Research Article |
Corresponding author: Ko Tomikawa ( tomikawa@hiroshima-u.ac.jp ) Academic editor: Michael Ohl
© 2016 Ko Tomikawa, Takafumi Nakano, Anna Sato, Yutaka Onodera, Akifumi Ohtaka.
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:
Tomikawa K, Nakano T, Sato A, Onodera S, Ohtaka A (2016) A molecular phylogeny of Pseudocrangonyx from Japan, including a new subterranean species (Crustacea, Amphipoda, Pseudocrangonyctidae). Zoosystematics and Evolution 92(2): 187-202. https://doi.org/10.3897/zse.92.10176
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A subterranean species of pseudocrangonyctid amphipod, Pseudocrangonyx gudariensis Tomikawa & Sato, sp. n., is described from the spring-fed stream Gudari-numa in Hakkoda Mountains, Aomori Prefecture, northern Japan. Pseudocrangonyx gudariensis is morphologically similar to P. coreanus Uéno, 1966 and P. febras Sidorov, 2009 based on its relatively small body size, small number of articles of rami of pleopods, and urosomite 1 without basal setae. However, P. gudariensis is distinguished from those species based on the following characteristics: from P. coreanus, antenna 2 of female without calceoli, palmar margins of gnathopods 1 and 2 with distally notched robust setae, inner margin of inner ramus of uropod 2 with 4 robust setae, and basal part of inner ramus of uropod 2 without slender seta; and from P. febras, carpus of gnathopod 2 without serrate robust setae on posterodistal corners, peduncle of pleopods 1 and 2 with setae, and longer article 2 of uropod 3. Phylogenetic analyses using nuclear 28S rRNA and histone H3, and mitochondrial cytochrome c oxidase subunit I and 16S rRNA markers showed that P. gudariensis is placed among known Pseudocrangonyx Akatsuka and Komai, 1922 species. However, its exact phylogenetic position within the genus could not be determined. The polyphyly of the Japanese Pseudocrangonyx species indicates that multiple colonization events of Pseudocrangonyx ancestors to the Japanese Archipelago could have occurred. The reliability of the past Pseudocrangonyx records from Japan is briefly discussed.
Crangonyctoidea , interstitial, biogeography, cryptic diversity
Amphipods that belong to the genus Pseudocrangonyx Akatsuka & Komai, 1922 inhabit subterranean waters of Japan, the Korean Peninsula, eastern China, and the Far East of Russia; this genus currently includes 20 species (
Pseudocrangonyx was originally established for the three Japanese subterranean species (
Over recent decades, additional species have been described from the Far East of Russia (e.g.,
During field surveys of the benthic invertebrate fauna in the spring-fed stream Gudari-numa in Hakkoda Mountains, Aomori Prefecture in the northern Honshu, two of the authors (AS and AO) and their colleagues collected several Pseudocrangonyx specimens. After careful examination of the materials, it was revealed that the collected Pseudocrangonyx amphipods represent an undescribed species. Thus, this new species is described herein. In addition, the phylogenetic position of the new species within Pseudocrangonyx was estimated using nuclear 28S rRNA and histone H3, and mitochondrial cytochrome c oxidase subunit I and 16S rRNA sequence data.
The taxonomic description was prepared by the first and third authors (KT and AS). The second author (TN) conducted the molecular analyses, the fourth author (YO) assisted in manuscript preparation, and the last author (AO) provided the material of the new species and conducted this study.
Specimens of Pseudocrangonyx species were collected from 14 localities in Hokkaido, Honshu, and Shikoku, Japan (Fig.
