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Home , Owenia (worm), Oweniidae, Spionida, Spirorbis spirorbis

Phylogenetic relationships within Rioja (Polych aeta, Annelida)

Gustavo Sene-Silva 1

ABSTRACT. The Oweniidae consist of five genera of tubiculous OCCUl"­ ring in ali oceans from tropical to po lar areas: Delle Chiaje, 1842, Myriochele Malmgren, 1867, Galarhowenia Kirkegaa rd , 1959, Myriowenia Hartman , 1960 and Myrioglobula Hartman, 1967. The gro up is regarded as monophyleti c based on lhe presence of dense fields of bidentate neuropodial hooks. Fo urteen species were submitted to a c1adi sti c anal ysis in PAU P 3. 1.1 with the usage of 19 morphological characters. The taxonomic status of the ingro up taxa co uld be evaluated and it has been found that: ( I ) Owenia, Myriowenia and Myrioglobula are monophyleti c, and (2) Myriochele, and Galalhowenia are both paraphyletic taxa. KEY WORDS. Pol ychaeta, Owen iidae, phylogeny, systematics

The Oweniidae Rioja, 1917 are polychaetes with large bathymetric range. They are usually collected from intertidal zones to shallow waters and are rare in great depths, being present in ali oceans from tropical to polar areas. The Oweniidae currently consist offive genera: Owenia Dell e Chiaje, 1842, Myriochele Malmgren, 1867, Galathowenia Kirkegaard, 1959, Myriowenia Hartman, 1960, and Myrioglo­ bula Hartman, 1967. They ali inhabit tubes. In terms of taxonomical diagnosis, these genera seem to be relatively well defined, except for Myriochele and Galathowenia. Some oweniid polychaetes, as for example Myriochele fragilis Nilsen & Holthe, 1985 and M. longicollaris Hartmann-Schroder & Rosenfeldt, 1989, have been described and ranked in the cited genus. Howeve r, the description of their head region (a collar-like cyJindrical structure anterior to the mouth) does not fit with th e ori ginal di agnos is of a globular head for Myriochele (MALMGREN 1867). Apparently, th e incJusion of these species in Myriochele was based purely on the absence of head ap pendages and on a thoracic region of three uniramous segments (Fig. IA), even though Galathowenia was al ready described by KIRKEGAARD (1959). Moreover, Myriochele species might have been equivocally cited in some biogeographical studies published in past reports, due to possible cases of bad fixation of coll ected material (BERKELEY 1949). This auth or suggests that some specimens with collar-Iike prostomial membranes could have their anterior ends contracted after the application of fixative substances and gained a globular appe­ arance, similar to the pattern fo und in Myriochele heeri Malmgren, 1867. This does not directly affect, however, an attempt to understand th e di stribution of the internai taxa within the Oweniidae according to an hypothesis of evolution oftheir characters under a phylogenetic perspective.

1) Departamento de Zoologia, Universidade Federal do Paraná. Caixa Postal 19020, 81531 -980 Curitiba, Paraná, Bras il . E-mail: [email protected] Former address: Zoomorphologie und Systematik (Abt. 2) , Fakultat für Biologie, Universitat Bielefeld, Germany.

Revta bras. Zool. 19 (4): 999 -1010, 2002 1000 Sene-Silva

FITZHUGH (1987, 1989) and PLElJEL (1991) are examples of attempts on lhe intern ai phylogeny of some families. Other works have treated the Polychaeta in general (WESTHEIDE et aI. 1999), or considered their general evolu­ tionary transformati ons (WESTHEIDE 1997), or even the relationship-Ievels of their internai taxa with morphological characters (RO USE & FAUCHALD 1997; ROUSE 1999) and also with molecular data (Mc H uG H 1997; KOJlMA 1998). Particularly in the Oweniidae, NILSEN & HOLTHE (1985) and MEYER & BARTOLOMAEUS (1996) proposed their ideas on the ground plan of this taxon based on hypothesised evolutionary steps of the transformati on of the neurochaetae (morphology and position along the body). Although these works did not involve other characters, whi ch would imply directly in the oweni id internai phylogeny, they are important contributions due to informati on on species bi ogeography, general descriptions of features, detail ed data on the morphology and morphogenesis of characters and mainly because of the preliminary in sights concerning possible evolutionary trans­ fo rmations within genera. This paper represents a cladi sti c analysis to umavel the phylogeny of the Oweniidae. Inferences on the transformation of each of the characters were possible and , consequently, a ground pl an of the group is hypothesised in accordance to the most primitive features found in the single most-parsim oni ous tree obtain ed. F urthermore, th e resulting fi nal topology could demonstrate the most suitable sister-group relati onship among each ofthe species studied, permitting an evalu ation of the validity of theirtaxonomi c ranking under Henni gian principies of monophyly (HENN IG 1966; WILEY 198 1; AMORIM 1997). MATERIAL ANO METHOOS

