fundamentally different kinds of Character 25 is: antenna biramous, or with a mandibular molar processes in isopods. A broad, vestigial second flagellum or scale (0) vs antenna flat or truncated, grinding molar process is char­ uniramous, and without a vestigial second acteristic of Phreatoicidea, Asellota, Microcer- flagellum or scale (1). Mysidaceans, tan­ beridea, Oniscidea, Valvifera, and most genera aidaceans, mictaceans, and asellotes are scored in the flabelliferan family Sphaeromatidae. A primitive for this character (0); all other taxa are thin, elongate, blade-like, slicing molar process, scored (1). The 'scale' drawn by Bruce (1980) with a row of teeth or denticles along the antero- on Keuphylia appears to us to be a non-articulat­ distal margin, is characteristic of the primitive ing sensory lobe on the second peduncular ar­ Anthuridea (Hyssuridae), and the flabelliferan ticle. families Anuropidae, Cirolanidae, Phora- Character 26 is: Antennae present (0) vs topodidae, and Protognathiidae; a reduced antennae vestigial in adults (1). Only Epicaridea blade-like molar process, or its apparent vestige, is scored derived (1) for this character. occurs in most species in the flabelliferan fami­ lies Aegidae, Corallanidae, Cymothoidae, and MANDIBLES Tridentellidae. Bruce (1981) suggested that the Of the many different 'characters' recognis­ molar process of Phoratopodidae is 'vestigial'. able on isopod mandibles, many show so much However, our observations of Phoratopus remex homoplasy that they are of little use at the sub- Hale indicate that, while the molar is slightly ordinal level of analysis. In some groups, such as reduced in size, it is nonetheless a well- many phreatoicids and asellotes, all of the typical developed, serrate, blade-like structure similar to peracaridan mandibular structures persist, at that of Cirolanidae. The serrate condition also least on the left mandible. However, reduction, exists in the Anuropidae and Protognathiidae, in loss, or extreme specialisation of the mandibular which it is (as in Cirolanidae) 'articulated' on the palp, molar process, spine row, and lacinia mo- body of the mandible. In Corallanidae and Tri­ bilis appears to have occurred at least several dentellidae (and the cirolanid genus Calyptolana times in most isopod suborders. Although clear Bruce) the molar process is also 'articulated' and trends can often be seen, especially within cer­ blade-like, but shows a loss of the serrate toothed tain family clusters, the high level of overall margin and a reduction in size (and even com­ homoplasy in modifications of most of these plete disappearance in some genera and species). PHYLOGENETIC ANALYSIS OF THE 1SOPODA 167

In the primitive anthurideans (Hyssuridae) the thorough understanding of pattern and homol­ blade-like molar process also occasionally 'ar­ ogy among these structures has been achieved. ticulates' on the body of the mandible and may In most Phreatoicidea, Asellota, Oniscidea, bear a serrate or toothed margin (Poore and Lew Calabozoidea, and Valvifera, a lacinia and spine Ton, 1988a; Wagele, 1981b). row, often closely associated with one another, In the sphaeromatid subfamilies Ancininae are usually present (at least on the left mandible). and Tecticeptinae (Ancinus, Bathycopea, and The lacinia and spine row are often modified, Tecticeps), the molar process is either absent or reduced, or lost in the various flabelliferan fami­ vestigial (Tecticeptinae) or modified as a thin lies and genera. A distinct lacinia and spine row blade-like structure (Ancininae). However, we are usually absent in the Anthuridea, although do not regard the molar of Ancininae to be ho­ remnants may persist in the primitive family mologous to the blade-like molar described Hyssuridae (Poore and Lew Ton, 1988a); the above for the Anthuridea and other flabelliferan unique 'lamina dentata' of anthurideans is pre­ families. In ancinines, the molar is apically acute sumably the homologue of one or both of these (not rounded), lacks teeth or denticles at the mandibular structures. In the Microcerberidea, antero-distal margin, and bears large knife-like the lacinia is absent and only a row of small serrations along the postero-distal margin. An­ spines is present. In the Phreatoicidea, a spinose cininae and Tecticeptinae possess all the other lobe may be present in lieu of a distinct lacinia features typical of Sphaeromatidae. and spine row, at least on the left mandible; the A molar process is absent in the Epicaridea and homology of this spinose lobe is uncertain, but it Gnathiidea, and in the flabelliferan families may represent either a fusion of the lacinia and Limnoriidae, Lynseiidae, Bathynataliidae, spine row, or a loss of the lacinia and specializa­ Keuphyliidae, Plakarthriidae, and Serolidae. tion of the spine row. A somewhat similar ap­ The molar process is also secondarily vestigial pearing modification occurs in certain Asellota or absent in some genera of Sphaeromatidae and (Asellus), Cirolanidae, and Keuphyliidae. The Idoteidae, and in a few anthuridean and onis- Limnoriidae have a somewhat similar structure cidean families. (called the 'laciniod spine'), and in the unusual In most isopods, the incisor is a multilobed genus Hadromastax only a single simple spine grasping structure, but in groups specialised for remains. In the Serolidae, two spine-like struc­ predation or parasitism the incisor is typically tures of uncertain homology are usually present, blade-like and/or acute, for piercing tissues (Pro- both articulating; one may represent the lacinia tognathiidae, Corallanidae, Tridentellidae, and the other a single, enlarged spine of the spine Aegidae, Cymothoidae, praniza stage of row, or both may be enlarged spines. In the Gnathiidea). In most Limnoriidae the incisor Phoratopodidae and Sphaeromatidae a large process bears a unique 'rasp and file' structure, gnathal lacinia, with an associated spine row, is and a similar condition appears to be approxi­ generally present. In the Bathynataliidae a large mated in the Lynseiidae (Menzies, 1957; Poore, gnathal lacinia is also present, but with no trace 1987; Cookson and Cragg, 1988). of the spine row. In the Anuropidae, Protog- The presence and size of the lacinia mobilis nathiidae, Corallanidae, Tridentellidae, Aegidae and spine row components vary greatly among and Cymothoidae the lacinia and spine row is the Peracarida. In the Isopoda, the nature of these absent or reduced to a few, vestigial, spinelike structures appears to be closely tied to lifestyle structures. Mandibular characters used in the (especially feeding behaviour) and hence analysis follow. strongly selected for and perhaps of limited phy- Character 27 is: mandible with a lamina den­ logenetic value above the generic level. The tata — a synapomorphy unique to the Anthu­ presence of both a lacinia and spine row (on both ridea. Character 28 is: mandibles of adult males the right and left mandible) is presumably the grossly enlarged, projecting anteriorly, forceps­ primitive peracaridan condition (Dahl and like — a synapomorphy unique to the Gnathiidea Hessler, 1982), and in many mysidaceans, mic- (although convergently approximated in the taceans, and amphipods a gnathal lacinia and unique cirolanid species Gnatholana mandibu- associated spine row persist. However, in many laris Barnard). Character 29 is: mandibles lost in isopod groups these structures have been modi­ adult females — also a synapomorphy unique to fied, reduced, or lost, especially on the right the Gnathiidea. Character 30 is: molar process a mandible. No doubt a wealth of phylogenetic broad flat grinding structure (0) vs molar process information will become available once a more a thin blade-like slicing structure (1). Taxa in 168 MEMOIRS OF THE QUEENSLAND MUSEUM PHYLOGENETIC ANALYSIS OF THE 1SOPODA 169

which the molar process is absent are scored '2' rami; or, exopod and endopod. Furthermore, the for this character. Character 50 describes four proximal articles and region of articulation be­ states of the mandibular incisor: broad and multi- tween the articles and lobes are rarely figured in toothed (0); teeth reduced to form a serrate or the literature. Caiman (1909) and Hansen (1925) crenulate margin (1); teeth lost (or fused?) to viewed this appendage as comprising only the from a conical projection with basal 'rasp and articles of the protopod, the two proximal articles file' (2); and, incisor modified as a recurved, being the precoxa and coxa, the outer lobe the hooklike, acute or subacute piercing-slicing basis, and the inner lobe an endite of the precoxa. structure (3). Character 91 is: mandibles mod­ In mysidacens, amphipods and tanaidaceans, ified as elongate scythe-like structures with a at least primitively, there are also two lobes that serrate cutting edge (Epicaridea and are clearly endites arising from the second and Gnathiidea). third articles, as well as a short palp. In mic- The following taxa are scored as lacking a taceans two lobes also exist, but the nature of mandibular palp (character 35): Ligiamorpha, their articulation and the proximal lobes of this Tylomorpha, Calabozoidea, Epicaridea, appendage are uncertain. Bowman and Iliffe Gnathiidea, Keuphyliidae, and Lynseiidae. Loss (1984) refer to these lobes as both endites and as of the mandibular palp in certain genera of An- endopod (the distal 'endite') and exopod (the thuridea and Asellota is assumed to have taken proximal 'endite'). Bowman et al. (1985) re­ place independently after the evolution of these ferred to these structures simply as the 'inner' suborders, i.e. it is a secondarily derived feature and 'outer' lobes. Mictaceans, like isopods, lack in these taxa. The situation in Valviferans is a maxillulary palp. debatable; Brusca (1984) suggested that pre­ In a number of isopod taxa the maxillules are sence of a mandibular palp was the primitive highly modified. In the anthurideans, the outer valviferan condition and loss of the palp oc­ lobe is a slender stylet and the inner lobe is curred after the origin of the unique species minute (presumably vestigial) or absent. The Holognathus stewarti, whereas Poore (1990) maxillules of anthurideans have rarely been il­ suggested that the ancestral valviferan had al­ lustrated (Poore, 1978, fig. 17b; Poore and Lew ready lost the mandibular palp and it reappeared Ton, 1988, fig. 7; and, Poore and Lew T^n, 1990, later in H. stewarti. We choose the more parsi­ fig. 3). In the primitive anthuridean family Hys- monious alternative and assume that the man­ dibular palp did not reappear within the suridae the maxillule bears apical denticles or Valvifera (sensu Brusca, 1984). Valviferans are spines; in the more advanced families (An- thus scored '0' for character 35. thuridae, Antheluridae, Paranthuridae) the api­ cal spines are largely reduced, or fused, often resulting in a simple serrate distal margin. Some­ MAXILLULES what similar conditions (outer lobe a long The typical isopod maxillule comprises 1 or 2 slender stylet with apical teeth, inner lobe re­ proximal articles, and two distal lobes — an duced or absent) exist in the Gnathiidea (praniza inner (medial) and outer (lateral) lobe. Most stage), Aegidae, Bathynataliidae, Cymothoidae, workers regard these lobes as endites although Lynseiidae, Plakarthriidae, and Tridentellidae. the precise homologies of the maxillulary arti­ In the Corallanidae the maxillule is highly mod­ cles is uncertain, and the two distal lobes are ified as a single elongate stylet with the apex referred to in the literature by a variety of terms, forming an acute recurved piercing hook. It e.g. inner and outer lobes, plates, endites, or seems unlikely that these are all homologously

FIG. 8. Examples of isopod maxillipeds. A, Oniscidea, Ligiamorpha (Ligia exotica, male, USNM 43352). B, Oniscidea, Tylomorpha (Tylos niveus, male, USNM 67703). C, Phreatoicidea (Phreatoicus australis, male, USNM 59116). D, Asellota (Paramunna quadratifrons; coxa and epipod not shown; SDNHM specimen). E, Asellota (laniropsis sp., male; SDNHM specimen). F, Asellota (Lirceus hoppinae, male, USNM 230328). G, Flabellifera, Cirolanidae (Anopsilana sp., male; SDNHM specimen). H, Flabellifera, SeTo\\dae(Serolisalbida, gta\\d female, USNM 123900). I, Flabellifera, Anutopidae (Anuropusantarcticus, non-gravid female, USNM 173141). J, Gnathiidea (Bathygnathia curvirostris, male, USNM 10580). K, Flabellifera, Cirolanidae (Excirolana chamensis, paratype, LACM type No. 3014). L, Flabellifera, Aegidae (Aega longicornis; type). M, Flabellifera, Cymothoidae {Lironeca convexa, female, attached oostegite not shown, from Brusca 1981). N, Gnathiidea (Gnathia stygia, USNM 112376). O, pylopod of Bathygnathia curvirostris, male, USNM 10580). P, pylopod of Gnathia stygia, USNM 112376). Q, Anthuridea (Cyathura guaroensis, from Brusca and Iverson 1985). 170 MEMOIRS OF THE QUEENSLAND MUSEUM

derived morphologies. The maxillules are ves­ scored '?' in the data matrix) the maxillae are tigial or lost in adult gnathiids and epicarids. highly modified or reduced to a single lobe or a Uncertainty regarding the homologies of the stylet (see below). In some groups, the maxillae maxillulary articles limits the number of poten­ are extremely reduced, vestigial, or absent alto­ tial characters available on this appendage for gether (Gnathiidea, Epicaridea, Anthuridea). In phylogenetic analysis. the Anthuridea the maxillae are minute and Character 31 is: maxillule present (0), vs re­ more-or-Iess fused with the paragnath (hy- duced or vestigial in adults (1), vs lost in adults popharynx), or absent altogether. In Protog- (2). Character 31 was left unordered in initial nathiidae the outer lobe is apparently absent analyses. Character 32 is: maxillule with palp (0) (Wagele and Brandt, 1988). In the oniscids the vs without palp (1). Character 92, the single maxillae are short and plate-like with 2 non-ar­ acute hook-like lobe, is unique to the Coral- ticulating lobes, but the homology of these 2 lanidae. lobes is not clear. Because the variety of maxil­ lary reductions in isopods are likely to be the MAXILLAE result of different evolutionary processes (non­ The homologies of the maxillary articles of homologous features), most of these charac­ isopods are also unsettled. As with the maxil­ teristics have not been included in the data set. lules, there are 1 or 2 proximal articles and 2 Character 36 is: maxilla modified into a stylet­ distal lobes — an inner (medial) lobe, and an like lobe with recurved apical (hooklike) setae, outer (lateral) lobe; the outer lobe is generally a condition seen in certain flabelliferan families divided into two. The proximal articles and ar­ (Corallanidae, Tridentellidae, Aegidae, Cy- ticulation of the two distal lobes are rarely il­ mothoidae). Character 33 is: maxillae highly lustrated in the literature. Caiman (1909) and reduced and 'fused' to the paragnath, or absent Hansen (1925) viewed the maxilla as lacking altogether (Anthuridea only). Among the rami and comprising only the protopodal articles Isopoda, only the Phreatoicidea retain the primi­ with their endites; that is, precoxa, coxa, and tive peracaridan filter setae row on the medial basis, with the coxa being expanded as an endite margin of the maxilla (character 74). forming the inner lobe, and the basis bearing an endite that forms the split (bilobed) outer lobe. MAXILLIPEDS As with the maxillules, the inner and outer lobes As in most other peracarids, the maxilliped of of the maxillae have usually been regarded as isopods consists of four distinct regions: a proxi­ endites, but they have been referred to in the mal article (the coxa); the basis, with an en­ isopod literature as rami, lobes, plates, endites, larged, distal, anteriorly directed, blade-like lobe and exopod/endopod. (the endite); an epipod of varying size and shape, The maxillae of mysidaceans retain both the lateral to the coxa; and, a palp (primitively com­ endopod and exopod, as simple one- or two-ar­ prising the remaining 5 articles of the appendage ticulate platelike structures, and both rami bear — the ischium through dactylus) (Fig. 8). Am- endites. Amphipod maxillae primitively re­ phipods differ from isopods in possessing semble those of isopods but without the divided (primitively) a 4-articulate maxillipedal palp, outer lobe, although in most modern groups they and two endites (an inner and an outer) arising are reduced to one or two simple lobes (as in from the basis and ischium respectively. many oniscideans). The maxillae of mictaceans The maxillipedal palp is reduced in some taxa are very similar to those of most isopods, with a in almost all suborders (most Oniscidea [Tri- divided outer lobe. The maxillae of tanaidaccans choniscidae, Tylidae, Oniscidae, Armadillidi- also resemble those of isopods, at least in their idae], Calabozoidea, many Anthuridea, primitive form (Halmyrapseudes, Sieg et al., Gnathiidea, Anuropidae, Aegidae, and Cy- 1982), although in most tanaidaceans the maxil­ mothoidae). Wagele's (1989a) claim that a 2-ar- lae are highly reduced. No isopods retain the ticulate maxillipedal palp with spines on only the primitive crustacean condition of a maxillary terminal article is a synapomorphy uniting the palp (the 'palp' of Cirolanidae referred to by genus Rocinela (Aegidae) as the sister group of Bruce, 1986 is actually the inner lobe). the Cymothoidae is incorrect. Most (if not all) Character 34 is: maxillary outer lobe un­ Rocinela have 3-articulate maxillipedal palps divided (0) vs divided into two lobes (1). Micta­ with spines on the two distalmost articles (the ceans, tanaidaceans, and isopods are apomorphic apical article is minute and easily overlooked). for this character, although in many groups (most In most isopod taxa, the maxillipedal endites can PHYLOGENETIC ANALYSIS OF THE ISOPODA 171

