# New host-parasite relationship: Rocinela signata (Aegidae: Isopoda: Crustacea) found in green sea turtles in Brazil

## TL;DR

A new isopod species was found to parasitize green sea turtles in Brazil, possibly using tumors as a habitat.

## Contribution

This is the first report of Aegidae isopods parasitizing sea turtles, with implications for disease transmission.

## Key findings

- Five Rocinela signata isopods were found attached to fibropapillomas on green sea turtles.
- Two Rocinela sp. isopods were found on FP-free turtles, suggesting varied attachment sites.
- The isopods may use fibropapillomas as a microhabitat and could be a vector for chelonid herpesvirus 5.

## Abstract

Associations between isopods and sea turtles are rarely documented. Here we report, to our knowledge, the first record of aegid isopods parasitizing sea turtles: Rocinela signata Schiödte & Meinert, 1879 and Rocinela sp. on juvenile green sea turtles, Chelonia mydas (Linnaeus), in the Santa Cruz Wildlife Refuge, Espírito Santo, Brazil. Between 2021 and 2023, 322 juveniles underwent morphometric and health assessments, including scoring of epibionts and ectoparasites. In total, 142 turtles (44.1%) presented fibropapillomatosis (FP). Five R. signata were found attached to fibropapillomas on five different turtles, and two specimens of Rocinela sp. were collected from two FP-free turtles—one attached to the neck and one to the eye. The consistent localization of R. signata on FP lesions suggests these tumors provide a favorable microhabitat, potentially via shelter and access to vascularized tissue. Given the capacity for R. signata to remain attached for prolonged periods, we hypothesize that R. signata may establish persistent parasitic associations with sea turtles and merits investigation as a potential vector of chelonid herpesvirus 5 (ChHV5). We discuss the possibility that post-disaster environmental stressors following the 2015 Fundão tailings dam collapse contributed to conditions favoring this novel host–parasite interaction.