Marine microturbellarians from Japan, with descriptions of two new species of Reinhardorhynchus (Platyhelminthes, Rhabdocoela, Koinocystididae)

By

Tsuyuki, Aoi
Reyes, Jhoe
Oya, Yuki
Wakeman, Kevin
Leander, Brian S.
Van Steenkiste, Niels

Type

Article

Date of Publication

2024-07-03

Original Publication

Zoosystematics and evolution

Volume

100

Pages

877--895

Subjects

Distribution , Flatworms , Japanese invertebrates , Kalyptorhynchia , marine meiofauna

Contributed by

Pensoft Publishers

Language

English

Published by

Sofia Pensoft

Identifiers

DOI: https://doi.org/10.3897/zse.100.120244

 

Abstract

Marine microturbellarians are an assemblage of meiofaunal flatworms abundant in sediments and on seaweeds around the world. The diversity and distribution of these animals in Japan are poorly understood. Here, we provide an overview of all recorded species in Japan and characterize two new species of the rhabdocoel genus Reinhardorhynchus based on morphological features and a molecular phylogeny inferred from 18S and 28S rDNA sequences. Reinhardorhynchus ryukyuensis sp. nov. can be distinguished from other species in the genus by the lack of an armed cirrus and by the presence of two larger opposing hooks and five smaller interconnected hooks in its male copulatory organ. Reinhardorhynchus sagamianus sp. nov. differs from its congeners because its male copulatory organ combines a bipartite cirrus armed with a belt of overlapping scale-like spines, an unarmed accessory cirrus, and two large distal accessory hooks. Our molecular phylogenetic analyses show that R. ryukyuensis sp. nov. and R. sagamianus sp. nov. form a clade with all the other species of Reinhardorhynchus for which DNA sequence data are available. Within this clade, R. sagamianus sp. nov. is in a clade that also includes R. riegeri and R. anamariae. The discovery of these new species highlights the importance of uncovering and documenting the hidden biodiversity along Japan’s coastal margin.