be hooked together by coupling setae (coupling In at least some isopod groups (e.g. some hooks), e.g. Phreatoicidea, Asellota, some Phreatoicidea, Asellota, Valvifera, Flabellifera, Valvifera, Epicaridea, Gnathiidea, most Flabel- Epicaridea, and Gnathiidea), the maxillipeds of lifera. Coupling setae also occur on the maxilli­ gravid females also bear posteriorly-directed, peds of some Mictacea and most Tanaidacea. oostegite-like, often setose lappets. The function Maxillipedal coupling setae are absent in Micro- of these lappets is not known, but they may cerberidea, Ligiamorpha, Tylomorpha, Calabo- function as an oostegite (to close the anterior zoidea, Anthuridea, and Amphipoda. They have region of the marsupium), or they may drive a presumably been lost in amphipods as a result of water current through the marsupium. the maxillipeds being fused together; this is also Several authors have suggested that the poste­ the case in certain tanaid families in which the rior cervical groove (fossa occipitalis) on the maxillipeds are fused, such as Leptognathiidae, head of some isopods represents the incomplete Pseudotanaidae, and Nototanaidae. Coupling line of fusion between the cephalon and first setae may be missing in the anthurideans owing thoracomere. However, these lateral or complete to the immovable fusion of the maxillipedal grooves occur sporadically in many distantly coxae and epipods to the head. Coupling setae related genera (Mesamphisopus, Idotea, Ligia, are also usually absent in isopod taxa that have some Sphaeromatidae, etc.) in many suborders, reduced endites e.g. Corallanidae, Aegidae, Cy- thus rendering this character unsuitable for phy- mothoidae, Lynseiidae, some Cirolanidae; or logenetic analysis at higher taxonomic levels. highly modified maxillipeds (Anuropidae, Character 37 is: left and right maxillipeds Plakarthriidae, Protognathiidae, Serolidae). fused together; this condition occurs only in In isopods (as in most peracarids) a lamellar amphipods and some tanaidaceans (not primi­ epipod usually arises from the coxa of the max­ tively, however). Character 38 is: coxae of max­ illiped. In several groups, the epipod may have illipeds fused to head; this derived condition its proximal part marked off from its distal part occurs only in the Anthuridea. Character 39 is: by a transverse suture (many Valvifera, Phrea­ maxillipedal endite without coupling setae (0) toicidea, and Flabellifera). In males and non- vs. with coupling setae (1). Mysidaceans lack ovigerous females, the epipods often seem to coupling setae, but they occur in at least some function as 'cheeks', forming an operculum for mictaceans, tanaidaceans, and isopods. Because the oral field. In gravid females of some taxa the character states of the mysidaceans and the (Anthuridea, many Flabellifera), the epipods amphipods may not be homologous, this charac­ tend to be oriented in such a way to function as ter was left unordered in initial analyses. Char­ accessory marsupial plates to prevent loss of the acter 41 is: maxilliped with 2-3 endites (0) vs 1 embryos from the anterior region of the mar- endite only (1). Amphipods have 2 maxillipedal supium. The isopod epipod is never branchial, as endites (one on the basis and one on the ischium), it is in tanaidaceans. In mysidaceans, the epipod mysidaceans have 0-3 endites, and all other taxa is posteriorly directed and carried under the in the analysis have one endite (on the basis). carapace. Epipods are known from all isopod Character 42 is: maxilliped biramous; in this suborders except Epicaridea, Gnathiidea, Micro- analysis, only the mysidaceans have a biramous cerberidea and Calabozoidea. Maxillipedal maxilliped (0), all other taxa have a uniramous epipods are also apparently absent in the families maxilliped (1). Character 44 is: maxillipedal Anuropidae, Corallanidae, and Plakarthriidae, basis elongated and waisted (medially nar­ and the unique genus Hadromastax. In rowed); this feature occurs only in the Lyn­ Cirolanidae, Aegidae, and Cymothoidae the seiidae and Limnoriidae. epipod is apparently reduced or absent in all life stages except brooding females. Wagele and PEREOPODAL COXAE Brandt's (1988) claim that Protognathia lacks In many isopods and amphipods, the coxae of maxillipedal epipods was based on their study of the pereopods are expanded laterally into flat­ the single manca-stage individual. Because this tened lamellar structures called coxal plates. We genus (and family) was erected on the basis of define lateral coxal plates as ventrolateral expan­ manca specimens, the status of the adult maxil­ sions of the pereopodal coxae that extend freely liped cannot be determined. Incomplete data on (as 'plates') to overhang the coxa-basis hinge of the precise distribution of occurrence of maxil­ the leg. Within the Crustacea, such lateral coxal lipedal epipods prevent us from using this poten­ plates occur only among the isopods and amphi­ tially important feature in the data analysis. pods. 172 MEMOIRS OF THE QUEENSLAND MUSEUM

In gammaridean amphipods, the presence of do not have true lateral coxal plates. However, well-developed lateral coxal plates is generally the reduction and fusion of the coxae with the viewed as the primitive condition, although this body wall is taken to be a derived state of 'coxal has not been demonstrated by any rigorous phy- plates present' and thus this group is scored as logenetic analysis of the Amphipoda as a whole. possessing lateral coxal plates. In many an- Coxal plates are lacking only in relatively thuridean species, the coxae are expanded as specialized amphipod groups, such as the tube- sternal coxal plates and appear to be fused along building Corophioidea, the vermiform and inter­ the ventral midline such that there is no clear stitial Ingolfiellidae, the pelagic Hyperiidae, and distinction between the sternite and the coxa. the aberrant Caprellidae. In these groups, the In the Asellota, Microcerberidea, and Phrea­ coxae form simple rings around the bases of the toicidea the coxae may be small or expanded (see pereopods. The lateral coxal plates of gam­ Figs. 1, 2, and 9), but they usually have well-de­ maridean amphipods are generally large and not fined, though largely immovable, articulations fused to their respective pereonal tergites; they with their respective pereonites (at least on some can usually be dissected free from the body with somites). Although they may be expanded ante­ the leg. riorly or posteriorly along the edges of their The lateral coxal plates of isopods are gener­ respective somites, they never extend ven­ ally fused dorsally and ventrally to their respec­ trolateral^ as free lamellar plates overhanging tive tergites, although on pereonites 2-7 (and the coxa-basis articulation (not even the enlarged occasionally pereonite 1) the line of dorsal fu­ first pair of coxae in the aselloteS/e/ie/n'um hang sion is usually demarcated. They are often quite ventrally to cover the coxa-basis articulation) large (flabelliferans, most valviferans, Tylomor- (Schultz, 1978; Wilson, 1980a). Thus we do not pha), although in some they may be small (some regard these three groups as having lateral coxal Valvifera). In some isopod groups — Valvifera, plates. In species of Asellota and Phreatoicidea Anthuridea, Calabozoidea, Serolidae, and some with small coxae, distinct tergal epimeres, lap­ Epicaridea and Oniscidea (in Porcellio, but pets, or spines may be present. probably not in Ligia) — the coxae also expand In the Calabozoidea, the lateral coxal plates are inward over the sternum. These sternal coxal large, though indistinguishably fused dorsally to plates have rarely been figured or discussed their respective pereonites (Van Lieshout, 1983; (Sheppard, 1957), and they may be absent in pers. obs.). The lateral coxal plates of onis- females bearing oostegites. Sternal coxal plates cideans are also large, and sometimes dorsal are clearly absent in many taxa, in both males sutures are visible, as in the Tylidae. and females (Phreatoicidea, Asellota, Plakar- In the Epicaridea, lateral coxal plates are pre­ thriidae, Phoratopodidae). Due to uncertainty sent in females, but are highly variable in size, regarding the accurate taxonomic distribution ranging from very small and often unrecognis­ and nature of the sternal coxal expansions, we able posteriorly (in Bopyrinae) to large and were unable to incorporate this feature into the prominent (in Orbioninae and Ioninae). Sternal data set. However, this anatomical feature coxal plates appear to be present at least in the clearly holds great potential as a source of im­ Bopyridae. portant data on isopod relationships, and bears In the flabelliferan families, large lateral coxal further investigation. It may eventually be plates are typically present on all pereonites (Fig. shown that sternal coxal plates co-evolved with 3). Usually they are indistinguishably fused to lateral coxal plates, but were subsequently lost the first pereonite (or largely so), but more in some families. The various conditions of clearly defined by so-called 'suture lines' on isopod coxae are summarized below. pereonites 2-7. In 4 families (Serolidae, Plakar- In the Anthuridea, the coxae are extremely thriidae, Keuphyliidae, and Bathynataliidae) all elongated and fused almost indistinguishably of the lateral coxal plates are enormously ex­ with their respective somites; this is perhaps an panded, and coxae 2-6 or 2-7 freely articulate adaptation to the elongate body form and tube- with their respective pereonites, including those dwelling lifestyle of anthurideans. They may be of the first pereonite (Wilson et al., 1976, Kens- well-defined ventrally, but at most are demar­ ley, 1978; Bruce, 1980, pers. obs.). In Serolidae cated dorsally only by a faint line. Strictly speak­ the degree of free articulation is minimal, but a ing, because anthurideans do not have large clear articulatory suture is present and move­ coxal plates that hang free to cover their coxa- ment of the coxal plate results in movement of basis articulations, by the above definition they the ventral coxal region on the sternum. In the PHYL0GENET1C ANALYSIS OF THE ISOPODA 173

or dendritic, and they are particularly large and convoluted in terrestrial species, presumably to compensate for loss of respiratory body surface area where the general body cuticle is hardened and waxy to prevent water loss. In some brackish and fresh-water amphipods, finger-like acces­ sory gills and sternal gills may also occur (fresh­ water Gammaridae, Crangonycidae, Hyalellidae and Pontoporeiinae). Whether the medial epipo­ dal gills of amphipods are homologous to the lateral epipodal gills of mysidaceans and other Malacostraca, or are uniquely derived in am­ phipods, is not known.

OOSTEGITES Although many isopods have oostegites on the first five pairs of pereopods, the number and placement actually varies considerably within any given suborder, and even within a family (and occasionally within a single genus, e.g. Sphaeroma). In some groups (Tylomorpha, Aegidae, Cymothoidae, many Epicaridea) FIG. 9. Lateral views of a flabelliferan and two oostegites may form on all 7 pairs of pereopods, phreatoicideans, illustrating development of the whereas in some genera of Arcturidae (Val- pereopodal coxae. A, Rocinela propodialis (type, vifera) only a single pair of oostegites ever USNM 29248). B, Phreatoicopsis terricola develops (on pereopods 4). The Asellota and the (USNM 78431). C, Phreatoicus australis (USNM Phreatoicidea almost always have oostegites on 59116; anterior is to the right). pereopods 1-4, and sometimes on the maxil- lipeds as well. The anthurideans usually have 3 Phoratopodidae (which is monospecific and or 4 pairs of oostegites. Other isopods are much known from only two female specimens) the more variable. In gammaridean amphipods, coxal plates are enormously expanded ventrolat- marginally setose oostegites usually occur on the erally, clearly marked off from their respective coxae of pereopods 2-5. In Mictacea, the mar- pereonite, but yet they are not freely articulating supium is formed by oostegites that may be (Hale, 1925; Bruce, 1981, pers. obs.). marginally setose and occur on the coxae of Character 43 is: without lateral coxal plates pereopods 2-6 (Hirsutia), or not setose and (0), vs with lateral coxal plates (1). Character 85 occur on pereopods 1-5 (Mictocaris). Among is: lateral coxal plates, if present, not fused with isopods, some groups have marginal setae on the their respective pereonites (Plakarthriidae, oostegites and others lack setae. Keuphyliidae, and Bathynataliidae are score 1; Oostegites are reduced or lost in many unre­ Serolidae is scored '?'). lated isopod groups that have evolved alternative or accessory means of incubating the embryos. PEREOPODAL EPIPODS For example, the evolution of sternal pockets or Character 45 is: with lateral epipods on per­ folds for incubating embryos is often correlated eopods (mysidaceans) (0) vs without lateral with the habit of conglobation, or folding the epipods on pereopods (mictaceans, tan- body ventrally so that the cephalon and pleotel- aidaceans, amphipods, isopods) (1). Character son are appressed. Harrison (1984a, b, c) pro­ 46 is: pereopods without medial epipods on per­ vides an excellent overview of brood pouch eopods (0) vs. with medial epipods on pereopods morphology in the family Sphaeromatidae, illus­ (1). Only the Amphipoda have medial epipodal trating the usefulness of these features at the gills arising from the coxae. In the gam- generic level. Some sphaeromatids have the marideans, these are usually paired, thin-walled, brood pouch composed only of oostegites. Other leaf-shaped, respiratory structures that are pre­ genera have a brood pouch composed of large, sent on pereopods 2-7 (although they may be opposing, sternal pockets formed of cuticular absent from 2 or 7). They may be stalked, foliate, folds; these may extend from the posterior mar- 174 MEMOIRS OF THE QUEENSLAND MUSEUM

