Morphometric study of a Brazilian strain of Carchesium polypinum (Ciliophora: Peritrichia) attached to Pomacea figulina (Mollusca: Gastropoda), with notes on a high infestation

Abstract

During an ecological study of the epibiotic relationship between ciliate protists and Pomacea figulina (Spix, 1827) (Gastropoda, Ampullariidae), originating from an urban stream in southeast Brazil, a high infestation by the peritrich ciliate Carchesium polypinum (Linnaeus, 1758) Ehrenberg, 1830 (Ciliophora, Peritrichia) associated to the shell of one mollusc among 23 was observed. We provided a morphological and morphometric study of C. polypinum using observations of specimens in vivo, after protargol staining, and examined using scanning electron microscopy. The Brazilian-population of C. polypinum is characterized by: size of zooid in vivo 89 µm x 57 µm on average; colony regularly dichotomously branched with usually up to 40 zooids; macronucleus usually J-shaped; single contractile vacuole located in the upper third of body; myoneme not continuous throughout the colony; stalks contract despite the discontinuity of their individual myonemes; polykinety comprises three peniculi, each consisting of three kineties. The high infestation showed here could be related to the preference for eutrophic environments showed by C. polypinum and suggested that ciliate epibionts may be ecologically important in aquatic habitats.