Biogeography 20. 133–136. Sep. 20, 2018

First record of the varunid crab Parapyxidognathus deianira from the coast of the Sea of

Akihiko Koyama, Norio Onikura

Fishery Research Laboratory, Kyushu University, 4-46-24 Tsuyazaki, Fukutsu, Fukuoka 811-3304, Japan

Summary: Parapyxidognathus deianira (family Varunidae) is a rare brackish-water crab, and there is increas- ing concern about its possible extinction in several region across Japan. We have sampled this species from 20 river estuaries in Kyushu, Japan, from 2014 to 2017. The occurrence of this species in the coast is being reported for the first time, following the sampling of this species from the Daikon River estuary in Fukuoka Prefecture. Crab and fish fauna at the collection site in the Daikon River suggest that the habitat con- ditions of P. deianira at the site are similar to that described in the previous reports of this species.

Key words: Brackish water, Conservation, Intertidal zone, New record, Riverine estuary, Varunid crab

Parapyxidognathus deianira (De Man, 1888) 2015; Kagoshima Prefecture, 2016; Kochi Prefec- (family Varnidae) is distributed in the tropical and ture, 2017). Distributional information is essential to subtropical Indo-West Pacific regions including conserve this species along with its riverine environ- Japan (Naruse, 2012), and inhabits gravelly sedi- ments. This paper reports the first record of this spe- ments in the middle of riverine estuaries (Iyooka et cies from the coast of the Sea of Japan, together with al., 2011). In Japan, the occurrence of this crab has a report on the co-occurring animals in this habitat. been reported from the Nansei Islands, including the P. deianira is readily distinguishable from the re- Amami-Oshima Island and the Okinawajima Island lated Ptychognathus altimanus (Rathbun, 1915) that (Kishino et al., 2001; Naruse, 2012); the Pacific shares the same habitat: the ratio of carapace width coast, from Chiba to Kagoshima Prefecture (Nomoto (CW) to carapace length (CL) is approximately 1.3 et al., 1999; Machida, 2009; Shin et al., 2010; Iyoo- in P. deianira, whereas it is approximately 1.0 in P. ka et al., 2011; Naruse, 2012; Yokooka et al., 2015; altimanus. The propodus and merus of the ambula- Kagoshima Prefecture, 2016); and the coast of East tory legs bear distinct spines on the distal portion of China Sea from Nagasaki to Kagoshima Prefecture the posterior margin in P. deianira, while no spine is (Kagoshima Prefecture, 2016; Nagasaki Prefecture, present in P. altimanus (Nomoto et al., 1999; Naruse, 2017). The habitat of this species has been deteri- 2012). We conducted field surveys to understand the orating owing to anthropogenic activities, such as distribution of this crab around the coast of Kyushu river improvements (Naruse, 2012), and there is con- from 2014 to 2017. These surveys were conducted cern about its possible extinction in several prefec- during the day, and benthic animals were collected tures (Chiba Prefecture, 2010; Nagasaki Prefecture, by two researchers by hand, as well as by using 2011; Oita Prefecture, 2011; Miyazaki Prefecture, hand nets and shovels. As a result, P. deianira was ——————————————————————— found in 20 rivers (Fig. 1). Most of the rivers where *Corresponding author:[email protected] P. deianira was collected were located in the vicin- (corresponding author: Akihiko Koyama) ity of the previously recorded sites of occurrence

− 133 − Record of Parapyxidognathus deianira in the Sea of Japan Akihiko Koyama, Norio Onikura

Fig. 1. Map showing the rivers in Kyushu, where Parapyxidognathus deianira was found through our survey, with a site in the Daikon River where three individuals of this species were collected.

