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Infection with a novel pentastome (Raillietiella sp.) in a juvenile endangered Galápagos tortoise (Chelonoidis niger)

Abstract:

Pentastomes are crustacean endoparasites in the lungs of herpetofauna and rarely mammals and birds. To date, the only pentastomes reported in chelonians, all aquatic turtles, are Diesingia megastomum from Brazil and Pelonia africana from South Africa. In March 2021, 185 juvenile tortoises (Chelonoidis niger) were confiscated after an attempted illegal exportation from the Galápagos. It is believed the tortoises were removed from nests on Santa Cruz Island. The young tortoises were individually wrapped in plastic and at seizure ten were dead and another 25 tortoises subsequently died. One of the tortoises, estimated to be 3 months old, had 11 pentastomes in the lungs. The pentastomes were identified as a Raillietiella sp. based on morphology. The specimens had a claviform body that tapers into a bifid tail, a 165.3 μm × 92.1 μm buccal cadre, and sharp tipped anterior and posterior hooks with the posterior hooks being larger than the anterior. The males have smooth copulatory spicules with a rounded, smooth base. All females were gravid. Molecular analysis confirmed that the parasites were a Raillietiella sp. Based on the COI gene, it was most similar (82.7% identical) to an undescribed Raillietiella species from a Caribbean anole (Anolis cristatellus) found in Florida followed by R. hebitihamata (81%), R. indica (80.7%), and R. orientalis (78.8–80.7%). Based on the 18S rRNA gene sequence (1799 bp), it was most similar (99.3% identical) to two undescribed Raillietiella species followed by R. aegypti from a berber skink (Eumeces schneideri) from Saudia Arabia. Phylogenetically, with both molecular targets, the Raillietiella sp. from the Galápagos tortoise grouped with other Raillietiella spp. and was basal within the group. Currently, the origin of this parasite (native to Galápagos or introduced) and the life cycle are unknown. Because some pentastome species, especially when in aberrant hosts, can be pathogenic, additional studies of parasites in native and introduced reptile and amphibian species in the Galápagos are needed to better understand the risk this parasite poses to Galápagos tortoises.