Research Article |
Corresponding author: Ko Tomikawa ( tomikawa@hiroshima-u.ac.jp ) Academic editor: Charles Oliver Coleman
© 2015 Ko Tomikawa.
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 (2015) A new species of Jesogammarus from the Iki Island, Japan (Crustacea, Amphipoda, Anisogammaridae). ZooKeys 530: 15-36. https://doi.org/10.3897/zookeys.530.6063
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A new species of anisogammarid amphipod, Jesogammarus (Jesogammarus) ikiensissp. n., is described from freshwaters in the Iki Island, Nagasaki Prefecture, Japan, based on results of morphological and molecular analyses. The new species is distinguished from all members of the genus by the combination of small number of setae on dorsal margins of pleonites 1–3, short and small number of setae on posterior margins of peduncular articles of antennae, mandibular article 1 without setae, well developed posterior lobes of accessory lobes of coxal gills on gnathopod 2 and pereopods 3–5, and pectinate setae on palmar margin of female gnathopod 2. A key to all the species of Jesogammarus is provided.
Jesogammarus , Anisogammaridae , Amphipoda , Iki Island, Japan, new species, taxonomy
The amphipod genus Jesogammarus Bousfield, 1979 has been recorded from fresh and brackish waters of the Japanese archipelago, the Korea peninsula, and the Chinese continent (
In 2010, Mr. Y. Tohyama of Hiroshima University provided a few specimens of freshwater amphipod collected from the Iki Island, Nagasaki Prefecture, Japan. They proved to belong to a previously unknown species of Jesogammarus. The Iki Island is located between Kyushu and the Tsushima Island, and 14 km from east to west and 17 km from north to south (Fig.
Specimens of Jesogammarus ikiensis sp. n. were collected from four localities in Iki Island, Nagasaki Prefecture, Japan (Fig.
Species, sampling localities, and numbers of specimens used for molecular phylogenetic study.
Species | Voucher | Locality | DDBJ Acc. No. | Reference | |
---|---|---|---|---|---|
COI | 16S | ||||
Eogammarus kygi | G1 | Naibetsu River, Eniwa, Hokkaido, Japan | LC052229 | LC052250 | this study |
Eogammarus possjeticus | G3 | Akkeshi, Hokkaido, Japan | LC052230 | LC052251 | this study |
Jesogammarus annandalei | G1162 | Lake Biwa, Shiga Prefecture, Japan | LC052231 | LC052252 | this study |
Jesogammarus fluvialis | G83 | Samegai, Shiga Prefecture, Japan | LC052232 | LC052253 | this study |
Jesogammarus fujinoi | G17 | Gobanmiki, Yamagata, Yamagata Prefecture, Japan | LC052233 | LC052254 | this study |
Jesogammarus hinumensis | G52 | Lake Hinuma, Ibaraki Prefecture, Japan | LC052234 | LC052255 | this study |
Jesogammarus hokurikuensis | G383 | Takinami, Fukui, Fukui Prefecture, Japan | LC052235 | LC052256 | this study |
