Lernanthropids (Siphonostomatoida: Copepoda) parasitizing the marine fishes of Kerala Coast (India): Species diversity, phylogeny and host-parasite interaction

This study provides new information on the distribution of 17 known species of lernanthropids recovered from 25 species of commercially valuable marine fishes of the Kerala coast, including two new host records. The sampled species comprised five genera viz. Lernanthropus, Lernanthropinus, Mitrapus, Aethon and Sagum, of which Aethon appeared dominant with the prevalence of 67.99 %. Lernanthropus comprised 10 species with the prev-alence ranged from 3.20-64.15 %, followed by Lernanthropinus comprising 4 species with the prevalence 4.8-43.04 %. Aethon, Sagum and Mitrapus were monotypic with the prevalence of 67.99 %, 33.77 % and 23.21 %, respectively. The data on host specificity revealed that approximately 59 % of the lernanthropid species prefer single host specific infection, while the remaining showed double or quadruple host parasitization. Seasonal prevalence revealed highest infection during post-monsoon and a gradual decrease towards monsoon season. Among the total species recovered, nine species belonging to the genera Lernanthropus, Lernanthropinus, Mitrapus and Aethon were found common to both northern (Malabar) and southern (Cochin) sampling stations of Kerala coast. Six species (belonging to Lernanthropus, Lernanthropinus and Sagum) were noticed exclusively to the Malabar coast; on the other hand, two species of Lernanthropus were recovered only from the Cochin coast. Diversity indices data revealed that, among the sampling stations, 'Ayikkara' along the northern Kerala coast showed the highest species richness (1.37 +/- 0.31) and diversity index (2.45 +/- 0.16) than that of the southern coastal regions. This study also attempted to resolve phylogenetic relationships among 12 lernanthropid species under 5 genera. The data confirmed the monophyletic lineage of lernanthropids from that of the taxa of Caligidae and Bomolochidae. Further, the species were examined for their phylogenetic relatedness with their counter parts retrieved from the literature. New records of COI barcode sequences for eight lernanthropid species are also provided.

Automated summary

This study provides new information on the distribution of 17 known species of lernanthropids recovered from commercially valuable marine fishes. It identifies the dominant species and provides insights into host specificity and seasonal prevalence. The study also examines phylogenetic relationships among lernanthropid species and provides new records of COI barcode sequences.