Diastylis uniplicata, Kim & Lee, 2021

Kim, Sung-Hyun & Lee, Chang-Mok, 2021, Diastylis uniplicata sp. nov. (Crustacea: Cumacea: Diastylidae) a new Korean cumacean, Zootaxa 4941 (3), pp. 443-450 : 444-449

Diastylis uniplicata sp. nov.

( Figs 1 –4)

(Korean Name: Han-jul-gin-kko-ri-ol-chaeng-i-sae-u, new)

Type material. Holotype: adult male, 5.9 mm, cat no. NIBRIV0000876388, Nokdo I., Ocheon-myeon , Boryeong-si, Chungcheongnam-do, Korea, 36°16'08.3"N, 126°16'00.7"E, depth 2 m, 7 June 1997, (C.M. Lee) collected by light trap (dissected) . Paratypes: 1 adult male, data same as holotype (dissected) ; 1 adult male, data same as holotype .

Diagnosis. Adult male. Carapace surface smooth, with a transverse ridge on frontal lobe, both sides of carapace with pair of oblique ridges beginning near antero-lateral corner, running upward and connecting to dorsal median carina, telson 1.7 times as long as pleonite 6, with 5–6 simple setae laterally, uropod peduncle 1.8 times as long as telson, with 34 microserrate setae bearing single subterminal setule medially. Female unknown.

Description. Holotype, adult male, 5.9 mm, cat no. NIBRIV0000876388.

Carapace ( Fig. 1A, B ) 0.3 times as long as body, 1.3 times as long as width, 1.9 times as long as depth, with transverse ridge on frontal lobe; both sides of carapace with 1 pair of oblique ridges beginning near anterolateral corner, running upward and connecting to dorsal median carina; each postero-lateral surface of carapace with horizontal ridge; dorsal surface with few setules; dorsal groove formed on front of oblique ridge and postero-medial surface of carapace; pseudorostral lobes 0.1 times as long as carapace; antero-lateral margin serrated; ocular lobe with 3 lenses. Pereon ( Fig. 1A, B ) 0.5 times as long as carapace. Pleon ( Fig. 1A ) subequal in length to carapace and pereon together.

Antenna 1 ( Fig. 1C ) peduncle 3-articulate; article 1 longest, with 1 simple and 1 plumose setae, both fine, hairlike; article 2 0.6 times as long as article 1, with 4 short simple setae; article 3 subequal in length to article 2, with 1 short simple seta and brush of setae. Main flagellum 5-articulate; article 1 with short simple seta; article 2 and article 3 unarmed; article 4 with 1 short simple seta and 1 aesthetasc; article 5 with 3 short simple setae and 1 aesthetasc. Accessory flagellum 4-articulate; article 1 and article 3 unarmed; article 2 with 2 simple setae; article 4 with 1 long simple seta.

Antenna 2 ( Fig. 1D ) peduncle 5-articulated, article 1 and article 2 with 1 plumose seta each, article 4 with 1 complex peduncle seta, article 5 with ranks of short simple setae; flagellum broken.

Labium ( Fig. 1E ) with numerous hair-like and 8 short stout setae on anterior and medial margins, posterior part broken.

Left mandible ( Fig. 1F ) with row of 9 lifting setae; incisor with 2 teeth; lacinia mobilis with 4 teeth.

Right mandible ( Fig. 1G ) with row of 12 lifting setae; incisor with 2 teeth.

Maxilla 1 ( Fig. 1H ) outer endite with hair-like setae on medial and lateral margins, 1 stout plumo-microserrate, 1 stout microserrate, 1 stout tricuspid setae and 2 stout simple setae bearing single subterminal setule terminally; inner endite with hair-like setae medially, 1 plumose seta laterally, hair-like and 13 stout simple setae terminally; palp with 2 setae.

Maxilla 2 ( Fig. 2A ) broad endite with several hair-like, 1 pappose, 2 plumo-microserrate and 17 plumose setae medially, 1 plumose, 3 pappo-microserrate, 7 microserrate and about 21 simple setae terminally; outer endite with few hair-like setae laterally, 1 simple and 4 stout microserrate setae terminally; inner endite with few hair-like and 4 stout microserrate setae terminally.

Maxilliped 1 ( Fig. 2B ) basis with several hair-like and 1 long plumose setae, medial lobe with several hair-like setae on surface, 6 plumose and 2 hook setae medially, 4 simple, 3 plumose and 1 stout pappose setae terminally; ischium not present; merus with 3 plumose setae mediodistally; carpus with 8 beak and about 28 plumose setae medially, 3 simple, 2 plumose and 1 long plumose setae distally; propodus with several simple, 2 serrate and 3 long plumose setae; dactylus with 2 simple and 2 microserrate setae.

