Two new genera and three new species of exceptionally rare and endemic freshwater mussels (Bivalvia, Unionidae) from the Mekong Basin

By

Jeratthitikul, Ekgachai
Čhirasak Sutčharit
Prasankok, Pongpun

Type

Article

Date of Publication

2024-10-4

Original Publication

Zoosystematics and evolution

Volume

100

Series / Issue

Issue: 4

Pages

1333--1345

Subjects

Freshwater mussels , Indochina , Mekong Basin , multi-locus phylogeny , multi-locus phylogeny , new taxa , Thailand

Contributed by

Pensoft Publishers

Language

English

Published by

Sofia Pensoft

Identifiers

DOI: https://doi.org/10.3897/zse.100.130929

 

Abstract

Two new genera and three new species of freshwater mussels in the tribe Pseudodontini (Bivalvia, Unionidae) are described from the Mekong Basin in Thailand based on an integrative taxonomic study involving morphology and multi-locus phylogenetic analyses (mitochondrial COI and 16S, and nuclear 28S genes). The monotypic genus, Lannanaia kokensisgen. et sp. nov., presents unique features of being rather compressed, sub-trigonal in outline with short and high shell, and with a distinct posterior wing. Another new genus, Isannaiagen. nov., is characterized by having a thin and moderately inflated shell, with rhomboidal to ovate outline. It includes two lineages that are genetically separated by 3.54% uncorrected COI p-distance, and are herein described as I. fortunatasp. nov. and I. occultatasp. nov. Phylogenetic analyses further revealed that these two new genera were nested within a clade of subtribe Pseudodontina, and with pairwise uncorrected COI p-distance to other genera ranging from 11.42 to 15.66%. Based on the present data, Lannanaiagen. nov. is known only from the Kok River in the north of Thailand, whereas the two species of Isannaiagen. nov. are restricted to tributaries of the Mekong River in the northeast of Thailand. The discovery of rare and probably endemic freshwater mussels in the Mekong Basin thus again highlights the importance of this region among freshwater biodiversity hotspots of the world.