(Shin et al., 2010; Iyooka et al., 2011; Naruse, 2012; margins of the propodus and merus of the ambulato- Kagoshima Prefecture, 2016; Nagasaki Prefecture, ry legs (Fig. 2). These features agree with the known 2017). Moreover, three individuals (one male, and characteristics of P. deianira. The specimens exam- two females) of P. deianira, were collected for the ined were deposited in the Fishery Research Labora- first time on the Sea of Japan coast, from a site in the tory of Kyushu University (KYUM). Daikon River (Fig. 1). CW and CL of the male were Iyooka et al. (2011) reported that this species 8.96 mm and 7.08 mm (CW/CL = 1.27), respective- preferred homogeneous coarse substratum occurring ly, and those of the two females were 10.10 mm and in the middle of the riverine estuary in Miyazaki 7.90 mm (CW/CL = 1.28) and 9.09 mm 7.25 mm Prefecture. In this study, individuals of this species (CW/CL = 1.25), respectively. All specimens had were found in the gap between oyster shells stuck to several spines on the distal portion of the posterior several boulders at the intertidal zone in the middle

Fig. 2. Dorsal view (a), ventral view (b), and fourth ambulatory leg (c) of a male Parapyxidognathus deianira sampled from the Daikon River. Arrows indicate the spines of the propodus and merus. Scale bar: 10 mm.

− 134 − Record of Parapyxidognathus deianira in the Sea of Japan Akihiko Koyama, Norio Onikura

of the Daikon River estuary (Fig. 1). The sediment References at the collection site was sandy gravel with some boulders and cobbles. In the same area, Hemigrapsus Asakura, A., & Watanabe, S. 2005. Hemigrapsus takanoi Asakura & Watanabe, 2005, and H. penicil- takanoi, new species, a sibling species of the latus (De Haan, 1835) were also found. Both of these common Japanese intertidal crab H. penicillatus crabs are typical brackish-water varunid crabs living (Decapoda: Brachyura: Grapsoidea). J. Crust. under cobbles and hard structures (Asakura & Wata- Biol., 25: 279–292. nabe, 2005). Moreover, several gobiid fish living Chiba Prefecture. 2011. Red data book and red list and spawning under hard substrates, Mugilogobius in Chiba Prefecture [original title in Japanese: abei (Jordan & Snyder, 1901), Redigobius bikolanus Chiba-ken reddo deta bukku reddo risuto]. http:// (Herre, 1927), and Tridentiger obscurus (Temminck www.bdcchiba.jp/endangered/endang_index.html & Schlegel, 1845), were also found (Kanabashira et (in Japanese) al., 1980; Onikura et al., 2009). Brachyuran crabs Iyooka, H., Kusuda, T., Shimatani, Y., Watanabe, R., and gobiid fish found together with P. deianira sug- Minagawa, T., Yamasaki, K. 2011. Habitat mod- gest that the environmental conditions of the habitat eling and habitat isolations for brackish crabs at of P. deianira in the Daikon River were similar to Kita River estuary. Journal of JOSE, Ser. G (En- that described in the previous reports of this species vironmental Research) 67: III_347–III_353. (in (Nomoto et al., 1999; Kishino et al., 2001; Naruse, Japanese with English abstract) 2012). Kagoshima Prefecture. 2016. Revision of wild life Since this species is mainly distributed in the in danger of extinction in Kagoshima Prefecture tropical and subtropical regions, it is doubtful wheth- [original title in Japanese: Kaitei kagoshima-ken er the population in the Daikon River (a temperate no zetsumetsu no osore no aru yasei doushokubut- region) is self-sustainable. However, climate change su]. Kagoshima environmental research and ser- may lead to further expansion of its distribution to vice, Kagoshima. 401 pp. (in Japanese) the eastern part of the Sea of Japan. Surveys of this Kanabashira, Y., Sakai, H., & Yasuda, F. 1980. Early species in the Sea of Japan contribute to understand- development and reproductive behavior of the go- ing the process by which such tropical species ex- biid fish, Mugilogobius abei. J. Ichthyol., 27, 191- pand their distribution. Further investigation is nec- 198. essary, not only to conserve this species, but also to Kishino, T., Nomoto, A., Kimura, S., Yonezawa, understand the relationship between climate change T., & Wada, K. 2001. Brachyuran crab species and the expansion of the distribution of tropical spe- recorded in the brackish waters of Amami-Oshi- cies. ma Island, Kagoshima Prefecture, Japan. Nanki Seibutsu 43: 125-131. (in Japanese) Acknowledgments Kochi Prefecture. 2017. Revision of red list of Ko- chi Prefecture in 2017 [original title in Japanese: We would like to thank Seiya Matsunaga for sup- Kochi-ken reddo risuto (doubutsu hen) 2017 porting our survey. Parts of this study were funded kaitei-ban]. http://www.pref.kochi.lg.jp/soshi- by the Research Institute of Marine Invertebrates ki/030701/redlist-animal.html (in Japanese) (201415IKU-2, Tokyo). Comments from an anon- Machida, Y., 2009. The distribution of a brack- ymous reviewer have improved the manuscript ish-water crab Parapyxidognathus deianira newly considerably. We would like to thank Editage (www. recorded from Kochi Prefecture, southern Japan editage.jp) for English language editing. (Brachyura: Varunidae). Bull. Inst. Nat.

