The following aspects on the population of the bopyrid Aporobopyrus curtatus infesting the porcelain crab Petrolisthes armatus from Farol Island were treated: description and biometry of the developmental stages, temporal distribution of the relative density and the sex-ratio. Furthermore, a probable life cycle of this parasite is proposed. Collections of the crab hosts were done in the Farol Island, Matinhos, Paraná State, Brazil, from November 1989 to April 1991. A total of 967 bopyrids were obtained from 529 porcelain crabs. Seven developmental and reproductive stages were recognized in the parasite population: cryptoniscus, immature female, mature female, ovigerous female, female with embryos, bopyridium and mature male. The relative density fluctuated from 0.09 (January/1990) to 0.33 parasites per host (April/1990 and April/1991). Among immature parasites, females predominated. However, the sex-ratio was 1:1 when they became adults. Cryptoniscus larvae invaded P. armatus from November to May, but adult couples of A. curtatus were present all year round, except in January. Immature females were absent only in four months and bopyridia in six months, out of 18 months. There was a synchronic development between host and its parasite: parasite larvae infested juvenile crabs, and mature parasites, mature hosts.
Bopyridium; cryptoniscus; infestation; porcelain crab