gin of the sternum and open anteriorly (posterior cuticle, and the developing embryos fill the pockets), or they may extend from the anterior body. sternal region to open posteriorly (anterior pock­ Oostegites appear to be absent altogether in the ets). In still other sphaeromatid genera, paired Microcerberidea, and sternal invaginations or invaginations of the sternal cuticle occur that folds are also apparently absent, although the extend into the body cavity but open via narrow female has been described for only a single spe­ slits (referred to as 'internal pouches'). Internal cies (Wagele, 1982a, b). Wagele speculated that pockets and pouches occur in sphaeromatid the embryos of microcerberids might be laid free genera that conglobate (or fold) and have re­ among sand grains — a behaviour currently un­ duced or lost the oostegites. In some cases, the known in any isopod species. However, since all oostegites are entirely lost (Dynamenella), and peracarids undergo direct development, and in other cases they are rudimentary (many spe­ many isopods rely on internal brooding, it would cies of Sphaeroma). All plant- and wood-boring seem more likely that the embryos of microcer­ species of Sphaeroma seem to show reduction of berids would also be brooded internally, in uteri the oostegites; non-boring species have all the or the general body cavity. oostegites fully formed, presumably working in In the parasitic epicaridean family Cryptonis- concert with the internal pockets to form the cidae, the embryos are brooded in sternal invagi­ marsupium. nations formed by ventrolateral folds of the body In the cirolanid genus Excirolana, there are 3 wall, whereas in the family Dajidae the brood pairs of greatly reduced oostegites, but these do pouch is formed from ventral extensions of the not form a marsupium. Instead, the eggs drop sternites. Gnathiids lack oostegites altogether from the oviducts into a pair of sacs ('uteri') and brood the embryos within the body cavity. formed by a single layer of cells and located in Klapow (1970) claimed that the fertilised ova the thorax lateral to the gut. These sacs have been develop within the ovaries themselves in Parag- viewed as enlarged oviducts (Klapow, 1970, nathia. At least some amphipods are also known 1972; Jones, 1983). The embryos are brooded to utilise internal brood chambers (Cystosoma). here, and since the sacs do not open to the outside As seen from the above review, aspects of during development this may be viewed as a oostegite morphology may be useful within form of ovoviviparity. In the cirolanid genus families and genera, but no clear pattern of Eurydice there are 5 pairs of oostegites, but in oostegite morphology is discernible at the level addition the sternum is displaced dorsally either of isopod suborders (except perhaps for the side of the nerve cord, with the marsupium and Phreatoicidea, the Asellota, and the Microcer­ developing embryos filling the entire pereon, beridea), and therefore oostegite characters were surrounding the gut. Klapow (1970) suggested not included in the data analysis. that the brooding modifications in Excirolana and Eurydice are related to the habitats in which SPERMATHECAL DUCT most species occur — wave washed sand Wilson (1986b) summarised and elaborated beaches. Harrison (1984a, b,c) suggested similar upon our knowledge of a unique vagina-like correlations in certain sand beach sphaeromatids anterodorsal copulatory structure, the 'sper­ that have large sternal brood pockets (Tholo- mathecal duct' (or less descriptively, the 'cutic- zodium, Sphaeromopsis, Dynamenella, Ancinus, ular organ') that occurs in female Asellota. Leptosphaeroma, Paradella). Although all other isopod suborders have not yet Ligiamorphans belonging to the conglobating been systematically surveyed for this structure, genera Armadillo and Armadillidium have a preliminary studies have so-far failed to reveal brood pouch composed of oostegites, but in ad­ its presence in any other groups. Character 47 is dition the sternum bears 5 pairs of invaginations presence of the asellote 'cuticular organ' or sper­ which surround the gut within the body cavity mathecal duct (Wilson, 1986b; Wilson, 1991). for brooding the embryos. The brood pouch in Only the Asellota is scored derived for this char­ the conglobating genus Helleria is also com­ acter. posed of oostegites, but the posterior wall of the marsupium extends into the pleon as a large GENITAL PORES pouch (Mead, 1963; Mead and Gabouriaut, Information on isopod genitalia has been re­ 1988). In the conglobating genus Tylos, portions cently summarised (Wilson, 1991). Important of the sternites of ovigerous females are dis­ patterns are apparent in the position of the genital placed dorsally and pressed against the dorsal pores. In the Malacostraca, genital pores typi- PHYLOGENETIC ANALYSIS OF THE ISOPODA 175

cally occur on the coxae of thoracopod 6 in whether they first migrated onto the sternite and females, and thoracopod 8 in males. These are then subsequently penetrated the coxae when the relatively conservative features, although the pores were covered by the expanding coxal peracarids show some variation. plates. Further, the precise position of the oopore The Phreatoicidea are the only isopods with is unknown for many groups. Character 48 is: both female and male pores located on the coxae. male penes on coxae (0) vs penes on sternite (1). In male phreatoicids, the genital papillae (penes) Character 49 is: penes on thoracomere 8 (0) vs occur on the medial side of coxae 7 and can be penes on pleomere 1, or on the articulating mem­ quite large; they are likely to be the primary brane between pleomere 1 and thoracomere 8 intromittent organs in this group. In all other (1). Only Valvifera, Ligiamorpha, Tylomorpha, isopod suborders, the penes are located on the and Calabozoidea are scored apomorphic for sternum, usually near the posterior margin of the character 49. sternite of thoracomere 8, rather than on the coxae. A single, notable, and important excep­ EXCRETORY ORGANS tion to this occurs in the asellote genus Ver- The primary excretory organs among the mectias Sivertsen and Holthuis, 1980 in which Malacostraca are antennal glands and maxillary the coxae of the seventh pereopods appear to be glands. All crustaceans have antennal glands divided into 2 pieces, one of which is slightly during their ontogeny, but many lose them in expanded medially onto the sternum and bears adulthood and instead rely on maxillary glands the penes upon it (Just and Poore, pers. comm.). as the primary excretory organs. Adult isopods, Within the Asellota, and the Isopoda in general, tanaidaceans, and cumaceans lack antennal the penes show a trend toward migration medi­ glands, or possess only a rudimentary antennal ally, often with fusion at the midline. Fusion of gland, and the maxillary gland is well developed the penes occurs throughout the Isopoda and this (Stromberg, 1972). Conversely, adult my- feature has probably evolved independently in sidaceans and amphipods (and the Eucarida) several suborders (Wilson, in press) making it of have well-developed antennal glands. Siewing little use for the present study. The coxae/penes (1952, 1953, 1956) noted that in at least some condition noted above in Vermectias may repre­ lophogastrid mysids (Eucopia) small functional sent an early evolutionary stage in the migration maxillary glands may also be present, thus of the penes from the coxae to the sternum, and possibly reflecting an ancestral condition in perhaps also an early stage in the evolution of which both pairs of segmental nephridia were sternal coxal plates upon which the penes may functional in adults. The condition in Mictacea be borne. In two suborders (Valvifera and Onis- is not known. Schram and Lewis (1989) have cidea) the penes arise from the sternum of pleom- suggested that a series of segmental glands may ere 1, or from the articulating membrane have primitively been present, one pair in each between pleomere 1 and pcreonitc 7. Among the crustacean head somite. Character 52 is: primary non-isopod Peracarida, a variable pattern also adult excretory organ antennal gland (0) vs max­ exists. The Mysidacea and the Mictacea have illary gland (1); no polarity is assumed. coxal openings for the vas deferens, whereas the Amphipoda and Tanaidacea have penes on the eighth thoracosternite. PLEOPODS The pleopods of isopods have multiple func­ In most female isopods and tanaidaceans, the tions, including respiration, swimming, and oopore is situated ventrally on the sternite of copulation. Two key synapomorphies uniquely pereonite 5. In the phreatoicids, however, the defining the Isopoda are: Character 4, thoraco­ pore is clearly present on the medial side of the abdominal heart, and Character 5, respiratory coxa. Coxal oopores also are found in the My­ pleopods. These features are obviously function­ sidacea, Amphipoda, and perhaps the Mictacea ally/anatomically linked. The only other mala- (although our inspection of non-ovigerous costracans known to utilise the pleopods as the female Mictocaris failed to reveal any oopores, principal respiratory organs are the stomatopods either sternal or coxal). The situation of the oo­ (Burnett and Hessler, 1973; Kunze, 1981), in pore is more complicated in those isopod groups which the heart also extends into the pleon. where the coxae arc expanded as sternal coxal The primitive malacostracan pleopod is a nar­ plates covering the ventral surface. Available row biramous limb with multiarticulate rami. data do not allow us to assess whether the oo­ This type of pleopod is found in the Mysidacea pores simply moved medially with the coxae, or and the Amphipoda. Broad, flat pleopods with 176 MEMOIRS OF THE QUEENSLAND MUSEUM PHYLOGENETIC ANALYSIS OF THE ISOPODA 177

TABLE 2. Comparison of basally derived Isopoda ('short-tailed' taxa). Legend: M = male; F = female.

Reduction of Fusion of Condition of Condition of Condition of Pereopodal pleomeres 1-2 pleomeres 3-5 pleopod 1 pleopod 2 pleopod 3 coxae M. biramous M, biramous Phreatoicidea not reduced free F, biramous F. biramous biramous free free, short & M , biramous narrow M, uniramous Asellota fused (endopod biramous free (to variously F, absent geniculate) fused) F, uniramous vlicrocerberidea free, not short fused M, uniramous M , biramous (ring-like) F, absent F, absent uniramous free M, uniramous M. biramous Atlantasellidae free, broad fused F, absent F, absent uniramous free strongly M. biramous fused dorsally; (in juveniles) M, biramous Calabozoidea reduced free F. biramous biramous with sternal F. biramous plates somewhat M, biramous M, biramous fused dorsally; free biramous Oniscidea reduced F. biramous F, biramous with sternal plates no more than two segments in the rami are found serve primarily for respiration. Loss of marginal in the Mictacea, Tanaidacea, and the Isopoda. setae typically occurs on pleopods 3-5, or 4-5, Character 53 is: narrow, multisegmented or just 5, and it may occur on both rami or only pleopodal rami (0) vs broad, flat, 1- or 2-articu­ on the endopods. In the family Cymothoidae, the late pleopodal rami (1). In phreatoicideans and mancas and juveniles have swimming setae on many asellotes, especially primitive Asellota ( the pleopods, but the obligate parasitic adults do Aselloidea, Stenetrioidea), the posterior not. pleopods bear 2-segmented exopods. In all other The Asellota and Microcerberidea share a isopods the pleopodal exopods are always uniar- number of pleopodal features. In both of these ticulate, although they may occasionally bear suborders females lack the first pair of pleopods transverse 'suture lines'. Character 77 is: ex­ (character 78), and in males the first pleopods (if opods of at least posterior pleopods biarticulate present) are uniramous (character 81). The first (0), vs no pleopods with biarticulate exopods (1). pleopods of males are fused together to assist the In all non-isopod peracarids (except Mic­ second pleopods in sperm transfer in the higher tacea), pleopods are primitively used for swim­ Asellota. In addition, the male second pleopodal ming. The pleopods of isopods are also exopod is a small, non-lamellar structure, well-developed for this function in most groups, whereas the endopod is modified as a copulatory with broad rami and swimming setae on at least gonopod (character 79). Female microcerberids some pairs. Several groups (Asellota, Microcer- also lack pleopods on the second pleonite (char­ beridea, adult Epicaridea, Ligiamorpha, Tylo- acter 82), and the third pleopods are uniramous morpha, adult Cymothoidae) no longer swim and fused into a single piece to form an oper­ with their pleopods, and use them only for respi­ culum over pleopods 4 and 5 (character 83). In ration. Calabozoidea are said to swim (Van Lie- male microcerberids, the second pleopodal ex­ shout, 1983:175), although behavioural opod is reduced to a simple 1- or 2-articulate observations may have not been made. In the ramus, probably not involved in sperm transfer; groups that do swim, a trend occurs in most the endopod is complex and highly variable in suborders wherein the posterior pleopods may be shape, but never geniculate (character 84). In the naked (with reduced or no marginal setae) and Asellota, females have uniramous second pleo-

FIG. 10. Comparison of male pleopods 1 and 2 in calabozoans, asellotans, and oniscideans. A, Calabozoa (Calabozoidea), penes and pleopods 1-2 in situ (ventral view). B, Calabozoa (Calabozoidea), left pleopod 1 (dorsal view). C,Armadillidium (Oniscidea). penes and right pleopod 1 in silu (dorsal view). D, Asellus (Asellota), right pleopod 1 (ventral view). E, Calabozoa, left pleopod 2 (ventral view). F, Asellus, right pleopod 2 (ventral view). G, Armadillidium, right pleopod 2 (ventral view). 178 MEMOIRS OF THE QUEENSLAND MUSEUM

pods (character 75), and males have the exopod families show a pleonite reduction like that seen of the second pleopod highly modified to func­ in the Asellota and Microcerberidea as the primi­ tion in concert with a large geniculate endopod tive condition. in sperm transfer (character 76). Character 80 is pleonites 1-5 either free or Terrestrial pleopodal respiration by use of variously fused, but never (in the primitive con­ pseudotracheae is found only in the Tylomorpha dition) with pleonites 1-2 free and 3-5 fused to and Ligiamorpha, though not in all families (not the pleotelson (0), vs pleonites 1-2 free and the Ligiidae or Trichoniscidae). In addition, the remaining pleonites and telson fused into single Oniscidea and the Calabozoidea share several integrated unit (1). The variety of pleonite reduc­ unique pleopodal similarities (Table 2, Fig. 10). tions seen throughout the isopods make it diffi­ The endopods of male pleopods 1 and 2 are cult to find further useful homologies. In two styliform and greatly elongated (only pleopod 2 taxa, Phreatoicidea and Limnoriidae, pleonite 5 in Ligiidae), presumably participating in copula­ is always manifestly longer than all other tion and/or sperm transfer (character 54). And, pleonites (character 73). In the Calabozoidea, on pleopods 3-5 (in both sexes) the exopods are pleomeres 1 and 2 are reduced to only the sternal broad, heavily chitinised, and opercular, while plates (character 86). the endopods are thick and tumescent (character Within the Malacostraca, broad fan-like 56). In most isopods, the endopods are thin uropods arising from the sixth pleomere and walled and nearly the same size as the exopods. functionally associated with the telson is the In the recently described family Lynseiidae plesiomorphic state. This 'tailfan' arrangement (Poore, 1987) the fifth pleopods are reduced to a is an integral aspect of Caiman's caridoid facies single plate (character 70). Poore suggested that (Hessler, 1983). Unlike other Eumalacostraca, this attribute was the only unique apomorphy of the Isopoda (and some other Peracarida) show a this family, and we agree. good deal of variation in uropod morphology and position (Figs 1-3) and the uropods function in OTHER PLEONAL FEATURES a variety of ways. The caridoid-like tailfan of the Most malacostracans have 5 free more-or-less Cirolanidae and related families has been taken equal pleonites, and primitively the 6th pleonite by many workers as evidence that these taxa are is free from the telson and pleomere 5. In the primitive isopods, or at least that they represent Microcerberidea and the Asellota, pleonites 1 an archtypical 'caridoid' isopod body plan. and 2 are completely free and the remaining However, isopods (like amphipods, tanaids, and pleonites and telson are fused into a single unit perhaps mictaceans) lack the 'caridoid escape with no lateral incisions indicating the fused behavior', and those groups with fan-like somites. (The single exception to this appears to uropods do not use their flattened uropods for be the odd asellote Vermectias, which has 3 free propulsion, as in true caridoids (e.g. my- pleomeres; Just and Poore, pers. comm.). A sidaceans, euphausiids, or natantians). Instead, somewhat similar condition appears to be the they appear to use their uropods as lift planes and primitive state for the Sphaeromatidae, but this steering devices (unpubl. obs. of living Bathy- is presumably a convergence. In sphaeromatids, nomus, Cirolana, and other flabelliferans). the primitive condition exhibits lateral incisions A review of the peracarid orders reveals a clear demarcating the vestiges of the fused pleomeres, trend toward reduction of the caridoid tailfan hence we do not regard this to be a condition morphology. Although it is well-developed homologous to that of asellotans. Some authors among the Mysidacea, the telson and uropods of have suggested a close affinity between the speleogriphaceans, mictaceans and ther- Serolidae and certain Sphaeromatidae (Ancinus, mosbaenaceans is less well developed as a true Tecticeps, Bathycopea) on the basis of a similar tailfan. This is presumably tied to loss of the pleonite reduction (Hansen, 1905a; Sheppard, 'caridoid escape behaviour' in these groups. 1933). However, in serolids pleonites 4-6 are However, in these three groups the flattened, fused to the telson and pleonite 1 is reduced, paddle-like shape of the uropods is retained and whereas in sphaeromatids pleonites 3-6 (at least) these appendages probably assist in swimming are fused with the telson, lateral incision lines in some way. In cumaceans, tanaids, amphipods, primitively demarcate the positions of the fused and many isopod taxa there is nothing resem­ pleomeres, and the first pleonite is never bling a caridoid tailfan. markedly reduced. Other isopods have variously In amphipods pleopods 4,5 and 6 are modified modified pleonites, but no other suborders or as 3 pairs of uropods (Character 6). The amphi- PHYLOGENETIC ANALYSIS OF THE ISOPODA 179

