A new Gammarus species (Crustacea, Amphipoda, Gammaridae) from Northwestern Islands, South Korea Author Kwon, So-Yeon 0000-0001-5807-1037 Department of Life Sciences, Dankook University, Cheonan, KOREA 31116 & sy. kwon 18 @ gmail. com; https: // orcid. org / 0000 - 0001 - 5807 - 1037 & National Marine Biodiversity Institute of Korea, Seocheon, KOREA 33662 sy.kwon18@gmail.com Author Kim, Min-Seop 0000-0001-5807-1037 sy. kwon 18 @ gmail. com; https: // orcid. org / 0000 - 0001 - 5807 - 1037 & National Marine Biodiversity Institute of Korea, Seocheon, KOREA 33662 sy.kwon18@gmail.com Author Heo, Jun-Haeng 0000-0003-0942-7126 Department of Life Sciences, Dankook University, Cheonan, KOREA 31116 & tyrant 1047 @ naver. com; https: // orcid. org / 0000 - 0003 - 0942 - 7126 tyrant1047@naver.com Author Kim, Young-Hyo 0000-0002-7698-7919 Department of Life Sciences, Dankook University, Cheonan, KOREA 31116 & yhkim @ dankook. ac. kr; https: // orcid. org / 0000 - 0002 - 7698 - 7919 yhkim@dankook.ac.kr text Zootaxa 2020 2020-12-23 4896 4 535 546 journal article 9206 10.11646/zootaxa.4896.4.5 b74e6677-e056-459b-8781-3f3ade783f8c 1175-5326 4387901 8F11E9BD-CA99-4999-8D99-27554C95EAB2 Gammarus baengnyeongensis sp. nov (Korean Name: Baek-ryeong-do-yeop-sae-u, new) ( Figs. 2–6 ) Type material. Holotype , adult male, 12.5mm , cat no. NIBRIV0000877256 , Yeonhwa-ri , Baengnyeongdo Island , Baengnyeong-myeon , Ongjin-gun , Incheon , South Korea , 37°55′37.5″N , 128°38′33.8″E , 14 July 2007 , collected by Y.H. Kim. Paratypes : 30 ³ ( NIBRIV0000877257 ) , 20 ♀ ( NIBRIV0000877258 , NIBRIV0000877259 ); all other data same as the holotype. 5 ³ , 15 ♀ , Daecheong-ri , Daecheongdo Island , Daecheong-myeon , Ongjin-gun , Incheon , South Korea , 37°49'5.8"N , 124°41'13.2"E , 5 November 2009 , collected by D.H. Ahn. Etymology. The species name is from the type locality, Baengnyeongdo Island located on the west coast of South Korea . Description. Holotype adult male , 12.5 mm , cat no. NIBRIV0000877256. Body ( Fig. 3A ) about 12.5 mm long; head as long as wide, subequal in length to pereonites 1–2 combined, rostrum rounded, flat; eye small, subreniform, black in alcohol. Antenna 1 ( Fig. 3B ) about 0.4 times as long as body length; peduncular articles with tufts of setae distally; length ratio of peduncular articles 1–3= 1.00: 0.75: 0.46; flagellum 18-articulate, each article with short distal setae; accessory flagellum 6-articulate, subequal to flagellum articles 1–3 combined, each article with short distal setae, article 6 comparatively short. Antenna 2 ( Fig. 3C ) 0.75 times as long as antenna 1; length ratio of peduncular articles 3–5= 1.00: 2.91: 3.16; flagellum 10-articulate, articles 1–7 with a rounded calceoli dorsally. Upper lip ( Fig. 3D ) subrounded, convex, densely pubescent ventrally. Lower lip ( Fig. 3E ), inner lobe absent; outer lobe pubescent medially and apically, mandibular process short and blunt. Left mandible ( Fig. 3F ), incisor 5 dentate; lacinia mobilis with 4 blunt teeth setal row with 11 setae; molar triturative, with 1 pappose seta; mandibular palp, article 2 with 13 simple setae, distal article missing. n FIGURE 2. Gammarus baengnyeongensis sp. nov. , A, paratype , adult male, 11.7 mm , cat no. NIBRIV0000877257, habitus; B, paratype , adult female, 9.2 mm , cat no. NIBRIV0000877259, habitus. Scale bars = 1.0 mm (A, B) FIGURE 3. Gammarus baengnyeongensis sp. nov. , holotype, adult male, 12.5 mm, cat no. NIBRIV0000877256: A, habitus; B, antenna 1; C, antenna 2; D, upper