Mating system and reproductive performance in the isopod Parabopyrella lata, a parasitic castrator of the ‘peppermint’ shrimp Lysmata boggessi

Abstract

Knowledge of marine host–parasite relationships has been increasing, but little is known about the reproductive strategies of the parasites. Theoretically, parasitic crustaceans inhabiting relatively small and scarce hosts should be monogamous. Parasites are also expected to exhibit higher reproductive performance (RP) than their free-living relatives, a strategy thought to have evolved to increase host-to-host transmission, or to be the outcome of living in a ‘stable, nutrient-rich environment’. Here, the parasitic isopod Parabopyrella lata and its shrimp host Lysmata boggessi were used to test for monogamy and augmented RP, and to examine whether or not P. lata castrates its host. Prevalence, population distribution, and reproductive performance were examined in P. lata over 1 year (2012–2013) off Homosassa Springs, Florida USA (28.8037° N, 82.5761° W). Prevalence of P. lata on L. boggessi was greater during the warmer months of the year and infested shrimps were almost exclusively males. P. lata lives in male–female pairs within the gill chamber of infested shrimps more frequently than expected by chance alone. The sizes of paired males and females were tightly and positively correlated with each other and with host size. Average fecundity (3660 ± 1146 eggs female−1) and reproductive output (61 ± 19%) in P. lata, as with other bopyrid parasites, was much greater than those reported for free-living isopods. This evidence supports the hypotheses that parasites such as P. lata are adapted to be monogamous, display augmented RP, and reproductively castrate their host.