are positioned in the posterior region of the pleotelson (terminal or subterminal). The uropods always arise on either side of the anus. Dahl (1954) suggested that the primitive phreatoicidean condition was flabelliferan-like ('cirolanoid'-like), unlike the adult morphology of living Phreatoicidea. This argument was based on observations made on developmental stages taken from the brood pouch of the South African phreatoicid Mesamphisopus capensis. We do not find Dahl's argument (or his illustra­ tions) convincing. The kinds cf morphological changes he described can be easily chained by natural developmental allometry coir.monly seen in most crustaceans. Brenton Knott (pcrs. comm.) has seen no evidence of lamellar FIG. 11. Keuphylia (Keuphyliidae). Ventral view of uropods or other 'cirolanoid' morphology in the pleoielson showing arrangement of uropods in developmental stages of any Australian phrea- ventral pocket. toicids. Character 57 is: uropods broad and flattened pod urosome and uropods appear to be used (0); uropods flattened but only somewhat primarily for strengthening the caudal portion of broadened (1); uropods styliform (2). This char­ the body, and to permit jumping by rapid poste­ acter was analysed unordered in initial analyses. rior flexion of the pleon (Barnard, 1969; Bous- Character 58 describes the shape of the pleotel­ field, 1973). In many Gammaridea, however, the son. State '0' is: telsonic region of the pleotelson third uropods still bear 'swimming' setae and well-developed and elongate, with the anus and may be used (along with the first two pairs) for uropods at the base of the pleotelson (at the paddling; males especially tend to have natatory position of pleomere 6) — this is the condition third uropods (Barnard, 1969; Bousfield, 1973). seen in mysidaceans, amphipods, mictaceans, However, the amphipod third uropod is usually and many isopods. State ' 1' is: telsonic region substyliform and not fan-like. The majority of very short, with the anus and uropods positioned Gammaridea probably do not use the third terminally on the pleotelson; this condition oc­ uropods for active swimming and these struc­ curs in the Tanaidacea, Phreatoicidea, Asellota, tures are often reduced or occasionally absent in Calabozoidea, Microcerberidea, Tylomorpha, sedentary groups. The uropodal exopod in am- and Ligiamorpha. Because the polarity and phipods is biarticulate, and the endopod is typi­ pecise homology of these conditions is uncer­ cally uniarticulate. tain, character 58 was left unordered in initial In tanaidaceans, amphipods, cumaceans, and analyses. A unique up-turned pleotelson apex many isopods, the uropodal rami are styliform. occurs in the Phreatoicidea (character 72). The uropodal rami of tanaidaceans also are long, In mysidaceans, mictaceans, tanaidaceans, multiarticulate appendages, whereas in isopods, and amphipods, the uropodal rami are composed the rami are always short and uniarticulate. The of 2 or more articles; in all isopods they are mictacean uropodal rami can be cither biarticu­ uniarticulate. Character 59 is: uropodal rami late (Mictocaris) or multiarticulate (Hirsutia). may be multiarticulate (0), vs uropodal rami In mictaceans, amphipods, and mysidaceans, always uniarticulate (1). In three families the uropods arise from pleomere 6 and the telson (Keuphyliidae, Bathynataliidae, Plakarthriidae) is a distinct somite. In isopods and living tanaids, the uropods arise not on the anteorlateral margin the sixth pleomere is fused with the telson, form­ of the pleotelson, but rather posterolaterally, ing a 'pleotelson', although primitive fossil tan- where they lie in shallow ventral channels or aids (see below) possessed free sixth plcomeres. furrows (character 55) (Fig. 11). In serolids there Many isopods have a well developed, elongate is also a tendency toward this feature, but it is not telsonic region of the pleotelson upon which the present in all species, hence they are scored '?' anus and uropods are basally positioned. Other for this character. isopods have a reduced, shortened telsonic re­ Character 60 is: uropodal exopod folded dor- gion of the pleotelson, and the anus and uropods sally over pleotelson (a unique sy napomorphy of 180 MEMOIRS OF THE QUEENSLAND MUSEUM

elongate, clavate peduncle with reduced rami — a unique apomorphy of the Bathynataliidae. Character 87 is: uropods of a single piece, rami fused to peduncle — a unique apomorphy of the Calabozoidea. In all living tanaidaceans and isopods, the sixth pleomere is fused to the telson, forming a pleotelson. However, fossil tanaids of the in- fraorder Anthracocaridomorpha have 6 free pleomeres (and thus lack a pleotelson), and this is presumably the primitive condition for this group (Schram, 1974; Sieg, 1984; Schram el al., 1986). Some cumaceans and thermosbaenaceans also have a pleotelson. A pleotelson is present in all isopods. Many authors have alluded to a free telson in some genera of anthuridean isopods. The pre­ sence of a free (unfused) sixth pleomere in some Anthuridea has been debated at least since Cai­ man (1909). Wagele (1981, 1989a) claimed that the sixth pleomere is always fused to the telson in anthurideans (thus a true pleotelson is always present). Bowman (1971) stated that the sixth pleomere was free in anthurideans. Kensley and Schotte (1989) stated, 'Pleonites 1-5 free or fused, pleonite 6 partly or completely fused with FIG. 12. Haliophasma geminata (Anthuridea). SEM telson'. In his diagnosis of Paranthura Poore of pleon (lateral view). Note deep fluting between pleomeres 5 and 6, and between and between (1984) stated, 'Pleonites usually distinct from pleomere 6 and lelson. Despite fluting, a con- each other and from telson.' Poore and Lew tinuious cuticular covering connects these somites Ton's (1985a) diagnosis of Apanthura stated, and no articular membranes are present. Also note 'pleonite 6 free from others and from telson', and large opercular first pleopods (compliments of B. their diagnosis of Cyathura (1985b) stated, Kensley). 'pleonite 6 free or fused to telson.' However, Anthuridea). Character 61 is: uropods modified Poore (pers. comm.) has most recently stated as a pair of ventral opercula covering the entire that he no longer believes the sixth pleonite to plcopodal chamber (a unique synapomorphy for ever be freely articulating with the telson in the Valvifera). Character 62 is: uropods form a anthurideans. ventral, operculatc, anal chamber beneath The sixth pleomere is clearly fused to the tel­ pleotelson, covering the anus and distal-most son (forming a pleotelson) in many anthurideans pleotelson region but not covering the pleopods (Pseudanthura). However, in many genera (a unique synapomorphy of the Tylomorpha). pleomere 6 appears to be free (Amakusanthura, Character 63 is: uropods directed vcntrally and Calathura, Exallanthura, Haliophasma, Heter- identical to other pleopods (a unique synapomor­ anthura, Leptanthura). In most species in these phy of the Anuropidae, and presumably an adap- genera, under both light and scanning micro­ tation to a swimming pelagic lifestyle). scopy, pleomere 6 and the telson are clearly Character 67 is: uropodal endopod claw-like. separated from one another dorsally by a deep We regard this as a unique synapomorphy of the groove (Poore and Lew Ton, 1988b, fig. 11a) Keuphyliidac. Although the uropodal endopod and, using forceps, the telson can often be flexed in Paralimnoria is acute, it is not recurved and against the sixth pleonite. This groove is often claw-like as in Keuphyliidae (and, the endopod shown in drawings and electron micrographs of ofLimnoria is neither acute nor claw-like). Char­ anthurideans (Fig. 12). Even in some species in acter 68 is: uropodal exopod claw-like (a unique which pleonites 1-5 are fused (medially or en­ synapomorphy of the Limnoriidae). Character tirely), the sixth pleonite may appear free 71 is: uropods highly modified and represented {Haliophasma geminata). by a single, elongate, clavate piece, or by an To resolve this issue, we sectioned specimens <©• - :\ ^~TK '>

FIG. 13. Paranthura elegans (Anthuridea). Median saggita! section through pleon showing fusion of pleom telson. Despite fluting, a continuous cuticular covering connects these somites and no articular membrane pleopods. Arrows indicate pleomere and telson. 182 MEMOIRS OF THE QUEENSLAND MUSEUM

PHREATOICIDEA

ASELLOTA

•24(0), 78, 79, 80, 81 MICROCERBERIDEA

3, 4, CALABOZOIDEA 5,8, 9, 20, .TYLOMORPHA 59, M6, 35, 39(0), 49, 54, 56 64 17, 22 . LIGIAMORPHA 48, 7 4 .VALVIFERA

• SPHAEROMATIDAE

. BATHYNATALI1DAE 43, 77 .KEUPHYLIIDAE

* 30(2), . PLAKARTHRIIDAE 55, 85 50(1) 39(0) .SEROLIDAE . PHORATOPODIDAE 18(1), 57(0), . EPICARIDEA 58(0) "30(2), 31(1), 35, 91 .GNATHIIDEA

. LIMNORIIDAE

4 30(2), 40, 44, 50(2) . LYNSEIIDAE

.CIROLANIDAE

.ANTHURIDEA

.ANUROPIDAE

. PROTOGNATHIIDAE 30(1) .CORALLANIDAE 50(3) .TRIDENTELLIDAE

'36 -AEGIDAE

39(0), 65 -CYMOTHOIDAE

FIG. 14. Cladogram of the Isopoda (Nelson strict consensus tree, built from 16 equal-length trees). Length = 133; C.I.=0.75. Character numbers on tree correspond to character list in Appendix I. Synapomorphies of terminal taxa are not shown on tree (see Appendix III). oiParanthura elegans a species common in San show unequivocally that no articular membrane Diego Bay. Under SEM and light microscopy, is present between the telson and the sixth this species appears to possess a free sixth pleonite (Fig. 12). In fact, the cuticle is even pleomere. However, our longitudinal sections thickerin the region of fusion than it is elsewhere PHREATOICIDEA PHREATOICIDEA ASELLOTA ASELLOTA MICROCERBERIDEA MICROCERBERIDEA CALABOZOIDEA CALABOZOIDEA TYLOMORPHA TYLOMORPHA LIGIAMORPHA LIGIAMORPHA "0 X VALVIFERA VALVIFERA •< SPHAEROMATIDAE SPHAEROMATIDAE r O BATHYNATALIIDAE BATHYNATALIIDAE m KEUPHYLMDAE KEUPHYLMDAE z PLAKARTHRIIDAE PLAKARTHRIIDAE m H SEROLIDAE SEROLIDAE n EPICARIDEA EPICARIDEA > > GNATHIIDEA GNATHIIDEA r •< LIMNORIIDAE LIMNORIIDAE LYNSEIIDAE LYNSEIIDAE o CIROLANIDAE CIROLANIDAE PHORATOPODIDAE PHORATOPODIDAE X m ANTHURIDEA ANTHURIDEA o ANUROPIDAE ANUROPIDAE -o PROTOGNATHIIDAE O PROTOGNATHIIDAE a CORALLANIDAE CORALLANIDAE > TRIDENTELLIDAE TRIDENTELLIDAE AEGIDAE AEGIDAE CYMOTHOIDAE CYMOTHOIDAE

FIG. 15. Two of the 16 equal-length trees from which the consensus tree (Fig. 14) was constructed. These trees emphasize mandibular features (characters 27-30,35,50,91) over character 39 (maxillipedal endite with vs. without coupling spines). Both trees are 129 steps long, with a C.I. of 0.78 (0.67 excluding uninformative characters). 184 MEMOIRS OF THE QUEENSLAND MUSEUM

on the pleon. Although specimens oiParanthura informative and cautious approach. In fact, bi­ have some flexibility between these two seg­ nary characters are treated no differently in ad­ ments, this is apparently due to the deep fluting ditive (ordered) vs nonadditive (unordered) of the cuticle at the area of fusion, and not due to analyses (unless such a program option is a true articular membrane. This fluting is what specifically selected); the only way in which the creates the deep dorsal groove that is so visible nonadditive analysis differs from the additive in this, and presumably other, species. Hence, one is in its effect on multistate characters. The unless additional observations of other species nonadditive analysis counts any character state indicate otherwise, we take the conservative ap­ change equally, as a single step, e.g. for a multi- proach and assume that anthurideans also state character, a change from state 0 to state 2, possess a pleotelson. or state 2 to state 0, is still counted as one step. Although fusion of pleomere 6 to the telson The non-additive analysis using the branch occurs in some species in at least four peracarid swapping algorithm of HENNIG86 (mhennig + suborders (tanaids, cumaceans, ther- bb) found 16 equally short trees (length = 129 mosbaenaceans, isopods), it appears to have steps; C.I. = 0.78). The Nelson strict consensus been derived independently in three, if not all tree of these 16 trees is 133 steps long (C.I. = four, of these groups. Only in the Isopoda do all 0.75) and is shown in Fig. 14. This tree could not species possess a pleotelson. Character 64 is: be improved by application of the successive pleomere 6 freely articulating with telson (0); character weighting method to the suite of 16 pleomere 6 always fused with telson, forming a trees from which it was derived. These results pleotelson (1). Only isopods are scored (1). were verified by analysing the data with PAUP 3.0. The PAUP analysis, using the MULPARS RESULTS AND DISCUSSION option, found the same 16 trees and produced an identical strict consensus tree. All statistics were identical for the PAUP and HENNIG86 trees. ANALYSIS PROCEDURE Our analytical strategy was as follows. We as­ Our final data set and consensus tree were sembled a data set based on the character analyses coded into MacClade format, along with the described above, and input data files were trees of Wagele(l 989a), Schmalfuss( 1989), and generated for HENNIG86, PAUP, and MacClade. others. MacClade was used to examine the ef­ The data were firstanalyse d with PAUP and HEN- fects on tree parsimony and character placement NIG86. A pool of multiple, equal-length trees was of different tree topologies generated by manual studied and all homoplasous characters were re­ branch swapping, and to determine precisely assessed. Several characters were eliminated from how other trees differed from our own by graphi­ the analysis at this stage because they were simply cally tracing character state changes for each too high in homoplasy and/or their precise homolo­ character. gies seemed questionable, e.g. sternal coxal plates. The final character list (the numbered characters THE CLADOGRAM OF ISOPODS noted in the previous section) and OTU-character In the following discussion, character numbers data matrix are provided in Appendices I and II. (see appendix I) are indicated parenthetically in Trees were first constructed with the charac­ boldface. Synapomorphies defining terminal ters polarised as indicated in the descriptive taxa are not shown on the tree (Fig. 14), but are character analysis above. However, it quickly listed in Appendix III and were noted in the became evident that, due to high homoplasy previous section (character discussions). In our levels (especially reversals) unambiguous judg­ consensus tree (Fig. 14), the Phreatoicidea un­ ments could not be made regarding character ambiguously arises as the basal most node, re­ state transformations. Hence, the final analyses taining two key symplesiomorphies that are lost were done with all characters unpolarised, i.e. in virtually all other isopod suborders: coxal programs set to nonadditive, and allowed to penes (48) and the large row of filter setae on the change in any direction. This procedure makes medial margins of the maxillae (74). The notion no assumptions as to what the primitive or that phreatoicids might represent an ancient derived states are for any characters in the data isopod group was first advanced by Chilton set. In respect for the high levels of homoplasy (1883) and repeated by several other workers in inherent in such a large data set (especially for the early part of this century. However, the arthropods), comparisons of trees generated specific hypothesis that Phreatoicidea are the from ordered and unordered characters is an most primitive living isopods has apparently PHYLOGENETIC ANALYSIS OF THE ISOPODA 185

