First record of the genus Pseudaeginella Mayer, 1890 (Crustacea, Amphipoda, Caprellidae) with a new species from Korean waters Author Shin, So-Yeon https://orcid.org/0000-0002-1175-5447 Department of Biological Sciences, Dankook University, 31116, Cheonan, Republic of Korea Author Lee, Chang-Mok https://orcid.org/0000-0002-4149-8429 Hanmin High School, 10955, Paju, Republic of Korea Author Heo, Jun-Haeng https://orcid.org/0000-0003-0942-7126 Environmental Impact Assessment Team, National Institute of Ecology, 33657, Seocheon, Republic of Korea Author Kim, Young-Hyo https://orcid.org/0000-0002-7698-7919 Department of Biological Sciences, Dankook University, 31116, Cheonan, Republic of Korea amphipod74@gmail.com text ZooKeys 2023 2023-07-13 1169 163 174 http://dx.doi.org/10.3897/zookeys.1169.105901 journal article http://dx.doi.org/10.3897/zookeys.1169.105901 1313-2970-1169-163 B9BC8CE9958B422BAFF80A4B1CCEDE4A 7B3D68E2DBC9540880163104AD2DF200 Pseudaeginella carinaspinosa sp. nov. Figs 2 , 3 , 4 , 5 Korean name: Deung-ga-si-min-dung-bae-ba-da-dae-beol-re, new Type material. Holotype , male, 4.1 mm, NIBRIV0000895338, South Korea: Geomun-Island, Geomun-ri, Samsan-myeon, Yeosu-si, Jeollanam-do, 34°01'08"N , 127°18'27"E , collected from SCUBA diving, depth 7 m, Y.C. Park, 5 November 2015. Paratype , female, 3.4 mm, NIBRIV0000904522 and 5 males, 5 females, DKUAMP202301, same data as for holotype. Additional material. 1 male , Jongdal-ri, Gujwa-eup, Jeju-si, Jeju-Island, 33°29'29"N , 126°54'47"E , collected from SCUBA diving, depth 3 m , Y.C. Park, 5 October 2015 ; 2 males , 1 female , Jongdal-ri, Gujwa-eup, Jeju-si, Jeju-Island, 33°29'29"N , 126°54'47"E , collected from SCUBA diving, depth 3 m , Y.C. Park, 7 October 2015 ; 2 males , Namhyeongje-Island, Dadae-dong, Saha-gu, Busan, 34°53'04"N , 128°57'04"E , collected from SCUBA diving, depth 10 m , Y.C. Park, 16 November 2015 . Description. Holotype , male , NIBRIV0000895338. Body (Figs 2A , 3A ) slender, 4.1 mm long. Head with a projection dorsally. Eye small, round. Pereonite 1 fused with head, suture not present, with a projection dorsally; pereonites 2-5 with a pair of middorsal projections, pereonites 2-4 with a posterodorsal projection, pereonites 3-5 with ventral projections, pereonite 2 with two anterolateral projections, pereonite 3 with an anterolateral projection, pereonite 6 shortest, with a middorsal projection; length ratio of pereonites 2-7 = 1.00: 1.24: 0.99: 0.77: 0.32: 0.36. Figure 2. Pseudaeginella carinaspinosa sp. nov. A male, 4.1 mm B immature female, 3.4 mm. Figure 3. Pseudaeginella carinaspinosa sp. nov., holotype, male, 4.1 mm, Geomun-Island, Geomun-ri, Samsan-myeon, Yeosu-si, Jeollanam-do, Korea A habitus, lateral view B antenna 1 C antenna 2 D upper lip F left mandible G right mandible H maxilla 1 I maxilla 2 J maxilliped. Male, 4.2 mm, Namhyeongje-Island, Dadae-dong, Saha-gu, Busan, Korea E lower lip. Scale bars: 1.0 mm ( A ), 0.2 mm ( B, C ), 0.1 mm ( F, G, J ), 0.05 mm ( D, E, H ). Antenna 1 (Fig. 3B ) slender, about 0.8 x body length; peduncular articles 1-2 with several setae; peduncular article 3 short; length ratio of peduncular articles 1-3 = 1.00: 1.32: 0.43; flagellum 14-articulate, subequal in length to peduncle, each article with 1 aesthetasc ventrodistally. Antenna 2 (Fig. 3C ) much shorter than antenna 1, exceeding the distal end of peduncular article 3; length ratio of peduncular articles 3-5 = 1.00: 3.24: 4.35; flagellum biarticulate, swimming setae absent; about 0.1 x peduncular articles 3-5. Upper lip (Fig. 3D ) rounded, notched