EFFECTS OF RHIZOCEPHALAN INFESTATION ON THE PATAGONIAN STONE CRAB Platyxanthus patagonicus

LEAL, GUSTAVO A.; CARSEN, ANDRÉS E.; KROECK, MARINA A.; BARÓN, PEDRO J.

La Serena, Chile

Congreso; The Crustacean Society Mid Year Meeting 2007; 2007

The Crustacean Society and Universidad Católica del Norte

Platyxanthus patagonicus is the only brachyuran known to host a rizocephalan parasite on the Atlantic Coasts of Patagonia. Even though the effects of rizocephalan on the physiology of many decapods are well documented, these have not been studied in P. patagonicus. The objective of this work was to determine the intensity and prevalence of a ?sacculina-like? rhizocephalan on P. patagonicus through a latitudinal gradient, and to describe the anatomical and physiological changes experienced by the host. A total of 2076 P. patagonicus individuals (1243 females and 833 males) were sampled with traps and by SCUBA diving in waters of San Matias (41º-42ºS), San Jose (42º15?-42º25?S) and Nuevo (42º15?-43ºS) gulfs from November of 2002 to March of 2007. Also, a data set of 1121 crabs (527 females and 594 males) captured by Otter trawling on the coastal shelf from Rawson Port to Escondida Island (43º15?-43º50?S) from June of 1988 to November 1989 was included in the analysis. All crabs were examined for the presence of rhizocephalan externae as an indicator of infestation. Parasitized crab sex was determined by examination of gonopore/gonopod presence. Overall intensity was 1.04 externae per crab. Parasitized males showed underdeveloped chelipeds, pleon widening, female-like pleopods and absence of male gonopods. Parasitized females lacked internal pleopod setae and displayed underdeveloped ovaries and normal-sized chelipeds. A total of 65 (35 males and 20 females) parasitized crabs were identified out of 3197 individuals examined. Altogether, prevalence was higher in males (2.45%) than in females (1.13%). Prevalence declined from northernmost (San Matias Gulf;  2.7% in males, 3.7% in females) to the southernmost (Escondida Island; 0.67% in males, 0.95% in females) sampling area. Differences in rhizocephalan prevalence between sexes and latitude may influence the operational sex ratios and reproductive potential of P. patagonicus populations, deserving consideration in the design of shellfisheries management rules. Financial Support: PICT-ANPCYT 14700is the only brachyuran known to host a rizocephalan parasite on the Atlantic Coasts of Patagonia. Even though the effects of rizocephalan on the physiology of many decapods are well documented, these have not been studied in P. patagonicus. The objective of this work was to determine the intensity and prevalence of a ?sacculina-like? rhizocephalan on P. patagonicus through a latitudinal gradient, and to describe the anatomical and physiological changes experienced by the host. A total of 2076 P. patagonicus individuals (1243 females and 833 males) were sampled with traps and by SCUBA diving in waters of San Matias (41º-42ºS), San Jose (42º15?-42º25?S) and Nuevo (42º15?-43ºS) gulfs from November of 2002 to March of 2007. Also, a data set of 1121 crabs (527 females and 594 males) captured by Otter trawling on the coastal shelf from Rawson Port to Escondida Island (43º15?-43º50?S) from June of 1988 to November 1989 was included in the analysis. All crabs were examined for the presence of rhizocephalan externae as an indicator of infestation. Parasitized crab sex was determined by examination of gonopore/gonopod presence. Overall intensity was 1.04 externae per crab. Parasitized males showed underdeveloped chelipeds, pleon widening, female-like pleopods and absence of male gonopods. Parasitized females lacked internal pleopod setae and displayed underdeveloped ovaries and normal-sized chelipeds. A total of 65 (35 males and 20 females) parasitized crabs were identified out of 3197 individuals examined. Altogether, prevalence was higher in males (2.45%) than in females (1.13%). Prevalence declined from northernmost (San Matias Gulf;  2.7% in males, 3.7% in females) to the southernmost (Escondida Island; 0.67% in males, 0.95% in females) sampling area. Differences in rhizocephalan prevalence between sexes and latitude may influence the operational sex ratios and reproductive potential of P. patagonicus populations, deserving consideration in the design of shellfisheries management rules. Financial Support: PICT-ANPCYT 14700