been previously suggested only by Schram Limnoriidae-Lynseiidae; (7) a clade of 4 flat- (1974). Synapomorphies defining the Phreatoi- bodied families (Bathnataliidae, Keuphyliidae, cidea include the upturned pleotelson (72) and Plakarthriidae, and Serolidae); and, (8) a clade elongate fifth pleomere (73). The most parsi­ of 7 predacious-parasitic taxa, including the An- monious tree depicts the loss of the antennal thuridea and 6 families currently recognised as scale (25) at the origin of the isopod line, with its flabelliferans. The latter clade culminates in the reappearance in the Asellota. An alternative, but Cymothoidae, hence we refer to this group as the less parsimonious scenario posits the loss of the 'Cymothoid-line'. antennal scale three times — in the Phreatoi- Greater resolution of the long-tailed clade ex­ cidea, the Microcerberidea, and above the asel- ists, of course, in each of the 16 primary trees. lote-line in the cladogram. These 16 trees differed little from one another, The Asellota-Microcerberidea and Oniscidea- and only in regard to subtle rearrangements of Calabozoidea lines arise next. The asellotans and the 8 long-tailed lines noted above. If preference microcerberids are sister groups. Among other is given to mandibular characters (characters things, they share the interesting attribute of a 27-30, 35, 50) over those of the maxillipedal 6-articulate antennal peduncle (24), a feature coupling spines (character 39), much more reso­ that also occurs in mysidaceans, but is not seen lution is achieved. Figure 15 shows two such in amphipods, mictaceans, tanaids, or any other trees. In these two trees the Valvifera and isopod group. They also share the following Sphaeromatidae are at the base of the long-tailed additional synapomorphies: females lack first line. Of the long-tailed taxa, only these two pair of pleopods (78); male second pleopods groups retain the primitive grinding mandibular with a small non-lamellar exopod and a large molar process (character 30); all taxa above Val­ endopod modified into a complex gonopod (79); vifera and Sphaeromatidae have a blade-like pleomeres 1 and 2 free, 3-5 fused to pleotelson slicing molar process (or the molar process is (80); and, male pleopod 1, if present, uniramous lost). (fused and working with the second pleopods in According to our analysis, the ancestral isopod sperm transfer in the higher Asellota) (81). morphology included a very short telsonic re­ All isopod taxa beyond the Asellota-Microcer­ gion on the pleotelson, positioning the anus and beridea line are distinguished by the presence of styliform uropods terminally or subterminally on lateral coxal plates (43) and the absence of 2-ar- the pleotelson. We refer to the groups that ticulate exopods on all pleopods (77). The Ligi- possess this shortened pleotelsonic morphology amorpha and Tylomorpha are sister groups, as the 'short-tailed' isopods (Phreatoicidea, supporting the contention that the Oniscidea is a Asellota, Microcerberidea, Oniscidea, and Cala­ monophyletic clade. The Calabozoidea is the bozoidea). This condition also occurs in extant sister group of the Oniscidea. (These three taxa tanaidaceans, although this could represent a are united by at least six synapomorphies: char­ parallelism because some fossil tanaidaceans are acters 16, 35,49, 54, 56, and 39-reversal). known to possess elongate telsons (Schram el All isopod taxa above the oniscidean line are al., 1986). These short-tailed forms are largely distinguished by three unique features: per- infaunal and are not strong swimmers. Most are eopods 1-3 are directed anteriorly, and pcr- herbivores or scavengers. eopods 4-7 are directed posteriorly (18); the The shift away from the short-tailed mor­ telsonic region of the pleon is greatly elongated, phology to the long-tailed morphology (elongate positioning the anus and uropod articulation telsonic region, positioning the anus and uropods anteriorly on the pleotelson (58); and, the basally on the pleotelson) occurred subsequent uropods are broad and flat (not styliform) (57). to the appearance of the oniscidean line. This We refer to these taxa as the 'long-tailed' reversion to a broad mysid-like tailfan within the isopods. Isopoda (characters 57 and 58 on the trees) ap­ The relationships of the long-tailed isopod taxa pears to have corresponded to the emergence of cannot be unambiguously resolved with our data isopods as active swimmers in the water column. set. They comprise an unresolved 8-way poly- However, as we noted earlier, isopods (and other tomy on the consensus tree. Each of these 8 lines non-mysidacean peracarids) lack the caridoid represents a distinct clade that appeared in all 16 'escape behaviour' and do not possess the mas­ primary trees. These 8 clades are: (1) Valvifcra; sive pleonal musculature seen in the true (2) Sphaeromatidac; (3) Phoratopodidae; (4) caridoid taxa. Thus, the main effect of 're-inven­ Cirolanidae; (5) Epicaridea-Gnathiidea; (6) tion' of a tailfan in swimming isopods was not 186 MEMOIRS OF THE QUEENSLAND MUSEUM

for direct propulsion, but more likely to provide Wagele accepted Dahl's (1954) conclusion that a planar surface or rudder during swimming. We phreatoicideans were derived from a cirolanoid have observed this apparent function in swim­ ancestor, thus forcing Wagele to derive the short- ming Bathynomus, Cirolana, juvenile Cy- tailed condition (terminal anus and uropods) in mothoidae, and others. Within the long-tailed the Isopoda three separate times — in the phrea- line, a trend can also be seen for enlargement of toicidean line, in the oniscid line, and in his the lateral coxal plates. This may serve to in­ asellote/calabozoidean line. Both our tree and crease the hydrodynamic streamlining of the Wagele's derive the Asellota after the Phreatoi­ body, perhaps in the same fashion as the enlarged cidea. However, Wagele concluded that the Cal- pleura on many swimming caridoid malacostra- abozoidea is the sister group of the Asellota, cans. Furthermore, as Hessler (1982) has noted, whereas we regard the calabozoids to be either enlarged lateral coxal plates were impractical in primitive oniscideans, or the sister group of the the Asellota (and Phreatoicidea) because the Oniscidea. Both trees also derive the oniscideans coxae are still mobile in these groups. Also above the phreatoicid/asellote lines, and then within the long-tailed line is a trend away from recognize several large groupings of the remain­ primary herbivory (Valvifera) and scavenging ing taxa (the long-tailed isopods, as we have (Sphaeromatidae), to active predation and even­ defined them). Both trees were unable to satis­ tually parasitism. Within this lineage, only the factorily resolve the relationships of the long- Valvifera and Sphaeromatidae retain the primi­ tailed line. Beyond these generalities, our tree tive grinding mandibular molar process — all differs markedly from that of Wagele. other taxa have a mandible modified more for Wagele's tree (1989a, fig. 107) depicts 9 taxa: carnivory, with the molar process (when present) Phreatoicidea, Calabozoidea, Asellota, Micro- modified as a slicing bladelike structure. Hence, cerberidea, Oniscidea, Valvifera, Anthuridea, emergence from the benthos appears to have 'Sphaeromatidea' (sic), and 'Cymothoida' (sic). been correlated with the evolution of a more Wagele's Sphaeromatidea included 7 flabel- active swimming lifestyle and carnivorous hab­ liferan families: Keuphyliidae, Lynseiidae, Lim- its. noriidae, Plakarthriidae, Sphaeromatidae, Corroborating evidence for this cladogram Serolidae, and Bathynataliidae. His Cymothoida comes in the form of embryological and ana­ included 8 flabelliferan families (Phora- tomical data from other studies. According to topodidae, Protognathiidae, Anuropidae, Wagele (1989a) the stomachs of phreatoicids Cirolanidae, Tridentellidae, Corallanidae, and asellotans are the most primitive of the Aegidae, and Cymothoidae), plus the Gnathiidea Isopoda, i.e. with straight, rather than curved, and Epicaridea (Wagele reduces the latter sub­ anterior filter channels. In addition, Stromberg order to family as the 'Bopyridae'). Wagele's (1972) has shown that the embryological median suggested new Suborder Sphaeromatidea was dorsal organs of isopods are of two types, one of not defined by any unique synapomorphies, but which occurs in the Oniscidea, the other being was based on a general suite of body shape restricted to the long-tailed taxa. Stromberg criteria that we regard as (1) incorrect, (2) not (1972) also demonstrated that the paired embry­ applicable to all the groups included in this ological lateral (= dorsolateral) organs of (axon, or (3) also present in other isopod taxa. isopods are also of two types, one type in Val­ We have analysed most of the characters that vifera, Flabellifera, and Anthuridea, the second Wagele used in his tree in our character discus­ type occurring only in Phreatoicidea and Asel­ sions above, but we have coded/assigned many lota. Furthermore, Hessler (1982) observed that, of them differently (and are thus not in agree­ of the isopods he studied, only the phreatoicids ment with Wagele's assignments of characters to and the Asellota retain a coxa with the primitive taxa), or we have opted not to use some of them capability of promotion/remotion, including an because we feel they are too poorly understood arthrodial membrane and some musculature. or are inappropriate due to their high levels of homoplasy at this level of analysis. Many char­ COMPARISON WITH WAGELES HYPOTHESIS acter assignments in Wagele's analysis appear to Wagele's (1989a) tree (Fig. 4D) is consider­ be incorrect, e.g. the synapomorphic suite used ably longer than our tree (length = 153, CI = to define his Sphaeromatidea; scoring the phrea­ 0.65). However, the two trees share some impor­ toicideans as having laterally compressed bo­ tant similarities. Both trees place the Phreatoi­ dies; assigning 2-articulate pleopodal exopods to cidea at the base of the isopod line. However, Phreatoicidea but not Asellota; scoring the Asel- PHYLOGENETIC ANALYSIS OF THE ISOPODA 187

Iota as possessing an endopod on pleopod 1 of in Calabozoa); and, in asellotan males the sec­ males; regarding7?ocme/a as having 2-articulate ond pleopodal endopod is always geniculate (it maxillipedal palps and protandric hermaphrodi­ is styliform in Calabozoa). The male first and tism, or they represent convergences/paral­ second pleopods of Calabozoa most closely re­ lelisms hidden within other character complexes semble those of oniscideans (Fig. 10). The pre­ (styliform uropods, shortened pleotelson, ver­ sence of all 5 pairs of pleopods in female miform body, etc.). Calabozoa, and the absence of a 6-articulate Wagele (1989a, b) has argued that a hypothe­ antennal peduncle and the typical asellotan tical, primitive, long-tailed morphology in pleonite condition (pleonites 1 and 2 well- isopods gave way to the short-tailed morphology developed and usually modified as a narrow ring, on numerous occasions, independently, as a con­ pleonites 3-6 fused indistinguishably with tel­ vergent adaptation to avoid predation by fishes. son) further argue against any relationship to the Our analysis suggests just the opposite, that the Asellota. In addition, calabozoans possess both primitive condition in isopods was the short- dorsally-fused lateral coxal plates and sternal tailed morphology, inherited from peracarid an­ coxal plates, conditions typical of oniscideans cestors that already possessed a trend toward but never seen in the Asellota (Table 2). telson reduction and loss of the caridoid tailfan. The pleopod morphology of Calabozoa shows Furthermore, it is the long-tailed isopods, not the many points of similarity to the highly modified short-tailed species, that are epibenthic and ac­ copulatory structures found in the oniscideans tive swimmers and more often confront preda­ (Fig. 10, Table 2). Male pleopods 1 and 2 possess tory fishes. The evolution of predator-avoidance elongate styliform gonopods, and the fused me­ strategies in isopods has not been extensively dian penes arise from the articulation between studied, but Brusca and Wallerstein (1979) and pereonite 7 and pleonite 1. Furthermore, the Wallerstein and Brusca (1982) provide compara­ pleopodal endopods of Ca/abozoa are somewhat tive and experimental data suggesting that, at thickened and tumescent as in terrestrial isopods. least for idoteids, they include features such as The adaptations of a primitive oniscidean to an smaller reproductive size, cryptic colouration aquatic lifestyle could predictably result in the and body ornamentation, and certain be­ differences seen between a typical oniscidean havioural traits. and Calabozoa. The maxillipeds of Calabozoa are very similar to those of the Ligiamorpha. The STATUS OF THE CALABOZOIDEA one feature of Calabozoa that distinguishes it It is evident from our observations of speci­ from typical oniscideans is its possession of mens of Calabozoa pellucida that it is not an primitive, unmodified, trilobed maxillae. In asellotan isopod, but is either a primitive, aquati- oniscideans the maxillae are reduced to simple cally-adapted oniscidean, or it is a unique crea­ bilobed plates. The totality of these data and the ture closely related to the Oniscidea. Van positioning of the Calabozoidea on the clado- Lieshout's (1983) and Wagele's (1989a) at­ gram suggest that this group represents either a tempts to unite the Calabozoidea and Asellota very primitive, relict, aquatic oniscidean taxon, were based largely on incorrect homology argu­ or a distinct taxon that has persisted from a line ments regarding the pleopods. Although the that led to the modern oniscideans. copulatory part of the calabozoan first pleopod could be the exopod, no one has shown the STATUS OF THE MICROCERBERIDEA uniramous pleopods of the Asellota to be either Our analysis suggests a close relationship be­ the exopod or the endopod. Furthermore, the tween the Asellota and the Microcerberidea. The detailed structures of the male first pleopod in synapomorphies shared between these two taxa both taxa are completely different (Fig. 10B vs. include the following: (1) antennal peduncle 6- 10D). The synapomorphies proposed by Wagele articulate; (2) female pleopod 1 absent; (3) male for a Calabozoidea-Asellota sister group are in­ pleopod 2 with endopod modified into a complex correct or are symplesiomorphies. For example: gonopod; (4) pleomeres 1-2 free, 3-5 fused to a similar telsonic reduction and uropod arrange­ pleotelson; and, (5) male pleopod 1 uniramous, ment occurs in the Phreatoicidea and the Onis­ if present (fused and working with second cidea (hence these features should actually be pleopods in sperm transfer in higher Asellota). symplesiomorphies on Wagele's tree); female The Microcerberidea were regarded as an- asellotans (and microcerberideans) lack the first thurideans by Karaman (1933), Pennak (1958), pair of pleopods (they are present and biramous Kussakin (1973), and others. Wagele (1983b, 188 MEMOIRS OF THE QUEENSLAND MUSEUM

1989a) reduced the Microcerberidea to a family would be to simply transfer the Atlantasellidae of the asellote superfamily Aselloidea, along to the Microcerberidea, allowing this suborder to with Asellidae, Stenasellidae, and Atlantasel- stand as a sister group to the Asellota sensu lidae. Wagele's arguments for including the mi- stricto. We would recommend this working hy­ crocerberids in the Aselloidea relied strongly on pothesis until more data are available, particu­ similarities in the setae of the first pereopod, as larly regarding the possible presence of the well as the characters already mentioned. Simi­ asellotan spermathecal duct in microcerberids lar setae, however, can be seen on the first per- and atlantasellids. In addition, we see no justifi­ eopods of the Phreatoicidea, so setation may not cation for the view espoused by Wagele (1983b) be a synapomorphy at this taxonomic level. As that the Microcerberidea evolved from aselloid Wagele (1983b) noted, the Atlantasellidae (orig­ ancestors in freshwater. inally included in the Aselloidea by Sket, 1979) have pleopods similar to the Microcerberidea, in STATUS OF THE PROTOGNATHIIDAE which the second pair is absent in females and The only two described specimens of Protog- the third pair is uniramous and fused into a single nathia (Schultz, 1977; Wagele and Brandt, piece that is operculate to pleopods 4 and 5 (in 1988) appear to be mancas, although Wagele and both sexes). Atlantasellids and microcerberids Brandt's (1988) definition of the family assumes also share the unique 'tubular' molar process on that the specimens are subadults or adults. The the mandible. drawing of this animal by Wagele and Brandt We agree with Wagele (1983b) regarding the (1988, fig. 1) even illustrates what appears to probable close relationship between Atlantasel- remnants of the embryonic yolk, typical of many lus and the microcerberids. These two groups isopod mancas. Wagele and Brandt claim that differ from each other primarily on the basis of Protognathia bathypelagica Schultz, 1977, is a features perhaps associated with body-size re­ 'missing link', or 'intermediate between' the duction and the interstitial habitus in the micro­ Cirolanidae and the Gnathiidea. Based on the cerberids (reduction of the mouth appendages, published illustrations, we do not believe that cylindrical body form), and Atlantasellus also Wagele and Brandt (1988) were actually dealing bears several unique synapomorphies (inarticu­ with the same species as Schultz (1977). In any late uropods, reduction of antennae). However, case, in our opinion Protognathia only superfi­ we consider these two groups to be distinct cially resembles the Gnathiidea and more closely enough from the Asellota that we do not recom­ approximates the manca of a large, predatory, mend placing them in that suborder, nor do we cirolanid-like or anuropid-like creature. The 'ar­ regard Wagele's (1989a) putative synapomor­ ticulating', serrate, bladelike molar process on phies of the superfamily Aselloidea to be the mandible of Protognathia is characteristic of justified. All Asellota have a highly evolved the Cirolanidae and the cymothoid-line, and this male copulatory system, usually with a strongly was no doubt the principal reason for Schultz's geniculate endopod on the male second pleopod (1977) original assignment of P. bathypelagica coupled with a short powerful exopod used for to the genus Cirolana. The general body aspect thrusting the endopod. Asellotans also have a is also similar to juveniles of the genus Syscenus distinct scale on the antenna, uniramous second (Aegidae), another flabelliferan family in the pleopods in females, and a unique spermathecal cymothoid-line. duct; these features appear to be lacking in Mi­ The proposed Gnathiidea-Pro/o^na//i/'a syn­ crocerberidea and Atlantasellidae. In the latter apomorphies of Wagele and Brandt (1988) do taxa, the male second pleopodal endopod is an not hold. First, the absence of the seventh per­ elongate, convoluted, straight or curved struc­ eopod and the expandable ventral cuticle is typi­ ture, and the exopod is degenerate. In addition, cal of isopod mancas. Second, the tailfan is the third pleopod is fused into a single piece in identical to that of some cirolanids and aegids. microcerberids and atlantasellids, whereas in Third, the mandible of Protognathia is not at all most Asellota both rami and the protopod are like that of the Gnathiidea, despite the possible separate and unfused articles. Many of the at­ similarity in function (predatory feeding). Ho­ tributes seen in microcerberids and atlantasellids mology arguments based on function alone constitute reductions, although the male copula­ should be viewed with caution. In fact, the tory pleopods of these groups are unlike any­ mandible of Protognathia has features typical of thing seen in the Asellota. Cirolanidae/Anuropidae (the articulated, serrate, In conclusion, the most conservative approach bladelike molar process) and the cymothoid-line PHYLOGENETIC ANALYSIS OF THE ISOPODA 189

