Research Article |
Corresponding author: Gi-Sik Min ( mingisik@inha.ac.kr ) Academic editor: Alan Myers
© 2018 Chi-Woo Lee, Ko Tomikawa, Takafumi Nakano, 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, Tomikawa K, Nakano T, Min G (2018) A new species of the genus Pseudocrangonyx (Crustacea, Amphipoda, Pseudocrangonyctidae) from Korea. ZooKeys 735: 27-44. https://doi.org/10.3897/zookeys.735.21697
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A new subterranean species of pseudocrangonyctid amphipod, Pseudocrangonyx daejeonensis sp. n. is described from the interstitial waters in Daejeon, Korea. Pseudocrangonyx daejeonensis sp. n. is distinguished from three morphologically similar congeners, P. coreanus Uéno, 1966, P. febras Sidorov, 2009, and P. gudariensis Tomikawa & Sato, 2016, by the characteristics of antenna 1, antenna 2, mandible, gnathopod 2, pleopods, uropods 1–2, and telson. Molecular phylogenetic analyses based on nuclear 28S rRNA and histone H3, and mitochondrial cytochrome c oxidase subunit I and 16S rRNA genes revealed that P. daejeonensis is a sister species of the unnamed Pseudocrangonyx sp. 3 inhabiting central Japan.
Crangonyctoidea , Korean Peninsula, interstitial water, molecular phylogeny
Amphipod species of the genus Pseudocrangonyx Akatsuka & Komai, 1922 have been known from subterranean waters and springs in Japan, the Korean Peninsula, Eastern China, and the Far East of Russia (
When
Recently, unidentified specimens of Pseudocrangonyx were collected during field surveys of interstitial invertebrates in Korea by the first author. In this paper, we describe and illustrate this amphipod as a new species. In addition, the phylogenetic position of the new species was estimated using nuclear 28S rRNA and histone H3, and mitochondrial cytochrome c oxidase subunit I (COI) and 16S rRNA sequence data.
Pseudocrangonyx specimens were collected from interstitial water in Heukseok-dong, Seo-gu, Daejeon, South Korea (Fig.
The specimens were dissected in 70 % ethanol and mounted in gum-chloral medium on glass slides under a stereomicroscope (Model SZX-7; Olympus, Tokyo, Japan). Specimens were examined using a Nikon Eclipse Ni light microscope (Nikon, Tokyo, Japan) and illustrated with the aid of a drawing tube. The body length from the tip of the rostrum to the base of the telson was measured along the dorsal curvature to the nearest 0.1 mm. The nomenclature of the setal patterns on the mandibular palp follows that of
Methods of the genomic DNA extraction, PCR and DNA sequencing were performed following
Samples used for the phylogenetic analyses. The information on the vouchers is accompanied by the collection locality and the INSDC accession numbers. Sequences marked with an asterisk were obtained for the first time in the present study. Acronyms:
Species | Voucher or isolate # | Locality or country | INSDC # | |||
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28S | Histone H3 | COI | 16S | |||
Pseudocrangonyx | ||||||
P. daejeonensis sp. n. | NNIBRIV1 (Holotype) | Daejeon, Korea | LC322136* | LC322138* | LC322137* | LC322135* |
P. daejeonensis sp. n. | NNIBRIV2 (Paratype) | Daejeon, Korea | LC322143* | |||
P. daejeonensis sp. n. | NNIBRIV3 (Paratype) | Daejeon, Korea | LC322140* | LC322142* | LC322141* | LC322139* |
P. gudariensis |
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Aomori, Japan | LC171498 | LC171500 | LC171499 | LC171497 |
P. yezonis | G1280 | Hokkaido, Japan | LC171518 | LC171520 | LC171519 | LC171517 |
P. yezonis | G1279 | Akita, Japan | LC171514 | LC171516 | LC171515 | LC171513 |
Pseudocrangonyx sp. 1 | G400 | Iwate, Japan | LC171479 | |||
Pseudocrangonyx sp. 1 | G1281 | Iwate, Japan | LC171521 | |||
Pseudocrangonyx sp. 2 | G1283 | Okayama, Japan | LC171525 | LC171527 | LC171526 | LC171524 |
Pseudocrangonyx sp. 2 | G1277 | Yamaguchi, Japan | LC171506 | LC171508 | LC171507 | LC171505 |
Pseudocrangonyx sp. 2 | G1278 | Yamaguchi, Japan | LC171510 | LC171512 | LC171511 | LC171509 |
Pseudocrangonyx sp. 3 | G404 | Shiga, Japan | LC171488 | LC171489 | ||
Pseudocrangonyx sp. 3 | G405 | Shiga, Japan | LC171491 | LC171493 | LC171492 | LC171490 |
Pseudocrangonyx sp. 3 | G406 | Shiga, Japan | LC171495 | LC171496 | LC171494 | |
Pseudocrangonyx sp. 4 | G1282 | Shiga, Japan | LC171523 | LC171522 | ||
Pseudocrangonyx sp. 5 | G402 | Shimane, Japan | LC171485 | LC171487 | LC171486 | LC171484 |
Pseudocrangonyx sp. 5 | G401 | Shimane, Japan | LC171481 | LC171483 | LC171482 | LC171480 |
Pseudocrangonyx sp. 5 | G1271 | Kagawa, Japan | LC171502 | LC171504 | LC171503 | LC171501 |
Pseudocrangonyx sp. 5 | G1295 | Kochi, Japan | LC171533 | LC171535 | LC171534 | LC171532 |
Pseudocrangonyx sp. 5 | G1296 | Kochi, Japan | LC171537 | LC171539 | LC171538 | LC171536 |
Pseudocrangonyx sp. 5 | G1294 | Ehime, Japan | LC171529 | LC171531 | LC171530 | LC171528 |
Pseudocrangonyx sp. 6 | G1297 | Gifu, Japan | LC171541 | LC171543 | LC171542 | LC171540 |
