Aoroides gracilicrus, Kim & Choi & Kim & Im & Kim, 2024

Kim, June, Choi, Jae-Hong, Kim, Yu-Jin, Im, Hyeong-Woo & Kim, Young-Hyo, 2024, Two new species of the family Aoridae (Crustacea, Malacostraca, Amphipoda) from Korean waters, ZooKeys 1210, pp. 117-132 : 117-132

Aoroides gracilicrus sp. nov.

Figs 2 A , 3 , 4 , 5 Korean name: Ga-neun-da-ri-teol-keun-ap-son-yeop-sae-u, new

Type material.

Holotype, South Korea • 3.3 mm • 1 ♂; Bijin-ri , Han-san-myeon, Tongyeong-si, Gyeongsangnam-do; 34 ° 42 ' 59 " N, 128 ° 27 ' 37 " E; 1 August 2019; collected from hand net; Y. H. Kim leg.; HNIBRIV 2426 .

Additional material.

South Korea • 3.1 mm • 1 ♂; Dolsando Island , Yeosu-si, Goheung-gun, Jeollanam-do; 34 ° 37 ' 19 " N, 127 ° 47 ' 55 " E; 20 March 2004; collected from hand net; Y. H. Kim leg., DKUAMP 202402 • 1 ♂; Beol-po port , Sanyang-eup, Tongyeong-si, Gyeongsangnam-do; 34 ° 49 ' 56 " N, 128 ° 21 ' 21 " E, collected from light trap; 24 August 2005; Y. H. Kim • 1 ♂; Sogagido Island , Nagwol-myeon, Yeonggwang-gun, Jeollanam-do; 35 ° 15 ' 08 " N, 126 ° 06 ' 04 " E; collected from hand net; 27 June 2007; Y. H. Kim leg. • 1 ♂; Daejin port , Hyeonnae-myeon, Goseong-gun, Gangwon-do; 38 ° 29 ' 56 " N, 128 ° 25 ' 34 " E; collected from light trap; 11 June 2009; Y. H. Kim • 1 ♂; Dokdo Island , Ulleung-eup, Ulleung-gun, Gyeongsangbuk-do; 37 ° 26 ' 01 " N, 131 ° 56 ' 52 " E; collected from hand net; 22 February 2019; Y. H. Kim leg.

Diagnosis.

Eyes well developed, oval. Antenna 1 slender, except peduncular article 1, elongated, moderately setose; flagellum longer than peduncle. Antenna 2 densely setose, stout, gland cone bluntly pointed; flagellum short, 3 - articulate, with two robust setae on each article distally. Mandible, incisor with five dentate, tricuspidate lacinia mobilis, molar triturative. Maxilla 1, outer plate with 10 dentate setae apically. Gnathopod 1 merochelate, massive, greatly larger than gnathopod 2, covered by plumose setae; coxa with a long robust and a plumose seta on anteroventral corner. Pereopod 7 slender, elongated, longer than pereopods 5 and 6. Uropod 1 with a large inter-ramal process. Uropod 3, outer ramus biarticulate. Telson short, fleshy, truncate distally.

Description.

Holotype, adult male, HNIBRIV 2426 .

Body (Figs 2 A , 3 A ) 3.3 mm long, dorsally smooth, laterally compressed; eyes well developed, oval.

Antenna 1 (Fig. 3 B ) slender, elongated, moderately setose, length ratio of peduncular articles 1–3 = 1.00: 0.95: 0.43; flagellum 10 - articulate, terminal article minute, length 0.87 × peduncle; accessory flagellum absent.

Antenna 2 (Fig. 3 C ) densely setose; gland cone bluntly pointed, short; peduncular articles 1–3 short, peduncular articles 4, 5 subrectangular; length ratio of peduncular articles 3–5 = 1.00: 1.22: 0.41; flagellum (Fig. 3 D ) 3 - articulate, with two robust setae distally on each article.

Upper lip (Fig. 3 E ) subovate, apical margin round and pubescent.

Lower lip (Fig. 3 F ), inner plate elongate-ovate, densely pubescent medially and distally; outer plate distally expanded, mediodistal margin round and pubescent; mandibular process developed.