Jesogammarus jesoensis | G164 | Sapporo, Hokkaido, Japan | LC052236 | LC052257 | this study |
Jesogammarus mikadoi | G13 | Rokugo, Akita Prefecture, Japan | LC052237 | LC052258 | this study |
Jesogammarus naritai | G1167 | Lake Biwa, Shiga Prefecture, Japan | LC052238 | LC052259 | this study |
Jesogammarus paucistulosus | G1037 | Mito, Ibaraki Prefecture, Japan | LC052239 | LC052260 | this study |
Jesogammarus shonaiensis | G192 | Sakata, Yamagata Prefecture, Japan | LC052240 | LC052261 | this study |
Jesogammarus ikiensis sp. n. | G515 | Katsumoto, Iki, Nagasaki Prefecture, Japan | LC052241 | LC052262 | this study |
Jesogammarus ikiensis sp. n. | G665 | Ishida, Iki, Nagasaki Prefecture, Japan | LC052242 | LC052263 | this study |
Jesogammarus ikiensis sp. n. | G695 | Ishida, Iki, Nagasaki Prefecture, Japan | LC052243 | LC052264 | this study |
Jesogammarus ikiensis sp. n. | G885 | Ishida, Iki, Nagasaki Prefecture, Japan | LC052244 | LC052265 | this study |
Jesogammarus ikiensis sp. n. | G886 | Ishida, Iki, Nagasaki Prefecture, Japan | LC052245 | LC052266 | this study |
Jesogammarus spinopalpus | G32 | Onjuku, Chiba Prefecture, Japan | LC052246 | LC052267 | this study |
Jesogammarus suwaensis | G88 | Lake Suwa, Nagano Prefecture, Japan | LC052247 | LC052268 | this study |
Jesogammarus suwaensis | G89 | Lake Suwa, Nagano Prefecture, Japan | LC052248 | LC052269 | this study |
Spasskogammarus spasskii | G35 | Akkeshi, Hokkaido, Japan | LC052249 | LC052270 | this study |
All appendages of the examined specimens of Jesogammarus ikiensis sp. n. were dissected in 99% 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
Total genomic DNA was extracted from pereopod musculature of each sequenced amphipod (Table
The nucleotide sequences were aligned using the multiple alignment algorithm in Clustal W (
Monophyly of the subgenera Jesogammarus and Annanogammarus were supported in COI, 16S, and COI + 16S trees (Figs
Uncorrected pairwise differences (%: p-distance) of partial COI (upper right) and 16S rRNA (lower left) gene sequences between species.
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1: Eogammarus kygi (N = 1) | 19.5 | 24.3 | 23.7 | 30.6 | 27.3 | 27.0 | 27.9 | 30.0 | 24.3 | 28.5 | 29.1 | 29.4 | 27.6 | 24.3 | 25.2 | |
2: Eogammarus possjeticus (N = 1) | 16.3 | 24.9 | 24.0 | 27.0 | 27.0 | 26.4 | 25.5 | 27.6 | 23.7 | 28.5 | 27.6 | 28.5 | 28.2 | 23.4 | 24.3 | |
3: Jesogammarus annandalei (N = 1) | 20.8 | 22.3 | 3.0 | 24.0 | 20.7 | 23.1 | 22.5 | 25.8 | 3.3 | 20.7 | 24.3 | 21.6 | 20.7 | 3.0–3.3 | 22.5 | |
4: Jesogammarus fluvialis (N = 1) | 20.4 | 22.0 | 2.0 | 24.0 | 19.5 | 22.5 | 21.9 | 25.2 | 2.1 | 20.7 | 22.8 | 21.6 | 20.4 | 1.8–2.1 | 22.8 | |
