# The First Report of Pennella (Crustacea: Copepoda) Infesting Stenella coeruleoalba Stranded in Malta: Morphological and Genetic Analyses

## TL;DR

A dead striped dolphin in Malta had a severe infestation of a large mesoparasite, suggesting a link between parasite levels and dolphin health.

## Contribution

First report of Pennella balaenoptera infesting a striped dolphin in Maltese waters, combining morphological and genetic analyses.

## Key findings

- Severe infestation of Pennella balaenoptera observed in a dead striped dolphin.
- Morphological and genetic analyses confirmed the parasite species.
- High parasite load may indicate compromised health of the host.

## Abstract

A striped dolphin was found dead in Maltese waters in July 2020, displaying a severe infestation of the mesoparasite Pennella balaenoptera. This parasite is the largest known mesoparasite to grow on cetaceans and the level of infestation is typically associated with the health status of its host. This incident emphasizes the importance of monitoring the presence of these parasites, to better understand the health of dolphins in the area and to contribute to conservation efforts.

Here, we document the stranding of a striped dolphin Stenella coeruleoalba (Meyen, 1833) (Mammalia: Delphinidae), which was found dead in Maltese waters in July 2020. The stranded dolphin exhibited a severe infestation of the mesoparasitic copepod, Pennella balaenoptera Koren and Danielssen, 1877 (Copepoda: Pennelidae). Parasites of this genus represent the largest known mesoparasites to infest cetaceans. Under normal circumstances, cetaceans may have a few P. balaenoptera individuals attached to them, but cetaceans with compromised health are more prone to heavy infestations. The identification of the parasite was accomplished through morphological and genetic analyses. This incident highlights the significance of monitoring mesoparasitic infestations, offering valuable insights into the health of cetacean populations and emphasizing the potential implications for conservation efforts in the region.