Biogeography 20. 103–110. Sep. 20, 2018

Discrimination of two freshwater , paucidens De Haan, 1844 and P. sinensis (Sollaud, 1911) using plumose setae of telson and appendix masculina

Tadashi Imai 1*, Kazuki Hayashi 2, Masayuki Nakaso 3, Seinen Chow 4, Kenji Nohara 5 and Takakiyo Oonuki 5

1 National Research Institute of Fisheries and Environment of Inland Sea, Japan Fisheries Research and Education Agency, 234 Yashima-higashi, Takamatsu, Kagawa, 761-0111 Japan 2 Kagawa Prefectural Fisheries Experiment Station, 75-5 Yashima-higashi, Takamatsu, Kagawa, 761- 0111 Japan 3 Chlorella Industry Co., Ltd., 1343 Hisadomi, Chikugo, Fukuoka 833-0056, Japan 4 National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa 236-8648, Japan 5 School of Marine Science and Technology, Tokai University, 3-20-1 Orido, Shimizu, Shizuoka, 424- 8610, Japan

Abstract: Live specimens of two freshwater shrimps, Palaemon paucidens De Haan, 1844 and P. sinensis (Sollaud, 1911) can be distinguished from the specific carapace color patterns. However, color pattern of spec- imen preserved in ethanol or diluted formalin slowly fades and is eventually lost. We re-examined previous information and chose the number of plumose setae on distal end of telson and appendix masculina as new identification characters. Number of plumose setae (average, range) was more in P. sinensis (9.0, 4-14) than in P. paucidens (A type, 2.1, 2-3; B type, 2.0, 1-3). Form and lateral setae arrangement of appendix masculina were found to be different between these two . These characters cannot be applied to females and young males as well as individuals with a malformed telson. Combining these characteristics with those previ- ously described (the presence or absence of a subterminal tooth on the upper edge of rostrum and different eye size etc.) will enable identification ofP. paucidens and P. sinensis even in color faded state more reliable.

Key words: appendix masculina; plumose setae of telson; invasive species; Palaemon miyadii; Palaemon paucidens; Palaemon sinensis.

Introduction southeastern Siberia and Sakhalin (Holthuis, 1950; Liu et al., 1990; Li et al., 2007; Cai & Dai, 1999; Freshwater , Palaemon paucidens De Cai & Ng, 2002; Labay, 2011) (Fig. 1b), and before Haan, 1844 is only the native species of the genus 1990 P. sinensis had not been reported from Japan Palaemon inhabiting freshwater areas in Japan (Liu et al., 1990). However, in 2005, P. sinensis was (Hayashi, 2000) (Fig. 1a). Chinese grass shrimp, P. discovered in an inland waterbody located in Shizuo- sinensis (Sollaud, 1911) (formerly known as Palae- ka Prefecture, central Japan (Oonuki et al., 2010). monetes sinensis) is distributed in China, Myanmar, Now P. sinensis is reported from 15 of 47 prefectures ——————————————————————— in Japan (Chow et al., 2018; Environment Division *Corresponding author:[email protected] of the Suginami Ward, 2016; Hasegawa et al., 2016;

− 103 − Discrimination of Palaemon paucidens and P. sinensis Tadashi Imai, Kazuki Hayashi, Masayuki Nakaso, Seinen Chow, Kenji Nohara and Takakiyo Oonuki

