Neocaridina ikiensis Shih, Cai, Niwa & Nakahara, 2017

Shih, Hsi-Te, Cai, Yixiong, Niwa, Nobuaki, Yoshigou, Hidenori & Nakahara, Yasuhiko, 2024, Fig. 4. A in Positive association between PTN polymorphisms and schizophrenia in Northeast Chinese Han population., Zoological Studies 63 (18), pp. 141-149 : 21

Neocaridina ikiensis Shih, Cai, Niwa & Nakahara, 2017

Specimens examined: See Shih et al. (2017).

Native distribution: This species is only distributed in Iki Island, Nagasaki Prefecture, western Japan ( Shih et al. 2017).

Remarks: This species was the second native species of Neocaridina discovered in the main islands of Japan; and its distribution is restricted to Iki Island, an offshore island in northern Kyushu ( Shih et al. 2017).

Fuke et al. (2021) questioned the validity of N. ikiensis , commenting that Shih et al. (2017) may not have adequately considered the genetic and morphological variations between their new species and the populations of N. denticulata in nearby regions, including what they referred to as “ N. denticulata ” from Fukue-jima Island, Goto, Nagasaki; Ishiki River, Kawatana, Nagasaki; Kuro River, Aso, Kumamota; and Machida R., Kokoneo, Oita. Their COI tree showed that N. ikiensis clustered together with several populations of their “ N. denticulata ”. By re-analyzing their sequences using longer lengths ( Table 3), along with ours, the results ( Fig. 3 ) indicate that N. ikiensis forms a sister clade with the Machida population. The samples collected from Kuro River and Ishiki River form one clade, which is sister to a clade composed of samples from the Goto Islands. The supported values of these two clades suggest that each clade may represent a separate species not previously recognized, here assigned as N. sp. 1 and N. sp. 2, from the Kuro/Ishiki River and from the Goto Islands, respectively. These two clades are distinctly differentiated from the taxa N. denticulata and N. aff. denticulata that our study recognizes based on both genetic and morphological data (cf. Fig. 3 ).

The group formed by N. sp. 1, N. sp. 2, and N. aff. fukiensis is sister to another group comprising N. ikiensis and the previously mentioned Machida population ( Fig. 3 ). Neocaridina aff. fukiensis is morphologically very distinct from N. denticulata (see Remarks under N. aff. fukiensis ), and the Machida specimens may represent another separate species, named here as N. sp. 3, that is genetically similar to N. ikiensis . Since Fuke et al. (2021) did not provide morphological characters for the species they identified, we cannot compare these three potential unknown species to any of the known ones.

Figures

Fig. 3. Bayesian inference (BI) tree for species of the genus Neocaridina from the East Asia Arc and the related taxa from East Asia, based on the cytochrome c oxidase subunit I (COI) gene. Probability values at the nodes represent support values for BI and maximum likelihood (ML). Only support values> 50% are shown on the nodes. For haplotype names, see table 1. *, sequences downloaded from GenBank.