lip; E, lower lip; F, left mandible; G, right mandible; H, maxilla 1; I, maxilla 2; J, maxilliped. Scale bars = 3 mm (A), 1 mm (B–C), 0.3 mm (D–J). FIGURE 4. Gammarus baengnyeongensis sp. nov. , holotype, adult male, 12.5 mm, cat no. NIBRIV0000877256: A, gnathopod 1; B, gnathopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5. Scale bars = 1 mm (A–E). FIGURE 5. Gammarus baengnyeongensis sp. nov. , holotype, adult male, 12.5 mm, cat no. NIBRIV0000877256: A, pereopod 6; B, pereopod 7; C, urosome1–3; D, uropod 1; E, uropod 2; F, uropod 3; G, telson. Scale bars = 1mm (A–B), 0.4 mm (C–G). Right mandible ( Fig. 3G ), incisor 4 dentate; lacinia mobilis trifurcate, with weak dentitions apically; setal row with 7 setae; mandibular palp well developed, article 2 with 2 A2-setae, 6 B2-setae, and 4 D2-setae; article 3 with 5 A3-setae, 3 B3-setae, 27 D3-setae, and 5 E3-setae. Maxilla 1 ( Fig. 3H ), inner plate subrectangular, with 15 plumose setae; outer plate with 11 dentate-spines apically; palp biarticulate, distal article with 4 slender spines apically and 5 subapical setae. Maxilla 2 ( Fig. 3I ) setose, inner plate with serrulate and plumose setae on inner margin, several serrulate and simple setae apically; outer plate slightly longer than inner plate, with stiff setae apically. Maxilliped ( Fig. 3J ), inner plate subrectangular, with 4 apical and 1 subapical spines; outer plate broad, with 12 blade spines medially and 10 simple setae apically; palp 4-articulate, article 1 unarmed, article 2 with numerous simple setae on inner margin and 2 tufts of a few simple setae on outer margin, article 3 elongate, with several pectinate and simple setae subapically, 2 dentate-spines apically. Gnathopod 1 ( Fig. 4A ) subchelate; coxa subquadrate, with 3 short setae anterodistally, and 1 short seta pos-terodistally; basis with long curved or 3 long pinnate setae posteriorly, several unequal simple setae anteriorly, 3 stiff cuspidate setae ventrodistally; carpus with several clusters of simple setae posteriorly and 5 stiff cuspidate setae distomedially; propodus subovate, narrowing distally, 1.37 times as long as carpus, with a row of simple setae ventrally, palm gently oblique, with 3 medial spines and 11 spines posteriorly; dactylus falcate, 0.73 times as long as propodus. FIGURE 6. Gammarus baengnyeongensis sp. nov. , paratype, adult female, 12.3 mm, cat no. NIBRIV0000877258: A, habitus; B, gnathopod 1; C, gnathopod 2; D, uropod 3. Scale bars = 3 mm (A), 0.5 mm (B–C), 0.4mm (D). Gnathopod 2 ( Fig. 4B ) similar to gnathopod 1; coxa subquadrate, width 0.46 times length, with 3 anterodistal setules, 1 posterodistal setule, and 3 unequal setae subposterodistally; basis subrectangular, narrowing proximally, with 8 long simple setae anteriorly and 4 cuspidate setae distally; carpus 0.63 times as long as basis, with 8 clusters of pinnate and simple setae posteriorly, and 3 clusters of simple setae anteriorly; propodus subchelate, 1.15 times as long as carpus, with 7 clusters of simple and pinnate setae posteriorly, 4 clusters of simple setae anteriorly, palm oblique, with 1 blunt medial spine and 4 small spines on palmar corner; dactylus falcate, 0.67 times as long as propodus. Pereopod 3 ( Fig. 4C ), coxa subrectangular, width 0.42 times length, with 3 anterodistal and 1 posterodistal setul; basis with 23 unequal simple setae posteriorly, 14 unequal simple setae anteriorly; merus elongate, with 9 clusters of simple setae posteriorly; carpus with unequal simple setae and 2 spines posteriorly, anterior