130ﾟ E

40ﾟ N

c-3

c-1 c-7 c-2 c-8 a c-4 b c-5 c-6 30ﾟ N

140ﾟ E

Fig. 1. Lateral and diagonal views of Palaemon paucidens A type (a), collected at Shin River, Kagawa Prefecture and P. sinensis (b) collected at Hasuike Park, Kochi Prefecture. Fig. 2. Sampling locations of Palaemon paucidens and P. sinensis Scale bars = 10 mm. in Japan. (a) Shin River, Miki Town, Kagawa Prefecture; (b) Kumomo River, Tosashimizu City, Kochi Prefecture; (c-1) central brook in the Mizumoto Park, Katsushika Hiraoka et al., 2018; Imai & Oonuki, 2014, 2017; Ward, Tokyo; (c-2) an unnamed pond, Hamamatsu City, Shizuoka Prefecture; (c-3) Takahashi River, Soja City, Oonuki et al., 2017; Saito, 2017; Saito et al., 2016, Okayama Prefecture; (c-4) Pond in the Takamiyama 2017; Shichiri et al., 2017; Yoshigo & Yoshigo, Park, Tonosho Town, Kagawa Prefecture; (c-5) Pond in the Hasuike Park, Tosa City, Koch Prefecture; (c-6) 2016) (Fig. 2). Howara River, Iwamatsu River System, Uwajima City, P. paucidens is also distributed in China and Ko- Ehime Prefecture; (c-7) Shiota River, Ureshino City, Saga Prefecture; (c-8) Lake Shimoezu (brook in the Suizenji- rea (Li et al., 2007; Kim, 2012), which has been ex- ezuko Park), Kumamoto City, Kumamoto Prefecture. ported to Japan for use as bait (Niwa, 2010; Saito et P. paucidens A and B types, and P. sinensis used in this study were collected at a, b and c-1 - c-8, respectively. al., 2011). Since P. paucidens and P. sinensis which Prefectures where P. sinensis was collected in the previous very closely resemble each other have been imported studies (Chow et al., 2018; Environment Division of the Suginami Ward, 2016; Hasegawa et al., 2016; Hiraoka to Japan without being distinguished, the occurrence et al., 2018; Imai & Oonuki, 2014, 2017; Oonuki et al., of P. sinensis in Japan is thought to have been caused 2010, 2017; Saito, 2017; Saito et al., 2016, 2017; Shichiri et al., 2017; Yoshigo & Yoshigo, 2016) are shown in red. by the imported P. sinensis (Niwa, 2010; Oonuki et al. 2010; Saito et al., 2011). Presence or absence of a mandibular palp used to discriminate P. paucidens upper edge of rostrum (Oonuki et al., 2010), molar and P. sinensis is a key characteristic to divide the process structure of the mandible (Labay, 2011), eye formerly genera Palaemon and Palaemonetes (Chace size (Imai & Oonuki, 2014), the projection shape of & Bruce, 1993; Jayachandran, 2001; Li et al., 2007). distal portion of telson (Hasegawa et al., 2016) and Recently, the genus Palaemonetes was demonstrated color pattern of tail fan (Shichiri et al., 2017) were to be junior synonyms of Palaemon (De Grave & reported to be diagnostic characteristics between the Ashelby 2013). As a reliable, non-lethal identifica- two species. However, the color patterns disappear tion method, Imai & Oonuki (2014) reported that in fixatives, and damaged or malformed individuals live samples of both species could be distinguished may not be identifiable by using a single morpholog- from the specific carapace color pattern. In addition, ical key. presence or absence of subterminal tooth on the We reviewed the morphological characters of

− 104 − Discrimination of Palaemon paucidens and P. sinensis Tadashi Imai, Kazuki Hayashi, Masayuki Nakaso, Seinen Chow, Kenji Nohara and Takakiyo Oonuki