in general (the acute bladelike incisor process of South Pacific genus Hadromaslax is currently tridentellids, corallanids, aegids, and cy- placed in the family Limnoriidae. However, as mothoids). Fourth, the maxillae of Protognathia Bruce (1988) noted, it appears to lack two key are quite different from those of gnathiids, in limnoriid attributes — a waisted maxillipedal which they are highly reduced (males) or absent basis and hook-like uropodal rami. Bruce and (females). The only derived feature that might be Miiller (pers. comm.) plan to remove this genus uniquely shared between Protognathia and the to its own family. However, judging by the man­ gnathiids is the plumose setation on the maxil- dibular anatomy and other features, Hadro­ lipeds. Protognathia, however, has a similar maslax appears to be very closely related to the setation on all of the other thoracopods as well, Limnoriidae/Lynseiidae clade. which is quite unlike the situation in gnathiids, The close relationship shown in our cladogram suggesting that the maxillipedal setation of Pro­ between Gnathiidea and Epicaridea is interest­ tognathia is merely a reflection of segmental ing and suggests that the possible common an­ parallelism (or serial homology) in this animal cestor of these two groups might have been a and not a homologous synapomorphy shared hematophagous parasite. In addition to the syn­ with the gnathiids. Finally, gnathiids have but 5 apomorphies noted on the cladogram, only in pairs of walking legs, 6 free pereonites, 2 pairs these two groups of isopods are the digestive of maxillipeds, and numerous other fundamental caeca reduced to a single pair (Stromberg, 1972). differences that suggest no close alliance what­ Stromberg (1967, 1971, 1972) also recognised soever to Protognathia. close ties between epicarideans, gnathiids, and The above evidence forces us to conclude that flabelliferans, based on embryological data. Protognathia shares no synapomorphies with Wagele's (1989a) alliance of the Epicaridea with the Gnathiidea. Our phylogenetic analysis cor­ the Cymothoidae appears unjustified. He united roborates these arguments and further suggests these taxa on the basis of five characters. Two of that Protognathia is part of the cymothoid-line. these characters are incorrect — epicarideans are The mandibles of Protognathia and Anuropus not protandric hermaphrodites (they are faculta­ are enlarged and have similar 'articulations', tive hermaphrodites) and cymothoids do not being oriented more transversely and ventrally have quadrate uropodal peduncles. The third than in most isopods, suggesting a possible close character, 'adults parasitic', is unlikely to be a affinity between these two groups. The large size homologous feature because cymothoids are of the pelagic Protognathia manca is also sug­ parasites only on fishes and epicarideans only on gestive of Anuropus, which may attain an adult crustaceans. The remaining two characters are size in excess of 70mm (a 6.6-13.0mm manca apparent convergences (discussed in the pre­ could fit within an anuropid developmental vious section) resulting from the parasitic life­ sequence). Better resolution of protognathiid af­ style of these taxa — hooklike pereopodal finities must await the capture of adults of this dactyls and reduced antennae. Retaining the Epi­ group. Certainly Wagele and Brandt's (1988) caridea as a separate suborder (or infraorder) has claim that Protognathia is a 'surviving primitive the further distinct advantage of not compressing isopod' is not correct; in both Wagele's (1989a) the broad diversity of this group into a single and our own tree, this taxon derives high up in highly heterogeneous family, as proposed by the flabelliferan line. Wagele (1989a). Recognition of the close relationships within a STATUS OF THE FLABELLIFERA cymothoid-line (Fig. 14) is not a new idea. Our analysis corroborates the hypothesis of Brusca (1981) analysed this relationship for four Wagele (1989a) and others that the Flabellifera, of these families, and Bruce et al. (1982) and as it is currently recognised by most workers, is Delaney (1989) elaborated on this. The cy­ not a monophyletic taxon. The Anthuridea, mothoid-line (Fig. 14) is primarily carnivorous, Gnathiidea, and Epicaridea appear to derive emphasising predation and scavenging early on from within the flabelliferan complex. However, (Cirolanidae and Anthuridea), then largely pre­ the two suborders proposed by Wagele, Cy- dation (Anuropidae, Corallanidae, and probably mothoida and Sphaeromatidea, are not sup­ Protognathiidae), then obligate predation or tem­ ported by our analysis. porary parasitism (Aegidae and Tridentellidae), Poore's (1987) proposed sister group relation­ and finally obligate hematophagous parasitism ship between the Lynseiidae and the Limnorii- (Cymothoidae). dae is corroborated by our analysis. The unusual We did not postulate any synapomorphies for 190 MEMOIRS OF THE QUEENSLAND MUSEUM

the family Sphaeromatidae, although four higher Crustacea, the shrimps and lobsters.' The possible ones exist: pleonites 1-2 free (primi­ only synapomorphy we can add to Sars' state­ tively), pleonites 3-6 fused to telson (with 0-3 ment is the fact that a 3:4 functional pereopod pairs of lateral incisions demarcating fused grouping seems to have evolved in concert with somites); uropodal endopod more-or-less fused the long-tailed condition, and shortly thereafter to peduncle and immovable; at least some max- the blade-like mandibular molar process. illipedal palp articles expanded into lobes; and, pleotelson vaulted, with pleopods held in cham­ UNRESOLVED PHYLOGENETIC PROBLEMS ber. In addition, in most sphaeromatid genera at Although we recommend some taxonomic least some pleopods bear pleats and unique changes (see conclusions), we do not propose a sqamiferous tubercles. However, because this new classification of the entire order at this time. family is so large and poorly understood, it is We feel that our phylogenetic hypotheses are unclear whether these features represent true synapomorphies, i.e. are primitive for the family. still not robust enough to do so — the precise A cladistic analysis and taxonomic revision of phylogenetic placement of several groups can­ the Sphaeromatidae is greatly needed. not yet be resolved to our satisfaction. Specifi­ Some flabelliferan groupings are not fully re­ cally, the relationships of the 8 long-tailed clades solved in our tree, suggesting that some families depicted in the consensus tree (Fig. 14) remain may be paraphyletic or, more likely, that we have somewhat enigmatic. We believe Wagele simply been unable to find satisfactory character (1989a) was premature in proposing his radical suites to eliminate all polytomies. This does not, new classification of the Flabellifera. Because however, affect the basic structure of the tree, or the long-tailed clade represents what appears to the sister group relationships of the clades that be a clearly monophyletic and easily-recognised depict the phylogeny of the group as a whole. group, with correlated anatomical and ecological If the relationships in our tree (Fig. 14) are attributes, we suggest that classificatory recog­ correct, the Flabellifera should be expanded to nition of this clade is warranted and desirable. once again include the Anthuridea, Gnathiidea, and Epicaridea, or it should be split into several OTHER POSSIBLE TREE TOPOLOGIES separate new groupings. However, because of Because many workers have emphasised a hy­ the unresolved nodes we do not recommend a pothetical cirolanid-like (or flabellifera-like) an­ classificatory change in the Flabellifera at this cestor for the Isopoda, we built several time. There seems little doubt, however, that the alternative trees to compare to ours. Each of anthurideans, gnathiids, and epicarideans are these alternative trees was analysed with the derived from deep within the currently recog­ program MacClade, with the same data set used nised Flabellifera. Classifying these three groups to construct our tree (Appendices I and II). Trees within the Flabellifera is not, of course, a new identical to our cladogram (Fig. 14), but with the idea. Indeed, Sars (1882) created the group Cirolanidae placed at the base, are 135 steps 'Flabellifera' specifically for those isopods with long. Trees with the entire long-tailed grouping tail-fans composed of lateral uropods and an placed at the base, rooted in the Cirolanidae are elongate pleotelson (hence the name). Stebbing (1893), Sars (1897), Richardson (1905), Smith 135 steps long. Trees with the long-tailed line at and Weldon (1923), Menzies (1962), Naylor the bottom, but otherwise with the taxa in that (1972), and many others generally followed group arranged exactly in our tree are 131 steps Sars' concept of Flabellifera, and included the long. All of these trees are longer and less parsi­ anthurideans (and usually the gnathiids) in this monious than the 16 shortest trees (129 steps) group. Sars (1897) was quite correct in his sum­ summarised in our consensus tree (Fig. 14). It mary of the situation nearly 100 years ago, when should be noted that if trees just one step longer he stated, 'It is not easy to give any exhaustive are included for consideration, it can require that diagnosis of this tribe (Flabellifera), as it com­ several hundred to several thousand new and prises isopods of extremely different structure. different tree arrangements be considered. Thus The only essential character common to all the selection of the shortest tree, even if it is shorter forms, is the relation of the uropods, which are by only one step, allows one to reject entire suites ... lateral and arranged in such a manner as to of alternative hypotheses. The ability to rule out form, with the last segment of the metasome, a these large suites of alternative trees is, of course, caudal fan, similar to that found in some of the the strength of the method of logical parsimony. PHYLOGENETIC ANALYSIS OF THE ISOPODA 191

BlOGEOGRAPHIC CONSIDERATIONS freshwater habitats in South Africa, Australia, Our analysis suggests that the Phreatoicidea New Zealand, and India, they must have had a and Asellota derived early in the evolution of the broad global marine distribution during the Isopoda, and are the most primitive living isopod Paleozoic. A few flabelliferans and presumed taxa. According to Wagele (1981, 1983b), the epicarideans are known from Mesozoic strata, occurrence of some members of these two while oniscideans and valviferans have been groups in fresh water suggests that their common found only in Tertiary (Oligocene) deposits. ancestor was a freshwater form, and that perhaps Very few specific biogeographic relationships the Isopoda as a whole arose in fresh water, the reveal themselves in an analysis at this level. marine environment having been invaded later. However, there are two striking patterns that are A more reasonable view, however, considers evident. First is the strong Gondwanan ties of the multiple invasions of fresh water from ancient long-tailed clade. Many of the long-tailed lines marine stocks. There are several good reasons to are strictly or primarily Southern Hemisphere in accept this second alternative. First, the invasion distribution: Keuphyliidae is known only from of freshwater habitats has obviously occurred the Australian region; Bathynataliidae from the many times in the past, as evinced by the many southern Indian Ocean and Australia; Plakar- unrelated isopod taxa that live in these habitats thriidae from the Southern Hemisphere; Phora- today, representing at least some genera in every topodidae from southern Australia; the Valvifera suborder except perhaps the Gnathiidea (in addi­ is probably Southern Hemisphere in origin tion to phreatoicideans, asellotans, and microcer- (Brusca, 1984); and species of Serolidae occur berids, freshwater species occur in at least the primarily in the Southern Hemisphere. In addi­ following genera: Calabozoidea (Calabozoa), tion, the majority of species of Cirolanidae and among the Oniscidea, Brackenridgia, Canlabronis- cus, Mexioniscus, Typhlotricholigioides, Xilillonis-Sphaeromatidae also are probably known from cus; among Anthuridea, Cruregens, Curassanthura, the Southern Hemisphere. Interestingly, the ear­ Cyathura, Paranthura; among Cirolanidae, Anop- liest derived Asellota not restricted to fresh water silana, Antrolana, Bahalana, Bermudalana, Ciro-are also largely Southern Hemisphere in dis­ lanides, Faucheria, Haplolana, Mexilana, tribution (Pseudojaniroidea, Stenetrioidea, and Speocirolana, Sphaeromides, Turcolana, Typhloci-the shallow-water Janiroidean families Para- rolana; among Cymothoidae, Artyslone, Asotana, munnidae and Santiidae). Braga, Lironeca, Nerocila, Paracymothoa, Philos- Secondly, all of short-tailed lines on the clado- tomella, Riggia, Telotha; among Sphaeromatidae, gram show strong relictual patterns of distribu­ Sphaeroma, Thermosphaeroma; among Valvifera, tion. The Phreatoicidea, which were once Austridotea, Idotea, Mesidotea, Notidotea; amongwidesprea d globally in marine environments, are Epicaridea, Probopyrus; and many others). now restricted to a few Gondwanan freshwater Second, fossil evidence (Schram, 1970, 1974) habitats. The higher Asellota (Janiroidea) are indicates that the Palaeozoic phreatoicideans, found primarily in the deep sea, where they have which are nearly indistinguishable from modern undergone a massive radiation to exploit an en­ taxa, lived in marine environments, not freshwa­ vironment only recently invaded by other isopod ter habitats. Modern Phreatoicidea and Asellota groups. The Microcerberidea are interstitial that live in freshwater are likely to be relics of a forms. The Calabozoidea so-far are known only past time when these groups were diversifying from freshwater wells (phreatic systems) in and invading many different environments. Out- Venezuela. And the Ligiamorpha and Tylomor- group data also suggest that the Isopoda prob­ pha are, of course, the only crustaceans to have ably evolved in a marine environment, because successfully radiated into all terrestrial environ­ amphipods, mictaceans, and tanaidaceans are all ments. primary marine groups. The fossil record is very Beyond these generalisations, the data are not sparse for isopods. There'are no known asellotan yet available to discern clear historical patterns fossils. The oldest isopod fossils are phreatoicid­ or test specific biogeographical hypotheses at the eans: Hesslerella shermani Schram, 1970, from subordinal/family levels. Testable phylogenetic middle Pennsylvanian marine deposits of North and biogeographic analyses are needed for each America; Permian fossils from several marine or suborder, and each of the long-tailed clades, in brackish-water localities of Laurasia; and Trias- order to determine putative ancestral geographic sic material from Australia (fresh water). Thus, ranges for each of these groups (viz. Brusca, although phreatoicideans are restricted today to 1984) before more general statements can be 192 MEMOIRS OF THE QUEENSLAND MUSEUM

