JOHNS and LANO LARVAL DEVELOPMENT OK L1BINIA EMARGINATA 



spawner, Callinectes sapidus, for example, larvae 

 will complete early development only at 25°C and 

 31.1%o (Costlow and Bookhout 1959) while an es- 

 tuarine xanthid, Rhithropanopeus harrisii , com- 

 pletes development at temperatures of 20°, 25°, 

 and 30°C and salinities between 2.5 and 40%<> 

 (Costlow et al. 1966). Throughout this study, all 

 gravid females were collected in near coast bay or 

 open coastal waters >30%» salinity). 



The duration of development within the genus 

 Libinia also varies. Boschi and Scelzo (1968) re- 

 ported that development for L. spinosa required 

 20-30 days (at 20°C) or an average of 8- 10 days per 

 stage. Libinia erinacea required 14 days (at 20°C) 

 or 9 days (at 25 C) to reach first crab stage (Yang 

 1967). Sandifer and Van Engel (1971) reported 

 that L. dubia needed only 9 days (at 25.5°-28.5°C) 

 for larval development. Libinia emarginata is in- 

 termediate with at least 14 days needed to reach 

 first crab stage. As pointed out by Sandifer and 

 Van Engel (1971), these differences in develop- 

 ment times may be explained, in part, by rearing 

 temperatures. For L. erinacea, total development 

 time is reduced by 5 days with a 5°C increase in 

 temperature. However, other factors must also 

 play a role in development for L. spinosa and L. 

 erinacea reared at the same temperature (20°C) 

 and given the same food source (Artemia) still 

 showed a 6- to 16-day difference in development 

 times. 



The number of larval stages for L. emarginata is 

 typical for the family Majidae (Gurney 1942; Hart 

 1960). Larvae from the three sources examined 

 showed few differences. South Carolina larvae 

 tended to be slightly smaller than Rhode Island 

 and field samples (Table 2). Morphology of larvae 

 was virtually identical in all cases, except for the 

 scaphognathite setal number being consistently 

 lower in South Carolina larvae. In this case, 

 reared larvae appear to represent accurate 

 "mimics" of wild larvae, even to specific setal 

 types. However, it is unknown if this similarity 

 also pertains to physiological or behavioral 

 parameters. 



In comparing larval descriptions of L. erinacea, 

 L. dubia, L. spinosa, and L. emarginata, we have 

 found that carapace setation and armature of the 

 abdominal somites are the most useful zoeal 

 characters (Table 3). Libinia erinacea and L. 

 spinosa may be distinguished by the presence of 

 lateral spines on abdominal somite 2, as opposed to 

 small knobs for L. dubia and L. emarginata. 

 Libinia spinosa may be differentiated from L. 

 erinacea by the lack of setation on the ventrolat- 

 eral margin of the carapace. The first zoea of L. 

 dubia and L. emarginata show no differences in 

 general morphology and setal numbers. The sec- 

 ond zoea of L. emarginata Usually has 10 setae on 

 the ventrolateral margin while L. dubia has 8 

 setae but as in stage I there appears to be no ready 



TABLE 3. — Comparison of diagnostic characteristics for zoeal stages of Libinia erinacea, L. spinosa, L. dubia, and L. emarginata. 



'From Yang (1967). 



2 From Boschi and Scelzo (1968), 



3 From Sandifer and Van Engel (1971). 



839 