these two species described previously, and the Nikon) (see Imai & Oonuki, 2014). Upper and lower number of plumose setae on distal end of telson and rostrum teeth were counted. Of upper rostrum teeth, shape and lateral setae arrangement of appendix those on the carapace posterior to the eye orbit was masculina are proposed as novel identification char- counted. Presence and absence of subterminal tooth acters. on the upper edge of rostrum was observed. Accord- ing to Imai & Oonuki (2014), eye length (EL) and Materials and Methods diameter of cornea (DC) were measured from the dorsal side. We investigated the presence or absence Specimens were collected at ten locations in Ja- of a palp on the mandibles in some individuals. pan between 2006 and 2018 (Fig. 2). P. paucidens A We reviewed previous descriptions of P. pauci- type sample was collected in Shin River, Miki Town, dens and/or P. sinensis by Kubo (1938), Holthuis Kagawa Prefecture (a). P. paucidens B type sample (1950; Figs. 14, 20, 21), Kim (1977; Figs. 72, 73), was collected in Kumomo River, Tosashimizu City, Suzuki & Sato (1994; p. 7), Bruce (1994) and Li et Kochi Prefecture (b), and P. sinensis samples were al. (2007; Figs. 65, 70), and found specific differ- collected at central brook in the Mizumoto Park, Kat- ences in the number of plumose setae on distal end sushika Ward, Tokyo (c-1), an unnamed pond, Ham- of telson, and shape and lateral setae arrangement of amatsu City, Shizuoka Prefecture (c-2), Takahashi appendix masculina. The number of plumose setae River, Soja City, Okayama Prefecture (c-3), Pond in between inner spines on the distal end of telson was the Takamiyama Park, Tonosho Town, Kagawa Pre- counted from the dorsal side under stereo micro- fecture (c-4), Pond in the Hasuike Park, Tosa City, scope. In second pleopod of male, length of appen- Kochi Prefecture (c-5), Howara River, Iwamatsu dix masculina and appendix interna, and range of River System, Uwajima City, Ehime Prefecture (c- 6), Shiota River, Ureshino City, Saga Prefecture (c- 7), and Lake Shimoezu (brook in the Suizenji-ezuko Park), Kumamoto City, Kumamoto Prefecture (c- 8). Shrimps were caught using D-shaped hand net (mesh size 2.5 mm; frame width 33 cm; handle length 60 cm). P. paucidens and P. sinensis were di- vided on site according to the difference of carapace color pattern (see Imai & Oonuki, 2014). Collected shrimps were then preserved in 10% formalin or 90% ethanol. Two types (A and B) of P. paucidens were genetically identified (see Chow et al. 2018). These fixed samples were used for morphological examination. Body length (BL, from orbital edge to the distal

end of telson) and carapace length (CL, from orbital Fig. 3. Appendix masculina and appendix interna of male second edge to posterior margin of carapace) of samples pleopod. (a) Palaemon paucidens A type, collected at Shin River, Kagawa Prefecture (male, 24.2 mm BL, 6.7 were measured using calipers. Individuals with mm CL); (b) P. sinensis collected at Hasuike Park, Kochi appendix masculina on second pleopod were de- Prefecture (male, 22.3 mm BL, 6.1 mm CL). Measurement position: length of appendix masculina (1-4), length of termined to be male. The numbers of rostrum teeth appendix interna (1-2) and range of setae on appendix were counted under stereo microscope (SMZ1270, masculina (3-4). Scale bars = 0.1 mm.

− 105 − Discrimination of Palaemon paucidens and P. sinensis Tadashi Imai, Kazuki Hayashi, Masayuki Nakaso, Seinen Chow, Kenji Nohara and Takakiyo Oonuki lateral setae on appendix masculina were measured excluded from the rostrum teeth count, because of (Fig. 3). partially broken rostrum. Range of upper rostrum teeth number (posterior and anterior from the eye Results orbit) of P. sinensis (1-2 + 3-5) was similar to two types of P. paucidens (A type, 1-2 + 3-6 and B type, The specimens identified as P. sinensis by cara- 1-2 +4-7) (Table 1). No notable difference in lower pace color pattern (Fig. 1b) had mandibles without rostrum teeth number was observed between species. a palp (Fig. 4b), and those of P. paucidens had Percentage of individuals having a subterminal tooth mandibles with a palp (Fig. 4a). Five individuals on the upper edge of rostrum in the A and B types of P. paucidens A type, two individuals of P. pauci- of P. paucidens and P. sinensis examined were 20.0, dens B type and one individual of P. sinensis were 91.3 and 2.9%, respectively. Values of EL/DC of P. sinensis (1.36-2.11) were higher than those of P.

Fig. 5. Distal portion of telson of Palaemon paucidens A type (a), collected at Shin River, Kagawa Prefecture (male, Fig. 4. Mandibles of Palaemon paucidens A type (a), collected 24.2 mm BL, 6.7 mm CL) and P. sinensis (b) collected at Shin River, Kagawa Prefecture and P. sinensis (b) at Hasuike Park, Kochi Prefecture (male, 22.3 mm BL, collected at Hasuike Park, Kochi Prefecture. Arrow shows 6.1 mm CL). Note the different number of plumose setae mandibular palp in P. paucidens. Scale bars = 0.5 mm. between species. Scale bars = 0.1 mm.

Table 1. Parameters of Palaemon paucidens A and B types, and P. sinensis used in this study. Number of individuals examined is shown in parenthesis.

