# Phylogenetic Placement of Whittingtonocotyle Neto, Rodrigues & Domingues, 2015 (Monopisthocotyla: Dactylogyridae) Inferred from the First Molecular Data of Both Described Species

## TL;DR

This study uses molecular data to determine the evolutionary placement of the parasite genus Whittingtonocotyle, finding it to be a distinct group closely related to Urocleidoides.

## Contribution

The first molecular analysis of Whittingtonocotyle species, revealing their monophyly and phylogenetic relationships.

## Key findings

- Whittingtonocotyle is a strongly supported monophyletic lineage.
- It is closely related to Urocleidoides species that infect the same host fish.
- Morphological and molecular data show partial incongruence, suggesting the need for more data.

## Abstract

This study provides the first molecular assessment of the two species of the genus Whittingtonocotyle, parasites of the erythrinid fish Hoplerythrinus unitaeniatus. The main objective was to evaluate the phylogenetic cohesion of Whittingtonocotyle and to explore its preliminary phylogenetic affinities within Dactylogyridae based on available molecular and morphological evidence.

Morphological examinations were performed in parallel with analyses of partial LSU rDNA and COI mtDNA sequences. Phylogenetic reconstructions were conducted independently for each marker to assess the monophyly of Whittingtonocotyle and to evaluate its relationships with other dactylogyrid taxa included in the available comparative dataset.

Both molecular datasets consistently recovered Whittingtonocotyle as a strongly supported monophyletic lineage. In the phylogenetic reconstructions, Whittingtonocotyle was recovered in proximity to Urocleidoides species parasitizing erythrinid fishes, although deeper backbone relationships showed limited statistical support.

Morphological data support the recognition of Whittingtonocotyle as a distinct genus, whereas molecular analyses indicate a close phylogenetic proximity to erythrinid-associated Urocleidoides. This partial incongruence, together with the limited resolution of deeper relationships, highlights the need for expanded taxon sampling and multilocus datasets to fully resolve the evolutionary placement of Whittingtonocotyle within Dactylogyridae.

The online version contains supplementary material available at 10.1007/s11686-026-01239-8.