Research Article |
Corresponding author: Gi-Sik Min ( mingisik@inha.ac.kr ) Academic editor: Alan Myers
© 2020 Chi-Woo Lee, Ko Tomikawa, Gi-Sik Min.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Lee C-W, Tomikawa K, Min G-S (2020) A new cave amphipod, Pseudocrangonyx wonkimi sp. nov. (Crustacea, Amphipoda, Pseudocrangonyctidae), from the Korean Peninsula. ZooKeys 960: 1-15. https://doi.org/10.3897/zookeys.960.53564
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A new species of pseudocrangonyctid amphipod, Pseudocrangonyx wonkimi sp. nov., was found in the groundwater of a cave in the southwestern Korean Peninsula. Pseudocrangonyx wonkimi sp. nov. is morphologically most closely related to P. joolaei
COI, Crangonyctoidea, groundwater, morphology, South Korea
The genus Pseudocrangonyx Akatsuka & Komai, 1922 is one of the stygobitic groups of groundwater environments in Eastern Asia (
Although only four species have been recorded in Korea, it is possible that the specific diversity of the genus Pseudocrangonyx in the Korean Peninsula may have been underestimated. This is because there are about 1,000 natural caves in South Korea (
Recently, we found an unidentified species of Pseudocrangonyx collected from a cave in the southwestern part of the Korean Peninsula. Based on the results of the morphological examination of these specimens, we herein describe and illustrate them as representing a new species. These specimens were also confirmed to represent a distinct new species through molecular analysis using the mitochondrial cytochrome c oxidase subunit I (COI) gene.
Pseudocrangonyx specimens were collected from the groundwater of Jungchangjin Cave, Yongseong-ri, Daedong-myeon, Hampyeong-gun, Jeollanam-do, South Korea (Fig.
Genomic DNA was extracted from the muscles of the appendages of two Korean Pseudocrangonyx specimens using LaboPass Tissue Mini (Cosmo GENETECH, Seoul, South Korea), according to the manufacturer’s instructions. The primer sets used for polymerase chain reaction (PCR) followed
Family Pseudocrangonyctidae Holsinger, 1989
Genus Pseudocrangonyx Akatsuka & Komai, 1922
Holotype : Female (NNIBRIV35119, BL = 8.9 mm), South Korea, Jeollanam-do, Hampyeong-gun, Daedong-myeon, Yongseong-ri, Jungchangjin Cave (35°6.05'N, 126°31.99'E), 17.II.2017, Yong Gun Choi leg.
Paratypes : 1 male (NNIBRIV36158, BL = 8.3 mm), 1 female (NNIBRIV36157, BL = 8.9 mm), collection data same as for the holotype.
Female larger than male; antennal sinus with rounded angle; eyes absent; pereonites 3–5 with short dorsal setae; sternal gill absent; antenna 1 shorter than body length; antenna 2 with calceoli in both sexes; mandible palp article 3 longer than article 2; maxilla 1 inner plate with 4 plumose setae; maxilla 2 inner plate with oblique inner row of 4 setae; pleopod peduncles with anterodistal setae, inner margin of pleopods 1 and 2 inner rami with bifid setae; uropod 1 outer ramus with 2 marginal robust setae; uropod 3 terminal article of the outer ramus shorter than adjacent spines.; telson cleft for 25.0–27.4%.
Female (NNIBRIV35119, 8.9 mm). Head (Fig.
Antenna 1 (Fig.
Pseudocrangonyx wonkimi sp. nov., holotype, female (BL = 8.9 mm): A–H, J–M paratype, female (BL = 8.9 mm): I. A Antenna 1, lateral view B accessory flagellum of antenna 1, lateral view C antenna 2, medial view D calceolus of antenna 2, medial view E upper lip, anterior view F right mandible, medial view G incisor and lacinia mobilis process of right mandible, medial view H incisor and lacinia mobilis process of left mandible, medial view I incisor process of left mandible, medial view J lower lip, dorsal view K maxilla 1, dorsal view L apical robust setae on outer plate of maxilla 1, dorsal view M maxilla 2, dorsal view.
Upper lip (Fig.
Pseudocrangonyx wonkimi sp. nov., holotype, female (BL = 8.9 mm). A Maxilliped, dorsal view B gnathopod 1, lateral view C serrate seta on posterodistal corner of carpus of gnathopod 1, lateral view D palmar margin of propodus and dactylus of gnathopod 1, lateral view E gnathopod 2, lateral view F serrate seta on posterodistal corner of carpus of gnathopod 2, lateral view G palmar margin of propodus and dactylus of gnathopod 2, lateral view.
Gnathopod 1 (Fig.
Pereopod 3 (Fig.
Pseudocrangonyx wonkimi sp. nov., holotype, female (BL = 8.9 mm). A Pereopod 3, lateral view B dactylus of pereopod 3, lateral view C pereopod 4, lateral view D dactylus of pereopod 4, lateral view E pereopod 5, lateral view F dactylus of pereopod 5, lateral view G pereopod 6, lateral view H dactylus of pereopod 6, lateral view I pereopod 7, lateral view J dactylus of pereopod 7, lateral view.
