Research Article |
Corresponding author: Chi-Woo Lee ( cwlee@nnibr.re.kr ) Corresponding author: Gi-Sik Min ( mingisik@inha.ac.kr ) Academic editor: Charles Oliver Coleman
© 2022 Yong-Uk Ahn, Chi-Woo Lee, 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:
Ahn Y-U, Lee C-W, Min G-S (2022) A new species of Gammarus (Crustacea, Amphipoda, Gammaridae) from South Korea. ZooKeys 1117: 53-69. https://doi.org/10.3897/zookeys.1117.89610
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A new species of freshwater gammarid, Gammarus somaemulensis sp. nov., was collected from Somaemuldo Island, South Korea. This new species is morphologically characterised by the absence of calceoli in antenna 2, absence of anteroproximal setae on bases in pereopods 6 and 7, outer ramus in uropod 3 with plumose setae on both margins, and a small terminal article of the outer ramus, which is shorter than adjacent spines. A description of the new species and morphological differences from related species are provided in the text. The new species was also compared to related species using partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Genetic distances of COI sequences between the new species and related species, consisting of 21.5–26.3% difference, support Gammarus somaemulensis sp. nov. as a valid species. Additionally, a key to identifying Gammarus species in South Korea is provided.
COI, freshwater, gammarid, Korea, morphology, new species, taxonomy
The genus Gammarus Fabricius, 1775 is one of the most speciose genera of Amphipoda, comprising more than 200 species (
Freshwater Gammarus was first reported in Korea by
In the present study, a new species of the genus Gammarus, collected from the island of South Korea is described, based on morphological differences and mitochondrial cytochrome c oxidase subunit I (COI) gene sequence analyses. In addition, a key to species of Gammarus in South Korea is provided.
Gammarus specimens were collected using hand-nets from three localities in South Korea (Fig.
Genomic DNA was extracted from muscle tissue of abdomen using LaboPass Tissue Mini Kit (Cosmo Genetech, Seoul, South Korea), according to the manufacturer’s instructions. COI sequences were obtained using the primer sets, LCO1490-JJ (5’-TAYTCHACYAAYCAYAAAGAYATYGG-3’) and HCO2198-JJ (5’-AWACTTCVGGRTGVCCAAARAATCA-3’) (
Species | Locality (numbers in parentheses are those in Fig. |
Coordinates | COI | Reference |
---|---|---|---|---|
Gammarus somaemulensis sp. nov. | Somaemuldo-Island, Hansan-myeon, Tongyeong-si, South Korea (1) | 34°37'23"N, 128°32'57.1"E | ON980527–ON980532 | This study |
G. wangbangensis | Kiji-ri, sinbuk-myeon, Pocheon-si, South Korea (2) | 37°54'58"N, 127°14'9.4"E | ON980560 | This study |
G. soyoensis | Sangbongam-dong, Dongducheon-si, South Korea (3) | 37°56'39.5"N, 127°5'17"E | ON980559 | This study |
G. sobaegensis | Sannae-myeon, Namwon-si, South Korea | 35°53'28"N, 127°47'24"E | AB893337 |
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G. baengnyeongensis | Baengnyeongdo Island, Baengnyeong-myeon, Incheon, South Korea | 37°55'37.5"N, 128°38'33.8"E | MW291608 |
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G. zeongogensis | Cheongsan-myeon, Yeoncheon-gun, Gyeonggi-do, South Korea | 38°00'46"N, 127°07'35"E | MW353844 |
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G. gageoensis | Gageodo Island, Heuksan-myeon, Jeollanam-do, South Korea | 34°03'N, 125°07'E | GU270652 |
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Order Amphipoda Latreille, 1816
Family Gammaridae Leach, 1814
Holotype : male, dissected on 14 slides (NNIBRIV92290), 9.0 mm, Maejuk-ri (34°37'23"N, 128°32'57.1"E), Somaemuldo Island, Hansan-myeon, Tongyeong-si, Gyeongsangnam-do, South Korea, October 7, 2021, collected by Y. U. Ahn. Paratypes: male, dissected on 10 slides (NNIBRIV92291), 8.4 mm; male, dissected on 10 slides (NNIBRIV92292), 8.8 mm; male, dissected on 10 slides (NNIBRIV92293), 8.2 mm; male, dissected on 11 slides (NNIBRIV92294), 8.4 mm; male, dissected on 11 slides (NNIBRIV92295), 8.9 mm; female, dissected on 10 slides (NNIBRIV92296), 8.2 mm; female, dissected on 10 slides (NNIBRIV92297), 7.8 mm; 11 males and 3 females in ethanol vials (NNIBRIV92298–NNIBRIV92311); all other data same as holotype.
The specific name somaemulensis is derived from the name of the type locality, Somaemuldo Island.
