Neocaridina denticulata (De Haan, 1844)

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 : 8-11

Neocaridina denticulata (De Haan, 1844) ( Figs. 4 , 5 )

Specimens examined: Japan: 1 male, cl 6.5 mm, 1 male, cl 5.2 mm, 6 males, cl 4.2–4.7 mm, ZRC 2023.0211, Kaya R., Ashida River system, Fukuyama City, Hiroshima Prefecture, N34°36'43", E133°15'33", coll. H. Yoshigou, 17 Oct. 2015; 1 female, cl 6.2 mm, 1 female, cl 5.9 mm, 11 females, cl 4.1–7.5 mm, NCHUZOOL 14965, 1 male, cl 4.2 mm, 9 males, cl 4.5–6.0 mm, NCHUZOOL 14964, 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 3.5 mm, NCHUZOOL 14944, Kurose R., Kurose River system, Higashihiroshima City, Hiroshima Prefecture, N34°23'14", E132°43'50", coll. H. Yoshigou, 27 Sep. 2015; 1 male, cl 3.3 mm, NCHUZOOL 14942, Shizuki R., Shizuki River system, Awaji City, Awaji Island, Hyogo Prefecture, N34°26'09.8", E134°53'22.8", coll. Y. Nakahara, 17 Sep. 2015; 1 female, cl 3.8 mm, 1 male, cl 3.7 mm, NCHUZOOL 14968, Iwatuki-gawa R., Takahashigawa system, Odagawa, Ihara City, Okayama Prefecture, N34°33'57.4", E133°28'50.4", coll. H. Yoshigou, 10 Oct. 2016; 1 female, cl 4.5 mm, 1 male, cl 4.1 mm, NCHUZOOL 14960, Misasa R., Ota-gawa system, Hiroshima City, Hiroshima Prefecture, N34°29'11", E132°31'51", coll. H. Yoshigou, 11 Feb. 2016; 2 males, cl 5.8, 5.9 mm, ZRC 2024.0055, Misasa R., Ota-gawa system, Hiroshima City, Hiroshima Prefecture, N34°29'11", E132°31'51", coll. H. Yoshigou, 11 Feb. 2016; 1 male, cl 3.6 mm, NCHUZOOL 14946, Kaya R., Ashida River system, Fukuyama City, Hiroshima Prefecture, N34°36'43", E133°15'33", coll. H. Yoshigou, 17 Oct. 2015; 1 male, cl 4.7 mm, NCHUZOOL 14958, Hazamagawa R., Shonaigawa system, Mizunami City, Gifu Prefecture, N35°22'03.9", E137°14'07.6", coll. Y. Nakahara, 21 Oct. 2015; 1 female, cl 4.7 mm, NCHUZOOL 14966, Ato-gawa R., Seno-gawa system branch of Kumano-gawa R., Hiroshima City, Hiroshima Prefecture, N34°22'53", E132°38'17", coll. H. Yoshigou, 5 Mar. 2015; 1 male, cl 4.3 mm, ZRC 2023.0212, Sunagawa R., Asahigawa system, Akaiwa City, Okayama Prefecture, N34°53'48", E134°01'05", coll. H. Yoshigou, 23 Nov. 2015. Mainland China: 1 female cl 8.7 mm, NCHUZOOL 15168, Pingyuan, Yunnan, coll. H.-T. Shih, 4 Nov. 2002; NCHUZOOL, Taihu (Lake), Changzhou, Jiangsu, coll. W.-R. Yun, 30 Jun. 2018; 5 males, cl 3.2–3.4 mm, 6 females, cl 3.9–4.5 mm, ZRC 2023.0213, Taihu (Lake), Changzhou, Jiangsu, coll. W.- R. Yun, 30 Jun. 2018.

Native distribution: Western part of the main islands of Japan ( Toyota et al. 2014; Mitsugi et al. 2017; Mitsugi and Suzuki 2018).

