Linking adults and cystacanths of a new species of Rhadinorhynchus Lühe, 1911 (Acanthocephala: Rhadinorhynchidae) from the Pacific coast of Mexico by using morphological and molecular data

Syst Parasitol (2025) 102:10 https://doi.org/10.1007/s11230-024-10205-9 Linking adults and cystacanths of a new species of Rhadinorhynchus Lühe, 1911 (Acanthocephala: Rhadinorhynchidae) from the Pacific coast of Mexico by using morphological and molecular data Mayra I. Grano‑Maldonado · Ana L. Sereno‑Uribe · José Carlos Hernández Payán Gerardo Pérez‑Ponce de León · Martín García‑Varela · Received: 29 September 2024 / Accepted: 4 November 2024 © The Author(s) 2024 Abstract During parasitological surveys of marine fishes and zooplankton in localities of the Northwestern Pacific coast of Mexico, 28 Gafftopsail pompano (Trachinotus rhodopus Gill) and 50 mysid crustaceans (Metamysidopsis frankfiersi Hendrickx & Hernández-Payán) we identified to be infected with adults and cystacanths, respectively of an acanthocephalan morphologically corresponding to the genus Rhadinorhynchus Lühe, 1911. DNA sequences of the small (SSU) and large (LSU) subunits of ribosomal DNA, and cytochrome c oxidase subunit 1 (cox 1) from mitochondrial DNA were obtained. Phylogenetic analyses revealed that the newly sequenced M. I. Grano‑Maldonado Facultad de Ciencias del Mar, Universidad Autónoma de Sinaloa, Av. Claussen s‑n, Mazatlán, Sinaloa, México A. L. Sereno‑Uribe · M. García‑Varela (*) Departamento de Zoología, Instituto de Biología, Universidad Nacional Autónoma de México, Ciudad Universitaria, C.P. 04510 Ciudad de México, México e-mail: J. C. H. Payán Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Av. Ciudad Universitaria 3000, C.P. 04510 Coyoacán, Ciudad de México, México G. P.-P. de León Escuela Nacional de Estudios Superiores unidad Mérida, Universidad Nacional Autónoma de México, Tablaje Catastral N°6998, Carretera Mérida‑Tetiz Km. 4.5, Municipio de Ucú, 97357 Mérida, Yucatán, México individuals in a clade with Rhadinorhynchus sp. from carangids in other localities of the Pacific coast of Mexico; together, all these individuals formed an independent lineage that is recognized herein as a new species, Rhadinorhynchus trachinoti n. sp. The new species is morphologically distinguished from the other 38 congeners by having a long and cylindrical proboscis armed with 12 longitudinal rows bearing 16–18 hooks each. The ecological information gathered from the parasites, together with genetic evidence, confirms that the Gafftopsail pompano is the definitive host of R. trachinoti n. sp., while mysid crustaceans serve as the intermediate host. Current records also indicate that R. trachinoti n. sp. is distributed along the Pacific coast of Mexico, from Mazatlán, Sinaloa in the north to Puerto Angel, Oaxaca in the south. This distribution aligns with the Mexican Coastal Current, which extends from the Gulf of Tehuantepec in Oaxaca to the entrance of the Gulf of California and southern Baja California. Introduction The helminth parasite diversity of marine fishes along the Pacific coast of Mexico has been documented for several decades, revealing a large biodiversity for some helminth groups such as monogeneans, digeneas, cestodes, nematodes and, to a lesser extent, acanthocephalans (Pérez-Ponce de León et al., 2007; García-Prieto et al., 2010; Violante-González et al., Vol.: (0123456789) 10 Page 2 of 15 2016, 2020; Villalba-Vasquez et al., 2022; MartínezFlores et al., 2023). The first record of an acanthocephalan parasitizing marine fishes is Mexico dates back to 1940 when the species Filisoma bucerium Van Cleave 1940 was reported from the Cortez Sea chub (Kyphosus elegans) (Peters) in Socorro Island (Van Cleave, 1940); since then, other seven adult acanthocephalans have been recorded, including Echinorhynchus gadi Zoega in Müller, 1776; Koronacantha mexicana Monks & Perez-Ponce de León, 1996; K. pectinaria (Van Cleave, 1940); Floridosentis pacifica Bravo-Hollis, 1969; Neoechinorhynchus roseum Salgado-Maldonado, 1978; Pomphorhynchus rocci Cordonnier & Ward, 1967, and an unidentified species of the genus Rhadinorhynchus Lühe, 1911; these species represent 12.3% of the biodiversity of acanthocephalans in Mexico (see García-Prieto et al., 2010; Martínez-Flores et al., 2023; Osuna-Cabanillas et al., 2024). Members of the genus Rhadinorhynchus are endoparasites of marine fishes throughout the world (Amin et al., 2011; Amin, 2020). Morphologically, the genus is characterized by having a long and cylindrical proboscis, with hooks of different sizes, trunk cylindrical, spinose anteriorly in one or two fields, neck prominent, proboscis receptacle longer than proboscis, lemnisci digitiform, gonopore terminal or subterminal; males possessing four cement glands and females possessing eggs with polar prolongation. The genus currently contains 39 species (Amin et al., 2011, 2019; Lisitsyna et al., 2019; Amin, 2020) although the WoRMS database consider 49 species (Gibson and Wayland, 2024) indicating that the species composition within the genus remains unsettled. It is well known that species of Rhadinorhynchus have diversified in marine environments and that they can infect fishes from the families Carangidae, Salmonidae, Scombridae Terapontidae, Tetradontidae, and Trichuridae (Amin et al., 2019; Amin, 2020; Violante-González et al., 2020; Santos-Bustos et al., 2021; Osuna-Cabanillas et al., 2024). Carangids (jacks and pompanos) play a principal role in the marine ecosystem and are economically important fish. Particularly, the Gafftopsail pompano (Trachionotus rhodopus Gill) is distributed mostly in marine tropical and subtropical waters across the Americas; it feeds mainly on crustaceans (zoea larvae, copepods, isopods, mysids, amphipods, and decapods) fishes, annelids, mollusks, sipunculids and Vol:. (1234567890) Syst Parasitol (2025) 102:10 algae (Thompson et al., 1979; Danemann, 1993). Due to its high abundance and common landings of artisanal fishing fleets, it has been targeted for metazoan parasites studies in some localities of Pacific coast of Mexico (e.g., Martínez-Flores et al., 2023; OsunaCabanillas et al., 2024). During a survey of parasitic helminths on the North Pacific coast of Mexico, adult specimens of an acanthocephalan were recovered from the digestive tract of Gafftopsail pompano (T. rhodopus), and cystacanths were obtained from the hemocoel of a recently described species of mysid crustacean, Metamysidopsis frankfiersi (Hendrickx & HernándezPayán, 2023). After a morphological examination of worms from both developmental stages, adults and cystacanths were identified as an undescribed species of Rhadinorhynchus sp. Therefore, the objectives of this study were: i) to describe a new species of Rhadinorhynchus from the Gafftopsail pompano (T. rhodopus) from the North Pacific coast of Mexico; ii) to link the cystacanths recovered from the mysid (M. frankfiersi) with the adult specimens from fish; iii) to test the systematic position of the new species among other congeners by using small (SSU) and large (LSU) subunit from nuclear ribosomal DNA (...truncated)