Antenna 2 with four clusters of long setae on posterior margin of peduncular article 4, calceoli absent; pereopods 3 and 4 with long straight setae on posterior margins of merus and carpus; pereopods 6 and 7 without anteroproximal setae on basis; inner ramus of uropod 3 reaching approximately 0.8 × as long as outer ramus, outer ramus with plumose setae on both margins, terminal article of outer ramus shorter than adjacent spines.
Head
(Fig.
Antenna 1
(Fig.
Gammarus somaemulensis sp. nov., male, holotype (NNIBRIV92290) A antenna 1, omitted from main flagellar article 7 B antenna 2 C upper lip D lower lip E left mandible F incisor and lacinia mobilis of right mandible G right maxilla 1 H palp of left maxilla 1 I maxilla 2 J maxilliped. Scale bars: 0.5 mm (A–D); 0.2 mm (E, G–J); 0.1mm (F).
Antenna 2
(Fig.
Upper lip
(Fig.
Lower lip
(Fig.
Mandible
(Fig.
Maxilla 1
(Fig.
Maxilla 2
(Fig.
Maxilliped
(Fig.
Gnathopod 1
(Fig.
Gammarus somaemulensis sp. nov., male, holotype (NNIBRIV92290) A gnathopod 1 B palm of propodus and dactylus in gnathopod 1, setae omitted C gnathopod 2 D palm of propodus and dactylus in gnathopod 2, setae omitted E pereopod 3 F pereopod 4 G coxal plate of pereopod 5 H basis to dactylus of pereopod 5 I dactylus of pereopod 5 J dactylus of pereopod 3. Scale bars: 0.5 mm (A, C, E–H); 0.2 mm (B, D); 0.1 mm (I, J).
Gnathopod 2
(Fig.
Pereopod 3
(Fig.
Pereopod 4
(Fig.
Pereopod 5
(Fig.
Pereopod 6
(Fig.
Gammarus somaemulensis sp. nov., male, holotype (NNIBRIV92290) A coxal pate of pereopod 6 B basis to dactylus of pereopod 6 C coxal pate of pereopod 7 D basis to dactylus of pereopod 7 E inner surface near posterodistal corner of basis in pereopod 7 F pleopod 1 G inner distal corner of peduncle in pleopod 1 H–J epimeral plates 1–3, respectively K–M pleonites 1–3, respectively. Scale bars: 0.5 mm (A–D, F, H–M); 0.2 mm (E); 0.05 mm (G).
Pereopod 7
(Fig.
Coxal gills present on gnathopod 2 and pereopods 3–7.
Pleonites 1–3
(Fig.
Epimeral plates 1–3
(Fig.
Pleopods
(Fig.
Urosomites 1–3
(Fig.
Uropod 1
(Fig.
Uropod 2
(Fig.
Uropod 3
(Fig.
Telson
(Fig.
Descrption of female. General appearance similar to male. Observed sexual dimorphism as follows:
Antenna 2
(Fig.
Gammarus somaemulensis sp. nov., female, paratype (NNIBRIV92296) A antenna 2, omitted from flagellar article 3 B gnathopod 1 C palm of propodus and dactylus in gnathopod 1, setae omitted D gnathopod 2 E palm of propodus and dactylus in gnathopod 2, setae omitted F uropod 3. Scale bars: 0.5 mm (A, B, D, F); 0.2 mm (C, E).
Gnathopod 1
(Fig.
Gnathopod 2
(Fig.
Oostegites
: present on gnathopod 2 (Fig.
Uropod 3
(Fig.
The specimens were collected from a small brook flowing along a cliff on Somaemuldo Island.
The COI sequences of Gammarus somaemulensis sp. nov. (GenBank accession numbers: ON980527–ON980532) were obtained from six individuals. Additionally, the sequences of G. wangbangensis (GenBank accession number: ON980560) and G. soyoensis (GenBank accession number: ON980559) were determined in this study. The intraspecific variation of the COI sequence of the new species ranged between 0.0–0.2%. The interspecific variation between new species and the related species ranged between 21.5–26.3% (Table
A matrix of the uncorrected p-distance of the COI sequence of this study.
