JOHNSON ET AL.: RHIZOCEPHALAN INFECTION IN BLUE KING CRABS 









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Figure 3— Olga Bay rhizocephalan: Degenerating and normal roots. PAS. N, normal tubule; C, cuticle; 

 D, tubules with sloughing epithelium; M, completely necrotic tubule; H. hemocytes. Bar = 0.05 mm. 



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DISCUSSION 



The presence of the rhizocephalan in female blue 

 king crabs appears to impair reproductive function. 

 Most parasitized crabs have empty ovaries or ovaries 

 that contain degenerate gonadal cells. We assume 

 that these traits are linked to reproductive failure, 

 although there are also unparasitized crabs within 

 each category. It is not unusual to find a few retained 

 ova— destined to be resorbed— in a normal post- 

 extrusion ovary. Therefore, these crabs are also a 

 source of degenerate gonadal cells. The 2-yr 

 reproductive cycle of the blue king crab might also 

 lead to presence of degenerate gonadal cells that had 

 been produced early in the cycle and had become 

 senescent. This speculation remains to be investi- 

 gated. 



The increase in the incidence of infection over time 

 in postextrusion crabs also suggests reproductive im- 

 pairment. Not only is the prevalence very low (10%) 

 among females that had recently extruded (with 

 uneyed embryos), it is zero among grasped premolt 

 females that were presumably about to molt, mate, 



Figure 4— Olga Bay rhizocephalan: Empty ovary of an infected 

 crab. Arrows point to roots of the parasite PAS. Bar = 0.2 



mm. 



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