Twenty three species of the strongylid nematodes (18 Cyathostominae and five Strongylinae) were collected 33 equines in Metropolitana region of Rio de Janeiro State, Brazil. Cylicostephanus longibursatus (90.9%; 1,078.4), Cylicostephanus goldi (81.8%; 236.9) e Cylicocuclus nassatus (75.8%; 39.1) were the most prevalent and abundance species, respectively. Cylicostephanus longibursatus showed highest dispersion (2,425.1) and one of smallest aggregation value (0.1). Five infracommunities (2, 3, 11, 24 and 25) showed equal parasite richness (4.0), however the values obtained from diversity indices were different because the unequal evenness of these samples.

Vinte e três espécies de nematóides estrongilídeos (18 Cyathostominae e cinco Strongylidae) foram coletadas de alíquotas, com aproximadamente, 10% do cólon dorsal de 33 eqüinos, provenientes da região Metropolitana do estado do Rio de Janeiro. Cylicostephanus longibursatus (90,9%; 1.078,4) C. goldi (81,8%; 236,9) e Cylicocyclus nassatus (75,8%; 39,1) foram as espécies mais prevalentes e com maior abundância média, respectivamente. Cylicostephanus longibur-satus apresentou o maior Índice de Dispersão (2.524,1) e menor Índice de Green (0,1), devido à presença em quase todas as infracomunidades, e ao baixo nível de agregação dos espécimes nas mesmas. Cinco infracomunidades (2, 3, 11, 24 e 25) apresentaram riqueza parasitária igual a quatro, porém os índices de Shannon e de uniformidade de Pielou foram distintos, devido à equitabilidade das infrapopulações

A quantitative and qualitative analysis of the parasite fauna of the sciaenid Stellifer minor (Tschudi) from Chorrillos, Peru, was made. Some characteristics of the infectious processes, in terms of intensity and prevalence of infection, as a function of host sex and size, are given. Moreover, comments on the characteristics of the parasite fauna, related with host role in the marine food webs are included. The parasite fauna of Stellifer minor taken of Chorrillos, Peru, include the monogeneans Pedocotyle annakohni, Pedocotyle bravoi, Rhamnocercus sp. and Cynoscionicola sp., the digenean Helicometra fasciata, the adult acantocephalan Rhadinorhynchus sp. and the larval Corynosoma sp., the nematode Procamallanus sp., the copepods Caligus quadratus, Clavellotis dilatata and Bomolochus peruensis and one unidentified isopod of the family Cymothoidae. A distinctive characteristic of the parasite fauna (Metazoa) of S. minor is the almost absence of larval forms.

The presence of three aspidocotyleans trematodes in marine fishes from Perú and Chile is reported. One of them, Lobatostoma veranoi from the intestine of Menticirrhus ophicephalu (Sciaenidae) is considered a new species. Distinct characteristcs of the new species are:a cirrus sac smaller than the pharynx; tail overlapping posteriorly the ventral disk; testis in the last third of the body and the presence of 64-66 marginal alveoli. The two other species are Lobatostoma pacificum Manter, 1940 found in Trachinotus paitensis Cuvier, 1830 from Perú and Chile and Lobatostoma Anisotremum Oliva & Carvajal, 1984 from the intestine of Anisotremus scapularis (Tschudi, 1844) from Perú.