Maxilliped 2 ( Fig. 2C ) basis subequal in length to remaining articles combined, with few hair-like, 4 short simple, 2 plumose and 3 long plumose setae; ischium short, with 1 short plumose seta distally; merus with 1 short simple, 1 plumose and 2 long plumose setae; carpus with 5 plumose and 7 long plumose setae medially, 1 long plumose seta laterodistally; propodus with 5 plumose and 4 plumo-microserrate setae medially, 1 long plumose seta laterally, 4 plumose setae distally; dactylus with 1 stout simple, 2 simple and 2 microserrate setae terminally.

Maxilliped 3 ( Fig. 2D ) basis 1.9 times as long as remaining articles combined, with hair-like, 10 short simple, 15 plumose setae and about 20 spiniform teeth medially, hair-like setae and 1 spiniform tooth laterally, 6 long plumose setae distally; ischium with 2 short simple and 2 plumose setae medially; merus subequal in length to ischium, with few hair-like, 1 simple and 2 plumose setae medially, few hair-like and 1 long plumose setae laterally; carpus 2.3 times as long as merus, with 3 long simple setae; propodus 0.9 times as long as carpus, with 3 long simple, 5 plumose and 2 long plumose setae medially; dactylus 0.9 times as long as propodus, with few hair-like, 2 short simple and 6 simple setae; exopod shorter than basis length, basal article with 2 plumose setae.

Pereopod 1 ( Fig. 2E ) basis subequal in length to remaining articles combined, with 11 short simple, 13 plumose, 4 long plumose setae and about 22 spiniform teeth medially, few hair-like, 8 plumose setae and about 20 spiniform teeth laterally, 7 long plumose setae distally; ischium 0.1 times as long as basis, unarmed; merus 1.6 times as long as ischium, with 1 simple seta laterodistally; carpus 1.3 times as long as merus, with 7 short simple and 1 simple setae; propodus 1.2 times as long as carpus, with 8 short simple and 7 simple setae; dactylus 1.3 times as long as propodus, with 7 short simple and 12 simple setae; exopod shorter than basis length, basal article with 7 plumose setae medially, 8 short simple and 1 plumose setae laterally.

Pereopod 2 ( Fig. 3A ) 0.7 times as long as remaining articles combined, with 12 short simple, 1 simple, 14 plumose setae and about 5 spiniform teeth medially, 3 short simple, 20 short plumose and 1 plumose setae laterally; ischium short, with 1 spiniform tooth; merus 4.7 times as long as ischium, with 4 short simple and 2 plumose setae medially, 4 short simple and 1 plumose setae laterally; carpus 3.0 times as long as merus, with 7 short simple and 10 simple setae medially, 12 short simple setae laterally, 3 stout microserrate and 1 stout simple setae distally; propodus 0.2 times as long as carpus, with 4 short simple and 1 simple setae; dactylus 2.4 times as long as propodus, with 2 short simple and 10 simple setae medially, 5 simple setae laterally, 5 simple setae terminally; exopod longer than basis length, basal article with 5 plumose setae medially, 3 short simple and 1 plumose setae laterally.

Pereopod 3 ( Fig. 3B ) basis 1.4 times as long as remaining articles combined, with few hair-like, 7 plumose and 3 short simple setae medially, 6 short plumose, 1 plumose and 9 short simple setae on lateral surface, 3 long plumose, 6 plumose, 3 short simple setae and 4 spiniform teeth laterally, 2 short simple and 1 long plumose setae distally; ischium 0.1 times as long as basis, 3 short simple, 1 simple and 3 annulate setae; merus 2.1 times as long as ischium, with 2 short simple and 4 annulate setae; carpus subequal in length to merus, with 4 short simple, 2 annulate and 4 long annulate setae; propodus 0.4 times as long as carpus, with 1 short simple and 1 long annulate setae; dactylus 0.6 times as long as propodus, with 1 short simple seta medially, 1 simple and 1 stout simple setae terminally; exopod subequal in length to basis, basal article with 1 plumose seta medially, 3 short simple and 2 plumose setae laterally.