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Hist., 5: 5–7. (in Jpanaese) Japanese with English abstract) Miyazaki Prefecture. 2016. Red list and red data Shin, K., Ishida, A., Matsuo, T., & Miura, T. 2010. book of Miyazaki Prefecture [original title in Decapods collected from the estuary of Banjo Japanese: Miyazaki-ban reddo risuto oyobi reddo River including the first record of ten species from deta bukku ni tsuite]. https://www.pref.miyazaki. Oita Prefecture. Nanki Seibutsu 52: 143-148. (in lg.jp/shizen/kurashi/shizen/page00193.html (in Japanese) Japanese) Yokooka, H., Yuhara, T., & Tagashira, R. 2015. First Nagasaki Prefecture. 2017. Revision of red list in record of Ptychognathus capillidigitatus (Crus- Nagasaki Prefecture (2011) [original title in Jap- tacea: Decapoda: Varunidae) in Shizuoka Prefec- anese: Nagasaki-ken reddo risuto (2011) chukan ture, Japan. Cancer, 24: 39-45. (in Japanese) minaoshi]: http://www.pref.nagasaki.jp/bunrui/ kurashi-kankyo/shizenkankyo-doshokubutsu/ (Received March 19, 2018; Accepted July 23, 2018) rarespecies/reddata/298016.html (in Japanese) Naruse, T. 2012. Parapyxidognathus deianira. Japa- nese Association of Benthology (ed), Threatened Appendix 1. The registration numbers of spec- animals of Japanese tidal flats: red data book of imens of Parapyxidognathus deianira collected in seashore benthos. Tokai University Press, Hada- our survey. no, 203 pp. (in Jpanese) Nomoto, A., Yodo, M., Kimura, S., Kishino, T., KYUM-PI 00003182 (Kamino R.); KYUM-PI Nishino, M., & Wada K. 1999. Six rare brachyu- 00003219 (Nagayoshi R.); KYUM-PI 00003281 ran species of the family Grapsidae, recorded (O R.); KYUM-PI 00003295 (Izaku R.); KYUM- from the Estuary, Wakayama PI 00003432 (Kumaya R); KYUM-PI 00003448 Prefecture. Nanki-Seibutsu 41: 5-9 (in Jpanaese) (Fukushima R.); KYUM-PI 00003498 (Uchimi Oita Prefecuture. 2011. Red data book in Oita Pre- R.); KYUM-PI 00003515 (Tsukinami R.); KYUM- fecture 2011 [original title in Japanese: Reddo PI 00003568 (Kumanoe R.); KYUM-PI 00003584 de-ta bukku iota 2011]. http://www.pref.oita.jp/ (Urajiri R.) KYUM-PI 00003597 (Mimi R.); soshiki/13070/rdbindex.html (in Japanese) KYUM-PI 00003657 (Omaru R.); KYUM-PI Onikura, N, Nishida, T, Inui, R, Nakajima, R, Egu- 00003684 (Morisaki R.); KYUM-PI 00003747 chi, K, Oikawa, S. 2009. Spawning sites and lat- (Usuki R.); KYUM-PI 00005652 (Kotsunagi R.); eral distributions of several Gobioid species found KYUM-PI 00005752 (Wakana R.); KYUM-PI in a backwater zone (wando-pool) of the brackish 00007081 (Shinden R.); KYUM-PI 00007138 (Dai- water area in the Kitagawa River, Miyazaki Pre- kon R.); KYUM-PI 00007205 (Irori R.); KYUM-PI fecture. Bull. Biogeogr. Soc. Japan., 64: 29-39. (in 00007285 (Hosoda R.).

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