Heterophyid trematodes (Digenea) from penguins: A new species of Ascocotyle Looss, 1899, first description of metacercaria of Ascocotyle (A.) patagoniensis Hernández-Orts et al. (2012), and first molecular data

Revision of Cryptogonimus Osborn, 1903 and Caecincola Marshall et Gilbert, 1905 (Digenea: Cryptogonimidae), supplemental description of Cryptogonimus chili Osborn, 1903, and description of a new species of Caecincola infecting basses (Centrarchiformes: Centrarchidae) in Tennessee and Alabama rivers

We provide a supplemental description of the type species for Cryptogonimus Osborn, 1903 (Digenea: Cryptogonimidae), Cryptogonimus chili Osborn, 1903, based on newly-collected, heat-killed, formalin-fixed specimens infecting rock bass, Ambloplites rupestris (Rafinesque), and smallmouth bass, Micropterus dolomieu Lacepède (both Centrarchiformes: Centrarchidae), from the Duck River, Tennessee (USA). We emend Cryptogonimus to include features observed in the present specimens of its type species and in the descriptions of its congeners: a broad (wider than long) oral sucker, an intestine that bifurcates in the posterior half of the forebody, a bipartite seminal vesicle, a hermaphroditic duct that is dorsal to the ventral sucker, a preovarian seminal receptacle, and a Laurer's canal that opens dorsally at the level of the anterior testis. We describe Caecincola duttonae sp. n. (Cryptogonimidae) infecting largemouth bass, Micropterus salmoides (Lacepède), from Neely Henry Reservoir (Coosa River, Alabama, USA). The new species differs from its congeners by having a combination of a less elongate body, an intestine that bifurcates at the level of the ventral sucker, caeca that terminate at the level of the testes, diagonal testes in the middle of the hindbody, and a vitellarium predominantly distributed in the hindbody. We emend Caecincola Marshall et Gilbert, 1905 (type species Caecincola parvulus Marshall et Gilbert, 1905) to include features of the new species and recently-described congeners: an elongate body, an intestine that bifurcates in the posterior half of the forebody, caeca that extend posteriad beyond the testes, tandem testes, and a vitellarium that is wholly or primarily in the hindbody. Our 28S and ITS2 phylogenetic analyses recovered Caecincola and Cryptogonimus as sister taxa; Caecincola was recovered as paraphyletic with 28S but monophyletic with ITS2. This is the first phylogenetic study of Cryptogonimidae that includes a nucleotide sequence for a species of the type genus Cryptogonimus. We regard Cryptogonimus diaphanus (Stafford, 1904) Miller, 1941 as a species inquirenda.

Small intestinal flukes of the genus Metagonimus (Digenea: Heterophyidae) in Europe and the Middle East: A review of parasites with zoonotic potential

The heterophyid trematode Metagonimus romanicus (Ciurea, 1915) (Digenea) is redescribed on the basis of type material from domestic dogs (Canis familiaris) in Romania, vouchers from experimentally infected cats (Felis catus) and adults recovered from golden hamsters (Mesocricetus auratus) infected with metacercariae from scales of chub (Squalius cephalus) and common nase (Chondrostoma nasus) (Cypriniformes: Leuciscidae) in Hungary. This trematode, endemic to Europe and neighbouring regions (northwestern Türkiye), was previously misidentified as M. yokogawai (Katsurada, 1912), a zoonotic parasite of humans in East Asia. However, the two species differ considerably both genetically and morphologically, e.g., in the position of the ventral sucker, the presence of the prepharynx, the anterior extent of the vitelline follicles and the posterior extent of the uterus. Metagonimus ciureanus (Witenberg, 1929) (syn. Dexiogonimus ciureanus Witenberg, 1929), described from domestic cats and dogs in Israel, is a valid species distributed in the Middle East and Transcaucasia, which is also confirmed by molecular data. It differs from all Metagonimus species, including M. romanicus, in having symmetrical testes instead of the oblique testes of the other congeners. The zoonotic significance of M. romanicus and M. ciureanus is unclear, but appears to be low in Europe, mainly because raw or undercooked, whole fish with scales are generally not consumed. Accidental infection of fishermen by metacercariae in the scales when cleaning fish is more likely, but has never been reported. Remains of cyprinoids with scales infected with metacercariae of Metagonimus spp. can be an important natural source of infection for dogs, cats, and other carnivores, which can serve as a reservoir for these parasites.

Description of new species of Trematoda from bats of Southeastern Mexico and a new classification for Brachylecithum rileyi n. comb. (Dicrocoeliidae)

To date, 23 species of trematodes have been reported in bats from Mexico. However, in some regions of Mexico, such as the Yucatan Peninsula, many species of bats do not have helminthological records. Here, we sampled bats in four localities in Southeastern Mexico from April 2017 to February 2022. Parasites were collected from the intestine of four species of bats: Pteronotus fulvus, Eumops nanus, Noctilio leporinus and Nyctinomops laticaudatus. Conventional morphological techniques and molecular tools with the 28S ribosomal gene were used to describe the helminths. We discovered that our parasites represent three new species and a new combination of trematodes. We found that the new species have morphological differences with their congeneric species, and we complement this information whit molecular data. Furthermore, we found morphological and molecular evidence that places Dicrocoelium rileyi within the genus Brachylecithum. This study points out the importance of comparing morphological and phylogenetic information.