Remarks: Neocaridina denticulata , the type species of this genus, was considered the only native species of the genus in the main islands of Japan ( Cai 1996; Liang 2004) until the publication of the name N. ikiensis for specimens from Iki Island, off the northern coast of Kyushu ( Shih et al. 2017). Key characters of N. denticulata include its relatively long rostrum, which generally reaches beyond the end of the antennular peduncle; the third and fifth pereiopods do not display sexual dimorphism; the endopods of the male first pleopods are distinctly broad, about 1.2 times as long as wide, and the appendix interna of the male second pleopods is short, not reaching the end of the endopod ( Cai 1996; Liang 2004). Our specimens agree well with these characters ( Figs. 4 , 5 ). Based on our study supported by molecular evidence, the species is confirmed to be distributed in the main islands of Japan, as well as the Jiangsu (Taihu Lake and Nanjing City) and Yunnan Provinces of China ( Fig. 3 ). Due to the limited samples across China used for genetic comparison, we are unable to comment if these populations in China are native.

When describing two new Neocaridina species from Taiwan, Shih and Cai (2007) presented genetic relationships by examination of COI sequences of their new species with a few known species from Taiwan, China and Japan. In their study, Neocaridina denticulata was represented by specimens from Lake Biwa (AB300191). Nishino (2017) and Fuke et al. (2021) questioned the validity of the species name used for the genetic material, as N. denticulata was presumed to be extinct from Lake Biwa before the incidental introduction of N. davidi in the 2000s, and N. davidi has since spread widely in and beyond the lake ( Nishino and Niwa 2004). Based on molecular and morphological evidence, however, Onuki and Fuke (2022) recently confirmed that both species are found in Lake Biwa. With more samples available, our current study shows that the Lake Biwa specimen (AB300191) is genetically closely clustered with many N. denticulata specimens from western Japan and China (Jiangsu and Yunnan) ( Fig. 3 ). The attribution of the name N. denticulata to this specimen by Shih and Cai (2007) was therefore correct.

Nagai and Imai (2021) reported a species of Neocaridina from Kakinohana spring, Nanjo City, Okinawa Island, the Ryukyus. They tentatively assigned their specimens to “ N. davidi Type II ( N. davidi koreana ?)” based on COI sequences. These sequences shared only one haplotype and genetically clustered together with our N. denticulata specimens collected from Shiga (Lake Biwa), Gifu, Hyogo, Okayama, Shimane, Hiroshima, and Yamaguchi ( Fig. 3 ), as well as one of Fuke et al. (2021) ’s Oita specimens (LC612373) ( Nagai and Imai 2021: fig. 3). This result suggests that the Okinawa specimens should be assigned to N. denticulata , and this species also occurs in Oita. The Chinese material (from Henan Province) named as N. davidi koreana (MW069609–MW069622) in Zhou et al. (2021) should also be assigned to N. denticulata .

Levitt-Barmats et al. (2019) reported the occurrence of “ N. denticulata ” in Israel. According to the authors, the Israeli specimens are most probably N. denticulata , as they showed no sexual dimorphism in the third pereiopods. However, their COI sequences of 15 specimens (MN336485–MN336499) from Japan (Okayama), cluster into two distinct clades, with three specimens belonging to N. denticulata and 12 belonging to N. aff. denticulata (results not shown). In our study, these two species have also been identified from Okayama ( Table 3). By including the longer Israeli COI sequences of Neocaridina ( Table 2) into our phylogenetic tree ( Fig. 3 ), all samples clustered well within the clade of N. davidi , except for one (MN336458) from HaHula Nature Reserve, which belonged to N. denticulata . While this specimen may represent the first recorded introduction of N. denticulata outside its natural range ( Japan and possibly China), we cannot exclude the possibility of mislabelling.

Figures

Fig. 4. Neocaridina denticulata (De Haan, 1844). (A) cephalothorax and cephalic appendages, lateral view; (B) telson; (C) distal portion of telson; (D) preanal carina; (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 6.5 mm, B, C, male, cl 5.2 mm, ZRC 2023.0211, Kaya R., Ashida river system, Fukuyama City, Hiroshima Prefecture, N34°36'43", E133°15'33'', coll. H. Yoshigou, 17 Oct. 2015).

Fig. 5. Neocaridina denticulata (De Haan, 1844). (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 6.5 mm, ZRC 2023.0211, Kaya R., Ashida River system, Fukuyama City, Hiroshima Prefecture, N34°36'43", E133°15'33'', coll. H. Yoshigou, 17 Oct. 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.