P. paucidens A type P. paucidens B type P. sinensis * Average and range of body length (mm) 30.1, 17.8-51.1 (25) 40.2, 27.7-56.2 (25) 23.5, 12.5-35.7 (70) Average and range of carapace length (mm) 8.4, 4.6-14.9 (25) 11.5, 6.4-16.1 (25) 6.7, 3.2-9.3 (70) Range of upper rostrum teeth number (posterior and anterior from the 1-2+3-6 (20) 1-2+4-7 (23) 1-2+3-5 (69) eye orbit) Range of lower rostrum teeth number 1-2 (20) 2-4 (23) 1-3 (69) Percentage of individuals having a subterminal tooth on the upper edge 20.0 (20) 91.3 (23) 2.9 (69) of rostrum (%) Ratio of eye length (EL) to diameter of cornea (DC) 1.13-1.58 (25) 1.19-1.63 (25) 1.36-2.11 (70) Average, mode and range of plumose setae number at distal portion of 2.1, 2, 2-3 (22) 2.0, 2, 1-3 (22) 9.0, 10, 4-14 (67) telson Ratio of appendix masculina length to appendix interna length 1.6-2.3 (12) 1.6-2.2 (13) 1.3-1.8 (23) Ratio of lateral setae range to appendix masculina length 72.1-82.0 (12) 60.5-76.0 (13) 2.7-32.8 (23) * Collection localities and number of individuals were Mizumoto Park (n =10), an unnamed pond in the Hamamatsu City (n = 6), Takahashi River (n =6), Takamiyama Park (n = 21), Hasuike Park (n = 8), Howara River (n = 7), Shiota River (n = 1) and Lake Shimoezu (n = 11).

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Fig. 6. Malformed distal portion of telson. (a, b, c) Palaemon paucidens A type (Shin River, Kagawa Prefecture) and (d) P. sinensis (Takamiyama Park, Kagawa Prefecture). Fig. 7. Frequency distributions of plumose setae number on distal portion of telson. (a) Palaemon paucidens A type collected at Shin River, Kagawa Prefecture, (b) P. paucidens B paucidens (A type, 1.13-1.58 and B type, 1.19-1.63) type collected at Kumomo River, Kochi Prefecture and (Table 1). (c) P. sinensis collected at eight localities shown in Fig. 2. Individuals having malformed distal portion of telson Distal portion of telson of P. paucidens and P. shown in Fig. 6 were not included. sinensis was comprised of median projection, two pairs of lateral spines and plumose setae (Fig. 5). Sublateral pair of spines was longer than lateral pair. was less than 40% (Fig. 3b, Table 1). We observed seven individuals (three P. paucidens A type, three P. paucidens B type and three P. sinensis) Discussion having abnormal distal portion of telson as shown in Fig. 6. Excluding these abnormal individuals, the In the present study, the number of plumose setae mode (range) of plumose setae numbers of A and B on the distal end of telson, and setae arrangement types of P. paucidens and P. sinensis were 2 (2-3), and shape of appendix masculina were proposed 2 (1-3) and 10 (4-14), respectively (Fig. 7, Table 1), to be new diagnostic characteristics between P. with a significant difference betweenP. paucidens (A paucidens and P. sinensis. However, the number of + B types) and P. sinensis (Tukey’s test, P<0.05). plumose setae on the distal end of telson may not be Length of the appendix masculina of P. paucidens applicable to malformed individuals as shown in Fig. was 1.6-2.3 times the appendix interna, and lateral 6 and Kamita (1970; Fig. 69J). Relative length of side area of appendix masculina covered by setae appendix masculina and appendix interna and setae was greater than 60% (Fig. 3a, Table 1). On the other arrangement on appendix masculina cannot be ap- hand, length of the appendix masculina of P. sinensis plied to female and young male without well grown was 1.3-1.8 times the appendix interna and lateral appendix masculina (Kamita, 1970; Fig. 67D, E, F). side area of appendix masculina covered by setae Therefore, in addition to these characters, identifi-