Map showing the collection localities of the specimens examined in this study and type localities of the known Japanese Pseudocrangonyx species. The closed circles indicate the localities of the referred materials used for the phylogenetic analyses. The star in red denotes the type locality of the new species; in purple, P. shikokunis; in blue, P. kyotonis; and in green, P. yezonis. Names of localities are shown in Table
All appendages of the examined specimens of the undescribed species were dissected in 70% ethanol and mounted in gum-chloral medium on glass slides under a stereomicroscope (Olympus SZX7). Specimens were examined using a light microscope (Nikon Eclipse Ni) and illustrated with the aid of a camera lucida. 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
The extraction of genomic DNA from appendage muscles of the Pseudocrangonyx materials preserved in 99% ethanol followed
The PCR reaction and DNA sequencing for a part of COI and 16S sequences followed
Samples used for the phylogenetic analyses. The information on the vouchers is accompanied by the collection localities and the INSDC accession numbers. Sequences marked with an asterisk were obtained for the first time in the present study. Acronym:
# | Species | Voucher or isolate # | Loclaity | INSDC # | |||
28S | Histone H3 | COI | 16S | ||||
Pseudocrangonyx | |||||||
1 | P. yezonis a | G1280 | Mukawa, Hokkaido | LC171518* | LC171520* | LC171519* | LC171517* |
2 | Pseudocrangonyx sp. |
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Aomori, Aomori | LC171498* | LC171500* | LC171499* | LC171497* |
3 | P. yezonis a | G1279 | Daisen, Akita | LC171514* | LC171516* | LC171515* | LC171513* |
4 | Pseudocrangonyx sp. | G400 | Ofunato, Iwate | LC171479* | |||
5 | Pseudocrangonyx sp. | G1281 | Ofunato, Iwate | LC171521* | |||
6 | P. kyotonis c | G1297 | Gujo, Gifu | LC171541* | LC171543* | LC171542* | LC171540* |
6 | P. kyotonis c | G1298 | Gujo, Gifu | LC171545* | LC171547* | LC171546* | LC171544* |
7 | Pseudocrangonyx sp. | G404 | Taga, Shiga | LC171488* | LC171489* | ||
8 | Pseudocrangonyx sp. | G405 | Taga, Shiga | LC171491* | LC171493* | LC171492* | LC171490* |
9 | Pseudocrangonyx sp. | G406 | Taga, Shiga | LC171495* | LC171496* | LC171494* | |
10 | Pseudocrangonyx sp. | G1282 | Otsu, Shiga | LC171523* | LC171522* | ||
11 | Pseudocrangonyx sp. | G1283 | Niimi, Okayama | LC171525* | LC171527* | LC171526* | LC171524* |
12 | P. kyotonis e | G402 | Matsue, Shimane | LC171485* | LC171487* | LC171486* | LC171484* |
13 | P. coreanus b | G401 | Ota, Shimane | LC171481* | LC171483* | LC171482* | LC171480* |
14 | P. shikokunis d | G1277 | Mine, Yamaguchi | LC171506* | LC171508* | LC171507* | LC171505* |
15 | Pseudocrangonyx sp. | G1278 | Mine, Yamaguchi | LC171510* | LC171512* | LC171511* | LC171509* |
16 | Pseudocrangonyx sp. | G1271 | Takamatsu, Kagawa | LC171502* | LC171504* | LC171503* | LC171501* |
17 | Pseudocrangonyx sp. | G1295 | Kami, Kochi | LC171533* | LC171535* | LC171534* | LC171532* |
18 | Pseudocrangonyx sp. | G1296 | Kami, Kochi | LC171537* | LC171539* | LC171538* | LC171536* |
19 | Pseudocrangonyx sp. | G1294 | Seiyo, Ehime | LC171529* | LC171531* | LC171530* | LC171528* |
P. febras | KF153114 | ||||||
P. holsingeri | KJ871679 | KF153111 | |||||
P. korkishkoorum | B1 | KJ871678 | KF153107 | ||||
P. korkishkoorum | B2 | KF153108 | |||||
P. korkishkoorum | B3 | KF153109 | |||||
P. korkishkoorum | N1 | KJ871676 | KF153105 | ||||
P. korkishkoorum | N2 | KJ871677 | KF153106 | ||||
P. kseniae | KJ871675 | KF153115 | |||||
P. susanaensis | KF153113 | ||||||
P. sympatricus | KF153112 | ||||||
P. tiunovi | KJ871674 | KF153110 | |||||
Outgroup | |||||||
Crymostygius thingvallensis | HQ286019 | HQ286032 | HQ286009 | ||||
Eocrangonyx primoryensis | HQ286011 | ||||||
Crangonyx floridanus | G1322 | Chiba, Chiba | LC171549* | LC171550* | LC171548* |
Twenty-one published sequences were obtained from the INSDC for use in molecular phylogenetic analyses (Table
The phylogenetic position of the Pseudocrangonyx amphipod from the Gudari-numa Stream within the genus was estimated based on the gene fragments of 28S, H3, COI, and 16S sequences. The alignments of H3 and COI was trivial, as no indels were observed. The 28S, and 16S sequences were aligned using MAFFT v. 7.299b L-INS-i (
Prior to construction a phylogenetic tree based on the concatenated sequences, maximum likelihood (ML) trees were constructed based on each of the 28S, COI, and 16S markers using RAxML v. 8.2.8 (
ML phylogenies were conducted using RAxML v. 8.2.8 with GTRCAT, immediately after nonparametric bootstrapping (BS) conducted with 1,000 replicates. The best fit-partitioning scheme for the ML analysis was identified with the Akaike information criterion (
New Japanese name: Gudarimekura-yokoebi
Holotype: Male (3.9 mm),
Japan, Aomori Prefecture: Aomori, Gudari-numa Stream (northern Honshu).