made regarding the biogeographic history of the the Asellota, but cannot be considered part of the Isopoda. Asellota unless the definition of the latter is expanded, which we do not recommend at this FUTURE RESEARCH time. Despite an extensive examination of available 4. The Oniscidea constitutes a monophyletic morphological characters, it is clear that the group. available data base needs to be expanded by the 5. The monotypic taxon Calabozoidea (Cala- addition of new characters and by resolution of bozoa) should be classified as primitive Onis­ homology complexes in others. Useful new cidea, or as the sister group of the Oniscidea characters almost certainly exist in patterns of (Calabozoa is neither an asellotan nor a sister frontal lamina and clypeus design, details of group of the Asellota). mandibular anatomy (especially of the lacinia 6. Isopods with broad, flat uropods and elon­ and spine row region), oostegite morphology, gate telsonic regions (well-developed tailfans) nature of the sternal coxal plates, and internal arose subsequent to the appearance of the phrea- anatomy, but the existing literature is insufficient toicid/asellote/microcerberid/oniscidean lines. to assemble a data base on such features and The apparent 'caridoid'-like tailfan of these additional direct observations are necessary. long-tailed isopods is thus not a primitive isopod These data will be needed to further resolve the feature, but is secondarily derived within the relationships within the long-tailed isopodclade. Isopoda and not homologous with the condition A phylogenetic analysis of the Sphaeromatidae seen in the mysidaceans and other true caridoid is also needed and would provide valuable infor­ crustaceans. mation for continued refinement of the flabel- 7. The evolution of the long-tailed morphology liferan taxa. may have corresponded with the emergence of isopods from infaunal environments and a sub­ CONCLUSIONS sequent radiation as active epifaunal swimmers. Paralleling this trend was a shift from a primary scavenging/herbivorous lifestyle to active pred­ 1. The Isopoda is a monophyletic group de­ atory habits, andeventually parasitism. Also par­ fined by the following synapomorphies: (a) ses­ sile eyes; (b) complete loss of free carapace folds alleling this trend was an enlargement of the (carapace reduced to a cephalic shield); (c) lateral coxal plates, perhaps functioning to in­ thoracopods entirely uniramous; (d) antennae crease hydrodynamic streamlining of the body. uniramous, without a scale (a 'scale' has either 8. Three taxa usually ranked at the subordinal reappeared in the Asellota, or it was lost twice, level (Anthuridea, Gnathiidea and Epicaridea) once in the Phreatoicidea and again in all other had their phylogenetic origins within the lineage non-Asellota); (e) pleomere 6 fused to telson, of families currently regarded as Flabellifera. forming a pleotelson; (f) biphasic moulting; (g) Thus, the definition of Flabellifera must either be heart thoraco-abdominal; (h) branchial structures expanded to accommodate these taxa, and/or the abdominal; (i) gut tube entirely ectodcrmally suborder Flabellifera should be reorganised into derived, without a true midgut region; (j) striated several separate groups. muscles with unique myofibril ultrastructure; (k) 9. The Protognathiidae is part of the 'cy- loss of the maxillulary palp; (1) antennules uni­ mothoid-group' of families and may be closely ramous, without a scale (scales reappear in the related to the families Cirolanidae and cirolanid genusBathynomus, in the Limnoriidae, Anuropidae. The Protognathiidae is not the sister and perhaps in the Epicaridea); and, (m) uropo- group of the Gnathiidea. dal rami always uniarticulate. Synapomorphies 10. The recently proposed new suborders of 'a-d' appear to be convergent in isopods and Wiigele (1989a), Sphacromatidea and Cy- amphipods, although a strong corroboration of mothoida (sic), are not corroborated by our phy­ this must await further analyses of all peracarid logenetic analysis. Wagele's proposition that the suborders. Synapomorphy 'e' may (or may not) ancestral isopod was a long-tailed form (flabel- be convergent to the condition in many tan- liferan, or cirolanid-like) is not supported by our aidaceans. Synapomorphies 'f-m' are unique to analysis. Our analysis indicates that the ancestral the Isopoda. isopod was a short-tailed form, with a shortened 2. The Phreatoicidea is the earliest derived telson and styliform, terminal uropods. The taxon of living isopods. Gnathiidea and Epicaridea should be retained at 3. The Microcerberidea is the sister group of the subordinal ranking until further analyses bet- PHYLOGENETIC ANALYSIS OF THE ISOPODA 193

ter resolve the relationships of the flabclliferan GW. Field work in Tasmania to collect phreatoi­ families. cids was funded by grants to RCB from NSF and 11. All of the primitive, short-tailed isopod the National Geographic Society. taxa (Phreatoicidea, Asellota, Microcerberidea, Oniscidea, Calabozoidea) exhibit what may be viewed as relictual distributions, in isolated LITERATURE CITED freshwater habitats, in ground waters, in the deep sea, or in terrestrial habitats. The most primitive ANDERBERG, A. AND TEHLER, A. 1990. Consen­ living isopods, the Phreatoicidea, also have the sus trees, a necessity in taxonomic practice. oldest known fossil record (middle Pennsyl- Cladistics 6: 399^102. vanian) and a modern Gondwanan distribution ARGANO, R. 1988. Isopoda. 397^101. In R.P. Hig- (Australia, Tasmania, New Zealand, southern ginsand H. Thiel (eds) 'Introduction to the Study Africa, and India). However, fossil phreatoicids are known from North American and European of meiofauna'. (Smithsonian Institution Press: marine deposits, suggesting that the present-day Washington, D.C.). freshwater Gondwanan pattern is a relict dis­ BALDARI, F. AND ARGANO, R. 1984. Description tribution. of a new species of Microcerberus from the South China Sea and a proposal for a revised 12. Unambiguous sister group relationships classification of the Microcerberoidea cannot be hypothesized for all isopod taxa with the current data base, and additional data are (Isopoda). Crustaceana46(2): 113-126. being sought in the form of new characters. A BARNARD, K.H. 1925. A revision of the family new formal classification of the Order Isopoda Anthuridae (Crustacea Isopoda) with remarks on must await better resolution of the phylogeny certain morphological peculiarities. Journal of based upon an expanded data set. (he Linnean Society, London (Zoology) 36: 109-160. BATE, C.S. 1861. On the morphology of some Am- phipoda of the division Hyperina. Annals and ACKNOWLEDGEMENTS Magazine of Natural History (Ser. 3) 8: 1-16. BATE, C.S. AND WESTWOOD,J.O. 1861-1868.'A We would like to thank the organising com­ history of British sessile-eyed Crustacea'. (John mittee of the International Crustacean Confer­ van Voorst: London). 536p. ence (Brisbane, July 1990) for the invitation and BELYAEV, G.M. 1966. 'Bottom fauna of the ultra- financial support provided to one of us (RCB) to abyssal depths of the world ocean'. (Moskva: be a Plenary Session speaker. That invitation Izdatelstvo Nauka.) 248 p. [In Russian]. provided the impetus for writing this paper. We BETTICA, A., SHAY, M.T., VERNON, G. AND are most grateful for the opportunity to have WITKUS, R. 1984. An fultrastructural study of shared our ideas with colleagues at that confer­ cell differentiation and associated acid ence. We also thank Gary Poore (Museum of Victoria, Melbourne) for organising a highly phosphatase activity in the hepatopancreas of valuable isopod workshop prior to the main con­ Porcellio scaber. Symposia of the Zoological ference; this workshop was fertile ground for Society of London No. 53: 199-215. scientific exchange and led to the refinement of BIRSTEIN,J.A. 1951. Freshwaterasellids(Asellota). some data and ideas presented herein. Wc are Fauna SSSR (Rakoobraznye) 7(5): 1-144. [In especially grateful to J.L. Barnard, Tom Bow­ Russian], man, Gary Brusca, Niel Bruce, Gary Poore, Fred BONNIER, J. 1897. Edriophthalmes. Resultatsscien- Schram, Jurgen Sieg, and Regina Wetzer for tifiques de la campagne du 'Caudan' dans le their extremely helpful reviews of our manu­ Golfe de Gascogne. Annals University de Lyon script; and to J.L. Barnard, N. Bruce, T. Bow­ 26: 527-689. man, R.R. Hessler, J. Just, B. Kensley, G. Poore, 1900. Contribution a I'etude des Epicarides — les J. Sieg, W. Wagele, R. Wetzer, and T. Wolff for Bopyridae. Travaux de la Station Zoologique de many insightful discussions on peracarid mor­ Wimereux 8: 1-396. phology and phylogenetics during the course of BOURDON, R. 1968. Les Bopyridae des mers this research. This research and paper was sup­ Europeennes. Memoires Museum National ported by National Science Foundation (NSF) d'Histoire Naturelle Paris (n.s., A, Zool.) 50: grants BSR87-96360 and 89-18770 to RCB, and 77^124. NSF grants BSR-8604573 and BSR-8818448 to BOWMAN, T.E. 1971. The case of the nonubiquilous 194 MEMOIRS OF THE QUEENSLAND MUSEUM

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POORE, G.C.B. AND LEW TON, H.M. 1985a. 1897. An account of the Crustacea of norway with Apanthura, Apanthuretta, and Apanthuropsis short descriptions and figures of all the species. Gen. Nov. (Crustacaea: lsopoda: Anthuridae) Vol. I. lsopoda. Part 111, IV. Anthuridae, from south-eastern Australia. Memoirs Museum Gnathiidae, Aegidae, Cirolanidae, Limnoriidae. of Victoria 46: 103-151. (Bergen Museum: Bergen). 43-80. 1985b. New species of Cyalhura (Crustacea: SCHMALFUSS, H. 1989. Phylogenetics in Onis- lsopoda: Anthuridae) from estuaries of eastern cidea. Monilore Zoologico Italiano n.s., Mono­ Australia. Memoirs Museum of Victoria 46: 89- graph 4: 3-27. 101. SCHOLL, G. 1963. Embryologische unlersuchungen 1988a. A generic review of the Hyssuvidae an Tanaidaceen Heterolanais oersledi Kr0yer. (Crustacea: lsopoda) with a new genus and new Zoologische Jahrbiicher (Anatomie) 80: 500- species from Australia. Memoirs Museum of 554. Victoria 49: 169-193. SCHRAM, F.R. 1970. Isopods from the Pennsyl- 1988b. Amakusanthura and Apanthura (Crustacea: vanian of Illinois. Science 169: 854—855. lsopoda: Anthuridae) with new species from 1974. Paleozoic Peracarida of North America. tropical Australia. Memoirs Museum of Victoria Fieldiana, Geology 33: 95-124. 49: 107-147. 1981. On the classification of Eumalacostraca. 1990. Accalathura (Crustacea: lsopoda: Paranlhu- Journal of Crustacean Biology 1: 1-10. ridae) from northern Australia and adjacent seas. 1986. 'Crustacea'. (Oxford University Press: New Memoirs Museum of Victoria 50: 379-402. York). P. 606. POWELL, C.V.L. AND HALCROW, K. 1982. The SCHRAM, F.R. AND LEWIS, C.A. 1989. Functional surface microslructure of marine and terrestrial morphology of feeding in the Necliopoda. 115- lsopoda (Crustacea, Peracarida). Zoomorpho- 122. In B.E. Felgenhauer , L.Watling and A.B. logie 101: 151-164. Thistle (eds)' Functional morphology of feeding PRICE J.B. AND HOLDICH, D.M. 1980a. The for­ and grooming in Crustacea'.Cruclacean Issues mation of the epiculicle and associated struc­ 6. (A.A. Balkema: Rotterdam). tures in Oniscus asellus (Crustacea, lsopoda). SCHRAM, F.R., SIEG, J., AND MALZAHN, E. Zoomorphologie 94: 321-332. 1986. Fossil Tanaidacea. Transactions San 1980b. An ullraslructural study of the integument Diego Society of Natural History 21: 127-44. during the moult cycle of the woodlouse, Onis­ SCHULTZ, G.A. 1969. 'How to know the marine cus asellus (Crustacea, lsopoda). Zoomorpho­ isopod crustaceans'. (William C. Brown: logie 95: 250-263. Dubuque, Illinois). 356p. RACOVITZA, E.G. 1912. Cirolanides (I-ere parlie). 1977. Balhypelagic isopod Crustacea from Antarc­ Archives Zoologie Experimental et General tic and southern seas. Antarctic Research Series (5)10: 203-329. 23:69-128. REMANE, A. AND SIEWING, R. 1953. Microcer- 1978. Protallocoxoidea new superfamily (lsopoda berus delamarei, eine marine lsopodenarl von Asellota) with a description of Protallocoxa der kiisle Brasiliens. Kieler Meeresforsch 9: weddellensis new genus, new species from the 278-284. Antarctic Ocean. Cruslaceana 34(3): 245-250. RICHARDSON, H. 1905. A monograph on the 1979. Aspects of the evolution and origin of the isopods of North America. Bulletin of the United deep-sea isopod crustaceans. Sarsia 4: 77-83. Stales National Museum, 54: 1-727. SHEPPARD, E.M. 1933. Isopod Crustacea. Part 1. SANDERS, H.L., HESSLER, R.R. AND GARNER, The family Serolidae. Discovery Reports 7: S.P. 1984. Hirsutia balhyalis, a new unusual 253-362. deep-sea benthic peracaridan crustacean from 1957. Isopod Crustacea. Part II. Discovery Reports the tropical Atlantic. Journal of Crustacean Bi­ 29: 141-198. ology 5: 30-57. SIEBENALLER, J.F. AND HESSLER, R.R. 1977. SANDERSON, M.J. 1990. Flexible phylogeny recon­ The Nannoniscidae (lsopoda, Asellota): Hebe- struction: a review of phylogenetic inference fustis n. gen. and Nannoniscoides Hansen. packages using parsimony [software review]. Transactions of the San Diego Society of Natural Systematic Zoology 39(4): 414^19. History 19: 1^13. S ARS, G.0.1882. Oversigt af Norges Crustaceer med SIEG, J. 1984. Neuere Erkennlnisse zum natiirlichen forelobige Bemaerkninger over de nye eller system der Tanaidacea. Zoologica 136: 1-132. mindre bekjendte Arter I. Chirsliania Videnskab SIEG, J., HEARD, R. AND OGLE, J. 1982. Tan­ Forhandlinger 18: 1-124. aidacea (Crustacea: Peracarida) of the Gulf of PHYLOGENETIC ANALYSIS OF THE ISOPODA 199

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1983. Peracaridan disunity and its bearing on On the problem of the antiquity of the deep-sea eumalacostracan phylogeny with a redefinition fauna. Deep Sea Research 7: 10-23. of eumalacostracan superorders. 213-228. In 1969. On the geological antiquity of the deep-sea F.R. Schram (ed.) 'Crustacean phylogeny'. bottom fauna. Okeanologia (Moscow) 1: 110- (A.A. Balkema: Rotterdam). 224. [In Russian], WEYGOLT.P. 1958. Die Embryonalentwicklungdes Amphipoden Gammaruspulexpulex (L.). Zool- ogisches Jahrbuch (Anatomie) 77: 51-110. APPENDIX 1. CHARACTERS USED IN WILSON, G.D. 1976. The systemalics and evolution THE PHYLOGENETIC ANALYSIS of Haplomunna and its relatives (Isopoda, Ha- plomunnidae, new family). Journal of Natural 1. Eyes stalked and basally articulated (0) — Eye History 10: 569-580. stalks reduced, lobe-like, but sometimes with basal 1980a. Superfamiliesof the Asellota (Isopoda) and articulation (1) — Eyes sessile (2). the systematic position of Stenelrium weddel- 2. Carapace covers all 8 thoracomeres and laterally /ense(Schultz). Crustaceana 38(2): 219-221. covers the bases of the maxillae and maxillipeds (0) 1980b. New insights into the colonization of the — Carapace reduced, lateral carapace folds still deep sea: Systemalics and zoogeography of the cover the bases of the maxillae and maxillipeds (1) Munnidae and the Pleurogoniidae comb. nov. — Carapace reduced to only a head shield, without (Isopoda; Janiroidea). Journal of Natural History lateral carapace folds (2). 14: 215-236. 3. Monophasic moulting (0) — Biphasic moulting (1). 1986a. Pseudojaniridae (Crustacea: Isopoda), a 4. Heart entirely thoracic (0) — Heart thoraco-abdom- new family for Pseudojanira stenetrioides Bar­ inal(l). nard, 1925, a species intermediate between the 5. Branchial structures cephalo-thoracic (0) — asellote superfamilies Stenelrioidea and Branchial structures abdominal (1). Janiroidea. Proceedings of the Biological 6. Pleomeres 4-6 not divided into two separate Society of Washington 99: 350-358. functional units (0) — Pleomeres 4-6 forming a 1986b. Evolution of the female cuticular organ in functional unit (the urosome), and pleopods 4, 5, the Asellota (Crustacea, Isopoda). Journal of and 6 modified as uropods (1). Morphology 190: 297-305. 7. Body not unusually broadened and flat (0) — Body 1987. The road to the Janiroidea: the comparative extremely broadened and flat, with large, expanded morphology and evolution of the asellote coxal plates, and with the cephalon deeply im­ isopods. Zeitschrift fiir zoologische Systematik mersed in or surrounded by the first pereonite (1). und Evolutionsforschung 25: 257-280. 8. Gut tube with endodermally derived midgut (0) — 1989. A systematic revision of the deep-sea sub­ Gut tube entirely ectodermally derived, without a family Lipomerinae, of the isopod crustacean true midgut region (1). family Munnopsidae. Bulletin Scripps Institu­ 9. Striated muscles of typical malacostracan type (0) tion of Oceanography (University of California) — Striated muscles with unique myofibril ultra- 27: 1-138. structure (1). 10. Second thoracomere (pereonite 1) free, not fused 1991. Functional morphology and evolution of to cephalon (0) — Second thoracomere entirely isopod genitalia. 228-245. In R. Bauer and J. fused to cephalon, with its appendages (the py- Martin (ed.) 'Crustacean sexual biology'. (Uni­ lopods) functioning with the cephalic appendages versity of Columbia Press). and acting as a second pair of 'maxillipeds' (1). WILSON, G.D. AND HESSLER, R.R. 1974. Some 11. At least some thoracopods with exopods (0) — unusual Paraselloidea (Isopoda, Asellota) from Exopods absent from all thoracopods (1). the deep benthos of the Atlantic. Crustaceana 27: 12. Hatching stage not a manca (0) — Hatching stage 47-67. a manca (1). 1981. A revision of the genus Eurycope (Isopoda, 13. Without a praniza stage (0) — With a praniza stage Asellota) with descriptions of three new genera. (!)• Journal of Crustacean Biology 1: 401-423. 14. Adult females bilaterally symmetrical (0) — Adult WILSON, G.D., THISTLE, D. AND HESSLER, R.R. females with loss of symmetry (1). 1976. The Plakarthriidae (Isopoda: Flabellifera): 15. Adults not parasitic on other crustaceans (0) — deja vu. Zoological Journal of the Linnean Adults obligate parasites on other crustaceans (1). Society 58: 331-343. 16. Without cuticular tricorn sensilla (0) — With ZENKEVITCH, L.A. AND BIRSTEIN, J.A. 1961. cuticular tricorn sensilla (1). PHYL0GENET1C ANALYSIS OF THE 1SOPODA 201

