Review of the genus Eutetrarhynchus Pintner, 1913 (Trypanorhyncha: Eutetrarhynchidae), with the description of Eutetrarhynchus beveridgei n. sp

Linking phenotypic to genotypic metacestodes from Octopus maya of the Yucatan Peninsula

Octopus maya is an endemic species of the Yucatan Peninsula. This species sustains the octopus’ fishery in the region and is the only cephalopod cultured in Mexico. It is known that O. maya harbor a large richness and abundance of metacestodes that have been tentatively identified by light microscopy alone. Since the larval stages of some orders of marine cestodes lack the taxonomic characteristics shown by the adult stages and on which cestode taxonomy is based, identification down to the species level is often unattainable. Hence, the goal of this study was to characterize the parasites, for the first time, at morphological and molecular levels. A total of 60 octopuses were collected from September to December 2017 from four fishery landing ports in Yucatán: Sisal, Progreso, Dzilam de Bravo, and Rio Lagartos (15 hosts per locality). Morphology of metacestodes was characterized by light and Scanning Electron Microscopy (SEM), while the genes 18S and 28S rDNA were sequenced for molecular characterization. Based on phenotypic characters and molecular data, seven taxa of metacestodes were identified, four of them belonging of order Trypanorhyncha: Eutetrarhynchus sp., Kotorella pronosoma, Nybelinia sp., Prochristianella sp. 1; and the three remaining taxa belonging to the order Onchoproteocephalidea: Acanthobothrium sp., Phoreiobothrium sp., and Prosobothrium sp. This work provides, for the first time, molecular support to the morphological characterization of metacestodes recorded in Octopus maya.

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Seven taxa of metacestodes from Octopus maya were identified

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First morphological and molecular match in cestodes of O. maya is presented

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Phylogenetic analysis indicate octopus cestodes grouped in four different groups of trypanorhynchs and onchoproteocephalids

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Prochristianella sp. 1 is the only species with 100% prevalence

Eutetrarhynchus pacificus n. sp. (Cestoda: Trypanorhyncha) from Raja inornata Jordan & Gilbert (Batoidea: Rajiformes) off the coast of California with comments on congeners

Eutetrarhynchus pacificus n. sp. is described from the spiral valve of Raja inornata Jordan & Gilbert off the coast of California, USA. The new species is distinguished from E. ruficollis (Eysenhardt, 1829) and E. leucomelanus (Shipley & Hornell, 1906) in having acraspedote rather than craspedote segments and a saccate rather than a branched uterus. It is distinguished from E. platycephali Palm, 2004 in lacking an enlarged hook in the eighth row of the basal armature and from E. beveridgei Schaeffner, 2013, which has a basal swelling and a distinctive basal armature. A partial redescription of E. ruficollis, the type-species of the genus, is provided based on available museum specimens, highlighting the need for a comprehensive redescription of this species to better define the characteristics of the genus. The presence of an undescribed species in museum collections is also noted. Based on the 28S ribosomal gene, the new species clustered with Dollfusiella in a molecular phylogenetic tree. The delimitation of Eutetrarhynchus and its relationship with Dollfusiella is discussed.

A new genus and two new species of trypanorhynch cestodes (Tentaculariidae) from the sharksCarcharhinus sorrah(Müller & Henle) andSphyrna lewini(Griffith & Smith) from off the coasts of Malaysia and Mexico

Two new tentaculariid species were found infecting carcharhiniform sharks from off the coasts of Malaysian Borneo and the southwestern coast of the Baja California Sur, Mexico. Both new species exhibit a homeoacanthous heteromorphous basal and a homeoacanthous homeomorphous metabasal armature. Since this hook arrangement is unique within the tentaculariids and the taxonomy in this group deeply depends on the tentacular armature, Reimeriella n. g. is erected to accommodate R. varioacantha n. sp. ex Carcharhinus sorrah (Müller & Henle) and R. mexicoensis n. sp. ex Sphyrna lewini (Griffith & Smith). Unlike R. mexicoensis n. sp., R. varioacantha n. sp. has a pars bothrialis not overlapping the pars bulbosa and the number of testes is higher. Reimeriella mexicoensis n. sp. possesses very large uncinate to falcate hooks in the basal armature, while in R. varioacantha n. sp. these hooks are almost the same in size as the remaining hooks in both the basal and metabasal armature. The latter species is the first tentaculariid species where the metabasal armature very closely resembles an eutetrarhynchid with a heteroacanthous typical homeomorphous metabasal armature and a high number of spiniform hooks per half spiral row (10-11 vs 6-7 in R. mexicoensis n. sp.) in the metabasal and apical armature. This pattern provides further morphological evidence for the close relationship of the Eutetrarhynchoidea and the Tentacularioidea. Reimeriella varioacantha n. sp. enriches the trypanorhynch fauna from off the coast of Malaysian Borneo while R. mexicoensis n. sp. is a novel record of a tentaculariid trypanorhynch from the Mexican Pacific.