Taxa The phylogenetic relati onship of fourteen species of Oweniidae was deter­ mined usin g phylogenetic systemati cs (HENN IG 1966). The characters were obtai­ ned from the primary literature OI' directly through the study of specimens. The pecies considered are: Owenia fusiformis Dell e Chiaje, 1842, Myriochele heeri Malmgren, 1867, Myriochele danielsseni Hansen, 1879, Calathowenia ontlata (Zachs, 1923), Myriochele pygidialis Hartman, 1960, Myriowenia californiensis Hartman, 1960, Myriowenia gosnoldi Hartman, 1965, Myrioglobula antarclica Hartman, 1967, Calathowenia scotiae (Hartman, 1978), Myriochele fragilis Nilsen & Holthe, 1985, Myrioglobula japonica Imajima & Morita, 1987, Myriochele logicollaris Hartmann-Schroder & Rosenfe ldt, 1989, Myriochele joinvillensis Har­ tmann-Schroder & Rosenfeldt 1989, and Owenia gomsoni Koh & Bhaud, 200 I. Choice of outgroup taxa A well-stabli shed sister-group for the Oweniidae is not in consensus, yet, sin ce they are related differently in each publicati on to a di stinct polychaete taxon (N!LSEN & HOLTHE 1985; ROU SE & FAUC HALD 1997; BARTOLOMAEUS 1997; ROUSE 1999). Grube, 1850 and Sabellidae Malmgren, 1867 were chosen as outgroups only in order to root the cladogram, once they represent real entities whi ch are, at least, closely related to the Oweniidae within the phylogeny of

Revta bras. Zool. 19 (4): 999 -1010, 2002 Phylogenetic relationships within Owen iidae ... 1001 polychaetes. Those groups, as well as the Owenii dae themselves, have been treated and recognized in the recent literature (RO USE & FAUC HALD 1997; BARTOLOMAEUS 1997; HAUSE & BARTOLOMAEUS 1998; SCHWE IGKOFLER et ai. 1998; ROUSE 1999) as closely related groups, w hi ch are capabl e of tube secreti on around the body, and are deposit-or filter-feeding worms. Moreover, they ali present at least a pair of peristomial grooved palps, whi ch defines the more inclusive clade C anali (ROUSE & FAUCHALD 1997). Parsimony analysis The computer program PAUP 3 .1 .1 (SWOFFORD 1993) was used to analyse lhe data matrix of 16 taxa and 19 characters (Tab. I). T hese were ali treated as un weighted and unordered. No autapomorphic characters were primaril y applied. The trees were rooted using lhe method of outgroup compari son accordi ng to standard procedures fo r cladistic analysis in order to polarise the transformations (W ATROUS & WHEELER 198 1; W ILEY 1981; AMOR IM 1997). The searches were performed using the command "Branch and Bound Search" and zero-Iength bran­ ches were coll apsed. The option "Root tree at internaI node with basal po lytom y" was appl ied. T he character transformations of the sin gle most-parsimoni ous tree were sludied using MacClade 3.05 (M ADD ISON & M ADD ISON 1992).

Table I. Data matrix with 16 taxa and 19 unweig hted and unordered characters. Characters coded as numbers lrom "O" to "3"; missing data coded as "7".

