CONOR and CONOR: LARVAE OF FOUR PORCELLANIDAE 



After the larva has spent a period of time as 

 a prezoea, the cuticle over the carapace is rup- 

 tured dorsally along the midline and the prezoea 

 molts to the first true zoeal stage. The rostrum 

 is the first portion of the body to be freed, fol- 

 lowed by the functional mouth parts and nata- 

 tory maxillipeds. The abdomen and telson are 

 the last portions to be withdrawn from the cu- 

 ticle. When the molt is completed, the natatory 

 setae and setae of the telson, previously com- 

 pacted and confined by the prezoeal cuticle, be- 

 come fully extended and serve to keep the larva 

 afloat and propel it through the water. The 

 rostral spine, partially invaginated into the 

 carapace in the prezoea, straightens out almost 

 immediately following the molt. The posterior 

 carapace spines which often, but not always, be- 

 come tightly coiled immediately after the cuticle 

 is shed may take several minutes to several hours 

 to uncoil. The cuticle is shed virtually intact 

 except for the original dorsal split. Often in 

 later molts, the delicate elastic cuticle covering 

 the pereiopod and pleopod buds is shriveled or 

 damaged in the cast exoskeleton. 



Larvae of all four species always pass through 

 two true zoeal stages and one megalopal stage 

 (terminology of Williamson, 1957) in the lab- 

 oratory as do certain other porcellanids (Le 

 Roux, 1961, 1966; Knight, 1966; Boschi, Scelzo, 

 and Goldstein, 1967; Gore, 1968, 1970, 1971a, 

 b, 1972) . This was true of larvae hatched in the 

 laboratory as well as those taken from the plank- 

 ton. 



In these four species, both zoeal stages dem- 

 onstrate the remarkable property of intermolt 

 growth in which certain of the larval appendages 

 increase in size, apparently throughout the dur- 

 ation of a stage, while the larval cuticle remains 

 intact. This phenomenon has been reported for 

 various other porcellanid larvae (Le Roux, 1961, 

 1966; Kurata, 1964; Knight, 1966; Gore, 1968, 

 1970, 1971a, b, 1972) but has not yet been 

 thoroughly investigated. Appendages may in- 

 crease in size as much as threefold between 

 molts as a result of this growth pattern. 



The number of specimens of each stage dis- 

 sected and examined is given in Table 1. The 

 ranges given in the descriptions refer only to 

 variations found within these specimens. Many 



other specimens were examined but not dis- 

 sected. 



LARVAL DEVELOPMENT OF 

 PETROLISTHES CINCTIPES (RANDALL) 



Larvae of P. cincti'pes were reared using the 

 mass culture method. The single megalopa thus 

 obtained as well as one megalopa from the 

 plankton were preserved and dissected for 

 purposes of description, 



PREZOEA 



(Figure 2) 



The prezoea of P. cinctipes is virtually spine- 

 less and hairless. The carapace has a generally 

 rounded appearance because the rostral and 

 posterior spines are curved downward and in- 

 ward toward the center of the body. These 

 spines are further compacted by being tele- 

 scoped and invaginated into their respective 

 portions of the carapace. The natatory setae 

 are nonfunctional, withdrawn into the ends of 

 the maxillipeds, and held in place by the prezoeal 

 cuticle. The primary red chromatophores ap- 

 pear in the following locations: one on either 

 side of the mouth; one distally on the basipodite 

 of each second maxilliped; one distally in ab- 

 dominal segment number two or between seg- 

 ments two and three; and one on either side 

 of the body between the bases of maxillipeds 

 one and two. The rostrum and posterior spines 

 are tipped with red, and an additional red band 

 appears on the rostrum proximal to the red tip 

 and separated from it by a white or colorless 

 band. 



With the exception of the chromatophore 

 numbers and arrangement, the prezoeal stages 

 of the four species do not diflfer significantly. 

 For this reason, a prezoea will be figured only 



Table 1. — Number of porcelain crab larvae dissected 

 and examined for this study. 



Species 



Zoea I 



Zoea II 



Megalopa 



Petrolisthes cirutipes 

 Pi'troIistkfS friomerus 

 Pachychelfs pubescens 

 Pachycheles rudis 



193 