Species | 1 | 2 | 3 | 4 | 5 | 6 | |
---|---|---|---|---|---|---|---|
1 | Gammarus somaemulensis sp. nov. | ||||||
2 | G. soyoensis | 0.215 | |||||
3 | G. sobaegensis | 0.219 | 0.228 | ||||
4 | G. baengnyeongensis | 0.243 | 0.248 | 0.256 | |||
5 | G. gageoensis | 0.251 | 0.235 | 0.230 | 0.210 | ||
6 | G. wangbangensis | 0.256 | 0.245 | 0.246 | 0.245 | 0.281 | |
7 | G. zeongogensis | 0.263 | 0.217 | 0.240 | 0.230 | 0.206 | 0.282 |
Gammarus somaemulensis sp. nov. is most similar to G. wangbangensis Lee & Seo, 1990 in the following features: 1) antenna 2 peduncular article 4 with few clusters of long setae, calceoli absent, 2) pereopods 3 and 4 with long straight setae on posterior margins of merus and carpus, 3) pereopods 5–7 with short setae on posterior margins of basis, and 4) outer ramus of uropod 3 with plumose setae on both margins, setae length of outer margin longer than width of proximal article. However, the new species differs from G. wangbangensis in the following features (features of G. wangbangensis in parentheses): 1) article 3 of mandibular palp with one group of B-setae (two groups of B-setae), 2) bases of pereopods 6 and 7 without anteroproximal setae (with long anteroproximal setae), 3) terminal article of outer ramus in uropod 3 shorter than adjacent spines (longer than adjacent spines), and 4) anteroventral margin of epimeral plate 1 with three or four setae (six or more setae).
Gammarus somaemulensis sp. nov. is also similar to G. sobaegensis Uéno, 1966 in the following features: 1) antenna 2 with long setae on peduncular articles, calceoli absent, 2) pereopods 3 and 4 with long straight setae on posterior margins of merus and carpus, and 3) inner ramus of uropod 3 reaching 0.8 × the length of outer ramus. However, the new species can be distinguished from G. sobaegensis by the following features (features of G. sobaegensis in parentheses): 1) posterior margin of peduncular article 4 in antenna 2 with four clusters of long setae (six or more clusters of long setae), 2) bases of pereopods 6 and 7 without anteroproximal setae (with anteroproximal setae), and 3) outer ramus of uropod 3 with plumose setae on both margins (outer margin without plumose setae).
Gammarus soyoensis Lee & Kim, 1980 also share the following features with the new species: 1) antenna 2 calceoli absent and 2) uropod 3 outer margin of outer ramus with plumose setae, terminal article shorter than adjacent spines. However, the new species can be distinguished from G. soyoensis by following features (features of G. soyoensis in parentheses): 1) male gnathopods 1 and 2 with medial palmar spine, each (without medial palmar spine), 2) setae on posterior margin of merus in pereopod 4 longer than width of merus (shorter than width of merus), and 3) setae on outer margin of outer ramus in uropod 3 longer than width of proximal article (shorter than width of proximal article).
The interspecific variation within the COI sequence ranged from 21.5–26.3% for G. somaemulensis sp. nov. and related species (Table
1 | Antenna 2 caceoli present | 2 |
– | Antenna 2 caceoli absent | 4 |
2 | Posterior margins of pereopod 3 merus and carpus with long straight setae | 3 |
– | Posterior margins of pereopod 3 merus and carpus with long curled setae | G. gageoensis |
3 | Length ratio of uropod 3 inner/outer ramus ~ 0.7 | G. baengnyeongensis |
– | Length ratio of uropod 3 inner/outer ramus ~ 0.5 | G. zeongogensis |
4 | Inner ramus of uropod 3 with plumose setae on outer margin | 5 |
– | Inner ramus of uropod 3 without plumose setae on outer margin | G. hoonsooi |
5 | Peduncular articles 4 and 5 of antenna 2 with long setae | 6 |
– | Peduncular articles 4 and 5 of antenna 2 with short setae | G. galgosensis |
6 | Setae on outer margin of outer ramus in uropod 3 short and sparse | 7 |
– | Setae on outer margin of outer ramus in uropod 3 long and numerous | 8 |
7 | Gnathopods 1 and 2 with medial palmar spine on propodus | G. odaensis |
– | Gnathopods 1 and 2 without medial palmar spine on propodus | G. soyoensis |
8 | Pereopods 5–7 with long setae on posterior margin of basis | 9 |
– | Pereopods 5–7 with short setae on posterior margin of basis | 10 |
9 | Peduncular article 4 of antenna 2 with three or four setal clusters on posterior margin | G. kyonggiensis |
– | Peduncular article 4 of antenna 2 with seven or eight setal clusters on posterior margin | G. longisaeta |
10 | Outer ramus of uropod 3 with plumose setae on outer margin | 11 |
– | Outer ramus of uropod 3 without plumose setae on outer margin | G. sobaegensis |
11 | Terminal article of outer ramus in uropod 3 longer than adjacent spines | G. wangbangensis |
– | Terminal article of outer ramus in uropod 3 shorter than adjacent spines | G. somaemulensis sp. nov. |
We greatly appreciate Dr. Charles O. Coleman, Emeritus professor Alan A. Myers, and Professor Zhonge Hou giving constructive comments and suggestions to the improvement of manuscript. This work was supported by grants from the Nakdonggang National Institute of Biological Resources (