Introduction
The caridean shrimp family, Chlorotocellidae has recently (Komai et al., Reference Komai, Chan and De Grave2019) been erected for four genera, previously placed in Pandalidae Haworth, Reference Haworth1825. Although all genera are relatively widely distributed in tropical to temperate waters of the Indo-Pacific, the family has not previously been recorded from Korea. One of the genera, Anachlorocurtis, is herein recorded in local waters for the first time.
The Indo-West Pacific shrimp genus Anachlorocurtis Hayashi, Reference Hayashi1975 currently comprises three species: two Western Pacific species, Anachlorocurtis commensalis Hayashi, Reference Hayashi1975 and A. australis Ahyong, Reference Ahyong2015; and the Red Sea species, A. occidentalis Horká et al., Reference Horká, De Grave and Ďuriš2014. All three species are obligate symbionts of antipatharian corals (Hayashi, Reference Hayashi1975; Horká et al., Reference Horká, De Grave and Ďuriš2014; Ahyong, Reference Ahyong2015). The morphology of Anachlorocurtis is highly distinctive, especially the slender and compressed body; the short, unique and variously shaped rostrum; the two prominent processes on the carapace; the shape of the pereiopods, as well as the specialized mouthparts. The cryptic colour pattern also seems well adapted to their host black corals (Figures 1 and 2) (Hayashi, Reference Hayashi1975; Horká et al., Reference Horká, De Grave and Ďuriš2014).
Fig. 1. Anachlorocurtis commensalis Hayashi, Reference Hayashi1975 and host antipatharian black corals: (A) Ovigerous female specimen (pocl 4.2 mm) and host antipatharian black coral, Myriopathes sp. from Dokdo Island (NIBRIV0000862964); (B) Male specimen (pocl 3.0 mm) from Namhyeongjedo Islet (SNU-KR_JH23); (C) Specimen (not vouchered) on the host antipatharian black coral, Myriopathes sp. from Seopseom Islet, Jejudo Island.
Fig. 2. Dorsal view of Anachlorocurtis commensalis Hayashi, Reference Hayashi1975: (A) Ovigerous female specimen (pocl 4.2 mm) from Dokdo Island (NIBRIV0000862964); (B) Ovigerous female specimen (pocl 3.4 mm) from Namhyeongjedo Islet (NIBRIV0000862965); (C) Male specimen from Seopseom Islet, Jejudo Island (NIBRIV0000863955).
The type species, Anachlorocurtis commensalis, is distinguished from its congeners by the following morphological characteristics: (1) posterior dorsal lobe on the carapace being feebly hooked, (2) weakly developed posterior submarginal tooth dorsally on the carapace, (3) rounded third abdominal segment in lateral aspect, (4) sixth abdominal segment about 2.0 times longer than deep, (5) three setae on the mesial margin of the endopod of the first pleopod of the male, (6) length of the appendix masculina of the second male pleopod shorter than the appendix interna, and (7) telson with three pairs of dorsal spiniform setae. This species has so far been reported in tropical to subtropical latitudes in the Western Pacific, with records from southern Taiwan (up to 21°55′N) to central Japan (down to 34°50′N) (Hayashi, Reference Hayashi1975; Horká et al., Reference Horká, De Grave and Ďuriš2014). The distribution largely corresponds to the geographic area influenced by the Kuroshio Warm Current (Figure 3A).
Fig. 3. Map of North-West Pacific Ocean: (A) Geographic distribution of Anachlorocurtis commensalis Hayashi, Reference Hayashi1975 and schematic map of surface currents; (B–D) Collection locality of Dokdo Island, Namhyeongjedo Islet, and Jejudo Island. 1, Namwan Bay, Pingtung County, Taiwan (Horká et al., Reference Horká, De Grave and Ďuriš2014); 2–4, Iriomote-jima and Kume-jima, Ryukyus Archipelago, Japan (Minemizu, Reference Minemizu2013); 5, Kii Peninsula, Japan (Hayashi, Reference Hayashi1975); 6–7, Izu-Oshima and Hachiiyo-jima, Izu Archipelago, Japan (Kuiter & Debelius, Reference Kuiter and Debelius2009). Schematic map of surface currents modified based on the report of Oceanographic Observation Division (2020: thickness of red current lines indicates current strength; dotted current lines indicates current is seasonal and/or interannual).
Jejudo Island is the first gateway to be affected by the branch of the Kuroshio Warm Current which flows into Korean waters via the Taiwan-Ryukyu region (Park et al., Reference Park, Park, Park, Choi, Lee, Byun, Lee, Kang, Shin, Lee and Sriraman2018; Oceanographic Observation Division, 2020). This warm current passes around Namhyeongjedo Islet in the Korea Strait and exits around Dokdo Island in the East Sea (Figure 3A). During sampling of symbiotic shrimps along the Korean peninsula between 2015–2019, several specimens of A. commensalis were observed and collected on the branches of antipatharian black corals by scuba diving at depths ranging from 20–60 m from three localities (for the exact method used to collect the shrimps, see figure 6B in Park et al., Reference Park, Lee and Park2021): Jejudo Island (33°13′N)) between the South Sea of Korea and the north-eastern East China Sea, Namhyeongjedo Islet (34°53′N) in the Korea Strait, and Dokdo Island (37°15′N) in the East Sea (Figure 1B–D). These records represent the first for the Korean fauna as well as extending the species' marginal distribution into a temperate region.
