Eutetrarhynchus sp.

Marmolejo-Guzman, Linda Yacsiri G., Iv, David, Hern, an G., andez-Mena, Castellanos-Martínez, Sheila & Aguirre-Macedo, M. Leopoldina, 2022, Linking phenotypic to genotypic metacestodes from Octopus maya of the Yucatan Peninsula, International Journal for Parasitology: Parasites and Wildlife 19, pp. 44-55 : 51-52

4.1. Eutetrarhynchus sp.

Currently five species comprehend the genus Eutetrarhynchus : Eutetrarhynchus beveridgei ( Schaeffner, 2014) , Eutetrarhynchus leucomelanus (Shipley and Hornell, 1906) , Eutetrarhynchus pacificus , Eutetrarhynchus platycephali ( Palm, 2004) and Eutetrarhynchus ruficollis (Eysenhardt, 1829) ( Beveridge et al., 2021) . All these species are characterized by a slender acraspedote scolex and two oval bothria in opposite arrangement. Tentacle sheaths spirally coiled, heteroacanthous armature with homeo- or heteromorphous, hollow hooks, the absence of basal swelling as well as the possession of either, a craspedote or acraspedote strobila ( Campbell and Beveridge, 1994; Palm, 2004). However, an accurate identification of Eutetrarhynchus species is complicated due to the morphological similarities with the species of the genus Dollfusiella like a slender acraspedote scolex, two oval bothria, heteroacanthous armature with homeo- or heteromorphous and acraspedote strobila ( Palm, 2004;

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Schaeffner, 2014).

According to Palm (2004), Beveridge et al. (2004) a taxonomic character that allows to differentiate between Eutetrarhynchus and Dollfusiella is the basal swelling on the tentacles reported in the latter. Unfortunately, in this study, it was not possible to obtain individuals with the tentacles completely everted, which in turn made impossible to observe such characteristics. Concerning the molecular identification of the parasites, our data showed that Eutetrarhynchus sp. found in O. maya grouped with Dollfusiella ( Figs. 4 and 5 ). However, the genetic distance, given by the length of the branch between our specimen and the Dollfusiella genus, is rather large ( Figs. 4 and 5 ). To date, the sequence of E. pacificus is the only available in the GenBank database and it does not group with that from the O. maya specimen. However, this could be explained by the size of the E. pacificus sequence (420 bp) that is shorter than Eutetrarhynchus from O. maya (1463 bp). Therefore, the first one does not provide enough data to make an adequate clustering and phylogenetic analysis. Consequently, we reserve ourselves to change the actual classification given by Guill´en-Hernandez´et al. (2018a) until new material is examined.

Figures

Fig. 4. Phylogenetic tree based on the Maximum Likelihood (ML) analysis of the species of the Order Trypanorhyncha found in Octopus maya constructed on partial large subunit ribosomal gene (28S) (likelihood = – 15209.189111). Bootstrap support values for ML are provided at the nodes; ex = host; the stage of development of the cestode in parentheses.

Fig. 5. Phylogenetic tree based on the Maximum Likelihood analysis of the species of the Order Trypanorhyncha found in Octopus maya constructed on partial small subunit ribosomal gene (18S) (likelihood = – 7987.787948). Bootstrap support values for ML are provided at the nodes; ex = host; the stage of development of the cestode in parentheses.