Molecular and morphological evidence of a new species of Crassicutis Manter 1936 (Digenea), a parasite of cichlids in South America

Some trematodes including three new species from freshwater fishes of Venezuela

The present paper comprises a systematic survey of trematodes found in 13 species of freshwater fishes in Venezuela collected in 1992, 1996 and 2001. The following 15 trematode species were recorded: Adults: Genarchella venezuelaensis sp. n., Thometrema dissimilis sp. n., Megacoelium spinicavum Thatcher et Varella, 1981, Doradamphistoma bacuense Thatcher, 1999, Crassicutis cichlasomae Manter, 1936, Parspina carapo Ostrowski de Núñez, Arredonto et Gil de Pertierra, 2011, Phyllodistomoides hoplerythrini sp. n. Larvae (metacercariae): Clinostomatopsis sorbens (Braun, 1899), Clinostomum marginatum (Rudolphi, 1819), C. detruncatum Braun, 1899, Ithyoclinostomum dimorphum (Diesing, 1850), Odhneriotrema microcephala (Travassos, 1922), Tylodelphys sp., Posthodiplostomum sp., Sphincterodiplostomum sp. All these parasites are reported from Venezuela for the first time and many of these findings represent new host records. The new species G. venezuelaensis sp. n., T. dissimilis sp. n. and P. hoplerythrini sp. n. were collected from the accessory respiratory organ of Loricariichthys brunneus (Hancock) (Loricariidae), from the stomach of Hoplerythrinus unitaeniatus (Spix et Agassiz) (Erythrinidae) and from the intestine of H. unitaeniatus, respectively. All parasites are briefly described and illustrated and problems concerning their morphology, taxonomy, hosts and geographical distribution are discussed. Megacoelium spinispecum Thatcher et Varella, 1981 is considered a junior synonym of M. spinicavum Thatcher et Varella, 1981, and Crassicutis opisthoseminis Bravo-Hollis et Arroyo, 1962 as a junior synonym of C. cichlasomae Manter, 1936.

Integrated characterisation of nine species of the Schistorchiinae (Trematoda: Apocreadiidae) from Indo-Pacific fishes: two new species, a new genus, and a resurrected but 'cryptic' genus

We report nine species of the Schistorchiinae Yamaguti, 1942 (Apocreadiidae Skrjabin, 1942) from Indo-Pacific marine fishes. Molecular data (ITS2 and 28S rDNA and cox1 mtDNA) are provided for all species and the genus-level classification of the subfamily is revised. For Schistorchis Lühe, 1906, we report the type-species Sch. carneus Lühe, 1906 and Sch. skrjabini Parukhin, 1963. For Sphinteristomum Oshmarin, Mamaev & Parukhin, 1961 we report the type-species, Sph. acollum Oshmarin, Mamaev & Parukhin, 1961. We report and re-recognise Lobatotrema Manter, 1963, for the type and only species, L. aniferum Manter, 1963, previously a synonym of Sph. acollum. Lobatotrema aniferum is phylogenetically distant from, but morphologically similar to, Sph. acollum and Lobatotrema is recognised as a 'cryptic genus'. We propose Blendiella n. gen. for B. trigintatestis n. sp. and B. tridecimtestis n. sp. These species are broadly consistent with the present morphological concept of Schistorchis but are phylogenetically distant from the type-species; a larger number of testes and some other subtle morphological characters in species of Blendiella serve to distinguish the two genera. We report three species of Paraschistorchis Blend, Karar & Dronen, 2017: P. stenosoma (Hanson, 1953) Blend, Karar & Dronen, 2017 (type-species), P. seychellesiensis (Toman, 1989) Blend, Karar & Dronen, 2017, and P. zancli (Hanson, 1953) Blend, Karar & Dronen, 2017. Lobatotrema aniferum, P. stenosoma, and Sch. carneus each have two distinct cox1 populations either over geographical range or in sympatry. Available evidence suggests that most of these species, but not all, are widespread in the tropical Indo-Pacific.

Components influencing parasitism by Dadaytrema oxycephala (Digenea: Cladorchiidae) in Neotropical fish

The components that mold the structure of parasitic fauna are used as objects of study in an attempt to find patterns in their distribution. It is known that phylogeny (represented by specificity), host ecological traits (for example, feeding habits, position of the water column, reproductive strategies, body size, and age), and the environment affect the distribution and occurrence of parasites. In tropical regions, digeneans show high diversity, and the species Dadaytrema oxycephala is known to parasitize a wide range of host species. In this context, the objective of the present study is to analyze the components that affect the occurrence of D. oxycephala in Neotropical fish. We used data from the literature that contained the abundance of this parasite, as well as the geographic location and host species, and evaluated the influence of ecological traits, specificity, and latitude on parasite abundance, using a generalized linear mixed model (GLMM). The abundance of D. oxycephala can be explained by trophic level and position in the water column and latitude. However, coevolutionary processes are also extremely important, and the distribution of this parasite was not equal, showing high abundance for the genus Piaractus, which are the preferred hosts, even if the parasite is considered generalist. In short, host ecological traits are the important components in the distribution and occurrence of D. oxycephala, as well as the latitude.

Discovery of a new species of Homalometron Stafford, 1904 (Digenea: Apocreadiidae) from the stripped mojarra, Eugerres plumieri in a coastal lagoon of the Gulf of Mexico

To date, 34 species of the genus Homalometron (Apocreadiidae) have been described; five of them in Mexican fresh or brackish water fish, whereas five have been reported as parasites of members of the fish family Gerreidae. While sampling wildlife vertebrates during a field course of parasitology at the Los Tuxtlas Biological Station (Instituto de Biología, Universidad Nacional Autónoma de México) in Veracruz, specimens of digeneans were collected from the intestine of the stripped mojarra, Eugerres plumeri in Sontecomapan Lagoon. Specimens were studied morphologically and molecularly, and we discovered that they represented a new species of Homalometron. The new species is morphologically like the other four congeners in having three pairs of well-developed oral papillae on the oral sucker: Homalometron elongatum; Homalometron lesliorum; Homalometron carapavae; and Homalometron papilliferum. Here, we describe the newly discovered species, increasing our understanding about the parasite diversity of brackish water fishes of Mexico.