CRUSTACEAN RESEARCH，NO. 38: 64-69，2009 Redescription of the first zoea of Zosimus αeneus (Linnaeus，1758) (Decapoda，Xanthidae) Hironori Tanaka，Toshiro Saruwatari and Takashi Minami Abstrαct.-The first zoea of the provide more detailed illustrations to poisonous xanthid crab Zosimus distinguish the first zoea of Z. aeneus from αeneus (Linnaeus，1758) is described related genera and make comparisons within and illustrated based on laboratory- this subfamily Zosiminae. reared specimens. Comparisons with previous descriptions of the first zoea from Japan，revealed a number of Material and Methods deficiencies in the earlier study. The An ovigerous female Z. aeneus was first zoea of Z. αeneus is redescribed collected from the Lovina beach，Bari ， and illustrated here in detail.The up- Singaraja，Republic of Indonesia on 4March dated morphological characters of the 2004. Newly hatched zoeae were preserved first zoea are used to make adetailed in 5%buffered formalin and later transferred comparison between other known to 80% alcohol for preservation. Dissection species of the subfamily Zosiminae，and was conducted using fine insect pins under to identify generic diagnostic larval aNikon SMZ-1000 stereomicroscope. characters of the subfamily. Observations，measurements and drawings were made under aNikon E c1 ipse E400 microscope equipped with adrawing Introduction tube. Setal counts on appendages and The genus Zosimus currently contains measurements were based on amean of seven species in the subfamily Zosiminae 10 specimens. Measurements taken for (Ng et al. ，2008). The only known larval dimensions of zoea are as follows. CL: development of 加 y Zosimus species is 出atby carapace length from the base of the Tanaka (1999) on Z. aeneus，who described rostral spine to the posterior margin of the the first to fourth zoeal stages. However， carapace. RDD: distance between the tips when the first zoeal description of Z. aeneus of dorsal and rostral spines. The values by Tanaka (1999) is compared with other are shown as mean :t SD，and their range known zoea descriptions in the subfamily in parentheses in the text. In this paper， Zosiminae，the coxa of the maxillule scored recommendations by Clark et al. (1 998) 6setae by Tanaka (1999) while all zosimine for standardization in larval descriptions zoeas examined by Clark et al. (2004) were used. The specimens used in this scored 7setae for this character (Clark & study，including the ovigerous female，are Paula，2003; Clark et al. ，2004) .The new deposited and registered in the Ibaraki sample，along with the analysis and the re- Nature Museum (INM・1-041799-041800). examination revealed that there are several improvements that could be made. Thepurpose of this study is to redescribe the first zoea of Z. aeneus，correct shortcomings in the previous description ， REDESCRIITION OFTHE FIRST ZOEA OFZOSIMUS AENEUS 65 setae; basis with 4setae arranged 1+1+1+1; Results endopod 3・segmented，with setation of 1 ， ，1 6 (3 subterminal and 3terminal); exopod Zosimus αeneus (Linnaeus，1758) incompletely 2・segmented，with 4plumose (Fig.1) natatory setae. First zoea Abdomen (Fig. 1K): 5somites plus Size: CL =0.57 :1: 0.02 mm(0.5 5-0.60 mm)， bifurcated telson; somite 2with apair of RDD =1. 37:1: 0.03 mm(1. 35-1. 40 mm)，10 dorsolateral processesdirected laterally ; speclmens. somite 3wi 出 a pair of dorsolateral processes Carapace (Fig. 1A-C): dorsal spine directed posteriorly; somites 3-5 with curved distally，slightly longer than rostral posterolateral spinous processes; somites 2-5 spine; rostral spine straight，nearly as long with apair of posterodorsal setae; pleopod as protopod of antenna，distally spinulate; budsabsen t. lateral spines much shorter than other Telson (Fig. 1K，L): each fork long， spines; apair of posterodorsal setae; ventral gradually curved dorsally，not spinulated; 2 margin without setae; eyes sessile. pairs of lateral spines，anterior long，posterior Antennule (Fig. 1D): uniramous， short; apair of dorsal spi nes posterior to endopod absent; exopod unsegmented with level of lateral small pair; posterior margin 2long ，2 shorter terminal aesthetascs，1 with 3pairs of stout spinulate setae. short terminal seta. Antenna (Fig. 1E): protopodal process distally multispinulate ，approximately equal Discussion in length to rostral spine; endopod reduced τb e previous description of the first zoea to small spine (1E，smaller arrow); exopod of Z. aeneus by Tanaka (1999) overlooked ca. 21% length of protopod，with 3unequal severalcharacters. Comparisons with setae (1 long subterminal，2 unequal the zoea of the present study revealed terminal) Oarger arrow). differences in several characters (Table Mandibles (Fig. 1F): asymmetrical， 1).