FISHERY BULLETIN: VOL. 84, NO. 1 



Figure 5.— Normal ovary with oogonia and previtellogenic 

 oocytes. PAS. Same scale as Fig. 4. 



and extrude. These facts suggest that the rhizo- 

 cephalan might preclude mating and subsequent ex- 

 trusion and attachment of fertilized ova. 



The external category of reproductive condition 

 we term "clean pleopod setae" would normally be 

 associated with immature crabs. In this study, it con- 

 tained both small females and females of mature size 

 (total size range 69-133 mm CL). The average size 

 at maturity of females in Alaskan populations lack- 

 ing the rhizocephalan ranges from 80 to 96 mm 

 (Somerton and Macintosh 1983). Crabs larger than 

 114 mm could reasonably be expected to be carry- 

 ing embryos or empty embryo cases, but 10 crabs 

 in the combined January-April sample (9 of which 

 had the rhizocephalan) were not. Two of the para- 

 sitized females were soft-shelled, suggesting that 

 molting can occur in parasitized females. 



Presence of the rhizocephalan in male crabs from 

 Olga Bay apparently did not interfere with normal 

 gonadal function. Species of Sacculina and many 

 other rhizocephalans cause a varying degree of ex- 

 ternal feminization and gonadal dysfunction of their 

 male hosts (Reinhard 1956). For example, Thomp- 

 sonia mediterranea causes external appendages of 

 males of Callianassa truncata to approach the 



female condition (Caroli 1931), but a species of 

 Thompsonia parasitizing Portunus pelagicus does 

 not affect males (Phang 1975). Briarosaccus callosus 

 parasitizes the blue, red, golden (Lithodes aequis- 

 pina), and deep-sea {Lithodes couesi) king crabs in 

 the Gulf of Alaska (McMullen and Yoshihara 1970; 

 Somerton 1981; Hawkes et al. 1985). Meyers 6 found 

 testicular regression and broadening of the abdomen 

 in Briarosaccus-'mfected male blue king crabs from 

 Glacier Bay. 



High prevalences of infection with rhizocephalans 

 have been reported previously in other decapod 

 species, so the high prevalence in blue king crabs of 

 Olga Bay is not surprising. McMullen and Yoshihara 

 (1970) found 14 of 21 golden king crabs, captured 

 near Kodiak Island, infected with B. callosus, and 

 Hawkes et al. (1985) reported 76% prevalence of the 

 same species in blue king crabs from Glacier Bay; 

 Phang (1975) reported prevalences between 24% and 

 68% of Thompsonia sp. in groups of Portunus pela- 

 gicus captured near Singapore; and Perry (1984) said 

 that sometimes over 50% of blue crabs sampled from 

 a single population in the Gulf of Mexico were in- 

 fected with Loxothylacus texanus. 



Although nearly 800 blue king crabs were sampled 

 from Olga Bay at quarterly intervals, no rhizoceph- 

 alan externas were observed, and the one red king 

 crab female found infected with what appeared to 

 be the same rhizocephalan also lacked an externa. 

 Due to the absence of externas, the Olga Bay rhizo- 

 cephalan cannot be indentified with certainty. Its 

 roots are similar histologically to those of other rhi- 

 zocephalans [Thompsonia (Potts 1915); Sacculina 

 (Fischer 1927; Dornesco and Fischer-Piette 1931); 

 and Peltogaster and Gemmosaccus (Nielsen 1970)], 

 corresponding best with the roots of Thompsonia, 

 which have a thinner cuticle than the others (Potts 

 1915). Roots of the Olga Bay parasite differ 

 histologically in several ways from those of 

 Briarosaccus callosus. They are of lesser diameter, 

 have a thinner cuticle, lack large peripheral nuclei, 

 often have a large lumen and flattened epithelium, 

 and seldom have the cytoplasmic vacuoles (probably 

 representing lipid storage) that are common in the 

 B. callosus roots. (Compare Figures 1, 2, and 3 with 

 Figure 6.) The Olga Bay parasite and B. callosus also 

 differ in that the roots of B. callosus are a bright 

 green when fresh (Hawkes et al. 1985) and blue- 

 green when fixed in Helly's solution, whereas the 

 roots of the Olga Bay parasite are colorless. 



6 T. Meyers, Assistant Professor of Fisheries, School of Fisheries 

 and Science, University of Alaska, 11120 Glacier Highway, Juneau, 

 AK 99801, pers. commun. October 1984. 



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