Characters Taxa 2 3 5 6 7 9 10 11 12 13 14 15 16 17 18 19

Spionidae O O O O O O O O O O O O O O O O O Sabellidae O O O O O O O O O O O O O O O O O Myriowenia gosnoldi O O O O O O O O O 3 O O Myriowenia caJiforniensis O 1 O O 1 O O O O O 3 O 1 O O Myriochele heeri O O O O O O O O O O 3 O O O Myrioglobula anlarctica O O O O O O O O O O 2 O O Myrioglobula japonica O O O O 1 O O O O O O 1 O O O Myriochele joinviJlensis O O O O O O O O O O O 2 O O O O Myriochele !ragi/is O O O O O O O O O O 3 O O O O Myriochele pygidialis O O O O O O O O O O 3 O O O Myriochele longicollaris O O O O O O O O O 3 O O Galathowenia scariae O O O O O O O O O 3 O O O Galathowenia Deu/ata O O O O O 1 O O O 3 1 O O O Myriochele danielsseni O O O 1 O O 1 O 3 2 O O O Owenia fusiformis O O O 2 O O O 3 2 O O O Owenia gomsoni O O O 2 O O O 3 2 O O O

Characters 1) Slit-li ke bucal opening: (O) absent; (l ) present. T he mouth of Myriochele heeri, Myrioglobula antarctica and M. japonica have an unconventional form , be ing rather elongated longitudinally, which gives them the appearance of an anterior slit (F ig. IA).

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2) Labial lobes: (O) absent; (1) present. HARTMAN (1960, 1967) described for Myriowenia species a pair of proximal rounded expansions localized in th e same region where th e peristomial palps attach to the anterior end. No other species of Oweniidae or outgroups have such character. 3) Peristomial grooved palps: (O) absent; (1) present. The involves the polychaete groups Spionida, and (ROUSE & FA U­ CHALD 1997), which are with ciliated longitudinal grooves along their peristomial palps. The homology between these palps is very well substantiated neurologicall y according to a series of studies performed by ORRHAGE (1964, 1978, 1980). They appear also in th e Oweniidae (included in Sabellida), though on ly in Myriowenia species. 4) Prolonged peristomial lips: (O) absent; (1) present; (2) present and lobed. A cylindrical membranous structure extended anteriorly from the mouth and cili ated in its inner surface with a pronounced longitudinal ventral slit repre­ sents elongated li ps found particularly in some oweniid taxa (Myriochele joinvillensis, M. fragilis, M. longicollaris, M. danielsseni, Galathowenia sco­ tiae and G. ondata). These lips are modified as dichotomously lobed structures in Owenia species (BERKELEY 1949). 5) Peristomial ventro-lateral eyespots: (O) absent; (1) present. Eyespots have been reported fo r many polychaete groups (FAUCHALD & ROUSE 1997), generally found in the dorsal surface of prostomium or peristomium. Ventro-lateral locali zed eyes on th e coll ar (oweniid peristomial region) are, however, obser­ ved onl y in some of the species studied, namely G. oculata, M. danielsseni, o. fusiformis, and O. gomsoni (see, for example, in WrLSON 1932; BLAKE & DEAN 1973; IMAJTMA & MORITA 1987). 6) Globular head region: (O) absent; (1) present. The cephali c region of Myriowenia californiensis, Myriochele heeri (Fig. IA), Myrioglobula antarctica and M. japonica have a notably globul ar shape. In the first mentioned taxon, however, a cylindrical area on the peristomium precedes the first setiger; in the other cited species th e globul ar region is directly adjacent to the first setiger. 7) Length of thoracic segments: (O) wider than long; (1) longer than wide. Myri­ owenia species have th ei r th oracic segments much longer th an wide and approxim ately as long as, at least, the median ones. 8) Constriction between first and second seti ger: (O) absent; (1 ) present. Some oweniid species, namely Galathowenia ondara, G. scotiae, Myriochele pygi­ dialis, M. danielsseni, M. fragilis and M. longicollaris, present a transverse constri ction that demarks a circul ar area between first and second seti gers (for examples see IMAJIMA & MORITA 1987; FIEGE et ai. 2000). PAR APAR (2001 ) has recently worked on a revision of some oweniid species with special concern for this character. He states that this constri ction on the thoracic region is an intermediate phase between a normal state ofthe and a breakage process of the anteri or end, which might involve asexual reproduction. His main observation demonstrated th at Myriochele scotiae Hartman, 1978 is a seni or synonym of Galathowenia wilson i Blake, 1984, being the former species a broken vers ion ofth e latter. He emended M. scotiae's description and suggested a new combination, Galathowenia scotiae (Hartman, 1978).

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Fig. 1. (A) Ventral view of anterior end of Myriochele heeri. (B) Dorso-lateral view 01 anterior end of Owenia fusiformis. (bo) Bucal opening, (dgr) dorsal glandular ridge , (ghr) globular head region, (Ne) neuropodium, (No) notopodium, numbers 1-4 correspond to setiger number.