Specimens used in this study are deposited in the National Institute of Biological Resources, Incheon (NIBR), Seoul National University, Seoul (SNU) and the Zoological Collections of the Oxford University Museum of Natural History, Oxford (OUMNH.ZC). Postorbital carapace length (pocl, in mm) was measured from the postorbital margin to the posterior dorsal margin of the carapace. Field collection numbers (fcn) were recorded for each specimen.
Results
Systematics
Superfamily PANDALOIDEA Haworth, Reference Haworth1825
Family CHLOROTOCELLIDAE Komai et al., Reference Komai, Chan and De Grave2019
Genus Anachlorocurtis Hayashi, Reference Hayashi1975
Anachlorocurtis commensalis Hayashi, Reference Hayashi1975
(Figures 1 and 2)
Synonymy
Anachlorocurtis commensalis Hayashi, Reference Hayashi1975: 172, figs. 1–3; Hayashi, Reference Hayashi2007: 147, figs. 538–539; Kawamoto & Okuno, Reference Kawamoto and Okuno2003: 64, colour photo; Kuiter & Debelius, Reference Kuiter and Debelius2009, colour photo: 162; Minemizu, Reference Minemizu2013: 129, colour photo; Horká et al., Reference Horká, De Grave and Ďuriš2014: 23, figs. 5g–p, 6d, 7e–g.
Material examined
Material from Korea: 1 non-ovigerous female (pocl 2.1 mm), 1 male (pocl 1.9 mm), Seopseom Islet, Jejudo Island, from Myriopathes sp., depth 30 m, 33°13.737′N 126°35.776′E, leg. JH Park, 16 December 2015 (ZC-2018-03-0019, ZC-2018-03-0020) (fcn JH914, JH915); 3 ovigerous females, 1 male, Seopseom Islet, Jejudo Island, from Myriopathes sp., depth 30 m, 33°13.744′N 126°35.742′E, leg. JH Park, 28 July 2019 (NIBRIV0000863955) (fcn JH122); 5 ovigerous females, 1 male, Munseom Islet, Jejudo Island, from Myriopathes sp., depth 35 m, 33°13.548′N 126°34.147′E, leg. JH Park, 15 August 2019 (NIBRIV0000863956, NIBRIV0000863957) (fcn JH110, JH111); 2 ovigerous females (pocl 4.2 and 4.45 mm), Gajicho reef, Dokdo Island, from white coloured Myriopathes sp., depth 42 m, 37°14.956′N 131°52.009′E, leg. JH Park, 26 August 2019 (NIBRIV0000862964; SNU-KR_JH91) (fcn JH90, JH91); 1 ovigerous female (pocl 3.4 mm), 1 male (pocl 3.0 mm), Namhyeongjedo Islet, Busan, from white coloured Myriopathes sp., depth 33 m, 34°53.055′N 128°57.040′E, leg. JH Park, 6 December 2019 (NIBRIV0000862965; SNU-KR_JH23) (fcn JH24, JH23). Comparative material from Taiwan: 1 ovigerous female (pocl 2.6 mm), 1 non-ovigerous female (pocl 2.0 mm), 2 males (pocl 2.0 mm), 4 individuals (pocl 1.6–1.9 mm), Guganshr reef, Namwan Bay, Pingtung County, from unidentified bushy black coral, depth 10 m, 12°56.531′N 120°45.546′E, leg. S. De Grave, 7 December 2009 (OUMNH.ZC-2010-02-0061) (fcn TAI-244); 1 non-ovigerous female (pocl 2.1 mm), 1 male (pocl 2.25 mm), same locality, from Cirrhipathes, 27 m, leg. S. De Grave, 10 December 2009 (OUMNH.ZC-2010-02-0062) (fcn TAI-326); 5 ovigerous females (pocl 2.5–2.9 mm), 1 non-ovigerous female (pocl 2.6 mm), 1 male (pocl 2.1 mm), 3 individuals (pocl 1.7–1.8 mm), same locality, from Cirrhipathes, 27 m, leg. S. De Grave, 10 December 2009 (OUMNH.ZC-2010-02-0010) (fcn TAI-327).
Description
For a detailed, illustrated description of A. commensalis from the type locality (Kii Peninsula, Japan), see Hayashi (Reference Hayashi1975); see also Horká et al. (Reference Horká, De Grave and Ďuriš2014) for figures of specimens from southern Taiwan.
