Temporal variation in population structure of the isopod Urobopyrus processae Richardson, 1904 (Isopoda: Bopyridae) infesting the branchial chamber of the night shrimp Ambidexter symmetricus Manning and Chace, 1971 (Decapoda: Processidae)

ABSTRACTCaridean shrimps are often infested by ectoparasites from the isopod family Bopyridae. Urobopyrus processae is a widespread species of bopyrid parasitizing the branchial (gill) chambers of members of the caridean family Processidae, including Ambidexter symmetricus. We examined hypotheses on differential infestation based on gender, castration of the host by the parasite, correlation between host and parasite size, and the fecundity of female parasites. Infestation rates varied from 1.3 to 32.1% between 2010 and 2011. Infested shrimps ranged from 1.26 mm to 6.24 mm carapace length (CL) between 2010 and 2011. Female shrimps were infested at a higher rate than males (2010 P = 0.0376; 2011 P = 0.0023). We report for the first time the differential selection between left and right branchial chambers in a caridean shrimp by a bopyrid parasite (P = 0.0209). Female parasite total length (TL) increased with host size (CL) in both years of sampling (2010 R2adj = 0.6863; 2011 R2adj= 0.8206). The size of male parasite TL was explained by both host CL (2010 R2adj = 0.4591; 2011 R2adj = 0.5490) and parasite female TL (2010 R2adj = 0.5606; 2011 R2adj = 0.6195). The number of embryos in a brood of the female parasite (85-3096) was varied positively with female TL (R2adj = 0.625). Our results show that the bopyrid-shrimp host relationship in processids is typical of those studied in other carideans, indicating similar selective pressures act on bopyrids infesting the branchial chambers of shrimps.