HAEFNER: REPRODUCTIVE BIOLOGY OFGERYON QUINQUEDENS 



FIGURE 7. — Isolated sperm from spermatheca of 83-mm CL 

 Geryon quinquedens. Nonmobile processes extend from nuclear 

 region surrounding a central, refringent structure, most likely 

 the acrosome (Brown 1966). Interference microscopy, 1300x. 



but expected. None of these crabs had swollen or 

 turgid spermathecae of the type shown in Figure 

 1. In most cases, only residual quantities of semi- 

 nal secretions were present in the receptacles, 

 indicating that most of the deposit had been used 

 in past ovulation(s) or absorbed. 



The presence of discolored vulval margins 

 among large crabs suggested that they may pro- 

 vide a physical criterion for copulation, similar to 

 those demonstrated for other brachyurans ( Veillet 

 1945; Butler 1960; Hartnoll 1969). Vulval mar- 

 gins of 93.5% of the females 2=70 mm CL examined 

 (n = 328) were blackened (Figure 8). All females 

 <70 mm CL had vulvae with intact margins. Not 

 included in Figure 8 are an unusually small 

 inseminated female (47 mm CL) and the ovigerous 

 64-mm CL specimen included in Figure 6b. 



One crab (47 mm CL) with small (1.2 mm long), 

 but open, mature-type vulva was sperm positive. 

 This unusually small crab had obviously mated 

 but the vulval margins were not blackened. It is 

 physically possible for a female this small to mate 

 with a male of similar size. I have observed 

 morphologically functional pleopods, with penis 

 inserted in the first pair, on male crabs as small as 

 38 mm CL. The size at which males become 

 physiologically mature is not known, but it must 

 be relatively small. 



Change in Vulvae 



Although variable in form, vulvae of G. 

 quinquedens undergo a recognizable growth and 

 development pattern which parallels growth in 

 body size and ovarian development. Six types are 

 recognized (Figure 9). The first form vulvae (a) are 

 slitlike and tightly closed. The observed size range 

 appears to be related to crab length (Table 2). 

 Form (b) vulvae are recurved, closed, and slightly 

 larger than the longest form (a) vulvae. Forms (c) 

 and (d), irregularly shaped and partially open, 

 range from a size comparable to the largest vulvae 

 of type (a) to that of type (e). Unusually large (d) 

 vulvae (2.6 mm) were observed in a 78-mm CL 

 crab. Form (e) vulvae are oval, gaping, and appear 

 to immediately precede the mature vulva. Form 

 (f) is the enlarged (2.4-3.9 mm), gaping, and usu- 

 ally blackened vulvae of the larger, mated crabs. 



TABLE 2. — Incidence of vulval type and size range in relation to 

 carapace length of female Geryon quinquedens. 



Type 



Carapace length 

 (mm) 



Vulval length range 

 n (mm) 



Change in Abdomen Width 



The abdomen width (Y) to carapace length (X) 

 relationship is allometric and is transformed to a 

 straight line by the equation: 



log Y = -0.875 +1.321 logX, n = 251; r = 0.990 



The relationship changes in the 60- to 75-mm 

 CL range (Figure 10) so linear regressions were 

 calculated separately for crabs with mature (f) 

 vulvae: 



FIGURE 8.— Size-frequency dis- 

 tribution of female Geryon quin- 

 quedens with immature gonopores 

 (white) and with discolored gonopore 

 margins (black). November 1974, 

 September 1975, and January 1976 

 collections pooled. 



 BLACKENED VULVAL MARGINS 

 O IMMATURE VULVAE 



50 60 70 80 



SHORT CARAPACE LENGTH (mm) 



00 MO 120 



99 



