Chaenocephalus aceratus

Chaenocephalus aceratus

In the blackfin icefish, 19 helminth species were recorded (from 3 to 13 species per host), including 3 species of trematodes, 4 species of cestodes, 5 species of nematodes and 7 species of acanthocephalans (table 3). Estimated species richness was 20 (Chao1), 24 (jackknife), or 22 (bootstrap) species. The diversity indices equalled 1.88 (Shannon), 0.78 (Simpson), and 0.63 (Pielou’s evenness).

All the cestode species, as well as nematodes of the genera Anisakis, Contracaecum and Pseudoterranova and acanthocephalans of the genus Corynosoma parasitized this fish host on the immature stages. Thus, C. aceratus is considered to be a definitive host for 7 out of 19 helminth species recorded. Nematodes predominated in the helminth community of blackfin icefish, they comprised 44.99 % of the total helminth number. The proportion of other groups of helminths was lower: 30.96 % for cestodes, 13.61 % for acanthocephalans, and 10.43 % for trematodes (fig. 1).

According to the prevalence, three species predominated in the helminth community in C. aceratus: the cestode Diphyllobothrium sp. (P = 100 %), the trematode N. georgiensis (P = 95.5 %), and the nematode Pseudoterranova sp. (P = 95.5 %) (table 3). Five other helminth species had an infection prevalence higher than 50 % and may be considered as subdominant species: bilocular and trilocular metacestodes, the nematode Contracaecum sp., and the acanthocephalans C. bullosum and C. hamanni. The nematode D. fraseri and the acanthocephalan C. evae were common, with an infection prevalence of 45.5 %. Other 10 species of helminths were found in less than 30 % of examined C. aceratus.