Coxal gills (Fig.
Brood plates (Fig.
Peduncles of pleopods 1–3 (Fig.
Pseudocrangonyx wonkimi sp. nov., holotype, female (BL = 8.9 mm). A, C, E Pleopods 1–3, lateral view, plumose setae on rami omitted B, D, F retinacula on peduncle of pleopod 1–3, lateral view G uropod 1, dorsal view H uropod 2, dorsal view I uropod 3, dorsal view J terminal article of uropod 3, dorsal view K telson, dorsal view.
Uropod 1 (Fig.
Telson (Fig.
Male (NNIBRIV36158, BL = 8.3 mm). Antenna 1 (Fig.
Gnathopod 1 (Fig.
Uropod 1 (Fig.
Telson (Fig.
Known only from the type locality.
The name of the new species is dedicated to Prof. Won Kim (Seoul National University, South Korea), who has significantly contributed to our knowledge of crustaceans in South Korea.
Sequences of COI gene (MT316534 and MT316535) were determined from two specimens (NNIBRIV35119 and NNIBRIV36158).
The topologies of the BI and ML trees were identical (Fig.
We revealed that Pseudocrangonyx wonkimi sp. nov. is most closely related to P. joolaei
Pseudocrangonyx wonkimi sp. nov. is morphologically similar to P. akatsukai Tomikawa & Nakano, 2018 in having 1) eyes completely absent, 2) sternal gill absent 3) urosomite 1 with ventral robust seta, 4) antenna 2 with calceoli in both sexes 5) carpi of gnathopods 1 and 2 with serrate robust setae on posterodistal corner, and 6) inner rami of pleopods with bifid setae on inner margin. However, the former is distinguished from the latter by the following features (features of P. akatsukai in parentheses): 1) pereonites 3–5 (1–7) with short dorsal setae, 2) antenna 1 shorter (longer) than as long as body length half, 3) male antenna 2 flagellum 0.33 (0.53) times as long as peduncular articles 4 and 5 combined, 4) carpi of gnathopods 1 and 2 with 1 (with 3–5) serrate robust setae on posterodistal corner, 5) length ratio of merus, carpus, propodus 1.0 : 1.0 : 1.0 (1.0 : 1.1 : 1.1) of pereopod 7, and 6) telson cleft for 25.0–27.4% (6.6–12.3%) of length.
Pseudocrangonyx wonkimi sp. nov. is similar to P. elegantulus Zhao & Hou, 2017 in having 1) urosomite 3 dorsal margin without seta, 2) sternal gill absent, 3) accessory flagellum of antenna 1 subequal first article of primary flagellum, and 4) antenna 2 with calceoli in both sexes. However, P. wonkimi is distinguished from the latter by the following features (features of P. elegantulus in parentheses), 1) pereonites 3–5 with (1–6 without) dorsal margin setae, 2) basal part of inner ramus of female uropod 1 with 4 (1) slender setae, 3) uropod 1 peduncle inner marginal with 3 (1) robust setae, 4) terminal article of uropod 3 almost reaching (fully exceed) robust setae on the distal part of the proximal article, and 5) carpus of male gnathopod 2 with (without) serrate robust seta on posterodistal corner. Pseudocrangonyx wonkimi sp. nov. is similar to P. shikokunis Akatsuka & Komai, 1922 in having 1) eyes absent, 2) mandible palp article 3 longer than article 2, and 3) carpi of gnathopods 1and 2 with serrate setae on the posterodistal corners. The new species is distinguished from the latter by the following features (features of P. shikokunis in parentheses), 1) antenna 1 shorter (longer) than half of the body length, 2) maxilla 1 inner plate with 4 or fewer setae (with 5 setae), and 3) male telson cleft for 27.4% (11.7%) of length. The new species is similar also to P. cavernarius Hou & Li, 2003 in having 1) body size about 8.0 mm, and 2) maxilla 1 inner plate with 4 plumose setae. It differs from P. cavernarius Hou & Li, 2003 by the following features (features of P. cavernarius in parentheses), 1) antenna 2 calceoli present (absent), 2) mandible palp article 3 longer (shorter) than article 2, 3) urosomite 3 dorsal margin without (with) setae, and 4) telson each lobe with (without) setae.
The authors are grateful to Professor Alan A. Myers, Dr Leonardo Latella, and an anonymous reviewer for their constructive comments on this manuscript. This work was supported by a grant from the Nakdonggang National Institute of Biological Resources (NNIBR), funded by the Ministry of Environment (MOE) of the Republic of Korea (NNIBR201901203). We are grateful to the Natural Environment Division of the Yeongsan River Basin Environmental Office for supporting the cave research (No. 510), and especially thank to Mr Yong Gun Choi, Jae Won Kim, and Kyu-Dong Chang. The first author is very grateful to Dr Takafumi Nakano (Kyoto University, Japan) for the help provided.