Left mandible (Fig. 3 G ), incisor with 5 blunt teeth and lacinia mobilis with 3–4 teeth; accessory setal row composed of two multicuspidate setae; molar triturative with pappose seta; palp slender, 3 - articulate; article 1 short, unarmed, length 0.28 × article 3; article 2 unarmed, length 0.84 × article 3; article 3 with two long setae distally.

Maxilla 1 (Fig. 3 H ), inner plate small with long pinnate seta apically; outer plate, apical margin with 10 dentate setal teeth; palp biarticulate, article 1 short, unarmed, article 2 swollen distally, apex round and weakly serrate, with seven robust setae, subapical portion with one pinnate seta.

Maxilla 2 (Fig. 3 I ), inner plate slender, slightly narrowing distally, apex and medial margin setose, with oblique row of plumose setae on surface; outer plate large, broad, with row of mediodistal setae, apex round, slightly notched subapically, pubescent laterally.

Maxilliped (Fig. 3 J ), inner plate subrectangular, medial margin with seven plumose setae submarginally, apex with four plumose and two stout robust setae; outer plate subrectangular, apex expending beyond end of palp article 2, medial margin straight with seven blunt robust setae gradually increasing in size distally and two elongate setae apically; palp 4 - articulate, article 1 short, articles 2 and 3 subrectangular, medial and laterodistal margins lined with long setae, article 4 falcate, with a nail.

Gnathopod 1 (Fig. 4 A ) merochelate, densely setose, moderate, greatly larger than gnathopod 2; coxa wider than long, width 2.51 × length, with one robust and one plumose setae on anteroventral corner; basis relatively long, slender, moderately broad, anterior and lateral margins with numerous plumose setae, posterior margin with 17 setae; ischium short, length 0.28 × basis, with five plumose setae anterolaterally; merus elongated, located below carpus, length 0.86 × basis, apex acute, ventral surface with numerous plumose setae; carpus moderate, subrectangular, length 1.05 × merus, anterior and posterior margins with numerous plumose setae; propodus slightly curved anteriorly, length 0.57 × carpus, posterior margin with numerous plumose setae; dactylus elongated, falcate, length 1.14 × propodus.

Gnathopod 2 (Fig. 4 B ) subchelate; coxa subquadrate, width 1.11 × length; basis subrectangular, width 0.32 × length, slightly curved posteriorly, anterior margin with plumose and simple setae, posterior margin with simple setae; merus 1.25 × ischium, half of posterodistal margin setose; carpus subrectangular, widening distally, ventrally setose; propodus subrectangular, length 0.83 × carpus, anterior margin with five clusters of setae and posterior margin setose, palm steeply angled, defined by one robust seta; dactylus falcate, overreaching palm, length 0.66 × propodus.

Pereopod 3 (Fig. 5 A ) setose; basis subrectangular, width 0.27 × length, anterior margin with 13 plumose and 10 simple setae, posterior margin with six simple setae; merus subquadrate, length 1.82 × ischium, with seven plumose and 12 simple setae anteriorly, 19 simple setae posteriorly; carpus subrectangular, length 1.29 × merus, with one robust seta posteroproximally; propodus rectangular, slender, length 1.04 × carpus, posterior margin setose; dactylus falcate, length 0.49 × propodus.

Pereopod 4 (Fig. 5 B ) similar to pereopod 3, but merus with plumose setae along with simple setae on posterior margin.

Pereopod 5 (Fig. 5 C ), coxa bilobate, wider than long; basis subrectangular, slightly narrowing distally, length 2.52 × width, both margins with unequal simple setae; merus widening distally, length 1.59 × ischium, posterior margin with five plumose and four simple setae; carpus rectangular, length 0.77 × merus, with two proximal and three distal robust setae; propodus slender, slightly widening distally, length 1.52 × carpus, anterior margin with 1-2 - 3 - 4 robust setae formula; dactylus falcate, length 0.48 × propodus.

Pereopod 6 (Fig. 5 D ) similar to pereopod 5, but less setose, unarmed.