Rich but morphologically problematic: an integrative approach to taxonomic resolution of the genus Neospirorchis (Trematoda: Schistosomatoidea)

Neospirorchis Price, 1934 is a genus of blood flukes that infect the cardiovascular system, including vessels surrounding the nervous systems of marine turtles. Although the genus comprises just two named species, the available molecular data suggest substantial richness which has not yet been formally described. The lack of description of species of Neospirorchis is probably explained by their small, slender, elongate bodies, which allow them to infect numerous organs and vessels in their hosts, such as the heart and peripheral vessels of nervous system, endocrine organs, thymus, mesenteric vessels, and gastrointestinal submucosa. This morphology and site of infection means that collecting good quality, intact specimens is generally difficult, ultimately hampering the formal description of species. Here we supplement limited morphological samples with multi-locus genetic data to formally describe four new species of Neospirorchis infecting marine turtles from Queensland, Australia and Florida, USA; Neospirorchis goodmanorum n. sp. and Neospirorchis deburonae n. sp. are described from Chelonia mydas, Neospirorchis stacyi n. sp. is described from Caretta caretta, and Neospirorchis chapmanae n. sp. from Ch. mydas and Ca. caretta. The four new species are delineated from each other and the two known species based on the arrangement of the male and female reproductive organs, on the basis of cytochrome c oxidase subunit 1 (cox1), internal transcribed spacer 2 (ITS2), and 28S ribosomal DNA (rDNA) molecular data, site of infection, and host species. Molecular evidence for three further putative, presently undescribable, species is also reported. We propose that this integrated characterisation of species of Neospirorchis, based on careful consideration of host, molecular and key morphological data, offers a valuable solution to the slow rate of descriptions for this important genus. We provide the first known life cycle data for Neospirorchis in Australian waters, from Moreton Bay, Queensland; consistent with reports from the Atlantic, sporocysts were collected from a terebellid polychaete and genetically matched to an unnamed species of Neospirorchis infecting Ch. mydas from Queensland and Florida.

The first new species of European Ascocotyle Looss, 1899 (Digenea: Heterophyidae) described in more than half a century

Ascocotyle (Phagicola) trentinii n. sp. is described based on adults from experimentally infected ducklings (Anas platyrhynchos domesticus) fed with metacercariae from the visceral serosa of the Mediterranean banded killifish, Aphanius fasciatus (Cyprinodontiformes: Aphaniidae), from coastal lagoons in northeastern Italy (Emilia-Romagna Region). The new species is placed into the subgenus Phagicola because of the presence of a single row of circumoral spines, vitelline follicles being confined between the ventral sucker and testes, and uterine loops not reaching anterior to the ventral sucker. Ascocotyle (P.) trentinii n. sp. differs from other members of the subgenus Phagicola, as well as other species of Ascocotyle, by the number (27–33) of circumoral spines which are 13.5–17 μm long and 3.5–5 μm wide, and by the morphology of a gonotyl which is composed of about 8 large refractile pockets. The occurrence of metacercariae in A. fasciatus indicates that the life cycle of the new species is completed in brackish water lagoons. It is the fourth species of Ascocotyle described in Europe and may be endemic to the Mediterranean region because its second (fish) intermediate host is endemic to this region.

•

A new species of Ascocotyle (Digenea: Heterophyidae) is described from Europe after more than half a century.

•

The new species is characterised by a unique number (27–33) of circumoral spines.

•

Mediterranean banded killifish,Aphanius fasciatus(Cyprinodontiformes), from coastal lagoons is a second intermediate host.

•

Ascocotyle pindoramensisfrom South America, which has no circumoral spines, is most closely related to the new species.

Ascocotyle longa (Digenea: Heterophyidae) infecting dolphins from the Atlantic Ocean

We report for the first time the infection of dolphins with Ascocotyle longa found in the intestines of three different species, Sotalia guianensis, Steno bredanensis, and Tursiops truncatus gephyreus, which were found washed ashore along the southeastern and southern Brazilian coast. The worms were identified based on morphological and molecular data using the 28S rDNA gene and the COI gene. Specimens of A. longa from the pinniped Otaria flavescens were also analyzed. As the first isolation of A. longa from cetaceans, the present study increases the distribution area and range of definitive hosts of this trematode, and provides new molecular data to complement the phylogeny of the group in future studies, thus contributing to the scientific knowledge of this potentially zoonotic parasite.

Current Knowledge of Small Flukes (Digenea: Heterophyidae) from South America

Fish-borne heterophyid trematodes are known to have a zoonotic potential, since at least 30 species are able to infect humans worldwide, with a global infection of around 7 million people. In this paper, a ‘state-of-the-art’ review of the South American heterophyid species is provided, including classical and molecular taxonomy, parasite ecology, host-parasite interaction studies and a list of species and their hosts. There is still a lack of information on human infections in South America with undetected or unreported infections probably due to the information shortage and little attention by physicians to these small intestinal flukes. Molecular tools for specific diagnoses of South American heterophyid species are still to be defined. Additional new sequences of Pygidiopsis macrostomum, Ascocotyle pindoramensis and Ascocotyle longa from Brazil are also provided.