Neotropical Monogenoidea. 52. Diechodactylus joaberi n. g., n. sp. from the banded knifefish Gymnotus carapo (Gymnotiformes: Gymnotidae) in southeastern Brazil.

Diechodactylus joaberi n. g., n. sp. is described from the body surface of the banded knifefish Gymnotus carapo L. (Gymnotiformes: Gymnotidae) from southeastern Brazil. The new genus is proposed to accommodate species with five pairs of hooks in anterior bilateral clusters on the haptor, three pairs of hooks in a single cluster on the posterior margin of the haptor, sclerites R1 associated with the superficial bar, and confluent intestinal caeca. The presence of five pairs of hooks in two bilateral clusters anterior in the haptor permits the differentiation of species of Diechodactylus from species of all known genera of the Gyrodactylidae. The genus is likely a member of a clade of the Gyrodactylidae comprising genera with a similar hook distribution.

[Parasitism of Hoplias malabaricus (Bloch, 1794) (Characiformes, Erythrinidae) by Quadrigyrus machadoi Fábio, 1983 (Eoacanthocephala, Quadrigyridae) at a pond, Aguaí, State of São Paulo, Brazil]. / Parasitismo de Hoplias malabricus (Bloch 1794) (Characiformes, Erythrinidae) por Quadrigyrus machadoi Fábio, 1983 (Eoacanthocephala, Quadrigyridae) de uma lagoa em Aguai, Estado de São Paulo, Brazil.

The parasitism of trahira, Hoplias malabaricus, by the acanthocephalan Quadrigyrus machadoi was studied. Fish were collected at a pond located on Palmeiras Farm (21 degrees 59'19''S, 47 degrees 12'04''W), municipal district of Aguaí, São Paulo, Brazil, during the period of January, 2002 to May, 2003. Among the 64 specimens analyzed, 56 (prevalence=87.5%) were infected with three to 573 specimens of Quadrigyrus machadoi (mean intensity=119.0+/- 120.6 and mean abundance=104.1+/-119.4). Most of the parasites were found in the mesenterium as cystacanths. Some fish contained adult female parasites in the intestine, but gravid females were not verified. Parasite indices were analyzed in relation to the biological parameters of sex and standard length of the trahira, as well as with regard to the dry and the rainy periods defined for the area. No differences in parasite indices between sexes were found. The smaller specimens were the most extensively infected and had higher intensities of infection than fish of greater lengths. No seasonal variations in prevalence, mean intensity of infection and mean abundance values were found. The health of the fish was not influenced by the presence of parasites, as shown by the relative condition factor.