midventrally. Lower lip (Fig. 3E ) well developed, smooth, without setae; inner lobe bilobed slightly (drawn from 4.2mm male). Left mandible (Fig. 3F ), incisor 5-toothed, lacinia mobilis 5-toothed, followed by 3 serrulate plates; molar present but reduced; palp triarticulate; article 2 about 1.6 x article 1; article 3 subequal to article 2 with a distal knob and setal formula of 1-5-1. Right mandible (Fig. 3G ), similar to left one, except incisor 6-toothed, followed by 1 serrulate and 2 smooth plates. Maxilla 1 (Fig. 3H ), inner plate absent; outer plate with 6 stout setal teeth apically; palp biarticulate, distal article with 3 apical robust setae and 1 subapical seta. Maxilla 2 (Fig. 3I ), inner plate with 2 long and 1 short setae apically; outer plate with 2 long and 1 short simple setae apically. Maxilliped (Fig. 3J ), inner plate small, with 2 simple setae apically; outer plate much larger than inner plate, with 3 simple setae apically and 3 simple setae medially; palp 4-articulate, article 2 longest, with 2 simple setae medially, distal article falcate, with a row of setules along inner margin. Gnathopod 1 (Fig. 4A ) small; propodus subrectangular, palm nearly straight with unequal simple setae, defined by 2 robust (grasping) setae proximally; dactylus falcate, bifid, with tiny accessory setae distally; length ratio of 6 articles = 1.00: 0.25: 0.43: 0.48: 0.84: 0.73. Figure 4. Pseudaeginella carinaspinosa sp. nov., holotype, male, 4.1 mm, Geomun-Island, Geomun-ri, Samsan-myeon, Yeosu-si, Jeollanam-do, Korea A gnathopod 1 B gnathopod 2 C gill 3 and pereopod 3 D gill 4 and pereopod 4 E pereopod 5 F pereopod 6 G pereopod 7 H abdomen, ventral view. Scale bars: 0.4 mm ( B ); 0.2 mm ( A, E-G ); 0.1 mm ( C, D ); 0.05 mm ( H ). Gnathopod 2 (Fig. 4B ) attached midanterior margin of pereonite 2; basis elongate, subequal to propodus, slightly widening distally, with pointed projection on anteroproximal margin and subpointed projection on anterodistal portion; propodus massive, convex dorsally, width 0.5 x length, with a small robust (grasping) seta on proximal projection, palm irregular and serrulate, with a poison tooth mesially; dactylus falcate, inner margin weakly serrulate; length ratio of 6 articles = 1.00: 0.23: 0.18: 0.14: 1.13: 1.05. Pereopod 3 (Fig. 4C ) very small, rudimentary, about 0.1 x gill, uniarticulate, with 2 long and short setae distally; gill elongate-ovate. Pereopod 4 (Fig. 4D ) similar to pereopod 3. Pereopod 5 (Fig. 4E ) long and normal; propodus, palm concave and serrate slightly with small setae, defined by 2 robust (grasping) setae; length ratio of 6 articles = 1.00: 0.32: 0.69: 0.60: 1.11: 1.05. Pereopod 6 (Fig. 4F ) similar to pereopod 5, but more slender; length ratio of 6 articles = 1.00: 0.26: 0.72: 0.73: 0.94: 0.87. Pereopod 7 (Fig. 4G ) similar to pereopod 6, but more slender and serrate; length ratio of 6 articles = 1.00: 0.26: 0.70: 0.70: 0.95: 0.76. Penes (Fig. 4H ) elongated, situated medially, width 0.31 x length. Abdomen (Fig. 4H ) without appendage, with a pair of lateral lobes and a dorsal lobe; plumose setae on dorsal lobe missing. Paratype , female (sexually dimorphic characters), NIBRIV0000904522. Body (Figs 2B , 5A ) 3.4 mm long, generally as in male, but stouter than male, pereonites 3, 4 with rounded brood pouches. Gnathopod 2 (Fig. 5B ) similar to that of male, but propodus more rounded than that of male. Abdomen (Fig. 5C ) similar to that of male, but with a pair of plumose setae. Figure 5. Pseudaeginella carinaspinosa sp. nov., paratype, female, 3.4 