Pereopod 7 (Fig. 5 E ) elongated, much longer than either pereopods 5 or 6; basis characteristic in form, subrectangular, slender, width 0.14 × length; anterior margin with four robust and one simple setae; ischium short, length 0.23 × basis, posterodistal corner with two setae; merus rectangular, length 2.29 × ischium; carpus rectangular, length 0.86 × merus; propodus elongate, length 1.64 × carpus; dactylus falcate, length 0.43 × propodus.

Uropod 1 (Fig. 5 F ), peduncle subrectangular, length 0.73 × inner ramus, with three dorsolateral and two dorsomedial robust setae, and a large inter-ramal process; outer ramus length × 1.09 inner ramus, with two robust setae on both margins, four robust setae on apex; inner ramus with three dorsal and four apical robust setae.

Uropod 2 (Fig. 5 G ), peduncle subrectangular, subequal in length to inner ramus, with one dorsomedial robust seta; outer ramus length 1.26 × inner ramus, with three dorsal and four apical robust setae; inner ramus with three dorsal and four apical robust setae.

Uropod 3 (Fig. 5 H ) short, length 0.52 × uropod 2; peduncle subequal to outer ramus, with two dorsolateral and two dorsomedial robust setae; outer ramus 0.73 × inner ramus, biarticulate, proximal article with six long setae subapically, terminal article minute, with two long setae on apex; inner ramus with two long setae on apex.

Telson (Fig. 5 I ) short and fleshy, longer than broad, concave distally, each lobe with two lateral robust setae and 5–6 unequal setae near the apex.

Female. Unknown.

Remarks.

The new species Aoroides gracilicrus sp. nov. resembles A. longimerus Ren & Zheng, 1996 from Dayawan, China, A. myojinensis Ariyama, 2004 from Myojin-zaki, Japan, and A. secunda Gurjanova, 1951 from Primorskii Krai, Russia, in having densely setose anterior margins of the basis and carpus of gnathopod 1. However, A. gracilicrus sp. nov. is distinguished from its congeners by the characters and character states shown in Table 1 and the following features (different characters and character states of A. longimerus , A. myojinensis , and A. secunda in brackets): 1) gnathopod 1, coxa with an anterior robust and a plumose setae (vs four plumose setae and a robust seta in A. longimerus , unarmed in A. myojinensis , and two robust setae in A. secunda ); 2) gnathopod 1, carpus slender and subrectangular (vs moderate in A. longimerus , and ovate in A. myojinensis and A. secunda ); 3) pereopods 3 and 4, anterior margins setose with plumose setae (vs sparse with simple setae in A. longimerus and A. myojinensis ); 4) pereopod 3, carpus with a robust seta posteriorly (vs two robust setae in A. longimerus , five robust setae in A. myojinensis , and three robust setae in A. secunda ); 5) pereopod 7, basis slender and subrectangular (vs elongate ovate in A. longimerus , A. myojinensis , and A. secunda ); and 6) uropod 3, both rami unarmed (vs both rami with robust setae in A. longimerus and A. myojinensis ).

Etymology.

The species name is derived from the Latin gracilis (= slender) and crus (= leg) in reference to the relatively slender basis of pereopod 7.

Distribution.

Korea (East Sea, South Sea).

Figures

Figure 2. Aoroides gracilicrus sp. nov. A male, 3.3 mm B Grandidierella naroensis sp. nov., male, 4.9 mm. Scale bars: 1.0 mm (A, B).

Figure 3. Aoroides gracilicrus sp. nov., holotype, male, 3.3 mm A habitus, lateral view B antenna 1 C antenna 2 D flagellum of antenna 2 E upper lip F lower lip G mandible H maxilla 1 I maxilliped J maxilla 2. Scale bars: 1.0 mm (A); 0.3 mm (B – D); 0.1 mm (E – J).

Figure 4. Aoroides gracilicrus sp. nov., holotype, male, 3.3 mm A gnathopod 1 B gnathopod 2. Scale bars: 0.6 mm (A); 0.3 mm (B).

Figure 5. Aoroides gracilicrus sp. nov., holotype, male, 3.3 mm A pereopod 3 B pereopod 4 C pereopod 5 D pereopod 6 E pereopod 7 F uropod 1 G uropod 2 H uropod 3 I telson. Scale bars: 0.3 mm (A – H); 0.2 mm (I).