Interactions Entre Le Parasite Probopyr Us Bithynis (Isopoda, Bopyridae) Et L'Un De Ses Hôtes, La Crevette Macrobrachium Amazonicum (Decapoda, Palaemonidae)

Abstract

Specimens of the prawn Macrobrachium amazonicum (Heller, 1862), parasitized by the isopod Probopyrus bithynis Richardson, 1904, were collected in the Lower Tocantins, Para, up to 300 km from the ocean. All the infested prawns displayed external sexual characters of the immature female. Of the prawns 99.6% carried a single parasite couple in either the right or in the left branchial cavity. The infestation level in the female host population varied between 1.6% and 7.3% in Cameta and between 6.4 and 54.5% upstream in Acaripucu, affecting respectively 4% and 11 % of the total prawn population. The length of the female isopod was positively correlated with the length of its host. The mean sizes of infested and non-infested female prawns, and of female parasites, displayed the same seasonal pattern of variation, with higher values from March to August during the time of the host's migration and reproduction, and lower values during the rest of the year during the recruitment of the prawns. The relationship between infestation level and host life cycle suggests a stable interaction between M. amazonicum and P. bithynis populations.