Neocaridina palmata ( Shen, 1948 )

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 : 17

Neocaridina palmata ( Shen, 1948) ( Figs. 8 , 9 )

Specimens examined: Japan: 1 male, cl 4.6 mm, 1 male, cl 4.5 mm, NCHUZOOL 14940, 7 males, cl 3.6– 5.5 mm, ZRC 2023.0215, 1 male, cl 4.2 mm, 1 male, cl 5.0 mm, ZRC 2023.0216, Sugo R., Yumesaki River system, Himeji City, Hyogo Prefecture, N34°56'31.9", E134°38'19.0'', coll. N. Niwa, 14 Aug. 2015.

Native distribution: Mainland China and northern Vietnam ( Cai 1996; Liang 2004).

Remarks: Shen (1948) described Caridina palmata based on specimens from “Sha-Ping-Pa”, Chungking (= Chongqing), southwestern China, with no mention of specific comparison with other congeners. It had been totally ignored in the Chinese fauna until Dai et al. (1993) redescribed and illustrated it in detail and transferred it to Neocaridina . Morphologically, N. palmata is similar to N. denticulata and N. davidi . However, it can be distinguished from N. denticulata and N. davidi by its distinct palm-shaped endopod of the male first pleopods (vs. pear-shaped in the latter two species); and the much longer and stouter appendix interna of the male second pleopods, as well as the stouter spinules surrounding the appendix masculina ( Figs. 8 , 9 ). It can be further distinguished from N. denticulata by the sexual dimorphism in the third pereiopods, and from N. davidi by the distinctly longer appendix interna of the male second pleopods.

Two specimens (1 male, cl 4.2 mm; 1 male, cl 5.0 mm; ZRC 2023.0216) from Himeji City, Hyogo are morphologically typical of N. palmata , but the COI data show them to be clustered within N. davidi ( Fig. 3 ). We suspect that interspecific hybridization might have occurred between the two species living in the same waterbody (see “DISCUSSION”). In their natural range in China, the two species have not been found from the same collection sites ( Cai 1996; Liang 2004), while in Japan they were found to be sympatric in the Sugo River.

Neocaridina palmata is mainly distributed in central and southern China, with the northern limit in the Hubei and Anhui provinces and a western limit in the Yunnan and Sichuan provinces, and its range extends to southern China ( Liang 2004) and northern Vietnam ( Li and Liang 2004). The sequences of specimens from northern Vietnam have been included in the phylogenetic tree ( Fig. 3 ). The occurrence of N. palmata at Sugo River, Himeji City, Hyogo Prefecture, represents the first confirmed record of the species ( Figs. 2 , 3 ) being introduced outside its natural range in China and Vietnam.

According to Cai (1996) and Liang (2004), Neocaridina palmata is a hardy, well-adapted species that can be found in various freshwater habitats, e.g., small streams, large rivers, and open water like ponds, reservoirs, and lakes in temperate and subtropical areas, and always occurs in abundance. The species may pose threats to native Japanese atyid species. Close monitoring of the species is highly recommended for follow-up action.

Figures

Fig. 8. Neocaridina palmata (Shen, 1948). (A) cephalothorax and cephalic appendages, lateral view; (B) telson; (C) distal portion of telson; (D) scaphocerite; (E) male 1st pleopod; (F) male 2nd pleopod; (G) uropodal diaeresis. Scale bars: A = 2 mm; B, D, E, F = 0.5 mm; C, G = 0.2 mm (A, D–G, male, cl 4.6 mm, NCHUZOOL 14940, Sugo R., Yumesaki River system, Himeji City, Hyogo Prefecture, N34°56'31.9", E134°38'19.0'', coll. N. Niwa, 14 Aug. 2015; B, C, male, cl 4.3 mm, ZRC 2023.0215, Sugo R., Yumesaki River system, Himeji City, Hyogo Prefecture, N34°56'31.9", E134°38'19.0'', coll. N. Niwa, 14 Aug. 2015).

Fig. 9. Neocaridina palmata (Shen, 1948). (A) 1st pereiopod; (B) 2nd pereiopod; (C) 3rd pereiopod; (D) the same, dactylus; (E) 5th pereiopod; (F) the same, dactylus. Scale bars: A, B, C, E = 0.5 mm; D, F = 0.2 mm (male, cl 4.6 mm NCHUZOOL 14940, Sugo R., Yumesaki River system, Himeji City, Hyogo Prefecture, N34°56'31.9", E134°38'19.0'', coll. N. Niwa, 14 Aug. 2015).

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.

Fig. 2. A neighbor-joining COI tree, based on 53 haplotypes (115 specimens) of Neocaridina species from the main islands of Japan and the related taxa from East Asia. Only bootstrap values> 50% are shown on the nodes. *, species collected from Japan in this study.