MARTIN ET AL.: MEGALOPAE OF STONE CRABS (MENIPPE) 



unsegmented with 6-8 setae arranged as shown. 

 Basal endite setation 28-33; coxal endite setation 

 15-17. Epipodite with 22 or 23 long, minutely 

 plumose setae, appearing simple under low mag- 

 nification. 



Maxilliped 2 (Fig. 2B). — Exopodite 2-segmented, 

 with setation 3, 5-8. Endopodite 4-segmented, 

 with setation usually 5, 2 or 3, 5 or 6, 9 or 10; 

 distal segment with 4 or 5 stout serrate setae. 

 Epipodite with 9 or 10 long minutely plumose 

 setae. 



Maxilliped 3 (Fig. 2A). — Exopodite 2-seg- 

 mented, with setation or 1, 6-8. Endopodite 

 5-segmented, with variable setation, usually 18- 

 20, 15 or 16, 5-9, 6-8, 7-10; ischium with scal- 

 loped medial border. Epipodite with 18 long 

 minutely plumose setae on distal two-thirds plus 

 8-12 plumose setae on proximal one-third. Pro- 

 topodite setation variable. 



Pereiopods (Figs. lA, B, H, I, 3B, C, D).— Che- 

 lipeds long, stout, subequal; dactylus with 4 irreg- 

 ular teeth; immovable finger with 3 teeth (Fig. 

 3B); tips of fingers overlap distally when approxi- 

 mated. No recurved hook on basi-ischium 

 (Fig. 3B). Second to fourth pereiopods similar; 

 dactylus with 5 (rarely 4) serrate spines ventrally 

 (e.g., Figs. IH, 3C, D); propodus with long ven- 

 trodistal spine (Fig. IH). Fifth pereiopod dactylus 

 (Fig. II) with 3 long pectinate setae, 1 markedly 

 toothed and concave (Fig. 3E), on distal ventral 

 border and 3 or 4 serrate spines ventrally. 



Pleopods (Fig. ID, E, F). — Decreasing in size 

 posteriorly. Pleopod 1 (Fig. ID) with 19-22 

 plumose setae; endopodite with 3 or 4 hooked 

 setae. Pleopod 4 (Fig. IE) with 19-21 plumose 

 setae; endopodite with 3 or 4 hooked setae 

 (Fig. 3F). Pleopod 5 (uropod) (Fig. IF) with 12-14 

 plumose setae; basal segment lacking setae or 



with 1 or 2 setae (field collections); endopodite 

 absent. 



Color. — Overall coloration rose-orange, with 

 dark blue-black chromatophores located as shown 

 in Figure lA, B. 



DISCUSSION 



The genus Menippe de Haan, 1833, presently 

 contains about 8 species, only 3 of which occur in 

 North America. The megalopa stage is now known 

 for 3 species in the genus: M. rumphii (Fabricious, 

 1798), M. nodifrons Stimpson, 1859, and M. adina 

 Williams and Felder, 1986. In addition, selected 

 characters of M. mercenaria (Say, 1818) are pre- 

 sented here for comparison; some characters of 

 that species are also obtainable from an unpub- 

 lished report by Kurata (fn. 4) (see Table 1). 



Laboratory-reared megalopae of M. adina were 

 virtually identical to megalopae presumed to be- 

 long to M. adina that were collected off south 

 Texas. Even meristic counts of the mouthpart se- 

 tation agreed exactly, with the only observed dif- 

 ferences being that field-collected megalopae 

 were slightly larger and occasionally bore 1 or 2 

 setae on the basal segment of the uropod. Thus, 

 we feel that our laboratory conditions have not 

 adversely affected development or introduced ab- 

 normal characters, and we have used these field 

 collections for the SEM figures of M. adina mega- 

 lopae (Fig. 3). 



We expected to find that characters of the 

 megalopa of M. adina are similar to those de- 

 scribed by Kurata (fn. 4) for the morphologically 

 similar (in adulthood) M. mercenaria, a species 

 known to hybridize with M. adina (see Williams 

 and Felder 1986). In general this is true. How- 

 ever, some characters reported by Kurata differ 

 from our observations on M. adina and from our 

 laboratory-reared megalopae of M. mercenaria 

 (Fig. 4). Kurata mentioned (but did not illustrate) 



Table 1 . — Comparison of characters in megalopae of the genus Menippe. Dash ( — ) indicates information not available from reference. 



^CL = carapace length; CW = carapace width. 



2From a megalops hatched from a stage 6 (rather than the typical stage 5) zoea. 



3See text footnote 4. 



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