margin unarmed; propodus more slender than and 1.20 times longer than carpus, with 6 spines and accompanied by setae along the posterior margin, and 5 setae anterodistally; dactylus with 1 short setae on hinge of the nail. Pereopod 4 ( Fig. 4D ) similar to pereopod 3, except coxa 4 with posteroproximal excavation and 6 posterodistal, 2 anterodistal setules; merus, carpus, and propodus with shorter setae than those of pereopod 3. Pereopod 5 ( Fig. 4E ), basis subovate, width 0.68 times length, posterior margin rounded, weakly serrate, with a row of marginal setules, anterior margin straight with 4 proximal setae, 4 spines accompanied by setules; merus, carpus, propodus setose, with a row of duad or triad spines on both margins. Pereopod 6 ( Fig. 5A ) similar to pereopod 5, except basis subrectangular. Pereopod 7 ( Fig. 5B ) similar to pereopod 6, except basis subquadrate, width 0.80 times length, slightly broader than that of pereopod 6 and slightly shorter than pereopod 6. Urosomites 1–3 ( Fig. 5C ) dorsally flat; urosomite 1 with 1–2–1 spines on dorsal margin from left to right; urosomite 2 with 2–2–2 spines; urosomite 3 with 1–0–1 spines on each side. Uropod 1 ( Fig. 5D ), peduncle subrectangular, 1.40 times longer than inner ramus, with a row of 6 dorsolateral and 3 dorsomedial spines; outer ramus subequal to inner one. Uropod 2 ( Fig. 5E ), peduncle 1.62 times longer than inner ramus, with a row of 4 dorsolateral and 5 dorsomedial spines; inner ramus with 1 spine on each margin, 3 apical spines; outer ramus with 1 lateral spine, 5 unequal apical spines, 1.27 times as long as inner one. Uropod 3 ( Fig. 5F ), peduncle short, 0.56 times as long as inner ramus, with 2 apical and 3 lateral spines on each margin; inner ramus with 2 spines and long simple setae apically; outer ramus biarticulate, 1.30 times longer than inner one, proximal article with 2 spines laterally, 4 spines and long simple setae distally, terminal article longer than adjacent spines; both rami surrounded by plumose setae. Telson ( Fig. 5G ) deeply cleft nearly to the base; each lobe with 2 spines accompanied by 8 simple setae apically, a tuft of four simple setae medially, two tufts of simple setae and a pair of penicillate setae laterally. Paratype , adult female, body 12.3 mm ( Fig. 6A ), cat no. NIBRIV0000877258. Antenna 2 ( Fig. 6A ) similar to that of male, except flagellum without calceoli. Gnathopod 1 ( Fig. 6B ) similar to that of male, except medial palmar spine lacking. Gnathopod 2 ( Fig. 6C ) similar to that of male, except medial palmar spine lacking. Uropod 3 ( Fig. 6D ) similar to that of male, except both rami with plumose setae on both margins, setae more than sparse in male; outer ramus 1.48 times longer than inner ramus. Molecular data. CO1 gene sequences (GenBank accession numbers MW291608 - MW291613 ) were obtained from 6 specimens of the new species. Additionally, one sequences were determined from G . zeongogensis specimen, and four sequences from four species retrieved from National Center for Biotechnology Information (NCBI). Intraspecific variation of the CO1 gene fragment of the new species ranged from 0.2% to 0.8%, while interspecific variation ranged from 29.1% ( G . baengnyeongensis sp. nov. and G . gageoensis ) to 40.8% ( G . baengnyeongensis sp. nov. and G . koreanus ) ( Figure 8 , Table 1 ). Remarks. Up to now, G . baengnyeongensis sp. nov. and G . zeongogensis Lee and Kim, 1980 have been regarded as the same species, because both species commonly bear calceoli on