Integrated data analysis allows the establishment of a new, cosmopolitan genus of marine Macrodasyida (Gastrotricha)

Abstract

Macrodasyida (phylum Gastrotricha) comprises 365 species distributed across 34 genera and 10 families. However, current classification is under revision due to the contradictory results of molecular and morphological cladistic analyses. Studies aimed at bridging the gaps took advantage of supplementary assessments of poorly known species and particularly from observations of new taxa showing original traits that could help to identify plesiomorphic character states in these anatomically diverse micrometazoa. We follow this path by describing three new interesting macrodasyidan species respectively from Italy, Brazil and Sweden. In many respects, the new species resemble most closely species of the genus Macrodasys ; however, details of the external morphology, in combination with the different lay-out of the reproductive system and the tiny spermatozoa lacking a visible flagellum, suggest they belong to a new genus, possibly in the family Macrodasyidae. These hypotheses are supported by the phylogenetic relationships of 47 taxa inferred from analyses of the 18S rRNA gene, which found the new species clustering with Thaidasys tongiorgii in a subset of a larger clade containing Macrodasys . Accordingly, the establishment of the following taxa is proposed: Kryptodasys gen. nov., K . marcocurinii sp. nov., K . carlosrochai sp. nov. and K . ulfjondeliusi sp. nov.

A New Species of Paraturbanella Remane, 1927 (Gastrotricha, Macrodasyida) from the Brazilian Coast, and the Molecular Phylogeny of Turbanellidae Remane, 1926

“…The species and respective GenBank accession numbers are listed in Table 1. The outgroup was composed of two Megadasys species and four Mesodasys species due to the close phylogenetic position of these taxa with the taxon Turbanellidae [4,40]. Each gene dataset was aligned separately using BioEdit Sequence Alignment Editor and Mafft v.7.402 (L-INS-I approach) [41].…”

“…Currently, there are 23 described species belonging to the genus Paraturbanella [6,17,33]. The new species bares closest resemblance to five species: P. africana Todaro, Dal Zotto, Bownes & Perissinotto, 2017 [17]; P. teissieri Swedmark, 1954 [19]; P. sanjuanensis Hummon, 2010 [23]; P. solitaria Todaro, 1995 [31]; and P. xaymacana Dal Zotto, Leasi & Todaro, 2018 [33], showing similar body and head shape, as well as peribuccal swelling [33].…”

“…The latter group is composed in its majority of hermaphroditic and marine species, which live interstitially in sandy bottoms [2,4]. The order Macrodasyida includes 10 families, 36 genera and approximately 380 described species [2,5,6]. They have a strap-shaped body, a pharynx with pharyngeal pores, and, usually, numerous adhesive tubes in the anterior, lateral and posterior regions.…”

“…Although knowledge of phylogenetic relationships within Turbanellidae is still limited, Turbanella and Paraturbanella species have several common characteristics, but the presence of extraordinary adhesive tubes easily distinguishes the genus Paraturbanella from Turbanella [2,6,[12][13][14][15][16].…”

An Introduction to the Study of Gastrotricha, with a Taxonomic Key to Families and Genera of the Group

“…Parts of the in-group phylogenetic relationships remain unclear, e.g., the evolutionary relationships between the representatives of the two orders or within the clearly paraphyletic family Chaetonotidae. Fortunately, relationships among taxa belonging to several families, especially of the Macrodasyida, are becoming less obscure [9,[12][13][14][15][16][17][18][19].…”