Parasites of elasmobranchs from the southern Gulf of Mexico: the bull shark Carcharhinus leucas (Müller & Henle, 1839) and the southern stingray Hypanus americanus (Hildebrand & Schroeder, 1928)

Elasmobranchs play an essential ecological role as top predators in marine ecosystems, and parasitological studies allow the assessment of both host health and the environmental conditions they inhabit. This study analyzed the parasitic diversity of two representative species from the southern coast of the Gulf of Mexico: the bull shark Carcharhinus leucas (Müller & Henle, 1839), captured at several fishing localities in the states of Campeche and Tabasco (Seybaplaya, Champotón, Ciudad del Carmen, and Barra de San Pedro), and the southern stingray Hypanus americanus (Hildebrand & Schroeder, 1928), collected in Seybaplaya, Campeche. In C. leucas, all ten examined specimens showed a 100% prevalence of parasitic infection, with a total of 175 individuals belonging to the groups Monogenea, Cestoda, Nematoda, and Copepoda. The identified taxa were Nesippus orientalis (Heller, 1865), Nemesissp. (Risso, 1826), Paralebion elongatus (Wilson, 1911), Erpocotyle carcharhini (Watson & Thorson, 1976), Granulinema carcharhini (Moravec & Little, 1988), and Nybelinia sp. (Poche, 1926), with cestodes being the most abundant group (64.57%). In 14 examined specimens of H. americanus, a total of 1,775 endoparasites were recorded (953 in males and 822 in females), belonging to the groups Cestoda and Nematoda. In this species, the genera Acanthobothrium (Van Beneden, 1849), Nybelinia (Poche, 1926), Oncomegas (Dollfus, 1929), Pterobothrium (Diesing, 1850), Phyllobothrium (Van Beneden, 1850), Grillotia (Guiart, 1927), and Anisakis (Dujardin, 1845) were identified. Oncomegas showed the highest prevalence (100%) and Phyllobothrium the lowest (7.14%), and Grillotia is reported for the first time in H. americanus from the Gulf of Mexico. Overall, the results reveal a high parasitic diversity dominated by cestodes, which may reflect alterations in coastal habitats. This study provides new parasite records and reinforces the value of parasitology as a tool for understanding biodiversity and assessing the ecological status of elasmobranchs from the southern Gulf of Mexico.