FISHERY BULLETIN: VOL. 75, NO. 4. 



that were dried in an 80°C oven for 24 h. The 

 weights for each stage were calculated from three 

 samples of five zoeae each. 



One-way analysis of variance was computed on 

 carapace length measurements taken on larval 

 stages from South Carolina reared, Rhode Island 

 reared, and field samples. If significant differences 

 (at P = 0.05) were found within stages, a Scheffe 

 Posterior comparison was used to determine 

 where the differences lay (Nie et al. 1975). 



The following abbreviations were used in all 

 descriptions: AN1 = antennule, AN2 = antenna, 

 MN = mandible, MAX1 = maxillule, MAX2 = 

 maxilla, MXP1 = first maxilliped, MXP2 = second 

 maxilliped, MXP3 = third maxilliped, PI to P5 = 

 pereopods 1 to 5, PL2 to PL6 = pleopods on abdom- 

 inal somites 2 to 6. Types of setae specified are as 

 described by Bookhout and Costlow (1974). 



RESULTS 



Development 



Development times in both the South Carolina 

 and Rhode Island reared larvae vary with temper- 

 ature and salinity. In the South Carolina larvae, 

 optimal and most advanced development occurred 

 at 25°C and 30%o. At these conditions, the second 

 stage appeared at day 3, megalopa at day 6 and 

 first crab at day 14. In other conditions tested, 

 development did not continue past the megalopa 

 (Table 1). 



In the Rhode Island reared larvae, complete de- 

 velopment occurred only at 20°C and 30%o with the 

 second zoeal stage appearing at day 5, megalopa at 

 day 8, and first crab at day 14. With other condi- 



TABLE 1. — Time to various developmental stages (in days) for 

 the spider crab, Libinia emarginata, reared at various 

 temperature-salinity combinations in both South Carolina and 

 Rhode Island. 



tions tested, development was varied (Table 1). 



South Carolina reared larvae tended to be 

 smaller than both Rhode Island reared and field 

 samples (Table 2). With statistical analysis, this 

 difference is significant in stage I (P<0.05) but 

 only between South Carolina reared and Rhode 

 Island reared. At no other stage were the size 

 variations found to be significant. 



TABLE 2. — Comparison of carapace lengths for South Carolina 

 reared, Rhode Island reared, and field sample larvae of Libinia 

 emarginata. 



'All larvae had died prior to this stage. 

 2 Second stage was not reached by day 15. 



'Indicates significant differences within a stage by one-way analysis of var- 

 iance (P = 0.05). 



1 Significant differences exist between the two means, according to Scheffe's 

 Posterior comparison. 



Larval Description 



Two zoeal stages and one megalopa were ob- 

 tained during the rearing period. Mandibles of the 

 zoea are without palps and have a complex trian- 

 gular biting surface. Since, in these stages, man- 

 dibles appear to have little diagnostic value and 

 are difficult to accurately portray, they have been 

 omitted from the following description. 



Zoea 1 



Size and weight — Average carapace length, 

 0.78 mm (range 0.76-0.80 mm), average total 

 length 2.19 mm (range 2.00-2.30 mm). Average 

 dry weight 0.0214 mg (range 0.0200-0.0224 mg). 



Carapace (Figure 1A, B) with dorsal and rostral 

 spines; lateral spines absent. Dorsal spine long 

 and slightly curved posteriorly; rostral spine 

 nearly as long as antennule and slightly curved 

 inward. Carapace large and somewhat rounded; 7 

 small plumose setae along the ventrolateral mar- 

 gin of carapace. Eyes sessile. 



Abdomen ( Figure 1C) with 5 somites; 6th somite 

 fused to telson. Somite 2 with small anteriorly 

 curved knobs on each side of lateral surface; so- 

 mites 3-5 with pair of small posterolateral spines. 

 Bifurcate telson; each furca bearing 1 spine. Inner 



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