Os parasitas são considerados elementos integrantes dos ecossistemas aquáticos e fornecem informações sobre a influência da degradação ambiental na riqueza e distribuição de espécies. Relatar a distribuição das espécies de Helmintos de Hoplias malabaricus em regiões da Amazônia com diferentes graus de desmatamento. O estudo foi realizado por meio de bancos de dados online sobre a fauna parasitária de H. malabaricus em Estados da Amazônia Legal e dados de amostragem da fauna parasitária de peixes no Acre e sul do Amazonas. A helmintofauna de H. malabaricus foi analisada e identificada em laboratório. Índices parasitários e análises estatísticas avaliaram a influência do desmatamento na riqueza e composição de espécies parasitárias. Um total de 42 espécies de parasitas de H. malabaricus foram distribuídos em seis estados da Amazônia legal. Nos níveis local (Municípios) e regional (Estados), o tamanho das áreas desmatadas influenciou negativamente a riqueza de espécies parasitárias, quanto maior a taxa de desmatamento nos ambientes, menor a riqueza de espécies parasitárias. Em conclusão, H. malabaricus apresentou uma fauna parasitária rica e bem distribuída por toda a Amazônia. Além disso, os efeitos do desmatamento em algumas regiões foram mais pronunciados em táxons de parasitas heteroxenos do que em monoxenos.

The Amazon region may present a high diversity of endoparasites with a high degree of endemism. In this sense, this study describes the endoparasite fauna in freshwater fish from the Upper Juruá, in the Western Amazon. The study was carried out around the municipalities of Cruzeiro do Sul, state of Acre, and Guajará, state of Amazonas, Brazil. Fish were caught between periods of droughts and floods, using passive and active sampling methods. In the laboratory, specimens were biometrically analysed and necropsied. As a result, a total of 23,740 endoparasites were recorded, belonging to 62 species, with 91 new host reports and 91 new occurrences for the Western Amazon. Nematoda and Digenea were the most diverse and abundant groups, and the increase in host fish richness and diversity influenced the diversity and richness of endoparasites in the environments. In this sense, the present study expands the number of new reports, and contributes data on the distribution and richness of endoparasites for South America.

Prochilodus nigricans is extensively exploited in fishing and aquaculture activities in the Brazilian Amazon, it is the definitive host for Neoechinorhynchus curemai Noronha, 1973. Thus, the present study aimed to evaluate the occurrence of N. curemai in P. nigricans and the parasite-host relationship in three rivers (Juruá, Crôa and Môa) in the municipality of Cruzeiro do Sul, state of Acre, Brazil. Fish were caught, weighed, measured, and subjected to necropsy, and the gastrointestinal tract and viscera were analyzed. A total of 178 specimens of N. curemai were found in 61 infected fish, with the (p= 58.62%). The prevalence, mean intensity, and mean abundance were higher in hosts from the Môa River, and lower from the Juruá River. Regarding the length-weight relationship, the b-value did not differ statistically from three (b=3) for fish species in the three locations, nor in parasitized and non-parasitized species. In addition, growth was considered isometric, and in the case of the relative condition factor, there was no difference in fish hosts between the three rivers. The correlation between parasite intensity, condition factor, length, and weight of P. nigricans was not significant. Thus, this parasite infestation varied between the habitats. However, this did not influence the growth and development of the hosts.

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