17. Without complex compound sensillar structures 35. Mandible with a palp (0) — Mandible without a of the oniscidean type at the lips of the antennae and palp(l). uropodal rami (0) — Complex compound sensillar 36. Maxillae not modified as follows (0) — Maxillae structures at the tips of the antennae and uropodal modified into stylet-like lobes with recurved apical rami (1). (hooklike) setae (1). 18. No functional pereopodal grouping (0) — 37. Maxillipeds separate (0) — Left and right maxil­ Functional pereopodal grouping 3:4 (1) — lipeds fused together (1). Functional pereopodal grouping 4:3 (2) — 38. Coxae of maxillipeds not fused to head (0) — Functional pereopodal grouping 2:5 (3). Coxae of maxillipeds fused to head (1). 19. Seventh pereonite present and with pereopods (0) 39. Maxillipedalendite without coupling spines (0) — — Seventh pereonite reduced and without per­ Maxillipedal endite with coupling spines (1). eopods (1). 40. Head sunk into first pereonite, flexing dorsoven- 20. Antennule biramous, or with scale (0) — Anten- Irally but not freely rotating (left to right) (0) — nule uniramous, without scale (1). Head set off from pereon and freely rotating (1). 21. Antennular peduncle 3-articulate with an un­ 41. Maxillipeds with 2-3 endites (0) — Maxillipeds divided third article (0) — Antennular peduncle with only 1 endite (1). 4-articulate, presumably by way of subdivision of 42. Maxilliped biramous (0) — Maxilliped uniramous third article (1). 22. Antennules arise above (anterodorsal to) antennae 43. Without lateral coxal plates (0) — With lateral (0) — Antennules arise on same plane as antennae, coxal plates (1). directly between them (1). 44. Basis of maxilliped not elongate and waisted (0) 23. Antennules not as described in the following (0) — Basis of maxilliped elongate and waisted (1). — Antennules greatly modified, 2-articulate, with 45. With lateral epipods on pereopods (0) — Without second (distal) article greatly expanded and scal­ lateral epipods on pereopods (1). loped (1). 46. Without medial epipods on pereopods (0) — With 24. Antennal peduncle 6-articulate (0) — Antennal medial epipods on pereopods (1). peduncle 5-articulate (1). 47. No special cuticular spermathecal ducts known to 25. Antennae biramous, or with a vestigial second occur (0) — Unique spermathecal cuticular organs ramus or scale (0) — Antennae uniramous, without present (1). vestigial second ramus or 'scale' (1). 48. Male penes on coxae (0) — Male penes on sternite 26. Antennae well developed (0) — Antennae ves­ (I)- tigial (1). 49. Penes on thoracomere 8 (0) — Penes on pleomere 27. Mandible without lamina dentata (0) — Mandible 1, or on the articulation between thoracomere 8 and with lamina dentata (1). pleomere 1 (1). 28. Mandibles 'normal' (0) — Mandibles of adult 50. Mandibular incisor process broad and multiden- males grossly enlarged, projecting anteriorly, for­ tate (0) — Mandibular incisor process with teeth ceps-like (1). reduced to form serrate or crenulate margin (1) — 29. Mandibles present in adult females (0) — Mandi­ Mandibular incisor process with teeth lost (or fused bles lost in adult females (1). ?) to form conical projection with basal 'rasp and 30. Molar process of mandible a broad, flat, grinding file' (2) — Mandibular incisor process modified structure (0) — Molar process of mandible an elon­ into recurved or hooklike, acute or subacute, pierc­ gate, thin, blade-like, slicing structure (often at­ ing-slicing structure (3). tached to body of mandible by a flexible 51. Embryos curve ventrally (0) — Embryos curve 'articulation', and often bearing marginal denticles dorsally (1). or teeth) (1) — Molar process of mandible absent 52. Primary adult excretory organs are antennal glands (2). (0) — Primary adult excretory organs are maxillary 31. Maxillule present (0) — Maxillule reduced or glands (1). vestigial in adults (1) — Maxillule lost in adults (2). 53. With narrow, multisegmented pleopodal rami (0) 32. Maxillule with a palp (0) — Maxillule without a — With broad, flat, 1-or 2-articulate pleopodal rami palp(l). (I)- 33. Maxillae not fused to paragnath (0) — Maxillae 54. Male pleopods 1 and 2 not as follows (0) — Male reduced, minute, fused to paragnath (or lost en- pleopod endopods 1 and 2 (only 2 in Ligiidae) tirely)(l). elongate, styliform, and participating together in the 34. Maxillae outer lobe undivided (0) — Maxillae copulatory process (1). outer lobe divided into two lobes (1). 55. Uropods arise from anteroventral margin of 202 MEMOIRS OF THE QUEENSLAND MUSEUM

pleotelson (0) — Uropods arise on posteroventral setae (0) — Medial margin of maxilla without row surface of pleotelson, in shallow grooves or chan­ of large filter setae (1). nels (1). 75. Female pleopod 2biramous(0) — Female pleopod 56. Both pleopodal rami thin and lamellar (0) — 2 uniramous (1). Pleopodal exopods broad and opercular; endopods 76. Male pleopod 2 not as follows (0) — Male pleopod thick and tumescent (1). 2 exopod modified to function in concert with large 57. Uropods broad and flattened (0) — Uropods styl- geniculate endopod in sperm transfer (1). iform (1). 77. Exopods of at least posterior pleopods biarticulate 58. Telsonic region of pleotelson well-developed, (0) — No pleopods with biarticulate exopods (1). with anus and uropods at the position of pleomere 78. Female pleopod 1 present (0) — Female pleopod 6 (at the base of pleotelson) (0) — Telsonic region 1 absent (1). greatly reduced and shortened, anus and uropods 79. Male pleopod 2 with lamellar exopod (if present) positioned terminally on pleotelson (1). and endopod either lamellar or modified (0) — Male 59. Uropodal rami multiarticulate (0) — Uropodal pleopod 2 with small non-lamellar exopod and a rami always uniarticulate (1). large endopod modified into a complex gonopod 60. Uropodal exopod not folded dorsally over pleotel­ son (0) — Uropodal exopod folded dorsally over 80. Pleomeres not as follows (0) — Pleomeres 1 and pleotelson (1). 2 free, 3-5 always entirely fused to pleotelson (1). 61. Uropods not modified as follows (0) — Uropods 81. Male pleopod 1 biramous, lamellar (0) — Male modified as a pair of opercula covering entire pleopod 1, if present, uniramous (fused and working pleopodal chamber (1). with pleopod 2 in sperm transfer in higher Asellota) 62. Uropods not modified as follows (0) — Uropods (!)• form ventral operculate chamber covering anal re­ 82. Female pleopod 2 present (0) — Female pleopod gion (1). 2 absent (1). 83. Female pleopod 3 biramous, not fused into a single 63. Uropods unlike pleopods; associated with pleotel­ piece (0) — Female pleopod 3 uniramous and fused son (0) — Uropods directed ventrally; identical to, into a single piece forming an operculum over and functioning with, pleopods (1). pleopods4&5 (1). 64. Pleomere 6 freely articulating with telson (0) — 84. Male pleopod 2 not as follows (0) — Male pleopod Pleomere 6 fused with telson, forming a pleotelson 2 exopod reduced to a simple, 1- or 2-articulate ramus, apparently not involved in copulation or 65. Pereopods 2-7 not prehensile (0) — Pereopods sperm transfer; endopod complex and highly varia­ 1-3 (or 1-7) prehensile (1). ble in shape, straight, curved, or slightly bent (but 66. Adults not obligate and permanent parasites on not fully geniculate) (1). fishes (0) — Adults obligate and permanent para­ 85. Lateral coxal plates 2-7 (if present) fused to their sites on fishes (1). respective pereonites and not articulating (0) — 67. Uropodal endopods not claw-like (0) — Uropodal Lateral coxal plates 2-7 (if present) not entirely endopods claw-like (1). fused to their respective pereonites (1). 68. Uropodal exopods not claw-like (0) — Uropodal 86. Pleomeres 1 & 2 not reduced to sternal plates (0) — exopods claw-like (1). Pleomeres 1 & 2 reduced to sternal plates only (1). 69. Pereonite VII not as follows (0) — Pereonite VII 87. Uropodal rami free (0) — Uropodal rami fused to tergite indistinct dorsally, shortened and largely or peduncles (1). entirely fused to pereonite VI (1). 88. Posterior pereopods 'normal' (0) — Posterior 70. Pleopod 5 not reduced to a single plate (0) — pereopods oar-like, with dactyls greatly reduced or Pleopod 5 reduced to a single plate (1). absent (1). 71. Uropods not modified as follows (0) — Uropods 89. Body not as follows (0) — Body deeply inflated modified as elongate, clavate structures with re­ (!)• duced rami (1). 90. Not parasites on gelatinous zooplankton (0) — 72. Apex of pleotelson not curved dorsally (0) — Parasites on gelatinous zooplankton (1). Apex of pleotelson curved dorsally (1). 91. Mandibles not modified as follows (0) — Mandi­ 73. Pleomere 5 not markedly elongate and much bles modified as elongate scythe-like structures longer than all others (0) — Pleomere 5 markedly with serrate cutting edge (1). elongate, manifestly longer than all other pleomeres 92. Maxillule not as follows (0) — Maxillule of a 0)- single elongate stylet-like lobe, with the apex form­ 74. Medial margin of maxilla with row of large filter ing an acute recurved piercing stylet (1). PHYLOGENETIC ANALYSIS OF THE 1SOPODA 203

APPENDIX II. THE DATA MATRIX

Mysidacea 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000700000 00 Mictacea 1170000770 0100000300 0001000000 0101000010 1100100000 1710007000 0000000000 0000007000 0000700000 00 Tanaidacea 1100000100 0100000200 0000000000 0001000010 1100100100 1110001100 0000000000 0000000000 0000700000 00 Amphipoda 2200010000 1000000200 0001100000 0000001000 0110110100 0000001000 0000000000 0000000000 0000100000 00 Phreatoic. 2211100110 1100000201 0001100000 0101000010 1100100000 1110001110 0001000000 0110000000 0000700000 00 Valvifera 2211100110 1100000101 0001100000 0101000010 1110100110 1110000010 1001000000 0001001000 0000000000 00 Epicaridea 2211100110 1101100100 0001110002 2107100010 111010010? 1110000010 0001100000 0001001000 0000000000 10 Gnathiidea 2211100111 1110000111 0001100112 1107100010 1110100107 1110000010 0001000000 0001001000 0000000000 10 Anthuridea 2211100110 1100000101 0001101001 0117000100 1110100100 1110000011 0001000000 0001001000 0000000000 00 Tylomorpha 2211100110 1100011701 7101100000 0101100000 1110100110 1111010110 0101000000 0001001000 0000000000 00 Ligiamor. 2211100110 1100011701 7101100000 0101100000 1110100110 1111011110 0001000000 0001001000 0000000000 00 Asellota 2211100110 1100000201 0000000000 0101000010 1100101100 1110001110 0001000000 0001110111 1000700000 00 Calabozo. 2211100110 1100010201 0701100000 0101100000 1110100110 1111011110 0001000000 0001001000 0000011000 00 Microcerb. 2211100110 1100000201 0000100000 0107000000 1100100100 1110001110 0001000000 0001001111 1111700000 00 Aegidae 2211100110 1100000101 0001100001 0107010000 1110100103 1110000010 0001100000 0001001000 0000000000 00 Anuropidae 2211100110 1100000101 0011100001 0107000070 1110100103 1110000010 0011000000 0001001000 0000000011 00 Bathynat. 2211101110 1100000101 7001100002 0101000010 1110100100 1110107010 0001000000 1001001000 0000100000 00 Cirolanid. 2211100110 110000010? 0007100001 0101000010 1110100100 1110000010 0001000000 0001001000 0000000000 00 Coralland. 2211100110 1100000101 0001100001 0107010000 1110100103 1110000010 0001000000 0001001000 0000000000 01 Cymothoid. 2211100110 1100000101 7001100001 0107010000 1110100103 1110000010 0001110000 0001001000 0000000000 00 Keuphylid. 2211101110 110000010? 0001100002 0101100010 1110100101 1110100010 0001001000 0001001000 0000100000 00 Limnoriid. 2211100110 1100000100 0007100002 0107000011 1111100102 1110007010 0001000100 0011001000 0000000000 00 Lynseiidae 2211100110 1100000101 0001100002 0101100001 1111100102 1110000010 0001000001 0001001000 0000000000 00 Phoratopd. 2211100110 1100000101 1001100001 0101000010 1110100170 1110000010 0001000000 0001001000 0000000100 00 Plakarth. 2211101110 1100000701 0001100002 0107000000 1110100101 1110100010 0001000000 0001001000 0000100000 00 Protognat. 2211100110 1100000101 0007100001 0107000000 1110100773 1110000010 0001000000 0001001000 0000000000 00 Serolidae 2211101110 1100000101 1001100002 0101000000 1110100101 1110700010 0001000010 0001001000 0000700000 00 Sphaeromt. 2211100110 1100000101 0001100000 0101000010 1110100100 1110000010 0001000000 0001001000 0000000000 00 Tridentll. 2211100110 1100000101 0001100001 0107010010 1110100103 1110000010 0001000000 0001001000 0000000000 00

APPENDIX III

Synapomorphiesof terminal taxa. Note: this is versals and multi-state character changes are not an exhaustive list of synapomorphies unique indicated by parentheses. to each terminal taxon; it is a list of only those Anthuridea: 27, 33, 38, 39(0), 60. ' , , 3 , Anuropidae: 23,63,89,90. present in the data set used for the current analy- Asellota- 24(0¥?1 47 75 76 sis (see Methods section and Appendix I). Re- Bathynataliidae: 71. 204 MEMOIRS OF THE QUEENSLAND MUSEUM

Calabozoidea: 86, 87. Microcerberidea: 39(0), 77, 82, 83, 84. Corallanidae: 39(0), 92. Phoratopodidae: 21, 88. Cymothoidae: 66. Phreatoicidea: 72, 73. Epicaridea: 14,15, 20(0), 26,31(2), 65. Protognathiidae: 39(0). Gnathiidea: 10, 13, 19,28,29. Serolidae: 21, 69. Keuphyliidae: 35,67. Tylomorpha: 57(0), 62. Limnoriidae: 20(0), 68, 73. Valvifera: 49, 61 Lynseiidae: 35,39(0), 70.