FISHERY BULLETIN: VOL. 71, NO. 1 



Table 5. — Comparison of maxilliped setation in Petrolisthes cinctipes and P. eriomerus. 

 (All serial listings are numbers of setae, arranged proximally to distally.) 



contrast, larvae belonging to species of the 

 present genera Poixellana, Pisidia, and Polyonx 

 exhibit several different patterns of armed tel- 

 son setae, a fact which, when coupled with the 

 confusion of adults of these genera in the past, 

 suggests that systematic problems still exist 

 among these groups. The only point worth not- 

 ing at this time is that second zoeae of two of 

 the three species currently bearing the genus 

 name of Pisidia and the second zoea of Petrolis- 

 thes novaezelandiae, which Wear suggests is 

 actually a Pisidia, all have similar setal arma- 

 tures and possess three pairs of pleopod buds on 

 the abdomen. All other porcellanid zoea II lar- 

 vae known to species have four pairs of pleopod 

 buds. In order to determine whether these two 

 characters are of any value in distinguishing the 

 larvae of the genus Pisidia from other larvae 

 with the Porcellana type telson, the second zoea 

 of Pisidia spinulifrons must be described, the 

 identity of Menon's (1937) "Petrolisthes" spe- 

 cies I and II, with three pleopod pairs, resolved 

 and Pisidia inaequalis, with four pleopod pairs, 

 reexamined as a member of the genus. 



In the course of this study, a number of spec- 

 imens of each stage were examined, and par- 

 ticular attention paid to morphological varia- 

 tion, especially in setal counts for the larval ap- 

 pendages, since larval variability has caused a 

 great deal of confusion in the literature on por- 

 cellanid and other anomuran larvae. Morpho- 

 logical variations in setal numbers, spine lengths, 

 etc. were found within individuals from the left 

 to the right sides, between individuals of the 



same species, and between individuals of the 

 different species studied. These findings em- 

 phasize the necessity of basing larval descrip- 

 tions, especially setal counts, on examination of 

 adequate numbers of larvae of each stage. 

 Throughout the descriptions given here, only the 

 range of setal numbers found is indicated. Be- 

 cause of the importance placed on setation for- 

 mulae in descriptions of crustacean larvae, some 

 of the setal count variations found and their 

 implications will be analyzed in a separate paper. 



Variability in the number of larval molts re- 

 quired to reach a specific point in development, 

 apparently in response to varying environmental 

 conditions, occurs in many Anomura (Table 6) 

 and other decapod groups as well (e.g., Broad, 

 1957; Costlow, 1965). This type of variation 

 has caused difl!iculties among larval systematists 

 for some time and has in part given rise to the 

 idea that either larvae produced under labora- 

 tory conditions are abnormal and should be dis- 

 counted altogether or that such stages are ex- 

 traneous and should be subgrouped under larval 

 stages most commonly noted. This concept of 

 substages or extra stages has served to confuse 

 the developmental picture (Efford, 1970), par- 

 ticularly among the porcellanids, where another 

 type of variability has been discovered which, 

 unfortunately, has lent further support to the 

 "substage" concept. 



Intermolt growth in which certain appendages 

 increase in size within a single larval stage with- 

 out molt is a type of variability prevalent in por- 

 cellanids. All four species described here show 



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