antenna 2. However, prominent evidence found in this study, showed that these are two different species. Gammarus baengnyeongensis has a broader palm and more gradual angle in gnathopod 2, and setose telson. Also, length ratio of the outer ramus to inner ramus of uropod 3 in G . baengnyeongensis is comparatively longer than that of G . zeongogoensis . Length ratio was 1.00: 0.71 ± 0.01 (n = 25) in G . baengnyeongensis , and 1.00: 0.55 ± 0.01 (n = 25) in G . zeongogensis ( Fig. 7 ). The difference shown in uropod 3, length ratio of outer ramus to inner ramus, between the two species was statistically significant (P <0.05, Fig. 7 ). Gammarus baengnyeongensis sp. nov. is similar to G . koreanus Uéno, 1940 in having a few tufts of short setae and calceoli on antenna 2. Karaman (1984) elevated G. ( Rivulogammarus ) pulex koreanus to species level, G . koreanus which reported in North Korea , with description only. Since then, he illustrated for G . koreanus and compared to similar species G . suifunensis Martynov, 1925 ( Karaman, 1991 ) . As a result of referring to previous studies, the new species is distinguished from suitable straight setae on carpi-propodi in gnathopods 1-2 and posterior margins of pereopods 3-4. As Pinkster (1983) and Goedmakers (1972) stated, differences in the shape of gnathopod 2 and length ratio of the outer and inner ramus of uropod 3 are “stable characteristics.” Previous molecular study also corresponded with this result, demonstrating that freshwater Gammarus in South Korea could be distinguished into 39 different species in total, based on mtDNA CO1 sequence ( Kim, 2008 ). In consequence, it is difficult to consider these as a mere intra-specific variation. TABLE 1. A matrix of the pair-wise genetic distance of the CO1 sequence of this study. Sequence divergence using the K2P distance parameter.
GenBank accession number 1 2 3 4 5 6 7 8 9 10 11
1. G. baengnyeongensis 1 MW291608
2. G. baengnyeongensis 2 MW291609 0.002
3. G. baengnyeongensis 3 MW291610 0.003 0.002
4. G. baengnyeongensis 4 MW291611 0.007 0.005 0.007
5. G. baengnyeongensis 5 MW291612 0.008 0.007 0.005 0.005
6. G. baengnyeongensis 6 MW291613 0.007 0.005 0.003 0.003 0.002
7. G. zeongogensis MW353844 0.331 0.335 0.338 0.342 0.345 0.342
8. G. gageoensis GU270652 0.295 0.291 0.295 0.295 0.301 0.298 0.295
9. G . koreanus EF570314 0.400 0.395 0.400 0.400 0.408 0.404 0.311 0.282
10. G. qinling MG550238 0.347 0.351 0.355 0.355 0.362 0.358 0.424 0.339 0.379
11. G. zhigangi MG550239 0.330 0.333 0.330 0.326 0.326 0.322 0.417 0.375 0.408 0.316
FIGURE 7. Difference of inner ramus length ratio in uropod 3. Gammarus baengnyeongensis sp. nov. had greater inner ramus length ratio to outer ramus compared to G . zeongogensis ( P <0.05). G . baengnyeongensis is also similar to G . fossarum Koch, 1835 , G . qinling Hou and Li, 2018 , and G . zhigangi Hou and Li, 2018 . In males, antenna 2 bear calceoli, and gnathopods 1 and 2 bear medial palmar spines. However, in G . baengnyeongensis , the basis of pereopod 7 is broader than those of G . fossarum , G . qinling , and G . zhigangi . Also, in G . baengnyeongensis , the outer ramus of uropod 3 has plumose setae (simple setae in G . fossarum ) on the outer margin, and ratio of the outer ramus to inner ramus in G . baengnyeongensis is comparatively longer than those of congeners. The differences stated above were stable and constant. We present morphologically different characteristics in Table 2 . Distribution. Korea (Baengnyeongdo Island, Daecheongdo Island).