mm, Geomun-Island, Geomun-ri, Samsan-myeon, Yeosu-si, Jeollanam-do, Korea. A habitus, lateral view B gnathopod 2 C abdomen, ventral view. Scale bars: 1.0 mm ( A ); 0.4 mm ( B ); 0.05 mm ( C ). Remarks. We compared the new species, Pseudaeginella carinaspinosa sp. nov., and related species of the genus Pseudaeginella (Table 1 ). Pseudaeginella carinaspinosa sp. nov. is similar to P. biscaynensis (McCain, 1968) and P. montoucheti (Quitete, 1971) in the following features: (1) head with an anteriorly curved middorsal projection; (2) antenna 2, peduncular article 2 with ventrodistal projection; and (3) pereonites 1-5 with dorsal projections. However, our new species is easily distinguished from P. biscaynensis and P. montoucheti by the following features: (1) gnathopod 2, basis with an anteroproximal projection; (2) pereonites 1-6 with strong dorsal projections; and (3) pereonite 6 with middorsal projection. Pseudaeginella carinaspinosa sp. nov. is also similar to P. colombiensis in the following features: (1) mandibular palp, article 3 with robust setae; (2) pereopods 3 and 4 with 2 setae. However, P. carinaspinosa is distinguished from P. colombiensis by the following features: (1) pereonites 2 and 5 with middorsal projections; (2) mandibular palp, setal formula 1-5-1; and (3) gnathopod 2, basis with an anteroproximal projection. Table 1. Comparison of characters of the males of Pseudaeginella species.
Characters Species (male)
P. arraialensis P. biscaynensis P. campbellensis P. colombiensis P. freirei P. hormozensis P. inae
Body length (mm) 6.7 4.0 6.3 3.8 3.4 3.3 4.7
Pereonites 2-6, dorsal projection (except hump) 1-0-0-0-0 1-1-1-0-0 3-0-0-0-0 0-2-2-0-0 4-1-1-1-0 0-0-0-0-0 0-0-0-0-0
Gnathopod 2, proximal projection of basis x x o x x x x
Pereopods 3 and 4, # of setae 2 1 2 2 2 2 1
Setal formula of mandible 1-7-1 (left) 1-8-1 (right) 1-5-1 1-10-1 1-3 1-6-1 (left) 1-4-1 (right) 1-4-1 1-6-1
Distribution Brazil; Gulf of Mexico Barbuda; Bermuda; Brazil; Florida; Papua New Guinea, Australia; Saint Lucia; Tanzania; Tortugas New Zealand Colombia Brazil Gulf of Oman; Persian Gulf Indonesia
References Ros, Lacerda and Guerra-Garcia 2017; Winfield and Guerra-Garcia 2020 Gable and Lazo-Wasem 1987 ; Guerra-Garcia 2002 , 2004 ; McCain 1968 Guerra-Garcia 2003 Guerra-Garcia Krapp-Schickel and Mueller 2006 Iwasa-Arai et al. 2019 Momtazi and Sari 2013 Krapp-Schickel and Guerra-Garcia 2005
Characters Species (male)
P. montoucheti P. polynesica P. sanctipauli P. telukrimau P. tristanensis P. vaderi P. carinaspinosa sp. nov.
Body length (mm) 3.2 3.6 3.6 3.2 3.5 5.8 4.1
Pereonites 2-6, dorsal projection (except hump) 3-3-3-2-0 2-0-0-0-0 3-3-2-2-2 3-3-4-2-1 2-2-2-1-1 0-0-0-0-0 3-3-4-2-1
Gnathopod 2, proximal projection of basis x x x x x x o
Pereopods 3 and 4, # of setae 2 1 unknown 2 (P3) 1 (P4) 1 2 2
Setal formula of mandible 1-5-1 or 1-6-1 1-5-1 1-6-1 (left) 1-7-1 (right) 1-5-1 1-5-1 1-4-1 1-5-1
Distribution Brazil; Western South Atlantic; New Zealand Bora Bora and Moorea, Society Islands; Seychelles Ile Amsterdam; Saint Paul Malaysia Tristan da Cunha; Amsterdam Island East Coast of Africa; Australia Korea
References Quitete 1971 ; Lacerda et al. 2011 Laubitz 1995 ; Mueller 1990 Laubitz 1995 Lim et al. 2017 Stebbing 1888 ; Laubitz 1995 ; McCain and Steinberg 1970 Guerra-Garcia 2004 Present study
Etymology. The species name is derived from the Latin carina (=back) and spinosa (= with spinose projection) with reference to the distinct dorsal spinose projection. Distribution. South Korea (Geomun-Island, Jeju-Island, Namhyeongje-Island).