Monday, October 2, 2017

[Crustacea • 2017] Neocaridina ikiensis • A New Species of Land-locked Freshwater Shrimp of the Genus Neocaridina (Decapoda: Caridea: Atyidae) from Iki Island, Kyushu, Japan

Neocaridina ikiensis
 Shih, Cai, Niwa & 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 (mitochondrial cytochrome oxidase I gene) 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 endemic 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.

 Fig. 5. Live coloration of Neocaridina ikiensis n. sp. (A)
and its habitat in Iki Island (B).
Fig. 1. Collection sites (marked in red circles) for Neocaridina ikiensis n. sp. in Iki Island. 

Family Atyidae De Haan, 1849
Neocaridina Kubo, 1938
Neocaridina ikiensis n. sp.

Etymology: The species is named after the type locality, Iki Island, Nagasaki Pref., western Japan. 

Ecological notes: Habitat (Fig. 5B) of the species is small streams, about 2 m wide, with slow flowing water. Stream banks were heavily vegetated. Collection sites were about 100 m to 1 km away from the coast. In one of the streams, a rice paddy is found adjacent to its upper reach, where substrate was muddy and with various sized rocks submerged in the water. The freshwater crab Geothelphusa dehaani (White, 1847) and the catadromous atyid shrimp Caridina typus H. Milne Edwards, 1837 were found sympatric with the new species.

Distribution: Presently known only from several streams in Iki Island, western Japan. 

Hsi-Te Shih, Yixiong Cai, Nobuaki Niwa and Yasuhiko Nakahara. 2017. A New Species of Land-locked Freshwater Shrimp of the Genus Neocaridina (Decapoda: Caridea: Atyidae) from Iki Island, Kyushu, Japan. Zoological Studies. 56;  DOI:  10.6620/ZS.2017.56-30

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