Records of oligochaetes in freshwater sponges, on bryozoans, and on colonial hydrozoans from Brazil.

Species of oligochaetes inhabiting other freshwater animals have been cited by Brinkhurst & Jamieson, 1980; Righi, 1984; Brinkhurst & Marchese, 1991. However, there are few published studies about the Brazilian species (Righi, 1984). Here, we report oligochaeta species inhabiting freshwater sponges, as well as on bryozoans and hydrozoans from some Brazilian aquatic ecosystems. The material was collected by divers mainly on large rocks (depth > 15 m) in the Paraná river channel (20o45’S and 51o40’W) and manually in the Jacaré-Guaçu river basin (21o53’S and 47o52’W) (Table 1). The aquatic worms were sorted under stereoscopic microscope, processed, and identified following Righi (1984), and Brinkhurst & Marchese (1991). The identification of bryozoans and hydrozoans followed Wood (1991) and Slobodkin & Bossert (1991) respectively, and the sponges were identified by Dra. Cecília Ribeiro-Volkmer. The organisms have been deposited in the collection of the Aquatic Entomology Laboratory of the Federal University of São Carlos, SP, Brazil, except for the freshwater sponges that have been deposited in the Museum of Natural Sciences of the Zoobotanical Foundation, Rio Grande do Sul, RS, Brazil. We recorded 4 species of aquatic oligochaetes of the Naididae family (Table 1). Other authors have also found Naididae inhabiting aquatic animals: e.g., Kahl & Konopacka (1981) found high abundance of Naididae, particularly the genus Nais, living in Spongilla lacustris; Anderson & Holm (1987) and Fernandez et al. (1991) studied commensal and predatory relationships between Chaetogaster and mollusks; and Marcus (1941) referred to Naididae on Brazilian bryozoans. Oligochaetes probably are neither particularly characteristic of nor strongly connected with their hosts, as has been pointed out for sponges by Kahl & Konopacka (1981). However, more information is required on this matter, especially considering that commensalism in freshwater may involve evolutionary advantages, such as better feeding opportunities, increased mobility, protection from disturbances, and reduced risk of predation (Tokeshi, 1993).