FISHERY BULLETIN: VOL. 79, NO, 3 



Table l. — Micropanope sculptipes, relative duration of larval 

 life in days at three temperatures. (Number of larvae started at 

 each temperature = 24.) 



Temp 

 = C 



Larval 

 stage 



Duration 



Minimum Mean Mode Maximum 



Total no. molting 

 to next stage 



20 



25 



6 

 5 

 2 

 

 12 

 9 

 9 

 1 



25-30 Did not survive beyond first zoeal stage 

 'Died in stage without further molt. 



texana (McMahan 1967), A^. sayi andA^. packardii 

 (Costlow and Bookhout 1967), Pilumnus 

 dasypodus (Sandifer 1974), and P. sayi (McDonald 

 and Lang 1976). However, crabs of the genus 

 Menippe develop through 5 or 6 zoeal stages prior 

 to metamorphosis (e.g.. Porter 1960; Ong and 

 Costlow 1970; Scotto 1979), Heterozius rotundi- 

 frons and Epixanthus dentatus have two zoeal 

 stages, and Pilumnus lumpinus has only one zoeal 

 stage (Saba et al. 1978). The latter three species 

 live in specialized and restricted habitats which 

 may account for the differences in number of de- 

 velopmental stages. However, Ozius truncatus 

 (four zoeal stages) and Heteropanope (Pilum- 

 nopeus) serratifrons (probably four zoeal stages) 

 are also species which live in restricted habitats 

 (Wear 1968), so other factors besides environment 

 may influence developmental time. Micropanope 

 barbadensis develops through either three or four 

 zoeal stages (Gore et al. 1981), and the elimination 

 of the "terminal" stage may be an adaptive 

 response to food supply, nutritional deficiencies, or 

 an inherited response from adult genotypes, ac- 

 cording to several hypotheses considered by these 

 authors. 



It is therefore difficult to directly compare the 

 duration of larval development for M. sculptipes 

 (about 26 d at 25° C) with larval development 

 times for other xanthid species. Species of Menippe 

 (5 or 6 zoeal stages) required at least 17-21 d at 25° 

 C to develop into megalopa (summarized by Scotto 

 1979). The duration of larval development seems 

 to be largely dependent on temperature, and the 

 experimental temperature conditions employed 

 by different researchers may vary considerably for 

 a number of reasons. Larval development time 

 decreased for Micropanope sculptipes as tempera- 



ture increased. This inverse relationship between 

 temperature and duration of larval development is 

 consistently observed for the larvae of different 

 xanthid species (Costlow et al. 1962; Costlow and 

 Bookhout 1971; Scotto 1979). Based on these data 

 and at 25° C, we may postulate a planktonic devel- 

 opment time on the order of 1 mo before metamor- 

 phosis to first crab in M. sculptipes. 



LARVAL DESCRIPTION 



First Zoea 



Carapace length (anterior margin of orbit to 

 median posterodorsal edge of carapace): 0.47 mm. 



Number of specimens examined: 14. 



Carapace (Figure 2 A, B). Typically brachyuran, 

 possessing rostral, dorsal, and 2 lateral spines. 

 Eyes sessile. Rostrum straight, naked, sharply 

 pointed, slightly shorter than carapace length. 

 Dorsal spine about equal in length to carapace, 

 curving gently posteriad, bearing a few scattered 

 minute tubercles. Lateral spines short, naked, 

 projecting perpendicular to sagittal plane. 

 Carapace elliptical, naked except for 2 small 

 dorsolateral setae originating midway between 

 dorsal and lateral spines; mediodorsal knob 

 [= "forehead protuberance" Yang 1967] naked. 



Antennule (Figure 2C). Flabellate rod with 3 

 aesthetascs, 2 naked setae at tip. 



Antenna (Figure 2D). Protopodite long, tapering 

 to point; spirally arranged spines present along 

 distal three-fourths length with spines larger, 

 longer toward tip. Exopodite one-sixth to one-fifth 

 protopodite length, naked throughout length, 

 with 1 short apical spine, 1 long and 2 short apical 

 nonplumose setae. 



Mandibles (Figure 2E). Well-developed incisor 

 and molar processes; no palp. 



Maxillule (Figure 2F). Coxal endite with 7 stout, 

 plumose setae. Basal endite with 5 denticulate 

 spines, about 20 minute hairs on lateral surface. 

 Endopodite two-segmented; proximal segment 

 with 1 long, nonplumose seta; distal segment with 

 2 subterminal , 4 terminal , sparsely plumose setae. 



Maxilla (Figure 2G). Coxal endite bilobed with 4 

 proximal, 3 distal plumose setae. Basal endite 

 bilobed with 4 (occasionally 5) proximal and 4 

 distal plumose setae. Endopodite bilobed; 3 termi- 

 nal sparsely plumose apical setae on proximal 

 lobe, 5 terminal (appearing as 3 apical, 2 slightly 

 lower) sparsely plumose setae on distal lobe; this 

 setal formula holds for remainder of stages. 



490 



