Cucullanus lithodorasi n. sp. (Nematoda: Cucullanidae), a parasite of Lithodoras dorsalis (Siluriformes: Doradidae) on the north coast of Brazil.

Cucullanus lithodorasi n. sp. (Nematoda: Cucullanidae), collected from the intestine of Lithodoras dorsalis (Siluriformes) and waters of the north coast of Brazil is described based on light and scanning electron microscopic observations.

Sperm characters of the aspidogastrean Rohdella amazonica (Aspidogastridae, Rohdellinae), a parasite of the banded puffer fish Colomesus psittacus.

The ultrastructural characteristics of the mature spermatozoon of the aspidogastrean Rohdella amazonica (Aspidogastridae, Rohdellinae) were studied by means of transmission electron microscopy. The sperm cell shows two axonemes of the 9 + '1' trepaxonematan pattern of Platyhelminthes, parallel cortical microtubules, a well-developed lateral expansion, external ornamentation of the plasma membrane, one mitochondrion, an electron-dense ring, a nucleus and granules of glycogen. The present results were compared with those observed in the aspidogastreans studied to date and in other Platyhelminthes.