5: Jesogammarus fujinoi (N = 1) | 25.1 | 24.0 | 20.6 | 20.7 | 19.8 | 15.3 | 10.5 | 18.9 | 22.5 | 20.4 | 9.3 | 24.6 | 21.3 | 22.8–23.1 | 27.9 | |
6: Jesogammarus hinumensis (N = 1) | 22.3 | 23.9 | 18.0 | 17.6 | 15.1 | 20.7 | 17.7 | 21.9 | 19.5 | 18.6 | 18.6 | 19.5 | 18.6 | 19.2–19.5 | 25.8 | |
7: Jesogammarus hokurikuensis (N = 1) | 24.3 | 24.3 | 20.3 | 20.2 | 11.2 | 15.6 | 17.1 | 21.3 | 22.5 | 19.5 | 12.6 | 23.7 | 19.8 | 22.2–22.5 | 26.1 | |
8: Jesogammarus jesoensis (N = 1) | 24.2 | 23.8 | 20.2 | 20.0 | 6.9 | 13.6 | 10.8 | 18.6 | 21.6 | 20.1 | 10.5 | 25.8 | 21.0 | 21.0–21.3 | 28.2 | |
9: Jesogammarus mikadoi (N = 1) | 25.1 | 24.7 | 21.0 | 20.7 | 15.4 | 16.4 | 15.6 | 14.3 | 24.0 | 20.4 | 18.9 | 25.8 | 21.6 | 23.7–24.0 | 28.5 | |
10: Jesogammarus naritai (N = 1) | 20.8 | 21.6 | 1.9 | 1.2 | 19.8 | 17.5 | 19.9 | 19.6 | 20.0 | 20.1 | 22.2 | 20.7 | 20.1 | 0.3–0.6 | 23.4 | |
11: Jesogammarus paucisetulosus (N = 1) | 24.2 | 25.2 | 18.7 | 18.8 | 16.3 | 15.6 | 16.3 | 16.4 | 18.7 | 18.3 | 19.8 | 21.0 | 21.0 | 20.1–20.7 | 25.2 | |
12: Jesogammarus shonaiensis (N = 1) | 25.5 | 25.1 | 21.9 | 21.4 | 7.3 | 15.5 | 10.3 | 7.3 | 15.1 | 20.8 | 17.4 | 22.8 | 20.4 | 21.9–22.2 | 27.9 | |
13: Jesogammarus ikiensis sp. n. (N = 5) | 23.4–23.5 | 24.0–24.2 | 18.2–18.3 | 18.3–18.4 | 18.0–18.2 | 12.7–12.8 | 17.8–17.9 | 18.2–18.3 | 18.6–18.7 | 17.6–17.8 | 16.8–17.0 | 17.4 | 18.6 | 20.4–20.7 | 26.1 | |
14: Jesogammarus spinopalpus (N = 1) | 23.0 | 24.6 | 17.0 | 17.0 | 17.1 | 15.9 | 16.6 | 16.7 | 16.8 | 16.6 | 16.4 | 17.1 | 14.8–15.0 | 19.5–19.8 | 24.6 | |
15: Jesogammarus suwaensis (N = 2) | 20.8–21.0 | 21.6–21.8 | 1.9–2.0 | 1.2–1.3 | 20.0–20.2 | 17.5–17.6 | 20.0–20.2 | 19.5–19.6 | 20.0–20.2 | 0.3–0.4 | 18.3–18.4 | 20.8–21.0 | 17.6–17.9 | 16.4–16.6 | 22.8–23.1 | |
16: Spasskogammarus spasskii (N = 1) | 22.2 | 22.8 | 20.6 | 20.8 | 22.7 | 22.0 | 22.2 | 22.3 | 23.0 | 20.8 | 21.1 | 22.4 | 21.5–21.6 | 21.0 | 20.6–20.7 |
Holotype:
(holotype,
Antenna 1 (Fig.
Jesogammarus (Jesogammarus) ikiensis sp. n., holotype, male, 13.1 mm,
Antenna 2 (Fig.
Mouthparts. Upper lip (= labrum) (Fig.
Jesogammarus (Jesogammarus) ikiensis sp. n., holotype, male, 13.1 mm,
Gnathopod 1 (= pereopod 1) (Fig.
Gnathopod 2 (= pereopod 2) (Fig.
Pereopod 3 (Fig.
Jesogammarus (Jesogammarus) ikiensis sp. n., holotype, male, 13.1 mm,
Pereopod 4 (Fig.
Pereopod 5 (Fig.
Pereopod 6 (Fig.
Jesogammarus (Jesogammarus) ikiensis sp. n., holotype, male, 13.1 mm,
Pereopod 7 (Fig.
Coxal gills on gnathopod 2 and pereopods 3–5 (Figs
Pleopods 1–3 (Fig.
Uropods. Uropod 1 (Fig.
Jesogammarus (Jesogammarus) ikiensis sp. n., Ishida, Iki, Nagasaki Prefecture, Japan. Holotype, male, 13.1 mm,
Telson (Fig.
(paratype,
Antenna 2 (Fig.
Gnathopod 1 (Fig.
Jesogammarus (Jesogammarus) ikiensis sp. n., paratype, female, 10.4 mm,
Gnathopod 2 (Fig.
