NOTE Sainte-Marie and Carriere: Fertilization of Chionoecetes opilio 



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Table 1 



Mating and spawning history of female snow crab, Chionoecetes opilio, that were not paired with a male after their molt to 

 maturity or that were paired with a male but lost their first clutch. Male mates were adolescent or adult. Median and range (in 

 parentheses) for clutch size and percentage of divided eggs are given for the second clutch. Clutch size is based on a (empty) to 

 4 (very full) scale for abdomen repleteness with eggs. Calculation of median clutch size includes females with no eggs (scored as 

 0). The percentage of divided eggs is followed by the number of clutches examined, in superscript. 



Second clutch 



Male after molt 



Total number 

 of females 



Females with 

 first clutch 



Male at 

 second spawning 



Females with 

 second clutch 



Size 



% Divided eggs 



No 

 Adolescent 



Adult 



9 

 3 



11 



4 

 3 



11 



No 

 No 



Adult 

 No 



0.0 (0-3) 

 2.5(1-4) 

 2.0 

 1.0(0-4) 



0.0" =1 

 97.5" =1 

 4.2 (0-56.7)"' 4 



carried by the 18 unsuccessful primiparous females 

 started to show signs of degradation about 2-A months 

 after spawning as many or all eggs changed from bright 

 to pale orange and eventually became almost white, 

 and clutches were sloughed or lost within 8-10 months 

 of spawning. The relatively high, 20.6%, incidence of 

 first clutch loss recorded for mated females may be a 

 laboratory artifact resulting from the 24-hour time limit 

 for mating and noncompetitive mating context. 



We examined 516-1,769 eggs from each second 

 clutch of six females that lost their first clutch and 

 of 52 females that hatched their first clutch, for a 

 combined total of 54,808 eggs. Divided eggs were at 

 the 128- or 256-cell stage. In 24 out of 55 females 

 that carried at least some divided eggs, the ratio of 

 divided eggs to total number of eggs in the pleopod 

 sample was not independent of pleopod position (x 

 test, P<0.05). One female had 89.5-100% divided eggs 

 on pleopods 1-7, but no egg was divided on pleopod 

 8. Eggs from this female were sampled a second time 

 to confirm the observation. The heterogeneous dis- 

 tribution of divided eggs in some clutches was not 

 expected and to our knowledge has not yet been docu- 

 mented. Most previous studies contain little or no 

 information on methods for sampling and determin- 

 ing viability of eggs. The reason for the contagious 

 distribution of divided eggs is unknown. Perhaps 

 attachment of eggs to individual pleopods is orderly 

 and follows an extrusion hierarchy, and sperm in the 

 fertilization chamber is temporarily or permanently 

 depleted during extrusion. Nevertheless, our find- 

 ing underscores the importance of sampling eggs 

 from throughout the clutch when assessing fertili- 

 zation success. We estimated the overall proportion 

 of divided eggs in a clutch as the mean of propor- 

 tions of divided eggs on each of the eight pleopods. 



Among females that lost their first clutch, 38.9% 

 did not spawn a second time (Table 1), and the re- 



mainder extruded second clutches from February to 

 March 1993. In the latter group, second clutches con- 

 tained 0-56.7% divided eggs when females had no 

 access to males or 97.5% divided eggs in the case of 

 one female that was paired with a male at the sec- 

 ond spawning (Table 1). 



Most females that were initially mated with adult 

 males and then hatched a first clutch of eggs pro- 

 duced a large second clutch with a high percentage 

 of divided eggs without remating (Fig. 1; Table 2). 

 Of the 34 successful primiparous females that mated 

 only at the molt to maturity, only two (5.9%) did not 

 spawn a second time, whereas two others produced 

 second clutches with <60% divided eggs (Fig. 1). 

 There was no significant difference in the size of the 

 second clutch (Kruskal-Wallis test, H=4.60, P=0.10) 

 or in the percentage of divided eggs in the second 

 clutch (#=2.50, P=0.29) among groups of females 

 mated only at the molt to maturity by adult males 

 with CW's of 40-60 mm (median clutch size: 3.0, 

 median percentage divided eggs: 88.9%, rc=13), 80- 

 100 mm (4.0, 96.0%, n=8), or 120-140 mm (3.0, 94.6%, 

 n=8). These data are consistent with the number of 

 sperm cells stored by female Chionoecetes after the 

 first spawning being unrelated to male CW (Adams 

 and Paul, 1983; Sainte-Marie and Lovrich, 1994). 

 Similarly, our data, although limited, indicate that 

 stored sperm from adolescent males also resulted in 

 the production of a large second clutch containing a 

 high proportion of divided eggs, and was as effective 

 as stored sperm from adult males (Fig. 1; Table 2). 

 Although virgin females mated with adolescent males 

 store as many sperm as those mated with adult 

 males, Sainte-Marie and Lovrich (1994) speculated 

 that the longevity of adolescent sperm might be less 

 than that of adult sperm because of a higher sperm- 

 cell to seminal-plasma ratio in ejaculate. However, 

 this was not apparent after one year of storage. 



