FISHERY BULLETIN: VOL. 75, NO. 4. 



TABLE 4. — Average carapace lengths, total lengths and dry weights for the larval stages of Libinia 

 emarginata, L. dubia, L. erinacea, and L. spinosa. 



Carapace length (mm) 



Total length (mm) 



Dry weight (mg) 



Species 



Zoea I Zoea II Megalopa Zoea I Zoea 



Megalopa 



Zoea I Zoea II Megalopa 



L emarginata 

 L dubia' 1 

 L erinacea 2 

 L. spinosa 3 



0.78 

 0.81 

 088 

 080 



0.94 

 0.97 

 1.03 

 096 



1.21 

 1.16 

 1.24 

 1.30 



2 19 

 2.35 



2.30 



269 

 2.78 



2.80 



2.14 

 2.11 



3.10 



'From Sandifer and Van Engel (1971) 



2 From Yang (1967). 



3 From Boschi and Scelzo (1968) 



0.0214 0.0654 



0.205 



means to distinguish the species. Libinia dubia 

 zoea, as described by Sandifer and Van Engel 

 ( 1971), are larger than L. emarginata zoea (Table 

 4), but statistical analysis of various samples 

 would be needed to determine if a consistent size 

 difference exists. Differences in setal types may 

 also occur, but these have not been described for L. 

 dubia. As with larvae of various species of Uca 

 (Hyman 1920), a rapid, reliable means to distin- 

 guish L. emarginata andL. dubia larvae to species 

 does not exist. 



Megalopae of all four species, however, are dis- 

 tinguishable. Libinia spinosa has a distinct dorsal 

 spine which curves posteriorly (Boschi and Scelzo 

 1968) while the dorsal spine of L. erinacea is long 

 and upright (Yang 1967). Libinia dubia and L. 

 emarginata megalopae both lack a dorsal spine. 

 The median cardiac protuberance of the L. dubia 

 megalopa is single but is paired in L. emarginata . 

 This difference is relatively easy to observe, thus 

 unlike zoeal stages, L. dubia and L. emarginata 

 megalopae may be identified to species. 



ACKNOWLEDGMENTS 



We express our appreciation to Walter Schaffer 

 and the crew of the Carol El from Mt. Pleasant, 

 S.C., for assisting in collection of gravid crabs, and 

 to Austin Williams, National Marine Fisheries 

 Service Systematics Laboratory, NOAA, who 

 confirmed identification of several of the sponge 

 crabs. Also, we are indebted to Tom Bigford for 

 help in the maintenance and rearing of the larvae 

 in Rhode Island. DMJ was the recipient of the 

 Slocum-Lunz Predoctoral Fellowship in Marine 

 Biology during part of this study. 



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