9) Y -like midventralline: (O) absent; (1) present. Five ofthe oweniid speeies studied (M. longicollaris, G. scotiae, G. oculata, O.fusiformis and o. gomsoni) present a pair of ventro-I aterallines (usually brighter than the rest of the body), whi eh originate posteriorly to the eollar margin and close to eaeh of the eyespots regions. These lines converge and meet eaeh other between the first and the seeond setigers on their ventral side. 10) Length of third segment: (O) isometrie to first segment; (1) shorter than first segment. The so-eall ed thoraeie segments in Oweniidae are reeogni zed as bein g mueh shorter than lhe anterior most abdominal ones. The third th oraeie seti ger is relati vely even shorter than the first and seeond ones in Myriochele dani­ elsseni, o. fusiformis (Fig. lB) and O. gomsoni. 11) Posi ti on of third notopodia: (O) dorso-lateral ; (1) dorsal. The notopodia faseicles of the third segment are closer to eaeh oth er when eompared to the ones of th e

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first and second segments in Myriochele danielsseni, o. fusiformis and O. gomsoni (Fig. lB, figures in NILSEN & HOLTHE 1985 and IMAJIMA & MOR ITA 1987). BLAKE (2000) refers to this same character as "setiger 3 short, constric­ ted dorsally" . 12) Length of median segments: (O) isometric to other segments; (1) elongated. Characteristicall y, the Oweniidae seem to have thei r median segments conspi­ cuously elongated when compared to the three more anterior and the more posteri or setigers. The same conditi on is not found in outgroups, where segments are wider than longo 13 ) Dorsal glandul ar ridges: (O) absent; (1) present. T hese are glands that appear on the dorso-lateral surface of the body from forth to seventh setiger and are disposed as two curved patches on each side of the segment. They begin just adjacent to its correspondent notopodium, bend to setiger' s lateral region until its middle section and then merge again to the dorsal surface reachin g the notopodium of the next setiger. This feature appears in Myriochele danielsseni and in Owenia species (Fig. 1B , illustrations in NILSEN & HOL THE 1985 and IMAJIMA & Mo RITA 1987). 14) Neurochaetal hooks in dense fields: (O) absent; ( I) present. Densely located hooks on the neuropodia are found on each owenii d studied so far (Fig. lB). FAUCHALD & ROUSE (1997) regarded this character as a significant synapo­ morphy of Oweniidae. 15 ) Position of first pai r of neuropodia: (O) from the first segment; (1) from th e second segment; (2) from the third segment; (3) from the forth segment. According to a revision from BLAKE (1996), the Spionidae presenl ali parapo­ dia birramous. In sabellids, the first thoracic segment bears only notopodia, and neuropodia (biramous parapodia) appear on second segment onwards (FITZHUGH 1989; FAUCHALD & ROUSE 1997). Within the ingroup taxa, neu­ ropodia appearing from the second segment is found in Myrioglobula species, whereas Myriochele joinvillensis present the first pair of neuropodia on the third segment. A li other oweniid species considered in this stud y have their first pair of neuropodia on the forth segment (Figs 1 A, B). 16) Shape of bifurcated neurochaetal hooks: (O) teeth longitudinally bifurcated; (1) teeth in an oblique plane to the manubrium; (2) teeth side-by-side in plane approx imately in right angle to the manubrium. Neurochaetal hooks have been reported for many polychaete groups (e .g. oweniids, spionids, capitellids, areni colids) and their homology have been demonstrated in recent papers (BARTOLOMAEUS 1995, 1997; MEYER & BARTOLOMAEUS 1996; BARTOLOM A­ EUS & MEYER 1997; HAUSEN & BARTOLOMAEUS 1998; SCHWEIGKOFLER ei ai. 1998). Particularly within the oweniids, these structures seem to present somewhat gradual modifications in respect to the compared position between both teeth: a longitudinal disposition very similar to that found in other polychaetes (like in spionids), then an intermediate condition with two teeth oblique to the other compared to the main manubrium axis and eventuall y a nearl y parallel one fo und in a few taxa.

