Welcome back to life: Validating the genus Illiosentis Van Cleave and Lincicome, 1939 (Leptorhynchoididae: Palaeacanthocephala), with the description of a new species from the pigfish (Orthopristis chrysoptera: Haemulidae) in Yucatán Peninsula, Mexico

The haemulid fish Orthopristis chrysoptera commonly known as pigfish is distributed in the Western Atlantic coast, Caribbean Sea and Gulf of Mexico. Specimens of O. chrysoptera sampled off the coast of Sisal, Yucatán, in the Gulf of Mexico were infected with two species of acanthocephalans from the family Leptorhynchoididae. One of them was identified as Dollfusentis bravoae and the other was allocated into the genus Illiosentis. However, the taxonomic status of Illiosentis has been controversial since it has been proposed as synonym of Tegorhynchus. Here, sequences the small (SSU) and large (LSU) subunits from the nuclear DNA and cytochrome c oxidase subunit 1 (cox 1) from the mitochondrial DNA were generated and aligned with sequences from GenBank from other leptorhynchoidid species. Phylogenetic analyses inferred with the concatenated data set (SSU + LSU+ cox 1) and cox 1 data set along, revealed that isolates of Tegorhynchus sp. and T. cetratus from GenBank were nested in two independent clades, suggesting that the genus is paraphyletic, indicating that Tegorhynchus needs a taxonomic review. Specimens identified in this study as Illiosentis sp., formed an independent genetic linage which is recognized herein as a new species, Illiosentis kukulkani n. sp. The new species is morphologically distinguished from the other five congeners by having a cylindrical proboscis armed with 20-21 longitudinal rows with 14 hooks each and by having a sensory papilla between 6 and 8 hooks from posterior region of the proboscis. Novel molecular evidence was also useful for testing the validity of the genus Illiosentis.