Transmission route used by parasitic lasidium larvae of the freshwater mussel Anodontites trapesialis on guppies Poecilia reticulata during short cohabitation

Abstract

We describe for the fi rst time the transmission route employed by the parasitic larvae of the fresh water mussel Anodontites trapesialis (Lamarck, 1819) during cohabitation on the guppy Poecilia reticulata Peter, 1859. The freshwater mussel and fi sh-host were employed as a model system to in vestigate the infection and parasite establishment. Laboratory experiments included video recording and histopathological analysis of the infection. In vivo video observations demonstrated that lasidium larvae could be transmitted to guppies during direct contact. A series of histology samples and pho tography suggest that this larva attaches and colonizes possibly on-site on the outer surface of the fish, causing cellular infl ammation in the epidermis layer with cellular hyperplasia in the zone of para site attachment. An evident hyaline layer, cellular hypertrophy, and a large number of undifferentiated proliferating cells were observed. Hemorrhagic tissue and swelling were observed in the epidermis and dermic zone. The total number of larvae per male and female guppy was 525 ± 86 and 494 ± 167, respectively. No parasitic preference was detected for male versus female parasitized fish.