Neocaridina aff. 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 : 17-21

Neocaridina aff. palmata ( Fig. 10 )

Specimens examined: Japan: 1 male, cl 4.2 mm, NCHUZOOL 14940, 1 female, cl 5.5 mm, 1 ovig. female, cl 5.1 mm, non-eyed eggs 1.0 × 0.7 mm, NCHUZOOL 14941, Sugo R., Yumesaki River system, Himeji City, Hyogo Prefecture, N34°56'31.9", E134°38'19.0'', coll. N. Niwa, 14 Aug. 2015; 1 female, cl 4.1 mm, NCHUZOOL 14954, Takahamagawa R., Takahamagawa system, Izumo City, Shimane Prefecture, N35°23'33.3", E132°43'37.1", coll. Y. Nakahara, 10 Mar. 2015; 1 female, cl 6.1 mm, NCHUZOOL 14965; Basen-gawa R., Go-no-gawa system, Miyoshi City, Hiroshima Prefecture, N34°46'51", E132°54'39", coll. H. Yoshigou, 28 Feb. 2016. 1 female, cl 4.7 mm, ZRC 2023.0217; Basen-gawa R., Go-no-gawa system, Miyoshi City, Hiroshima Prefecture, N34°46'51", E132°54'39", coll. H. Yoshigou, 28 Feb. 2016. Korea: 1 female, cl 5.0 mm, NCHUZOOL 14972, aquarium, coll. Jul. 2005. Mainland China: 1 female, cl 3.9 mm, NCHUZOOL 15169, Jiangle, Fujian, coll. H.-T. Shih, 5 Jul. 2004; 1 female, cl 4.3 mm, NCHUZOOL 15172, Nanping, Fujian, coll. H.-T. Shih, 5 Jul. 2004; 1 male, cl 4.1 mm, NCHUZOOL 15170, Yunnan, coll. H.-T. Shih, 5 Nov. 2002; 1 ovig. female, cl 6.2 mm, non-eyed eggs 0.9 × 0.7 mm, ZRC 2023.0218, Shilin, Yunnan, coll. Y. Cai, 11 Apr. 2005; 1 female, cl 6.0 mm, NCHUZOOL 15171, Kunming, Yunnan, coll. H.-T. Shih, 5 Nov. 2002.

Native distribution: Korea and mainland China.

Remarks: This species is morphologically very close to N. palmata , and currently we can only separate them based on subtle differences displayed by the available specimens ( Fig. 10 ), e.g., the position of the appendix interna located at 0.35 times the length of the endopod (vs. 0.30 in N. palmata ); the telson terminating in a prominent projection (vs. hardly discernible in N. palmata ) and a broader scaphocerite (2.8 times as long as wide vs. 3.4 in N. palmata ) (cf. Figs. 8 , 9 ).

Shih et al. (2017) assigned a specimen that they obtained from South Korea (aquarium dealer) to “ N. koreana ”. The specimen (NCHUZOOL 14972) was reexamined morphologically in the current study, but we are unable to confirm its identity morphologically as it is a female specimen. However, COI sequence data ( Figs. 2 , 3 ) firmly indicated that it should be re-assigned to N. aff. palmata instead.

Kakui and Komai (2022) reported the first occurrence of the freshwater ectoparasitic platyhelminth Scutariella japonica from Yasuharu River, Sapporo, Hokkaido, Japan and discussed the identity of the host shrimps, a species of Neocaridina . Phylogenetic analyses using COI ( Kakui and Komai 2022: fig. 5) showed that the host species is clustered with “ N. koreana ” identified by Shih et al. (2017) (see above), sister to N. palmata , and also close to two clades, “ N. davidi ” (types I and II, after Nagai and Imai 2021). The authors thus tentatively referred their shrimps to “ N. sp. aff. davidi ”. The Hokkaido COI sequences (LC664097, LC664098, LC664099) were re-analyzed in our study and the results show that genetically they are conspecific with our material of “ N. aff. palmata ” ( Fig. 3 ). The specimens from the same clade in Kakui and Komai (2022: fig. 5) would also be assigned to the same species, including specimens from Hyogo (AB524970), Shimane (AB524966, AB524968), and Chiba (LC664096), and Chinese material from Henan Province (MW069628, MW069631, MW069644, MW069650, MW069652, MW069653, MW069657, MW069661, MW069670).

Notably, based on one of the specimens, the drawings of the endopod of the male first pleopods, the appendix masculina of the male second pleopods, and the form of the dactylus and propodus of the male third pereiopods provided by Kakui and Komai (2022: fig. 3E, F, H) clearly exhibit morphological characteristics consistent with N. davidi , despite the authors initially believing this specimen to be a young male. It is worth noting that our current study observed both N. aff. palmata and N. davidi living sympatrically in the streams at Hyogo, Himeji City and Shimane, Izumo City. The conflict between genetic and morphological findings suggests the possibility of interspecific hybridization (see “DISCUSSION”). Further investigation with both morphology and DNA testing would facilitate a taxonomic decision.

The species is found in Fujian (Jiangle and Nanping) and Yunnan (Shilin and Kunming) in southern China, as well as the Korean Peninsula, so we presume that China and Korea are likely its native range. We have recorded its presence in several Japanese localities, including Hyogo, Shimane, Hiroshima, Chiba, and Hokkaido ( Fig. 3 ). These localities are considered to represent one or more introductions, especially since the sites (Sites 2, 8 and 10 in Fig. 1 ) are also associated with other introduced species ( Table 3).

Figures

Fig. 10. Neocaridina aff. palmata. (A) cephalothorax and cephalic appendages, lateral view; (B) 1st pereiopod; (C) 2nd pereiopod; (D) 3rd pereiopod; (E) the same, dactylus; (F) 5th pereiopod; (G) the same, dactylus; (H) male 1st pleopod; (I) male 2nd pleopod. Scale bars: A–D, F = 0.5 mm; E, G, H, I = 0.2 mm (male, cl 4.2 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. 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. 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.

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. 1. Collection sites (nos. 1–18, black circles) for species of Neocaridina in the main islands of Japan (Honshu and Kyushu). For locality names and haplotypes, see table 1. Nos. 19–21 (gray circles) are the additional localities in Fuke et al. (2021).