Posterior margin of bases of pereopods 5–7 more expanded than in male (Fig.
Brood plates (= oostegites) (Fig.
Uropod 3 (Fig.
Egg number: 175.
The number of setae and/or setal bundles on posterior margin of peduncular articles of antennae is variable: antenna 1, two or three on article 1, three or four on article 2, one or two on article 3; antenna 2, two to four on article 4, three to five on article 5. Most specimens have a pair of setae on dorsal margins of pleonites 1–3 but several specimens have three setae. The length ratio of inner ramus of uropod 3 to outer ramus ranged from 0.2 to 0.3 in both sexes. The number of plumose setae on inner margin of outer ramus of uropod 3 varied from two to eight in males and one to three in females. Ovigerous females have 58 to 175 eggs.
Jesogammarus ikiensis sp. n. is assigned to the subgenus Jesogammarus in having well developed posterior accessory lobe of coxal gills on gnathopod 2 and pereopods 3–5, and pectinate setae on palmar margin of female gnathopod 2. The new species is distinguished from J. fontanus Hou & Li, 2004, J. hebeiensis Hou & Li, 2004, J. hinumensis Morino, 1993, and J. spinopalpus Morino, 1985 by absence (vs. presence) of setae on article 1 of mandibular palp. Jesogammarus ikiensis is distinguished from J. mikadoi Tomikawa, Morino & Mawatari, 2003 by absence (vs. presence) of setae on dorsal margin of pereonites 5–7 and two or three (vs. more than seven) setae on dorsal margins of pleonites 1–3. Jesogammarus ikiensis is distinguished from J. paucisetulosus Morino, 1984 by medium eye, major axis of eyes 0.4 × height of head (vs. small, less than 0.3), posterodistal corner of peduncular article 1 of antenna 1 with a robust (vs. slender) seta, posterior margin of peduncular article 2 of antenna 1 with three or four (vs. more than five) setae and/or setal bundles, and posterio-marginal setae on peduncular article 4 of antenna 2 shorter (vs. longer) than width of article 4 in male;. Jesogammarus ikiensis differs from the J. jesoensis complex including J. fujinoi Tomikawa & Morino, 2003, J. hokurikuensis Morino, 1985, J. jesoensis (Schellenberg, 1937), J. shonaiensis Tomikawa & Morino, 2003, by two or three (vs. more than seven) setae on dorsal margins of pleonites 1–3 and three or four (vs. two) setae and/or setal bundles on posterior margin of peduncular article 2 of antenna 1. Jesogammarus ikiensis differs from J. ilhoii Lee & Seo, 1992 by absence (vs. presence) of pectinate setae on palmar margin of propodus of male gnathopod 2 and two or three (vs. more than ten) setae on dorsal margins of pleonites 1–3.
The specific name is from the Latinized Japanese ikiensis (of Iki), referring to the type locality of the new species.
Known only from Iki Island.
River and irrigation ditch.