Revta bras. Zool. 19 (4): 999 -1010,2002 Phylogenetic relationships within Oweniidae ... 1005

17) Neurochaetal capitium: (O) appearing above rostrum; ( I) vestigial. Un li ke other oweniids, Myriowenia species present hooks with vesti gial capitia, whereas the other species studied are clearl y bifurcated. 18) Flattened posterior segments: (O) absent; (1) present. Dorso-ventrally flattened posterior most segments were cited for Myrioglobula species and Myriochele heeri (IMAJ IMA & MORITA 1987). A cylindrical condition seems to be encoun­ tered in other oweniid taxa. 19) Tentacle-like pygidial cirri: (O) absent; (1) present. A pair of long terminal cirri located dorsally to the anal opening has been described for Myriowenia gosnoldi. This structure is not found in any other oweniid species. The pygidial region of Myriochele longicollaris is unknown (HARTMANN-SCHRODER & ROSENFELDT 1989; PARAPAR 2001).

RESULTS ANO OISCUSSION

Cladistic analysis The "Branch and Bound Search" command obtained one minimum-Iength tree for the data matrix (Tab. I). This single tree has a length of 29 steps with a consistency index (CI) of 0.793, retention index (RI) of 0.878 and rescaled consis­ tency index (RC) of 0.696. The tree is represented in figure 2. Monophyly of the Oweniidae Three characters supported the monophyleti c status of the Oweniidae in this study. Although found in a distinct segment in some species, neuropodi al hooks from the fo urth segment is observed basally in the phylogeny of these polychaetes. Of the outgroups used, setae appear from the first (Spionidae) or from the second (Sabellidae) segment, so the presence of neuropodial hooks in more anterior segments in some oweniid species should be interpreted as reversals. T his charac­ terizes a monophyletic group, Myrioglobula, with neurochaetae appearing from the second setiger. Another state represents a diagnostic feature of Myriochele joinvi­ llensis, with neurochaetae appearin g from the third seti ger. The two other characters th at make th e Oweniidae a monophyletic clade are present in ali species included in the present study: (1) the neuropodial patches with fields of densely concentrated bifurcated hooks and (2) the conspicuously elongated median segments in the abdominal region. Myriowenia monophyletic status The monophyly of Myriowenia is supported by three synapomorphies. The first is the vestigial apical tooth on neuropodial hooks, as the tree obtained showed that it is more likely that the longitudinally bifurcated hooks with well-developed teeth were already present in the stem species of the Oweniidae. The second feature is the elongated state of the three thoracic segments, while other oweniids have retained the short ancestral condition. Another particular character for this taxon is the pair of labial lobes located close to the inserti on of the basis of each of the peristomi al tentacles and the head.

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Myrioglobula relationships Regarding the cladogram in figure 2, one can see that Myriochele heeri, Myrioglobula antarctica and M. japonica form together another monophyletic group within the Owenii dae. A sli t- like mouth, a globul ar head (Fig. IA) and dorso-ventra ll y f1 attened posteri or segments (lMAJlMA & M OR ITA (987) are the synapomorphi es of this taxon. Also, the monophyly of Myrioglobula is characteri zed by the presence of neurochaetae fro m the second segment onwards (see above).

Spionidae Sabellida. M. gosnoldi M. californiensis M. heeri M. antarctlca M.japonlca M. joinvillensis M.lragllls M. pygidialis M. longlcollaris G. scotiae G.oculata AI. danlelssenl O. lusiformis O. gomsoni

Fig. 2. Th e single-most parsi monious tree obtained lrom data matrix (Tab. I) with length 01 29 steps and CI 0.793.

Owenia monophyly and its outgroups The clade that extends from Myriochele joinvillensis to Owenia gomsoni (Fig. 2) is defined by the presence of a cylindrical collar-li ke structure surrounding the mouth. Thi s latter structure represents th e buccallips, which extends anteri orl y from th e mouth with a longitudinal ventral sli t and a densely cil iated inner-surface. The monophyletic group comprising from M. f ragilis to O. gomsoni has the transversal fo ld between first and second segments as synapomorphy. Since this character is not fo und in Owenia, it was interpreted as a reversal for thi s genu . The 'side-by-side' type of neuropodial hooks with teelh in obliq ue position to the manubrium characteri zes lhe next step in lhe cladogram. Within this group, no character coul d define a more precise position for Myriochele longicollaris and Calathowenia scotiae, but both share the Y -li ke line on the ventral side of the body

