Bomolochidae Claus, 1875 (Cyclopoida: Copepoda) Parasitizing the Marine Fishes of Kerala Coast (India): Host-Parasite Interaction and Species Diversity

Abstract

Purpose

This study aims to assess region-wise host-parasite interaction and diversity indices of bomolochid species infecting marine fishes along the Kerala coast. Also, it aims to generate COI barcodes and analyse the phylogenetics.

Methods

Marine fish species along the Kerala coast were sampled for the period 2016–2023 and examined for parasitization by bomolochid copepods. Host preference, prevalence, site-specificity, mean intensity, and biodiversity indices of recovered parasite species were assessed specifically in northern and southern regions of this coast. Mitochondrial COI sequences from bomolochid species were also generated, and their phylogenetic relationships were assessed with those of their counterparts found in the NCBI database.

Results

Among the sampled fishes, 21 species from 20 genera and 14 families showed parasitization with 20 species of bomolochids. Four host families: Sciaenidae, Acanthuridae, Engraulidae, and Sillaginidae were recorded as new to the bomolochid infection along the Indian coast. Recovered bomolochid species, including nine Bomolochus species, six Nothobomolochus species, two Pumiliopes species, and one each of Pseudorbitacolax, Ceratocolax, and Orbitacolax species, with overall prevalence ranging from 0.28% to 57%. 65% of species prefer single-host, and 35% rely on two or three host species. The northern region encompassed all 20 bomolochid species, whereas only 10 species represented the southern region. Six species showed no region-specific host preference, but their prevalence showed marked differences (4.8–73.8%). The host preference of some bomolochid species spans multiple fish species within the same genus or family, as well as across different genera and families, with a varying degree of prevalence, either region-dependent or independent. The northern region displayed the highest species richness and diversity index compared to the southern region. However, the evenness values from both regions were found to be similar. The mitochondrial COI sequences from five bomolochid species signify the reliability of COI DNA barcoding for the identification of bomolochids at the species level. The analysis of phylogenetic relationships with those of its counterparts found in the NCBI database revealed that Bomolochidae constituted a biphyly topology that is distinct from that of the outgroup, i.e., Harpacticoida.

Conclusion

The generated information on bomolochid new host record, host preference, prevalence, site specificity, seasonality, diversity and genetic divergence forms the basis not only for further exploration of the species diversity and genetic variation of bomolochids but for analyzing the ecological and evolutionary aspects of species diversity and genetic variation of bomolochids and new host record along the Indian coasts and Indo-pacific region as well.