Colour pattern
Korean specimens exhibited camouflaged colour patterns depending on the colour of their host antipatharians (Figure 1C). In general, the transparent body has a red or reddish-brown axis ventrally, similar in colour to the skeletal axis of their host antipatharian. Several transverse bands are present along the entire dorsal part of the body, consisting of whitish chromatophores, similar in colour to the host antipatharian polyps (Figures 1 and 2). A similar colour pattern is present on the carapacial appendages, pereiopods, pleopods, telson and uropods. The specimens observed on dark orange coloured Myriopathes sp., show comparably coloured transverse bands on their body to their host antipatharian polyps. Similar colour patterns were also reported from A. occidentalis from the Red Sea (Horká et al., Reference Horká, De Grave and Ďuriš2014), with the colour pattern of the third species in the genus not known (Ahyong, Reference Ahyong2015).
Host and habitat
All Korean material was observed on the antipatharian black coral colonies, Myriopathes spp. (Cnidaria; Hexacorallia; Antipatharia), which are attached on rocky reef slopes or larger rocks on a sandy bottom. This species was not observed on nearby whip black coral Cirrhipathes sp. (Cnidaria; Hexacorallia; Antipatharia) and octocoral species.
Distribution
Anachlorocurtis commensalis has been reported from tropical (21°56.531′N) to temperate (37°14.956′N) areas in the Western Pacific (Figure 3): Japan [Kii Peninsula (type locality); Izu-Oshima and Hachiiyo-jima, Izu Archipelago; Iriomote-jima and Kume-jima, Ryukyus Archipelago] (Hayashi, Reference Hayashi1975; Kawamoto & Okuno, Reference Kawamoto and Okuno2003; Kuiter & Debelius, Reference Kuiter and Debelius2009; Minemizu, Reference Minemizu2013; Horká et al., Reference Horká, De Grave and Ďuriš2014); Taiwan (Namwan Bay, Pingtung County) (Horká et al., Reference Horká, De Grave and Ďuriš2014); and now Korea (Jejudo Island; Namhyeongjedo Islet, Busan; Dokdo Island) (present study).
Discussion
The material examined herein, corresponds closely to the previous descriptions by Hayashi (Reference Hayashi1975) and Horká et al. (Reference Horká, De Grave and Ďuriš2014), especially in the varied shape of the rostrum, the hooked large posterior tooth and feebly developed posterior submarginal tooth on the carapace, the proportions of the sixth abdominal segment (about 2.0 times as long as maximal depth), the proportions of the ambulatory propodi (about 8.0 times as long as proximal length), as well as the relatively short length of the appendix masculina of the second male pleopod (shorter than appendix interna). Additionally, the differential shape of the rostrum between adult females and males also agrees with previous records (see figure 5 in Horká et al., Reference Horká, De Grave and Ďuriš2014). Only a minor difference between the previous records and the present material is evident in first pleopod. The mesial margin of the first pleopod of male paratype was stated to harbour ‘a few short simple setae’ and illustrated with three short setae by Hayashi (Reference Hayashi1975), whilst the present Korean and Taiwan specimens typically have over 10 short setae on this mesial margin.
Subtropical and tropical symbiotic shrimps are being steadily reported in Jejudo Island and southern part of Korean Peninsula (Koo & Kim, Reference Koo and Kim2003; Lee & Ko, Reference Lee and Ko2011, Reference Lee and Ko2014; Lee & Ko, Reference Lee and Ko2013; Park et al., Reference Park, De Grave and Kim2019a, Reference Park, De Grave and Kim2019b, Reference Park, De Grave and Park2020a, Reference Park, Lee, Lee and De Grave2020b, Reference Park, Lee and Park2021; Park & De Grave, Reference Park and De Grave2021; Park & Fransen, Reference Park and Fransen2021). But they have never been reported from further north, i.e. Dokdo Island in the East Sea, which is heavily influenced by the Kuroshio Warm Current (Ryu et al., Reference Ryu, Jang, Choi, Kim, Song, Cho, Ryu, Kim, Sagong, Lee, Yeo, Bahn, Kim, Lee, Lee, Choo, Pak, Park, Ryu, Khim and Hwang2012).
Acknowledgements
JHP and TP are grateful to Dr Hyun Soo Rho (Korean Institute of Ocean Science and Technology, Korea) for introducing a little-known locality, Gajicho reef in Dokdo Island. The authors also thank Dr Boon-Soon Kang (Korea Hydrographic and Oceanographic Agency, Korea) for providing literature of surface currents in the neighbouring seas of Korea for this study.
Author contributions
JHP designed the study, identified the Korean specimens, and drafted the manuscript. SDG provided taxonomic identifications of the comparative material from Taiwan and improved the manuscript. TP designed the study, planned the field survey and improved the final manuscript. JHP and TP participated in the field survey. All authors read and approved the final manuscript.
Financial support
Project funding was provided by grant of the National Institute of Biological Resources (NIBR201902107) and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2021R1A6A3A14038556).
Ethical standards
Two Korean researchers (JHP and TP) participated in the field survey for material collection under permits issued by the government of the Republic of Korea.
Availability of data and materials
Specimens used in this study are deposited in NIBR, Incheon; SNU, Seoul, and the Zoological Collections of OUMNH.ZC, Oxford. Comparative specimens are deposited in the Zoological Collections of the OUMNH, Oxford.
