Abstract
This study is a first report of an interstitial ostracod from Southeast Asia. The ostracod species, Paracobanocythere vietnamensis sp. n., was found in the marine interstitial environment of Phu Quoc Island, Vietnam. Thus far, three species of this genus have been described. The morphology of the carapace as well as the appendages of this new species are quite similar to Paracobanocythere hawaiiensis and Paracobanocythere watanabei. However, we found that they could be easily distinguished according to the morphology of the male copulatory organ. Additionally, we estimated the evolutionary distances among these three species based on nucleotide and amino acid sequences of the mitochondrial CO1 gene. Similar morphologies of carapaces and appendages, and relatively small evolutionary distances according to CO1 between Paracobanocythere vietnamensis sp. n. and Paracobanocythere watanabei suggest that these two species are very closely related.
Highlights
Ostracods are small bivalve crustaceans that inhabit various aquatic environments
Paracobanocythere vietnamensis sp. n. closely resembles pincer-like structure (Ps). watanabei and P. hawaiiensis according to the appendage morphology, including chaetotaxy and shapes of the podomeres; they have divergent male copulatory organ morphologies (Table 3)
This is possibly due to the simplification of appendage morphologies driven by the adaptation to the interstitial environment (Hartmann 1973, Maddocks 1976, Danielopol 1976) and the relatively large size of reproductive characters such as the male copulatory organ (Polilov and Beutel 2009)
Summary
Ostracods are small bivalve crustaceans that inhabit various aquatic environments. They are one of the major constituents of the meiobenthos, especially interstitial animals inhabiting the pore space in sediment (Giere 2009). The new species belongs to the genus Paracobanocythere, which shows typical features of interstitial taxa, including a small and dorso-ventrally depressed carapace inhabiting the interstices between grains of coarse sand (Gottwald 1983, Hartmann 1991, Higashi and Tsukagoshi 2011). Three species of this genus have been described; these include Paracobanocythere hawaiiensis Gottwald, 1983 (type species), from the island of O’ahu in Hawaii, as well as P. grandis Higashi & Tsukagoshi, 2011 and P. watanabei Higashi & Tsukagoshi, 2011, from the sand beach in Shizuoka Prefecture, on the Pacific coast of central Japan. We describe a new species from Vietnam and supply DNA sequence data of the mitochondrial cytochrome c oxidase subunit 1 (CO1) gene from the three described Asian species
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