P. holsingeri | Russian Far East | KJ871679 | KF153111 | |||
P. korkishkoorum | B1 | Russian Far East | KJ871678 | KF153107 | ||
P. korkishkoorum | B2 | Russian Far East | KF153108 | |||
P. korkishkoorum | B3 | Russian Far East | KF153109 | |||
P. korkishkoorum | N1 | Russian Far East | KJ871676 | KF153105 | ||
P. korkishkoorum | N2 | Russian Far East | KJ871677 | KF153106 | ||
P. kseniae | Russian Far East | KJ871675 | KF153115 | |||
P. susanaensis | Russian Far East | KF153113 | ||||
P. sympatricus | Russian Far East | KF153112 | ||||
P. tiunovi | Russian Far East | KJ871674 | KF153110 | |||
P. elegantulus |
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China | KY436646 | KY436647 | ||
Outgroup | ||||||
Crymostygius thingvallensis | HQ286009 | |||||
Eocrangonyx primoryensis | HQ286011 | |||||
Crangonyx floridanus | G1322 | Chiba, Japan | LC171549 | LC171550 | LC171548 |
The OTU set for phylogenetic analyses was almost identical to that used in the previous phylogenetic analyses in
Holotype: Female (NNIBRIV1, 3.8 mm), Heukseok-dong (36°15.65'N, 127°20.43'E), Daejeon, Korea, collected by Lee CW on 31 May 2017. Paratypes: 1 male (NNIBRIV2, 2.7 mm), 1 female (NNIBRIV3, 2.3 mm), 3 females (
Etymology. The specific name is an adjective derived from the type locality name of the new species.
Female [NNIBRIV1, 3.8mm]. Head (Fig.
Antenna 1 (Fig.
Pseudocrangonyx daejeonensis sp. n., holotype, female (3.8 mm): A–D, F–K paratype female (2.3 mm): E. A antenna 1, lateral view B accessory flagellum of antenna 1, lateral view C antenna 2, medial view D upper lip, anterior view E upper lip, anterior view F left mandible, medial view G incisor, lacinia mobilis, and molar process of left mandible, medial view H incisor and lacinia mobilis of right mandible, medial view I lower lip, ventral view J maxilla 1, dorsal view K maxilla 2, ventral view.
Upper lip (Fig.
Gnathopod 1 (Fig.
Coxal gills (Figs
Peduncle of pleopod 1 (Fig.
Pseudocrangonyx daejeonensis sp. n., holotype, female (3.8 mm). A pleopod 1, anterior view B retinacula on peduncle of pleopod 1, anterior view C pleopod 2, anterior view D pleopod 3, anterior view E uropod 1, dorsal view F uropod 2, ventral view G uropod 3, dorsal view H telson, ventral view. Plumose setae on pleopodous rami omitted.
Uropod 1 (Fig.
Male [NNIBRIV2, 2.7 mm]. Antenna 1 (Fig.
Pseudocrangonyx daejeonensis sp. n., paratype, male (2.7 mm). A antenna 1, lateral view B accessory flagellum of antenna 1, medial view C antenna 2, lateral view D calceolus of antenna 2, medial view E gnathopod 1, medial view F palmar margin of propodus and dactylus of gnathopod 1, medial view G gnathopod 2, lateral view H palmar margin of propodus and dactylus of gnathopod 2, lateral view.
Gnathopod 1 (Fig.
Uropod 1 (Fig.
Variation. Peduncle of pleopod 1 with or without seta on outer margin.
This species is known only from the type locality.
The BI tree (mean ln L = −14039.10; Fig.
Pseudocrangonyx daejeonensis is morphologically similar to P. coreanus in having 1) relatively small body size (smaller than 6 mm), 2) eyes completely absent, 3) carpus of gnathopod 2 without serrate robust setae on posterodistal corner, 4) outer margin or outer distal corner of pleopods 1 and 2 with setae, 5) inner basal margin of inner ramus of pleopods without bifid setae, and 6) small number of articles (less than 5) of rami of pleopods. However, the former is distinguished from the latter by the following features (features of P. coreanus in parentheses): 1) antenna 1 shorter (longer) than 0.4 times as long as body length, 2) antenna 2 of female without calceoli (with calceoli), 3) uropod 1 not exceeding (slightly exceeding) tip of uropod 2, and 4) outer ramus of uropod 2 without robust seta (with robust seta).
Pseudocrangonyx daejeonensis is also similar to P. febras Sidorov, 2009 and P. gudariensis Tomikawa and Sato in
Although the phylogenetic position of P. coreanus remains uncertain, the results of the previous molecular phylogenetic studies (
The phylogenetic position of P. daejeonensis also sheds light onto the complex faunistic relationships between the Pseudocrangonyx species inhabiting the Japanese Archipelago and those inhabiting the Far Eastern continental area. Common ancestors of the Japanese Pseudocrangonyx species were considered to have migrated from the continental part to the Japanese Archipelago (
The uncorrected p-distance of 15.0 % for COI, calculated using MEGA7.0.16 (
The authors are grateful to Professor Gordon S. Karaman and Emeritus Professor Alan A. Myers for their constructive comments on this manuscript. This work was supported by grants from “A Survey of Invertebrate Species in Korea” of the Nakdonggang National Institute of Biological Resources (NNIBR) and the National Institute of Biological Resources (NIBR), funded by the Ministry of Environment (MOE) of the Republic of Korea (NIBR201722202). A part of this study was also financially supported by JSPS KAKENHI Grant Numbers JP15J00720, JP17H00820, and JP17K15174.