τbese include: the presence of apair of incisor process with distinct largeteeth ，and dorsal setae of carapace ，出 e spinules on the small teeth on molar process; palp absen t. rostral spine，the terminal setation of the Maxillule (Fig. 1G): coxal endite with 7 anntenule，the endopod spine of antenna， setae; basial endite with 2setal processes， coxal and basial setation of the maxillule ， 2cuspidate spines and 3setae; endopod coxal seta of the first maxilliped and the 2・segmented，proximal segment with 1seta; lateral spine of the telson. distal segment with 6(2 subterminal +4 In the xanthid subfamily Zosiminae，nine terminal) setae. genera are currently assigned: Atergαtis ， Maxilla (Fig. 1H): coxal endite bilobed Atergatopsis ，Lophozozymus ，Paraterg α，tis ， with 4+4 setae; basial endite bilob ed Platypodia ，Pulcratis ，Platypodiell α，Zosimus with 5+4 setae; endopod bilobed ，with and Zozymodes (see Guinot，1967; Serene， 3+5 (2 subterminal +3 terminal) setae; 1984; Ng & Huang，1997; Ng et al. ，2008). scaphognathite margin with 4plumose setae Although this subfamily contains alarge and 110ng stout distal process. number of species，the larval development First maxilliped (Fig. 11): coxa with 1 has been documented only in nine plumose seta; basis with 10 plumose setae species:Atergatis βoridus ，A. reticulatus ， arranged 2+2+3+3; endopod 5-segmented， A. subdentatus，Atergatopsis germaini， with setation of 3，2，1，2，5(1 subterminal Loρhozozymus ρictor ，Platypodia eydouxi ， and 4terminal); exopod incompletely Platypodiella spectabilis ，Zosimus aeneus and 2・segmented，with 4plumose natatory setae. Zozymodes xanthoides (see Terada，1980; Second maxilliped (Fig. 1]): coxa without Clark & Ng，1998; Tanaka，1999; Fransozo et 66 H. TANAKAET AL. L Fig. 1. Zosimus aeneus (Li nnaeus，1758): first zoea; A ，lateral view of carapace; B ，anterior view of carapace; C ，rostral spine; D ，antennule; E ，antenna; F，mandibles; G ，maxillule; H ，maxilla; 1，first maxilliped; J，second maxilliped; K， dorsal view of abdomen; L，dorsal view of telson. Scale: 0.1mm. REDESCRIPTION OFTHE FIRST ZOEA OFZOSIMUS AENEUS 67 Table 1. Acomparison between the first zoea of Zosimus aeneus described by Tanaka (1999) and 出 is present study. Characters Tanaka (1999) present study Carapace: pair of dorsal setae ND present spinules on rostral spine ND present Antennule: aesthetascs and seta 3a 4a+1 Antenna: endopod spine ND present Maxillule coxal endite 6 7 basial endite 5 5and 2setal processes First maxilliped: coxa ND 1 Telson: lateral corner 2sp +1 2sp (11arge +1 smaller sp) a: aesthetasc ，sp: spine ，ND :no data . α1. ，2001; Tanaka & Konishi，2001; Clark & & Paula，2003; Clark et al. ，2004). Paula，2003; Clark et al. ，2004). However，it became clear that the coxal However，current taxonomy of Zosiminae maxil1 ule has 7，not 6setae ，and the first based on adult and first stage zoeal zoea of Z. aeneus shows numerous features morphological characters is problematic in common with Zosiminae first zoeas (see Clark et al. ，2004) ，with Nget al. (2008: described to date. 193. 194) commenting that the subfamily The earlier larval descriptions and is probably not anatural grouping. With illustrations of A. reticulatus by Terada respect to the larval characters，the actaeine， (1 980) are inadequate for modern Actaeodes tomentosus seems to be better morphological comparative work. The placed within the Zosiminae rather than present redescription of the first zoeal stage Actaeinae，at least on the basis of the of Z. aeneus introduces awhole new set presence of three setae on the antennal of morphological characters for detailed exopod and similar lateral spines on the comparisons with other members of the telson fork. Thefirst zoeal description of Z. subfamily Zosiminae (Table 2). Wemade aeneus by Tanaka (1999) is compared with the same comparisons of larval characters other known members of the subfamily as made in Clark et al. (2004) and it was Zosiminae，and coxa of the maxillule scored found that the antennal protopod/ exopod 6setae by Tanaka (1999) while all zosimine percentage is 21%，which is remarkably high， zoeas examined by Clark et al. (2004) scored and at present Zosimus is different from 7setae for this character. The zoeas of L. other genera in the subfamily Zosiminae. pictor are also rather aberrant from what is There is apossibility that accumulated data known for other zosimines since the rostral on the antennal protopod/ exopod ratio in spine is without distal spinulation，the lateral other genera willlead to the better evolution carapace spines are lightly spinulate，the of the taxonomy of Atergatoposis and antennal protopod is smooth and not armed Actaeodes of the Zosiminae. with spinules，and the telson fork has two Further studies of larval development fine lateral spines (Clark & Ng，1998; Clark are clearly necessary，and there is a g Table2 .A comparison of larval