− 107 − Discrimination of Palaemon paucidens and P. sinensis Tadashi Imai, Kazuki Hayashi, Masayuki Nakaso, Seinen Chow, Kenji Nohara and Takakiyo Oonuki cation of color-faded P. paucidens and P. sinensis Acknowledgements may be more reliable by incorporating the presence or absence of subterminal tooth on the upper edge of We thank Dr. K.-I. Hayashi for providing infor- rostrum and eye size. mation on Palaemon miyadii. The characteristics of P. sinensis (rostrum with- out subterminal tooth on the upper edge, appendix Reference masculina small, about 1.5 times as long as appendix interna and setae of appendix masculina only on the BRIC, 2018. http://m.ibric.org/miniboard/read. distal margins) resemble those of Palaemon miyadii php?Board=species&id=32319&Page= (Kubo, 1938) (formerly known as Leander miyadii) 1&&PARA6=Y&PARA0=7. Accessed 14 May described by Kubo (1938), which is distributed in 2018. China and Korea (Kubo, 1938; Kim, 1977). Al- Bruce, A. J., 1994. A re-examination of Palaemone- though P. sinensis is not recorded from Korea, the tes sinensis (Sollaud, 1911) (Crustacea; Decapo- distribution of P. sinensis in China overlaps with that da; ). The Beagle, Records of the of P. miyadii. Carapace color patterns of P. miyadii Museums and Art Galleries of the Northern Terri- and P. sinensis are very similar to each other accord- tory, 11: 1–7. ing to the color photographs (BRIC, 2018). Kubo Cai, Y. & Dai, A. Y., 1999. Freshwater shrimps (1938) did not describe an important character, that (Crustacea: : ) from the Xish- is the mandible. In mandibles of P. miyadii drawn by uangbanna region of Yunnan Province, southern Kim (1977; Fig. 71c, d), there is a palp on the right China. Hydrobiologia, 400: 211–241. not on the left. Since there has been no diagnostic Cai, Y. & Ng, P. K. L., 2002. The freshwater palae- characteristics between P. sinensis and P. miyadii, monid prawns (Crustacea: Decapoda: Caridea) of the later might be a junior synonym of P. sinensis. Myanmar. Hydrobiologia, 487: 59–83. Both P. paucidens and P. sinensis are sold as rec- Chace, F. A. Jr & Bruce, A. J., 1993. The caridean reational fishing bait under the Japanese trade name shrimps (Crustacea: Decapoda) of the Albatross ‘Shirasa ebi’ (Niwa 2010; Saito et al. 2011, 2017; Philippine Expedition 1907-1910, Part 6: Super- Saito, 2018). According to Niwa (2010), ‘Shirasa family Palaemonoidea. Smithsonian Contributions ebi’ imported to Japan was collected in south of to Zoology, 543: 1–152. Daegu, Korea and in Liaoning, Jilin, Hebei, Jiangsu, Chow, S., Imai, T., Ikeda, M., Maki, S., Oonuki, Zhejiang and Henan, China. Since distribution of T., Muto, F., Nohara, K., Furusawa, C., Shichiri, P. sinensis and P. miyadii overlaps in most of these H., Nigorikawa, N., Uragaki, N., Kawamura, A., areas, P. miyadii may have been already been intro- Ichikawa, T., Ushioda, K., Higuchi, M., Tega, duced to Japan. However, no P. miyadii has been T., Kodama, K., Itoh, M., Ichimura, M., Matsu- observed in Japan to date. The type specimen of P. zaki, K., Hirasawa, K., Tokura, K., Nakahata, K., miyadii has not been found, and Kubo (1938) gave Kodama, S., Hakoyama, H., Yada, T., Niwa, K., no deposition information on the specimens used Nagai, S., Yanagimoto, T., Saito, K., Nakaya, M. for his description. P. miyadii is not listed in Kubo’s & Maruyama, T., 2018. A DNA marker to dis- collections stored in the Tokyo University of Marine criminate two types of freshwater shrimp Palae- Science and Technology (formerly Tokyo University mon paucidens and distribution of these two types of Fisheries) (Usami and Watanabe, 2010). Rede- in Japan. Nippon Suisan Gakkaishi, 84: 674–681 scription with the new specimen (a neotype) collect- (In Japanese with English abstract). ed in China or Korea is necessary to solve this issue. De Grave, S. & Ashelby, C. W., 2013. A re-apprais-

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