762 



Fishery Bulletin 93(4). 1995 



5% 



o 



4 - A 



3 



2 



1 







et □ m w a 



HA M A 1 11 A 



10% 



A |k 



20% 



40% 



100% 



10 



100 



Log (percent undivided eggs + 1) 



Figure 1 



Scattergram of clutch size and percentage undivided eggs for second 

 clutches of female snow crab, Chionoecetes opilio, that hatched their 

 first clutch. Females were mated either with adolescent (squares) or 

 adult (triangles) males after their molt to maturity and were subse- 

 quently prevented (open symbols) or allowed (solid symbols) to mate 

 with an adult male at second spawning. The open triangle in the lower 

 right corner of the scattergram represents two females with no clutch. 



Among successful primiparous females, there was 

 no significant difference in the size of the second 

 clutch ( Kruskal-Wallis test, #=2.45, P=0. 12 ) or in the 

 percentage of divided eggs (H=0A4, P=0.51) between 

 those with (median clutch size: 3.0, median percent- 

 age divided eggs: 96.9%, n=20) and those without (3.0, 

 96.3%, n=34) access to males at second spawning 

 (also see Table 2). It is likely that remating occurred 



in a majority of females with access to 

 males at second spawning because we ob- 

 served precopulatory embraces in 18 of 20 

 pairs and copulation in five pairs. Al- 

 though the proportion of divided eggs in 

 second clutches was high for females iso- 

 lated from males, one might have expected 

 an even higher proportion in females 

 paired with males owing to the potential 

 for acquiring additional, fresh sperm. 

 However, it was hypothesized for C. opilio 

 that stored sperm can be evacuated from 

 the spermathecae by the second mate us- 

 ing his gonopods (Beninger et al., 1991; 

 Elner and Beninger, 1992). If this or any 

 other mechanism to prevent a rival's 

 sperm from fertilizing eggs (see for ex- 

 ample Diesel, 1990) exists in C. opilio, then 

 successive matings would not contribute 

 additively to the pool of sperm available 

 to fertilize a new clutch. Nevertheless, our 

 results indicate that the viability and num- 

 ber of sperm remaining in spermathecae 

 after one year of storage were not limiting 

 for the fertilization of a second clutch in fe- 

 males mated only at the molt to maturity. 



The success of female C. opilio in fertil- 

 izing a second clutch of eggs with stored 

 sperm and the contrasting failure of female C. bairdi 

 (Paul and Paul, 1992) can probably be explained by 

 the = 10-fold greater number of sperm cells stored 

 after the first spawning by C. opilio (Sainte-Marie 

 and Lovrich, 1994). Moreover, mean size and fecun- 

 dity of females are less in C. opilio than in C. bairdi 

 (Haynes et al., 1976); therefore, fewer sperm cells are 

 mobilized to fertilize a clutch in the former species. 



