Morphological identification and first molecular characterization of Lobothorax typus (Isopoda: Cymothoidae) parasitizing Trichiurus lepturus (Scombriformes: Trichiuridae) in the Philippines

Parasitic diseases pose a threat to fisheries, negatively affecting the livelihood and food security of billions of people worldwide. Among these, parasitic isopods of fish are not well documented and studied. Thus, we examined the buccal cavity of 385 randomly selected saltwater fishes sold in a fish market in Naic, Cavite, Philippines. Here, 7/385 (1.82%) saltwater fishes, exclusively Trichiurus lepturus, harbored a parasitic isopod. Morphological observation and sequencing analysis of cytochrome c oxidase I (COI) and 16S rRNA genes confirmed the identity as Lobothorax typus. Phylogenetic tree based on these sequences showed that it is closely related to isolates from India and Japan. As such, further studies on the risk factors associated with L. typus infestation are urgently needed.