Three new species of Creptotrema (Trematoda, Allocreadiidae) with an amended diagnosis of the genus and reassignment of Auriculostoma (Allocreadiidae), based on morphological and molecular evidence

Abstract

Diversity of Creptotrema was investigated using morphological and molecular tools, including data for Creptotrema creptotrema (type-species). Three new species, parasites of Brazilian fishes, are described: Creptotrema conconae n. sp. (type-host, Imparfinis mirini Haseman), Creptotrema schubarti n. sp. (type-host, Characidium schubarti Travassos) and Creptotrema megacetabularis n. sp. (type-host, Auchenipterus osteomystax (Miranda Ribeiro)). The diagnosis of the genus was amended to include new features. The new species differ from each other mainly in terms of body shape, relative sucker size, and testes position. DNA sequences were obtained from Creptotrema spp. from Brazil, including 28S, ITS and COI. Genetic divergences among the new species and C. creptotrema varied from 2.1 to 5.2% (21–49 bp) for 28S, and 6.6 to 16.4% (21–45 bp) for COI. Phylogenetic analysis (28S) placed the newly generated DNA sequences of Creptotrema in a clade (Creptotrema clade sensu stricto) composed of C. creptotrema, the new species described herein, and all species previously described as Auriculostoma, revealing that Auriculostoma is best interpreted as a synonym of Creptotrema based on the principle of priority of zoological nomenclature. Creptotrema funduli, the single sequence of the genus previously available, was not grouped within the Creptotrema clade sensu stricto, suggesting the need for reevaluation of the taxonomic status of this species. Our results showed that Creptotrema represents a monophyletic genus of trematodes widely distributed across the Americas, which currently comprises 19 valid species of parasites of teleosts and anurans.

Discovery of a new genus and species of Allocreadiidae (Trematoda) in Mexico: Mesoamericatrema magnisacculus n. gen. n. sp

“…In particular, the number of oral papillae can be variable, however, the papillae that are constant in number are the internal papillae close to the mouth (4) and the posterior external papillae (5). This peculiarity of the number of internal and posterior oral papillae had already been observed in other genera such as Creptotrema (Razo-Mendivil et al, 2014;Hernández-Mena et al, 2016;2019;Montes et al, 2021), Paracreptotrema (Choudhury et al, 2006 Franceschini et al, 2021), who mentioned that the grouping of these trematodes is related to their hosts which are freshwater fishes of Neotropical origin. Species of all Neotropical genera have been recorded in Mexico, but other genera of allocreadiids have also been previously recorded, such as Allocreadium Looss, 1900, Crepidostomum Braun, 1900, Megalogonia Surber, 1928and Margotrema Lamothe-Argumedo, 1970(Perez-Ponce de León et al, 2007Galaviz-Silva et al, 2013), which have rather a Neartic affinity, so that Mexico is clearly a country where historical geological processes have favored the coexistence of parasites and hosts (and other animals) with different biogeographical affinities (Aguilar-Aguilar et al, 2003;Miller et al, 2005;Pérez-Ponce de León & Choudhury, 2005;Chakrabarty & Albert, 2011;Choudhury et al, 2017;Morrone, 2014;2020).…”

“…The discovery of the new genus named Mesoamericatrema n. gen. was based on the comparative study of internal and external morphological characters (using SEM), on the host association, and on the phylogenetic analysis of the 28S region (domains D1, D2, and D3) of the ribosomal RNA unit. Morphologically, the new genus presents a very large cirrus sac in proportion to the length of its body (1: 2.1-2.9), a characteristic that easily differentiates it from the other genera of Allocreadiidae, since generally the species of the other genera have a cirrus sac that does not extend beyond the posterior margin of the ventral sucker, and when it does, the sac is not as large in proportion to the length of the body (Scholz et al 2004;Caira & Bogéa, 2005;Choudhury et al, 2006;Pérez Ponce de León et al, 2016;Franceschini et al, 2021). Scanning Electron Microscopy (SEM) images show that the external surface of the body of Mesoamericatrema n. gen. does not have spines, but it does have oral and ventro-lateral tegumental papillae, features it shares with other species of allocreadiids.…”

“…The new genus can be easily distinguished from Acrolichanus Ward, 1917, Bunodera Railliet, 1896, Bunoderella Schell, 1964, Crepidostomum Braun, 1900, Creptotrema Travassos, Artigas & Pereira, 1928, Creptotrematina Yamaguti, 1954, Megalogonia Surber, 1928, Paracrepidostomum Lü & Wu, 1996, Rastridostomum Bilqees, Khatoon, Bibi & Mutiur-Rehman, 2007, Trematichtys Vaz, 1932, because Mesoamericatrema n. gen. does not have oral lappets or oral lobes on the oral sucker (Caira & Bogéa, 2005;Franceschini et al, 2021), while the other genera have lobes or lappets protruding from the oral sucker.…”

“…In the present century, four new genera have been described in the Americas: Auriculostoma Scholz, Aguirre-Macedo & Choudhury, 2004; Paracreptotrema Choudhury, Pérez Ponce de León, Brooks & Daverdin, 2006; Paracreptotrematoides Pérez Ponce de León, Pinacho-Pinacho, Mendoza-Garfias, Choudhury & García-Varela, 2016; and Pseudoparacreptotrema Pérez Ponce de León, Pinacho-Pinacho, Mendoza-Garfias, Choudhury & García-Varela, 2016. However, more recently it was found that Auriculostoma is a synonym of Creptotrema (Franceschini et al, 2021). The discovery in recent decades of new genera, their validity, and taxonomic changes, in principle, have been due to the boom in combining DNA sequence analysis with traditional morphological characters.…”

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The trematodes of Allocreadiidae are mainly parasites of freshwater fi sh and the family contains 18 valid genera. Since 2004, 4 genera have been described in the Americas: Paracreptotrema, Paracreptotrematoides, Pseudoparacreptotrema and Auriculostoma, of which the latter was recently synonymized with Creptotrema by Franceschini et al, (2021). During a study in 2018 on fi sh parasites of Lacantún River, Chiapas, Mexico, allocreadiids were collected from the intestine of Atherinella alvarezi and morphological differences with other genera of the family were immediately noted.

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