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.
Highlights
Gastrotrichs are microscopic, benthic invertebrates found in both freshwater and marine ecosystems worldwide[1]
Www.nature.com/scientificreports genus based on the discovery of specimens belonging to a group of new species found in different regions of the world, including areas considered well investigated with regard to the gastrotrich fauna
General organization of the adhesive apparatus, and the arrangement and composition of the reproductive apparatus of the three new taxa are comparable to species of the genus Macrodasys
Summary
Gastrotrichs are microscopic, benthic invertebrates found in both freshwater and marine ecosystems worldwide[1]. The two genera described most recently, Hummondasys Todaro, Leasi & Hochberg, 2014 and Thaidasys Todaro, Dal Zotto & Leasi, 2015, were established on the base of peculiar specimens found in geographic areas never investigated before with regard to the gastrotrich fauna Both genera are monotypic and so far are only known from their respective type locality: Hummondasys found at Negril in Jamaica, and Thaidasys collected at Phuket island in Thailand[8,9]. This scenario may lead to the wrong conclusion that nowadays relevant innovation regarding the Gastrotricha may originate only from remote areas and consist of rare and species-poor taxa having a restricted geographic distribution In contrast with this vision, here we propose the establishment of a new www.nature.com/scientificreports/.
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