Revta bras. Zool. 19 (4): 999 - 1010, 2002 Phylogenetic relationships within Oweniidae ... 1007 with G. oculata, Oweniafusiformis and o. gomsoni (reversal fo r M. danielsseni). G. oculata, M. danielsseni, Owenia fusiformis and O. gomsoni are disposed in a single clade characterized by a pair of peristomial ventro-Iateral eyespots. Owenia was found to be sister- group to Myriochele danielsseni. Four char­ acters form the set of synapomorphies at thi s levei, one of them being the neuropo­ dial hooks with both teeth approximately at the same pl ane at ri ght angles to the shaft, homoplastic to a similar condition fo und in Myrioglobula antarctica. In Owenia and Myriochele danielsseni, the third thoracic segment is reduced when compared to the other first one, and the distance between its notopodi a is shorter than what occurs on the first segment. Additionally, dorsal glandular ridges along the elongated abdominal segments are present onl y in this clade (Fig. 2). The genus Owenia was obtained as a monophyleti c group. The anteri or cylindrical structure (lips) fo und in more basal groups (see above) is modified in this taxon as lobes divided dichotomously, forming a crown-like structure. BERKELEY (1949) proposed such homology in the way that both organs are coll ar-like in appearance and possess ventral medi an gland s, which secrete the mucous material used in their tubes. M oreover, their relative morphological position - a peristomial rin g immediately anterior to the first seti ger - and the presence of the ventro-I ateral eyespots near the basis of the pe ri stomium of some species reinforces Berkeley' s evidences. As a consequence of the congruence of the characlers used, th e present analysis showed another important result: the paraphyly of Myriochele and Gala­ thowenia. The species of both genera form togeth er a grade "inserted between" Myriowenia and Owenia, appearing th e Myrioglobula species locali zed as a sister­ group of Malmgren' s Myriochele heeri, and Myriochele danielsseni as closely related to Owenia. This fact suggests that the of the fa mily might suffer substantial alterations at the generic leveI. CONCLUSIONS This cladistic analysis of some species of Oweniidae proposes the mono­ phyletic status of the family, even considering that not ali described species of this taxon were included. Such species might very likely fit well within any of the different leveis of th e present phylogeny (Fig. 2). Hence, not onl y must their general features agree with any of the nodes on whi ch they could be most probabl y related, but also with the ground plan encountered for the group. MEYER & BARTOLOMAEUS (1996) proposed a different interpretati on con­ cerning the number of thoracic seti gers in the ground plan of Oweniidae. In that paper, the condition found in My rioglobula antarctica for the neurochaetal patches (from the second segment onwards) should be interpreted as more plausibl e to be fou nd in the stem species of the Oweniidae, because it is also present in terebellidan and sabellidan groups. It is possible that the neuropodi al to ri from the second segment onwards are lhe plesiomorphic state of thi s charac ter fo r Terebellida and Sabellida. However, thi s has not been demonstrated in th e present cladisti c tests for lhe Oweniidae, where lhe congru ence among the used characters showed th at the most likely condition is the neuropodial tori present from th e fourth seti ger onwards.

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The inte rna I s is te r-group re la ti o n s hip a m o n g the oweniid s p ecies was a lso o bta ine d (Fig . 2). The results s ho w e d that o nly three of the five gen e ra are m o n o phy le tic: Myriowenia, Myrioglobula a nd Owenia. The o the r two genera (Myriochele a nd Galathowenia) are p a raphy le tic. Myriochele's p a ra phy letis m e n ­ countered in this s tudy agrees with the a n teri o r ins ig ht o fNLLSEN & H OLTHE (1985).

ACKNOWLEDGMENTS. The aUlh or wishes lo speciall y lhank Prof. DI'. Dalto n S. Amorim and Prof. Dr. Martin L. Chlistoffe rsen for their substantial parti cipati on on the rheoretical background in lhi s project and with the bibliography. I am in debred lO Prof. DI'. Thomas Bartolomaeus, Dr. Frederik Pl eijel and an anonymous reviser fo r their brilliant comments on lhe ll1anuscript. Prof. BaItololl1 ae us is also gralefull y ackn owledged fo r the kind allowance for the usage of hi s techni cal resources. Dr. Harald Hausen and Prof. DI'. Antônio Carlos Marques gave very helpful technical support with the compute I' prograll1s. T hi s sludy was suppOlted by FAPESP (Proc. 97/06496-3) and CA PES.

REFERENCES

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Received in 11 .11 1.2001; accepted in 30. IX.2002.

Revta bras. Zool. 19 (4): 999 - 1010, 2002