A New Species of Land-locked Freshwater Shrimp of the Genus Neocaridina (Decapoda: Caridea: Atyidae) from Iki Island, Kyushu, Japan

Authors

Hsi-Te Shih1,*, Yixiong Cai2, Nobuaki Niwa3, and Yasuhiko Nakahara4

1 Department of Life Science and Research Center for Global Change Biology, National Chung Hsing University, 250, Kuo Kuang
Road, Taichung 402, Taiwan
2 National Biodiversity Centre, National Parks Board, 1 Cluny Road, Singapore 259569, Republic of Singapore
3 Faculty of Science, Kyoto University, Kitashirakawa, Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
4 SEIBU Environmental Research Co., LTD, Mikawachishin-machi, Sasebo-City, Nagasaki, 859-3153, Japan

(Received 17 August 2017; Accepted 23 September 2017; Published 17 October 2017; Communicated by Benny K.K. Chan)

Hsi-Te Shih, Yixiong Cai, Nobuaki Niwa, and Yasuhiko Nakahara (2017) A new species of land-locked freshwater shrimp, Neocaridina ikiensis (Decapoda: Caridea: Atyidae), is described from Iki Island, Kyushu, Japan, based on morphological and molecular evidence. This new species can be distinguished from its congeners by a suite of characters, including rostrum structure, number of post-orbital rostral teeth, male first and second pleopods and telson structure. The molecular evidence of mitochondrial cytochrome oxidase subunit I (COI) shows this species has sufficient interspecific divergence, and its high intraspecific variation suggests that it evolved on this island over a long period of time. Based on the molecular clock estimation, the speciation of N. ikiensis n. sp. is supposed to be related with the quiescent periods of volcanoes on this island. This is the second native species of Neocaridina known, after N. denticulata (De Haan, 1844), from the main islands of Japan.
Key words: Neocaridina ikiensis, Mitochondrial cytochrome oxidase subunit I, New species, Morphology, Molecular clock.
*Correspondence: Tel/Fax: 886-4-22856496. E-mail: htshih@dragon.nchu.edu.tw

BACKGROUND

The genus Neocaridina Kubo, 1938 is a group of freshwater shrimps with land-locked habit, consisting of about 25 species, distributed in East Asia, including eastern Russia, Korea, main islands of Japan, Ryukyus, Taiwan, continental China and Vietnam (Liang 2004). Species of this genus have also been introduced to Hawaii (Englund and Cai 1999) and Germany (Klotz et al. 2013; Weber and Traunspurger 2016). While N. davidi (Bouvier, 1904) (= N. sinensis (Kemp, 1918); see Shih and Cai 2007; Klotz et al. 2013) is distributed both on continents and islands, six species seem to be endemic to the East Asia Arc, i.e. main islands of
Japan, Ryukyus and Taiwan (Fujino and Shokita 1975; Cai 1996; Naruse et al. 2006; Shih and Cai 2007). With regard to the main islands of Japan, it has long been believed that only one species, N. denticulata (De Haan, 1844), is endemic, although N. davidi is also recorded and considered to be an introduced species (Nishino and Niwa 2004; Niwa et al. 2005; Niwa 2010; Fujita et al. 2011;
Toyota and Seki 2014). In addition, individuals of “N. heteropoda heteropoda” and “N. heteropoda koreana” have been recorded in main islands of Japan (Toyota and Seki 2014: 51-52).

Recent investigation of the Neocaridinaspecies across western Japan (from Nagasaki, Kyushu to Gifu, central Honshu), showed that the species richness is much higher than previous thought, although some have been considered as introduced (see above). While the study of these alien species will be published elsewhere (Shih et

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