FISHERY BULLETIN: VOL. 71, NO. 1 



observations are presented here to clarify some 

 aspects of the ecology of both the larval and 

 adult stages. 



for at least 2 days, and available for observations 

 on behavior at some time during the 2-year pe- 

 riod of the study. 



METHODS 



The species used were Petrolisthes cinctipes 

 (Randall), Petrolisthes eriomerus Stimpson, 

 Pachycheles rudis Stimpson, and Pachycheles 

 pubescens Holmes. Adults of all of these species 

 occur in the rocky intertidal or the shallow sub- 

 tidal zone of the northeastern Pacific but their 

 habitats differ (Haig, 1960). The Petrolisthes 

 species occur in the upper intertidal beneath 

 loosely bedded rocks and boulders, whereas the 

 two Pachycheles species are crevice and burrow 

 dwellers. P. rudis was collected from beneath 

 root mats of the surf grass Phyllospadix in the 

 lower intertidal zone and P. pubescens was col- 

 lected from burrows and crevices in rocks. Both 

 larvae captured alive in the plankton and larvae 

 reared from eggs candied by females in the lab- 

 oratory were available. 



Gravid females were maintained in the lab- 

 oratory at ambient sea temperatures until hatch- 

 ing occurred. Thereafter, larvae were cultured 

 in filtered seawater kept at several constant 

 temperatures and fed Artemia nauplii. Larvae 

 captured in the plankton were similarly main- 

 tained in the laboratory. A detailed account of 

 methods used in rearing and handling the larvae 

 is given elsewhere (Conor and Conor, 1978). 



RESULTS 



In laboratory cultures, larvae of each of the 

 four species showed similar basic patterns of 

 locomotion, feeding, respiration, and cleaning, 

 as well as changes in these patterns through 

 time. Consequently, separate accounts for each 

 species will not be given. Basic body and ap- 

 pendage form is suflficiently similar in the first 

 and second zoeae for Figures 2 and 3, of second 

 zoeal appendages, to be referred to in the text 

 for both stages. The descriptions given below 

 are summarized from observations repeated 

 throughout the rearing study as each of the cul- 

 tures was examined daily. Table 1 gives the 

 number of larvae of each stage kept in culture 



PREZOEA 



Females of all four species studied here release 

 their larvae in the form of a prezoea (Figure 1) . 



Figure 1. — Prezoea of Pachycheles pubescens, showing 

 rounded form. 



Cravid females were maintained in the labora- 

 tory for as long as 35 days, showing normal 

 locomotion, feeding, and cleaning behavior be- 

 fore their eggs hatched. The following numbers 

 of broods were hatched in the laboratory: 

 Pachycheles rudis, 35; P. pubescens, 2; Petro- 

 listhes eriomerus, 11; P. cinctipes, 10. In each 

 case female behavior during hatching was of 

 the normal type described elsewhere (Conor and 

 Conor, 1973), and the larvae released were pre- 

 zoeae which molted to viable first zoeae. The 

 behavior patterns of the prezoea are simpler 

 than those of later stages. Respiratory motions 

 in the prezoea are effected by the fanlike sca- 

 phognathite of the second maxilla. The type of 



Table 1. — Number and source of larvae of different 

 stages available for behavioral observations. 



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