FISHKRY BULLETIN Vol. 



Piliannus danypodu.^, Sandifer 1974; Eurypuno- 

 pcus depresstis, Costlow and Bookhout 1961a). 

 These xanthids usually possess 8 or 9 natatory 

 maxillipedal setae in the third zoeal stage and 

 pleopod buds first appear in this instar. However, 

 third zoeae oiMenippe, which also possess 8 nata- 

 tory maxillipedal setae, lack pleopod buds and the 

 latter do not appear in known Mcnippc larvae 

 until the fourth stage (10 natatory maxillipedal 

 setae). Menippe larvae, as do other xanthid larvae, 

 otherwise attain the sixth abdominal somite in the 

 third stage. 



A similar situation is found among known lar- 

 vae of the Cancridae (e.g., Cancer borcalis. Sastry 

 1977b; C. irniratiis,Sa»try 1977a), which exhibit 8 

 natatory maxillipedal setae but no pleopod buds in 

 the third zoeal stage, while 10 natatory maxil- 

 lipedal setae and pleopod buds are exhibited in the 

 fourth stage, as in Mcnippc. Thus Mcnippc again 

 shows, in this respect, a closer relationship to the 

 Cancridae than to the Xanthidae. 



Another heterochronic feature is the mandibu- 

 lar palp, which appears in the fourth (i.e., last) 

 zoeal stage in all xanthid genera except Mcnippc. 

 Fourth stage Menippe larvae in the western North 

 Atlantic may thus be distinguished from other 

 stage IV xanthid larvae in lacking a mandibular 

 palp as well as in possessing 10 natatory maxil- 

 lipedal setae, as noted above. In all other laborato- 

 ry cultured xanthid genera with 9 or 10 natatory 

 maxillipedal setae the mandibular palp is present. 

 Again, Menippe larvae seem closer to cancrid lar- 

 vae than to xanthid larvae, in that the mandibular 

 palp appears in the fifth (usually the last) zoeal 

 stage. 



Comparison of M. nodifrons maxillipedal 

 coxopodal setation with that of other xanthid and 

 cancrid larvae, which may be a significant feature, 

 was not analyzed because of the lack of descrip- 

 tions and illustrations of this larval character. The 

 coxopodal setation has been described for only one 

 other xanthid, Neopanope texana (McMahan 

 1967). Setal number of M. nodifrons agreed with 

 that of A^. le.xana for the first four zoeal stages, 

 increasing in the fifth and sixth stages of M. nodi- 

 frons . 



Assuming then, that data just presented are 

 evidence of retained, primitive features, it can 

 then be postulated that Menippe larvae are re- 

 capitulating, in the sense of retarded het- 

 erochronic maturation (Gould 1977), a larval 

 development now accelerated in other xanthid lar- 

 vae. The presence of the fifth zoeal stage, the ir- 



regular occurrence of the sixth stage, the delayed 

 appearance of mandibular palp and pleopod buds, 

 and retention of coxopodal setation in cultured 

 species of .V/. nodifrons and M . merccnaria are all 

 evidence which indicates this might have hap- 

 pened. Evolution has apparently acted in the lar- 

 vae of other xanthid genera to reduce the number 

 of zoeal stages. 



In summary, because of the greater number ol' 

 zoeal stages and the tardy appearance of both 

 pleopod buds and mandibular palp, Menippe may 

 lie the most primitive genus of the family Xanthi- 

 dae. Whether the genus is transitional between 

 the Cancridae and the Xanthidae remains 

 speculative. As noted above, larvae of the family 

 Cancridae, phylogenetically primitive to the Xan- 

 thidae. also exhibit five zoeal stages and pleopodal 

 and mandibular features which appear 

 in a similar developmental sequence to those of 

 Menippe. The more advanced xanthid larvae, on 

 the other hand, pass through only four zoeal stages 

 and exhibit sequential features typical of larvae of 

 the family Gimeplacidae, a group considered to be 

 more advanced than xanthids (Lebour 1928; 

 Kurata 19681. 



Carapacial Armature 



Mcnippc larvae have well-developed dorsal, 

 rostral, and smaller lateral spines, a feature found 

 in all cancrid and most xanthid larvae. Thus, little 

 can be inferred regardmg phylogenetic relation- 

 ships using these features. 



The reason for such spines remains conjectural. 

 Lebour (1928) stated that these well-developed 

 carapacial spines were used "in directing move- 

 ment and keeping up |the larvae in] the surface- 

 layers, and their reduction appears to be 

 associated with habits near the bottom." Her sup- 

 position may be correct. Menippe nodifrons larvae 

 reared in this study were active swimmers near 

 the surface in earlier stages. Their locomotion was 

 usually in a forward direction with the dorsal 

 spine pointed anteriorly. 



Antennal Morjiliology 



In considering antennal features, xanthid lar- I 

 vae were first divided into either two (Hyman 

 1 925) or three ( Lebour 1 928) groups. In the former, 

 l)()th authors noted that the length of the antennal 

 exopodite is either about equal to the protopodite 

 (primitive) or rudimentary (advanced). In the 



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