Evidence from integrative taxonomy reveals non-monophyly in Pseudocharopinus (Copepoda: Lernaeopodidae), with description of a new species from the Southwestern Atlantic

Abstract

A new species, Pseudocharopinus tenshken n. sp., is described and illustrated as a parasite of juvenile Squalus acanthias from Argentine waters in the South Atlantic. Although morphologically similar to Pseudocharopinus bicaudatus, a species widely distributed on the same host, distinct morphological differences are evident. The new species differs from P. bicaudatus in its dorsal shield, which is more elongated and has more developed sclerites. Additionally, the cephalothorax of the new species reaches 82% of the trunk length, whereas it is shorter in P. bicaudatus. In contrast, the maxilla in P. bicaudatus extends up to 65% of the trunk length, while in P. tenshken n. sp., it reaches 76% of the trunk length. These morphological distinctions are supported by a genetic divergence of 17% from P. bicaudatus. In the COI phylogenetic tree, a strongly supported clade is observed, consisting of (Pseudocharopinus malleus (P. bicaudatus + Lernaeopoda bivia)). Then, Salmincola spp. appears in a clade with low support, followed by Pseudocharopinus pillai. Later, another strongly supported clade includes (Pseudocharopinus tenshken n. sp. (Brianella corniger + Pseudocharopinus pteromylaei)). Based on our results, the genus Pseudocharopinus should be considered non-monophyletic. These findings suggest that at least two independent Lernaeopodid infection events occurred in chondrichthyans.