Diversity, ecological status and species associations of myxozoans (Cnidaria: Myxosporea) parasites of Labeo senegalensis Valenciennes, 1842 (Cyprinidae) from lake Maga in Cameroon.

Abstract

Classical parasitological methods, including fish autopsy and search of myxozoan species, were applied to examine 229 specimens of Labeo senegalensis collected monthly from Lake Maga, Cameroon, between October 2018 and August 2019. The myxosporean fauna of L. senegalensis was diverse and abundant, with 16 species recorded. Among these, Myxobolus sp.2, Myxobolus sp.6, Myxobolus sp.10, Thelohanellus sp.2, and Thelohanellus sp.3 were common. Intermediate occurrence was observed for Myxobolus sp.1, Myxobolus sp.3, Myxobolus sp.4, Myxobolus sp.5, Myxobolus sp.7, Myxobolus sp.8, Myxobolus sp.11, Thelohanellus sp.1 and Thelohanellus sp.4, whereas Myxobolus sp.9 and Myxidium sp. were scarce. The mean cyst load was high for Myxobolus sp.2, Myxobolus sp.5 and Thelohanellus sp.1; low for Myxobolus sp.3, Myxobolus sp.4, Myxobolus sp.6, Myxobolus sp.8, Myxobolus sp. 11, Thelohanellus sp.2 and Thelohanellus sp.3; and very low for Myxobolus sp.1, Myxobolus sp.7, Myxobolus sp.9 and Thelohanellus sp.4. Multiple infections were common: parasitism by five species occurred most frequently (26.8 %), followed by parasitism by six species (18.7 %). Monospecific infections were rare, with only four cases (1.8 %) recorded. Dice's coefficient combined with Forbes' index revealed eight strong associations between pairs of parasite species, significantly deviating from random expectations; six of these involved common parasite species. Conversely, five associations were less frequent than expected and involved species that typically colonized distinct host organs. Analysis of cyst load correlations indicated 15 positive and 8 negative Kendall's rank correlations among species. These findings suggest that polyspecific infections and positive interspecific interactions may contribute substantially to the pathogenic potential of myxozoan parasites in L. senegalensis.