A new species of the genus Caprella Lamarck, 1801 (Crustacea, Amphipoda, Caprellidae) from Korea Author Heo, Jun-Haeng Environmental Impact Assessment Team, National Institute of Ecology, Seocheon, Korea 33657 Author Shin, So-Yeon Department of Biological Sciences, Dankook University, Cheonan, Korea 31116 Author Kim, Young-Hyo Department of Biological Sciences, Dankook University, Cheonan, Korea 31116 text Zootaxa 2024 2024-04-02 5432 3 436 444 http://dx.doi.org/10.11646/zootaxa.5432.3.7 journal article 10.11646/zootaxa.5432.3.7 1175-5326 10906702 7B21A290-CA19-412E-983D-2BFEC263EB1F Caprella megabranchia sp. nov. (Korean name: Keun-a-ga-mi-ba-da-dae-beol-re, new) Caprella brevirostris .— Martin, 1977: 156 , fig. 4.— Kim & Lee, 1978: 3 , fig. 3. Type material. Holotype , adult male, 12.6 mm , cat no. NIBRIV0000909913, Woangdolcho , Hupo-ri , Hupo-myeon , Uljin-gun , Gyeongsangbuk-do , Korea , 36°43′57″N , 129°43′56″E , S.H. Kim , by SCUBA diving, 27 May 2016 . Paratype , adult female, 6.9 mm , cat no. DKUAMP202304, data as holotype. The remaining paratypes ( 7 males , 2 females , cat no. DKUAMP202303) in the collection of the corresponding author . Additional material. 2 males , 2 females , Woangdolcho , Hupo-ri , Hupo-myeon , Uljin-gun , Gyeongsangbuk-do , Korea , 36°43′12″N , 129°43′42″E , S.H. Kim , by SCUBA diving, 12 November 2017 ; 448 males , 394 females , Woangdolcho , Hupo-ri , Hupo-myeon , Uljin-gun , Gyeongsangbuk-do , Korea , 36°43′58″N , 129°43′50″E , S.H. Kim , by SCUBA diving, 30 May 2018 ; 42 males , 41 females , Namhyeongje-Islet , Dadae-dong , Saha-gu , Busan , Korea , 34°53′04″N , 128°57′07″E , S.H. Kim , by SCUBA diving, 4 June 2018 ; 1 male , 1 female , Sanyang-eup , Tongyeong-si , Gyeongsangnam-do , Korea , 34°46′14″N , 128°23′51″E , Y.H. Kim , by sieving, 30 July 2019 ; 9 males , Gajin-port , Jugwang-myeon , Goseong-gun , Gangwon-do , Korea , 38°22′03″N , 128°30′44″E , Y.H. Kim , by sieving from fishing gear, 29 April 2020 ; 2 males , Ulleung-Island , Ulleung-eup , Ulleung-gun , Gyeongsangbuk-do , Korea , 37°29′14″N , 130°55′11″E , J.H. Choi , by SCUBA diving, 24 May 2023 . Etymology. The specific name, “ megabranchia ” is derived from the Greek mega (large) and branchia (gill), with reference to the large gills. FIGURE 1. Caprella megabranchia sp. nov. , A, adult male, 12.6 mm, habitus; B, adult female, 6.9 mm, habitus. Scale bars: A = 2 mm, B = 1.0 mm. FIGURE 2. Caprella megabranchia sp. nov. , holotype, adult male, 12.6 mm, cat no. NIBRIV0000909913: 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; K, gnathopod 1; L, gnathopod 2. Scale bars: A = 2.0 mm, B, C = 0.6 mm, D–I = 0.1 mm, J = 0.2 mm, K = 0.4 mm, L = 1.0 mm. Description. Holotype , adult male . Body ( Figs. 1A , 2A ) long and slender, 12.6 mm long, surface smooth. Head round with a small projection dorsally; eye small and round. Head and pereonite 1 fused, suture present, 0.82 times as long as pereonite 2. Pereonite 2 longest; pereonite 3 length 1.25 times as long as pereonite 4, pereonites 3, 4 with large and circular gills ventrodistally; pereonites 5–7 smooth, with 6-articulate pereopod. Length ratio of pereonites 2–7=1.00: 0.74: 0.59: 0.87: 0.26: 0.23. Antenna 1 ( Fig. 2B ) 0.58 times as long as body; peduncular articles 2, 3 narrowing on both sides, covered with tubercles, length ratio of peduncular articles 1–3 = 1.00: 1.62: 1.38; flagellum 14-articulate, 0.45 times as long as peduncular articles, each article with short setae distally. Antenna 2 ( Fig. 2C ) setose, much shorter than antenna 1, barely reaching the distal end of peduncular article 2 of antenna 1; length ratio of peduncular articles 3–5 = 1.00: 3.71: 3.86; peduncular articles 4, 5 with unequal swimming setae ventrally; flagellum biarticulate, subequal in length to peduncular article 5, flagellum article 1 with unequal swimming setae ventrally, proximal article elongated, 4.20 times as long as distal article. Upper lip ( Fig. 2D ) rounded, notched midventrally with pubescence generally. Lower lip ( Fig. 2E ) well developed, inner and outer lobes with patch of pubescence. Left mandible ( Fig. 2F ), incisor and lacinia mobilis 5-teethed; setal row with 3 pectinated setae; molar truncate, with 1 pappose seta; mandibular palp absent. Right mandible ( Fig. 2G ) similar to left except setal row with 2 pectinated setae. Maxilla 1 ( Fig. 2H ) inner plate absent; outer plate with 6 stout setal teeth (3 bifid and 3 denticulate) apically; palp biarticulate, proximal article short, distal article with 8 apical robust setae and 5 teeth on apical margin, inner margin with a row simple setae and long simple setae laterally. Maxilla 2 ( Fig. 2I ), inner plate broadly round, with simple setae on apical and subapical margins; outer plate longer than inner one, with simple setae on apical and subapical margins. Maxilliped ( Fig. 2J ), inner plate subrectangular, with 1 blunt and 1 small robust seta on apical margin and 1 small robust seta on subapical margin; outer plate larger than inner plate, reaching the distal end of palp article 1, inner margin serrated, with 3 robust setae and 4 curved simple setae, outer margin with rounded groove; palp 4-articulate, article 2 convex inner margin, with unequal simple setae, article 3 subrectangular, with unequal simple setae on lateral and medial margin, distal article large, falcate, length ratio of articles 1–4 = 1.00: 1.44: 1.72: 1.83. Gnathopod 1 ( Fig. 2K ) small, basis expanded posteriorly; carpus strongly expanded posteriorly, with unequal simple setae; propodus subtriangular, narrowing distally, palm with unequal simple setae, defined a pair of robust (grasping) setae; dactylus falcate, with an accessory tooth, irregular serrations on inner margin; length ratio of 6 articles = 1.00: 0.35: 0.35: 0.58: 1.10: 1.03. Gnathopod 2 ( Fig. 2L ) attached to rather anterodistal portion of pereonite 2; basis elongated, narrowing proximally, with a lump laterodistally; ischium short, with a lump laterally; propodus massive, width 0.41 times length, nearly as long as basis, anterior margin irregular mid to distal, palmar margin with triangular projection near distal margin, strong and acute poison tooth situated nearly triangular projection, medial process bearing a robust (grasping) seta, anterior and posterior margin with unequal simple setae; dactylus falcate. Pereopod 5 ( Fig. 3A ) setose, 6-articulate; basis with triangular process posterodistally; ischium short; merus expanded posteriorly, with long simple setae; carpus produced posterodistally, with unequal simple setae; propodus longest, with a row of setal tufts on anterior and posterior margins; dactylus stout, falcate; length ratio of 6 articles = 1.00: 0.27: 1.13: 1.13: 2.40: 1.40. Pereopod 6 ( Fig. 3B ) similar to pereopod 5, but more setose and elongated than that of pereopod 5; length ratio of 6 articles = 1.00: 0.31: 0.93: 1.19: 2.25: 1.19. Pereopod 7 ( Fig. 3C ) similar to pereopod 5, but more setose and elongated than that of pereopod 5; length ratio of 6 articles = 1.00: 0.26: 0.95: 1.26: 2.26: 1.26. Abdomen ( Fig. 3D ) with a pair of appendages, its distal end round and with short simple setae laterally; a pair of medial lobes round, with sparse simple setae. Paratype , adult female, DKUAMP202304. Body ( Figs. 1B , 3E ) 6.9 mm long, smooth, generally as in male, but pereonite 2 short, pereonites 3, 4 with rounded brood pouches; gills elliptical. Antenna 1 ( Fig. 3F ) short, slender than that of male; peduncular articles 2, 3 without tubercles; flagellum 12- articulate. FIGURE 3. Caprella megabranchia sp. nov. , holotype, adult male, 12.6 mm, cat no. NIBRIV0000909913: A, pereopod 5; B, pereopod 6; C, pereopod 7; D, abdomen; paratype, adult female, 6.9 mm, cat no. DKUAMP202304: E, habitus; F, antenna 1; G, antenna 2; H, gnathopod 1; I, gnathopod 2. Scale bars: A–D, F, G, I = 0.4 mm, E = 1.0 mm, H = 0.2 mm. Antenna 2 ( Fig. 3G ) strongly exceeding distal of peduncular article 3. Gnathopod 1 ( Fig. 3H ) similar to that of male. Gnathopod 2 ( Fig. 3I ) attached to rather anteroproximal portion of pereopod 2; propodus subovate, anterior margin smooth, palmar margin longer than that of male, with weakly triangular projection near distal margin, poison tooth blunt, situated nearly triangular projection, proximal process bearing a robust (grasping) seta. DNA sequences. CO1 gene sequences (GenBank accession numbers OR721851–OR7218514) were obtained from four specimens of the new species. Intraspecific variation of the CO1 sequence of the new species ranged from 0% to 3%.