Since species of the J. jesoensis complex including J. fujinoi, J. hokurikuensis, J. jesoensis, J. shonaiensis are difficult to distinguish from each other due to high variability of morphological characters (
1 | Accessory lobes of coxal gills on gnathopod 2 and pereopods 3–5 well developed, both anterior and posterior lobes subequal in length or posterior lobe longer than anterior one; palmar margin of propodus of female gnathopod 2 with pectinate setae | 2 (subgenus Jesogammarus) |
– | Accessory lobes of coxal gills on gnathopod 2 and pereopods 3–5 weakly developed, anterior and posterior lobes unequal in length, often posterior lobe rudimentary; palmar margin of propodus of female gnathopod 2 without pectinate setae | 10 (subgenus Annanogammarus) |
2 | Article 1 of mandibular palp with setae | 3 |
– | Article 1 of mandibular palp without setae | 6 |
3 | Dorsal margin of pleonites 1–3 each with 1–2 setae; eye large; article 1 of mandibular palp with 1 robust seta; female pereopods densely setose | J. (J.) hinumensis Morino, 1993 |
– | Dorsal margin of pleonites 1–3 each with more than 4 setae; eye small to medium; article 1 of mandibular palp with 2 or 3 robust setae; female pereopods not densely setose | 4 |
4 | Peduncular article 1 of antenna 1 with robust seta on posterodistal corner | J. (J.) spinopalpus Morino, 1985 |
– | Peduncular article 1 of antenna 1 with slender seta on posterodistal corner…5 | |
5 | Inner ramus of uropod 3 length 1/4 × outer ramus; inner margin of outer ramus of uropod 3 with 4–6 plumose setae | J. (J.) fontanus Hou & Li, 2004 |
– | Inner ramus of uropod 3 length 1/3 × outer ramus; inner margin of outer ramus of uropod 3 with about 10 plumose setae | J. (J.) hebeiensis Hou & Li, 2004 |
6 | Dorsal margin of pereonites 1–3 each with 2 long setae | J. (J.) mikadoi Tomikawa et al., 2003 |
– | Dorsal margin of pereonites 1–3 without setae | 7 |
7 | Posterior margin of peduncular article 2 of antenna 1 with fewer than five setae and/or setal bundles; posteromarginal setae on peduncular article 4 of antenna 2 shorter than width of article 4 in male; posterodistal corner of peduncular article 2 of antenna 1 with robust seta (occasionally lacking) | 8 |
– | Posterior margin of peduncular article 2 of antenna 1 with more than 5 setae and/or setal bundles; posteromarginal setae on peduncular article 4 of antenna 2 longer than width of article 4 in both sexes; posterodistal corner of peduncular article 2 of antenna 1 without robust seta | J. (J.) paucisetulosus Morino, 1984 |
8 | Dorsal margins of pleonites 1–3 each with 2 or 3 setae; posterior margin of peduncular article 2 of antenna 1 with 3 or 4 setae and/or setal bundles | J. (J.) ikiensis sp. n. |
– | Dorsal margins of pleonites 1–3 each with more than 7 setae; posterior margin of peduncular article 2 of antenna 1 with 2 setae and/or setal bundles | 9 |
9 | Palmar margin of propodus of male gnathopod 2 without pectinate setae | J. (J.) jesoensis complex |
– | Palmar margin of propodus of male gnathopod 2 with pectinate setae | J. (J.) ilhoii Lee & Seo, 1992 |
10 | Dorsal margin of pleonite 3 with robust setae; posterior margin of peduncular article 4 and 5 with more than 5 long-setal bundles | J. (A.) naritai Morino, 1985 |
– | Dorsal margin of pleonite 3 without robust setae; posterior margin of peduncular article 4 and 5 with less than 3 short-setal bundles | 11 |
11 | Posterodistal corner of bases of pereopods 5–7 with long setae | J. (A.) annandalei (Tattersal, 1922) |
– | Posterodistal corner of bases of pereopods 5–7 without short setae | 12 |
12 | Dorsal margins of pleonites 1–3 each with 2–4 setae | J. (A.) fluvialis Morino, 1985 |
– | Dorsal margins of pleonites 1–3 each with more than 10 setae | 13 |
13 | Posterodistal corner of peduncular article 1 of antenna 1 with robust seta; palmar margin of propodus of female gnathopod 2 with simple setae only | J. (A.) koreanus Lee & Seo, 1990 |
– | Posterodistal corner of peduncular article 1 of antenna 1 without robust seta; palmar margin of propodus of female gnathopod 2 with weakly pectinate setae | J. (A.) debilis Hou & Li, 2005 |
I thank Mr. Y Tohyama (Hiroshima University) for providing specimens and Ms. S. Tashiro (Hiroshima University) for assistance in collection. Thanks are also due to Ryu Uchiyama (nature photographer) for providing photographs of live specimens. I am grateful Dr. Cene Fišer (University of Ljubljana) and two anonymous reviewers for their critical reading of and valuable comments on this manuscript. This work was partly supported by grants from the Japan Society for the Promotion of Sciences (JSPS: 25242015 and 25840140).