Stowaways: Marine Leeches Infecting Olive Ridley Sea Turtles Entangled in Ghost Nets in Maldivian Waters

ABSTRACT: Sea turtles are known to host a wide variety of organisms, including parasitic marine leeches of the family Ozobranchidae. Leeches are sanguivorous (blood feeders) and are typically found on soft skin areas of turtles, such as the cloaca and corners of eyes and mouth. Superinfection with this parasite can lead to severe damage to the host. Additionally, Ozobranchidae have been shown to be a potential candidate as a mechanical vector for the tumor-inducing fibropapilloma-associated turtle herpesvirus. Marine Ozobranchidae have been found in all major ocean basins infecting all hard-shelled sea turtle species. Records from the Indian ocean are scarce but indicate a widespread distribution. In this study, we present the first cases of ozobranchid leeches found on sea turtles in the Maldives. The host turtles were entangled in abandoned, lost, or discarded fishing nets (also known as ghost nets), and treated at the Olive Ridley Project's Marine Turtle Rescue Centre in Baa Atoll in the Maldives. All hosts were olive ridley turtles (Lepidochelys olivacea), which are typically not resident to the country, but are often observed entangled in ghost nets. The entangled turtles are thought to be carried over great distances when floating in various ocean currents. Ozobranchid leeches were identified to the species level with morphological and barcoding methods and compared to previously published sequences from around the globe. The presence of parasitic leeches on entangled turtles and potential epidemiological implications for the endemic populations of sea turtle species throughout the Indian Ocean are discussed.