New observations on seuratoid nematodes parasitic in fishes of the Paraná River, Brasil.

The present paper comprises a systematic survey of nematodes of the superfamily Seuratoidea collected from fishes of the Paraná River, southern Brazil, in 1992-1995. The following species were recorded: Neoparaseuratum travassosi Moravec, Kohn et Fernandes, 1992, Spectatus sp., Seuratoidea gen. sp. larvae, Cucullanus brevispiculus Moravec, Kohn et Fernandes, 1993, C. pinnai pinnai Travassos, Artigas et Pereira, 1928, C. pinnai pterodorasi subsp. n., C. rhamphichthydis sp. n., C. zungaro Vaz et Pereira, 1934, and Dichelyne pimelodi sp. n. C. pinnai pterodorasi (type host Pterodoras granulosus) differs from C. p. pinnai in the shape of the oesophagus and in the position of the nerve ring. C. rhamphichthydis (only females) (type host Rhamphichthys rostratus) is characterized mainly by the postoesophageal position of the excretory pore and deirids, complex structure of the cuticular lining of oesophastome and by markedly narrow body, whereas D. pimelodi (one male) (type host Pimelodus sp.) by the length of spicules (1.46 mm), postoesophageal position of the excretory pore and deirids and by the arrangement of genital papillae. Most species are briefly described (females of C. brevispiculus and Seuratoidea gen. sp. larvae for the first time) and illustrated and some problems concerning their taxonomy, hosts and geographical distribution are discussed.