Pereopod 4 ( Fig. 3C ) basis subequal in length to remaining articles combined, with 3 plumose setae medioproximally, 3 plumose and 6 short simple setae on lateral surface, 3 short plumose, 4 plumose setae and 3 spiniform teeth laterally, 1 long plumose and 1 short simple setae distally; ischium 0.1 times as long as basis, with 1 simple, 3 plumose and 2 annulate setae distally; merus 2.6 times as long as ischium, with 4 simple setae medially, 2 short simple and 3 annulate setae laterally; carpus subequal in length to merus, with 5 simple setae medially, 3 annulate setae laterally, 4 long annulate setae distally; propodus 0.5 times as long as carpus, with 1 long annulate and 1 complex pedunculate setae; dactylus 0.8 times as long as propodus, with 1 short simple seta mediodistally, 1 simple and 1 stout microserrate terminally; exopod subequal in length to basis, basal article with 2 short simple and 2 plumose setae laterally.

Pereopod 5 ( Fig. 3D ) basis 0.7 times as long as remaining articles combined, with 1 simple and 3 plumose setae mediodistally, 1 short simple seta on medial surface, 1 short simple and 2 plumose setae laterodistally; ischium 0.2 times as long as basis, with 1 plumose seta medially, 3 annulate setae laterodistally; merus 2.1 times as long as ischium, with 1 short plumose seta mediodistally, 4 annulate setae laterally; carpus 1.2 times as long as merus, with 1 annulate and 4 long annulate setae medially, 4 annulate setae laterally, 2 simple setae distally; propodus 0.3 times as long as carpus, with 1 complex pedunculate and 1 long annulate setae mediodistally; dactylus subequal in length to propodus, with 1 short simple seta medially, 1 simple and 1 stout simple setae terminally; exopod absent.

Telson ( Fig. 3E ) 1.7 times as long as pleonite 6, with 5-6 short stout simple setae laterally, 2 stout simple setae terminally. Uropod ( Fig. 3E ) peduncle 1.8 times as long as telson, with numerous hair-like, 3 short simple setae and 34 short microserrate setae bearing single subterminal setule medially, 15 short simple setae laterally. Uropod endopod 3-articulate, 0.6 times as long as peduncle; article 1 with several hair-like setae, 5 short microserrate setae bearing single subterminal setule and 3 short simple setae bearing single subterminal setule medially, 3 pedunculate and 2 short simple setae laterally; article 2 0.7 times as long as article 1, with several hair-like setae and 5 short simple setae bearing single subterminal setule medially, 2 short simple setae laterally; article 3 1.8 times as long as article 2, with several hair-like setae and 7 short simple setae bearing single subterminal setule medially, 4 short simple setae laterally, 1 stout simple seta bearing single subterminal setule terminally. Uropod exopod 2-articulate, 1.1 times as long as endopod; article 1 short, with 1 short simple seta laterally; article 2 with several hair-like and 16 short simple setae laterally, 1 short simple and 3 simple setae terminally.

Etymology. The new species name uniplicata is from the combination of the Latin words uni, meaning ‘one’ and plica, meaning ‘fold or ridge’, alluding to the single oblique ridge on the carapace.

Remarks. This new species Diastylis uniplicata sp. nov. has a unique combination of characteristics: carapace surface smooth, with a transverse ridge on frontal lobe; both sides of carapace with a pair of oblique ridges beginning near antero-lateral corner, running upward and connecting to the dorsal median carina; telson 1.7 times as long as pleonite 6, with 5–6 simple setae laterally. The most similar species are D. antillensis Sars, 1873 and D. planifrons Calman, 1912 , which have a pair of oblique ridges beginning near the antero-lateral corner and running upward. These species, however, lack a transverse ridge on frontal lobe of carapace. Also, oblique ridges on the carapace in D. antillensis and D. planifrons are W-shaped in dorsal view, compared C-shaped in D. uniplicata sp. nov..

Depth. 2 m.

Distribution. Korea (Yellow Sea).

Figures

FIGURE 1. Diastylis uniplicata sp. nov., holotype, adult male, 5.9 mm:A, habitus, lateral view; B, carapace and pereon, dorsal view; C, antenna 1; D, antenna 2; E, labium; F, left mandible; G, right mandible; H, maxilla 1. Scale bars = 1.0 mm (A, B), 0.2 mm (C, D), 0.1 mm (E–G), 0.05 mm (H).

FIGURE 2. Diastylis uniplicata sp. nov., holotype, adult male, 5.9 mm: A, maxilla 2; B, maxilliped 1; C, maxilliped 2; D, maxilliped 3; E, pereopod 1. Scale bars = 0.2 mm (D, E), 0.1 mm (B, C), 0.05 mm (A).

FIGURE 3. Diastylis uniplicata sp. nov., holotype, adult male, 5.9 mm: A, pereopod 2; B, pereopod 3; C, pereopod 4; D, pereopod 5; E, pleonite 6, telson and uropods. Scale bars = 0.3 mm (E), 0.2 mm (A–D).