Male [
Antenna 1 (Fig.
Upper lip (= labrum) (Fig.
Gnathopod 1 (= pereopod 1) (Fig.
Pseudocrangonyx gudariensis Tomikawa & Sato, sp. n., holotype, male (3.9 mm),
Pseudocrangonyx gudariensis Tomikawa & Sato, sp. n., holotype, male (3.9 mm),
Pseudocrangonyx gudariensis Tomikawa & Sato, sp. n., holotype, male (3.9 mm),
Coxal gills (Fig.
Peduncles of pleopods 1 and 2 (Fig.
Uropod 1 (Fig.
Pseudocrangonyx gudariensis Tomikawa & Sato, sp. n., holotype, male (3.9 mm),
Telson (Fig.
Female [
Pseudocrangonyx gudariensis Tomikawa & Sato, sp. n., paratype, female (3.1 mm),
Lacinia mobilis of left mandible 5-dentate.
Gnathopod 1 (Fig.
Brood plates (Fig.
Uropod 1 (Fig.
The specific name is an adjective derived from Gudari-numa, the type locality of the new species.
This species is known only from the type locality. The specimens were collected from interstitial water in the gravelly bottom. Water temperature of the habitat was stable and around 7°C throughout the year (Baba and Ohtaka unpublished).
Pseudocrangonyx gudariensis is morphologically similar to P. coreanus described from the Korean Peninsula. The deposited female paratypes of the latter species have calceoli on antenna 2 and pleopods without bifid setae on inner basal margin of inner ramus, which are features that were not mentioned in the original description (
Pseudocrangonyx gudariensis is also similar to P. febras from river basin of Primorye, Russia in having 1) relatively small body size (smaller than 6.5 mm), 2) eye completely absent, 3) palmar margins of gnathopods 1 and 2 with distally notched robust setae, 4) small number of articles (less than 6) of rami of pleopods, and 5) urosomite 1 without basal setae. However, P. gudariensis is distinguished from the latter by the following features (features of P. febras in parentheses): 1) carpus of gnathopod 2 without serrate robust setae on posterodistal corners (present), 2) peduncle of pleopods 1 and 2 with setae (absent), and 3) article 2 of uropod 3 longer (shorter) than setae on distal part of article 1.
The obtained BI tree (Fig.
Bayesian inference tree for 2,397 bp of nuclear 28S rRNA plus histone H3 and mitochondrial COI and 16S rRNA markers, with the map modified from Fig.
The other monophyletic lineage (BS = 93%, PP = 0.99) consisted of unidentified Pseudocrangonyx species from Shiga Prefecture (#7–10), and from Shikoku (#16–19), plus P. coreanus sensu
As mentioned in the Remarks, P. gudariensis is morphologically similar to P. coreanus and P. febras. These three species share the following characteristics: relatively small body size, absence of basal setae on urosomite 1, and small number of articles of rami of pleopods. However, our phylogenetic analyses failed to recover monophyly of P. gudariensis + P. febras. In addition, P. coreanus sensu
Our phylogenetic results also revealed that the species diversity of Japanese Pseudocrangonyx is quite high, and they should be classified into the known three species and additional undescribed species. Therefore, taxonomic studies should be conducted to determine the systematic accounts of these undescribed amphipods. First, however, the taxonomic status of the three known species described by
In addition to P. gudariensis, P. kyotonis sensu
Our phylogenetic analyses also shed light onto the taxonomic account of Eocrangonyx Schellenberg, 1936. This genus have been placed under the family Pseudocrangonyctidae along with Pseudocrangonyx (
We thank Dr Yuji Abe (Taga Town Museum), Kokichi Aoya (Daisen City), Dr Mark J. Grygier (Lake Biwa Museum), Naoyuki Nakahama (Kyoto University), Ryosuke Okano (Ehime University), Dr Tomislav Karanovic (Sungkyunkwan University), and Naoshi Sato (Ofunato City) for providing specimens of Pseudocrangonyx. KT thanks Satoko Tashiro (Hiroshima University), Yukiko Narahara-Nakano (Hiroshima University), and Daisuke Saiga (Hiroshima University) for supporting field work. Thanks are also due to Dr Ronald Vonk (Naturalis Biodiversity Center), Professor Boris Sket (University of Ljubljana), and Dr Michael Ohl (Museum für Naturkunde) for their critical reading and valuable comments on this manuscript. This work was partly supported by JSPS KAKENHI Grant Numbers JP25242015, JP25840140, JP15J00720. The open access publication of this manuscript was supported by the Museum für Naturkunde.