A checklist of helminth parasites of Elasmobranchii in Mexico

A comprehensive and updated summary of the literature and unpublished records contained in scientific collections on the helminth parasites of the elasmobranchs from Mexico is herein presented for the first time. At present, the helminth fauna associated with Elasmobranchii recorded in Mexico is composed of 132 (110 named species and 22 not assigned to species), which belong to 70 genera included in 27 families (plus 4 incertae sedis families of cestodes). These data represent 7.2% of the worldwide species richness. Platyhelminthes is the most widely represented, with 128 taxa: 94 of cestodes, 22 of monogeneans and 12 of trematodes; Nematoda and Annelida: Hirudinea are represented by only 2 taxa each. These records come from 54 localities, pertaining to 15 states; Baja California Sur (17 sampled localities) and Baja California (10), are the states with the highest species richness: 72 and 54 species, respectively. Up to now, 48 elasmobranch species have been recorded as hosts of helminths in Mexico; so, approximately 82% of sharks and 67% of rays distributed in Mexican waters lack helminthological studies. The present list provides the host, distribution (with geographical coordinates), site of infection, accession number in scientific collections, and references for the parasites. A host-parasite list is also provided.

Dollfusiella qeshmiensis n. sp. (Cestoda: Trypanorhyncha) from the cowtail stingray Pastinachus sephen (Forsskål) in the Persian Gulf, with a key to the species of Dollfusiella Campbell & Beveridge, 1994

A new species of the genus Dollfusiella Campbell & Beveridge, 1994 is described from Pastinachus sephen (Forsskål) in the Persian Gulf. Dollfusiella qeshmiensis n. sp. is allocated to the genus Dollfusiella based on the possession of two bothria, prebulbar organs, a heteroacanthous typical armature with tightly spaced rows of hollow hooks, a basal swelling and a characteristic basal armature without prominent macrohooks. The presence of an enlarged external seminal vesicle in Dollfusiella qeshmiensis n. sp. distinguishes this species from D. michiae (Southwell, 1929), D. bareldsi (Beveridge, 1990), D. owensi (Beveridge, 1990), D. geraschmidti (Dollfus, 1974), D. angustiformis Schaeffner & Beveridge, 2013, D. hemispinosa Schaeffner & Beveridge, 2013, D. spinosa Schaeffner & Beveridge, 2013 and D. taminii Menoret & Ivanov, 2014. The new species is distinguished from the remaining species within the genus by a combination of the following morphological features: the number of testes per segment, the number of testis columns and the number of homeomorphous hooks per half spiral row in the metabasal region. In the most recent taxonomic key to the species of Dollfusiella, the presence or absence of enlarged, microscopically visible spinitriches on the scolex was used as the first distinguishing character dividing the congeners into two groups. Since the existence of visible microtriches on the scolex peduncle of D. vooremi (São Clemente & Gomes, 1989), a species so far grouped among the species lacking visible microtriches on the scolex, has been recently demonstrated, and given the fact that the presence of microscopically visible microtriches on the scolex is variable in some eutetrarhynchid species, a new key to the species of Dollfusiella is provided in which the spinitriches have been given less priority.

Trypanorhynch cestodes (Eutetrarhynchidae) from batoids along the coast of Argentina, including the description of new species in Dollfusiella Campbell et Beveridge, 1994 and Mecistobothrium Heinz et Dailey, 1974

During a recent parasitological survey of elasmobranchs along the coast of Argentina, two new species of eutetrarhynchid cestodes of the genera Dollfusiella Campbell et Beveridge, 1994 and Mecistobothrium Heinz et Dailey, 1974 were collected from batoids. Dollfusiella acuta sp. n. was found in four arhynchobatid skates, i.e. Sympterygia acuta Garman (type host), Sympterygia bonapartii Müller et Henle, Atlantoraja castelnaui (Miranda Ribeiro) and Atlantoraja platana (Günther), and Mecistobothrium oblongum sp. n. in the eagle ray Myliobatis goodei Garman. Dollfusiella acuta sp. n. has a tentacular armature consisting of basal rows of uncinate hooks, a distinct basal swelling with uncinate, falcate and bill hooks, and a heteroacanthous metabasal armature with heteromorphous hooks (bothrial uncinate hooks and antibothrial falcate hooks), hooks 1(1') not separated, testes in two columns and an internal seminal vesicle. The tentacular armature of M. oblongum sp. n. is characterised by basal rows of uncinate hooks, a basal swelling with uncinate and falcate hooks, a typical heteroacanthous metabasal armature with heteromorphous hooks (uncinate and falcate to spiniform), and hooks 1(1') separated and of a constant size along the tentacle. It also possesses an elongate scolex, numerous testes arranged in 5-6 irregular columns, and an internal seminal vesicle. The discovery of M. oblongum in M. goodei represents the first record of species of Mecistobothrium in the southwestern Atlantic Ocean. An amended description of Dollfusiella cortezensis (Friggens et Duszynski, 2005) is also provided to clarify details of the scolex and tentacular armature. Members of Dollfusiella in the southwestern Atlantic are specific to a single host species or to a particular host family, while M. oblongum was found in a single host species. Although globally some plerocerci of eutetrarhynchids have been found in teleosts, extensive examination of teleosts off the coast of Argentina suggests that the transmission pathways of these species are exclusively based on invertebrates as intermediate or paratenic hosts.