Morphological abnormalities in the cladoceran Ilyocryptus spinifer (Apipucos Reservoir, Pernambuco State, Brazil).

In a sample taken from Apipucos Reservoir (Recife, PE, Brazil) for taxonomic study, a high percentage (40%) was found of cladoceran Ilyocryptus spinifer individuals with morphological abnormalities on their postabdomen. There was not a fixed pattern of the malformations, which varied in gravity, and could affect the postanal spines or terminal claws. The postabdominal abnormalities are described and compared to the ones described in the literature. The hypothesis of the morphological abnormalities being induced by an occasional environmental toxicant is discussed.