Acanthostomum yahuarcaquense n. sp. (Digenea: Cryptogonimidae) infecting the intestine of an aquatic coral snake, Micrurus surinamensis (Cuvier, 1817) (Serpentes: Elapidae) from the flooded rainforest habitat of the Yahuarcaca Lake System (Amazon River, Colombia) and phylogenetic analysis of Cryptogonimidae

We herein describe Acanthostomum yahuarcaquense Cajiao-Mora and Bullard n. sp. (Digenea: Cryptogonimidae) based on specimens we collected from the intestine of an aquatic coral snake, Micrurus surinamensis (Cuvier, 1817) (Serpentes: Elapidae) captured within the flooded rainforest habitat of the Yahuarcaca Lake System (Amazon River) Leticia, Amazonas, Colombia. We assign the new species to Acanthostomum Looss, 1899because it lacks a gonotyl and has an elongate body, spinose tegument, funnel-shaped oral sucker with circumoral spines, ceca each having a posterolateral and nearly terminal pore, and excretory vesicle arms reaching anteriad to the pharynx. The new species differs from its 19 accepted congeners by having 24–30 circumoral spines (vs. fewer than 20 or aspinose), a vitellarium extending from the anterior margin of the ovary to the posterior half of the body (vs. from testis or ovary but ending in anterior half of body), and paired elongate, symmetrical ceca each having an anal pore (vs. asymmetrical ceca, a single cecum, or lacking anal pores). Our 28S phylogenetic analysis recovered a paraphyletic Acanthostomum (including Neocladocystis spp. and Tanganyikatrema fusiforme Kmentová, Georgieva, and Bray, 2020; both Cryptogonimidae) within a clade sister to other cryptogonimids. We discuss the implications of using nonugens and excessively short nucleotide sequences to compare species and to test phylogenetic relationships. Regarding advancing the systematics of the family, we discuss oral sucker shape and position, circumoral spine distribution, tegumental spine distribution, ceca symmetry, anal pore presence/absence and position, and gonotyl presence/absence and position as useful genus-level features. Many of these features remain indeterminate for several species. This is the first published study of a parasite infecting a tetrapod in the Yahuarcaca Lake System, first to record a parasite infecting a coral snake (Micrurus spp.) in Colombia, and only the second trematode species reported from the aquatic coral snake.