LARVAL PSEUDOPROLEPTUS SP (NEMATODA: CYSTIDICOLIDAE) FOUND IN THE AMAZON RIVER PRAWN MACROBRACHIUM AMAZONICUM (DECAPODA: PALAEMONIDAE) IN BRAZIL

Previously undescribed infective larvae of the cystidicolid nematode Pseudoproleptus sp. (probably conspecific with the nematode originally described as Heliconema izecksohni Fabio, 1982, a parasite of freshwater fish in Brazil), were found encapsulated in the hemocel of the Amazon river prawn Macrobrachium amazonicum (Heller) (Decapoda: Palaemonidae) from the natural canals on the Mexiana Island (Amazon River Delta), Para State, Brazil. The prevalence in prawns (body length 48-110 mm) examined in January and March 2008 (n = 44) was 32%, with an intensity of 1-6 (mean 2) larvae per crustacean. The nematode larvae (body length 19.7-25.7 mm), characterized by the cephalic end provided with a helmet-like cuticular structure having a thickened free posterior margin, are described based on light and scanning electron microscopy. Apparently prawns play a role as intermediate hosts for this nematode species. This is the first record of a larval representative of Cystidicolidae in South America and the first record of it species of Pseudoproleptus Khera, 1955, in the Neotropics. Heliconema izecksohni is transferred to Pseudoproleptus as Pseudoproleptus izecksohni (Fabio, 1982) n. comb.