Eocuma orbiculatum, Kim & Lee & Kim, 2020

Kim, Sung-Hyun, Lee, Chang-Mok & Kim, Young-Hyo, 2020, Eocuma orbiculatum sp. nov. (Crustacea, Cumacea, Bodotriidae) from Korean waters, ZooKeys 910, pp. 79-91 : 79

Eocuma orbiculatum sp. nov. Figures 1 , 2 , 3 , 4 , 5

Type material.

Holotype: adult male, 11.92 mm, NIBRIV0000812748, Hangdong Port, Sedong-ri, Wando-gun, Jeollanam-do, Korea, 34°23'38.2"N, 126°50'29.3"E, Y.H. Kim, 22 June 2008.

Description.

Holotype, adult male, NIBRIV0000812748.

Length: 11.92 mm, excluding uropods. Carapace (Figs 1A, B , 2A-C , 3A, B ) 0.26 × body length, 1.4 × width; surface covered with minute shallow pits; lateral margins of carapace, pereon, and pleon lamellate; pseudorostrum a little in advance of antero-lateral horns with rounded apices, without lateral horns; dorsal median carina extending from eye-lobe to posterior margin of carapace; a pair of dorso-lateral carinae well-marked, extending from near the antero-lateral horns to 4/5 way of carapace; ocular lobe (Fig. 2B ) with 3 lenses. Pereon (Fig. 2A, B ) 0.7 × carapace. Pleon (Fig. 2A ) 1.3 × cephalothorax.

Antenna 1 (Fig. 2D ) peduncle 3-articulate; article 1 flattened, broader at base, with several hair-like, 10 short simple, and 4 complex pedunculate setae; article 2 0.4 × article 1, with 2 short simple and 3 complex pedunculate setae; article 3 1.4 × article 2, with 2 complex pedunculate setae distally. Main flagellum 3-articulate; article 1 with 3 aesthetascs; article 2 with 1 aesthetasc; article 3 with 2 simple setae, 1 long simple seta, and 1 aesthetasc terminally. Accessory flagellum minute, with 1 short simple and 2 complex pedunculate setae.

Antenna 2 (Fig. 2A, E ) extending beyond pleotelson; peduncle 5-articulated; article 2 with 1 or 2 plumose setae; articles 4-5 with numerous simple setae, article 5 with 2 complex pedunculate setae dorso-distally.

Left mandible (Fig. 2F ) with row of several hair-like and 14 setae; incisor with 4 teeth; lacinia mobilis with 3 teeth. Right mandible (Fig. 2G ) with row of several hair-like and 14 setae; incisor with 2 teeth.

Maxilla 1 (Fig. 2H ) outer endite with a few hair-like setae medially, 1 simple seta laterodistally, 13 stout simple setae terminally; inner endite with several hair-like setae medially, a few hair-like setae laterodistally, 4 microserrate and 2 stout tricuspid setae terminally; palp broken, with 2 setae.

Maxilla 2 (Fig. 4A ) broad endite with several hair-like, 26 plumose, and 3 microserrate setae medially, 6 plumose, 25 simple, 11 microserrate, 2 plumo-microserrate, and 1 pappo-serrate setae terminally; outer endite with a few hair-like and 7 stout microserrate setae terminally; inner endite with 6 stout microserrate setae terminally.

Maxilliped 1 (Fig. 4B ) basis with a few hair-like setae mediodistally, 1 long plumose seta on medial distal corner, 13 simple setae on lateral surface, a few hair-like setae laterodistally; medial lobe with 1 coupling hook and 8 plumo-microserrate setae medially, 3 stout simple setae on medial distal surface, 1 plumose and 2 stout simple setae terminally; ischium absent; merus with a few hair-like, 8 short simple, and 2 long plumose setae; carpus 2.1 × merus, with 21 plumose and 8 stout setae medially, numerous hair-like setae on lateral surface, 1 short simple seta laterally, 1 long plumose seta on laterodistal corner; propodus 0.5 × carpus, with a few hair-like, 20 plumose, 1 simple, 1 microserrate, and 1 plumo-microserrate setae medially, a few hair-like and 3 short simple setae medially, 3 long plumose setae distally; dactylus 0.7 × propodus, a few hair-like and 2 simple setae medially, 2 stout microserrate setae terminally.

Maxilliped 2 (Fig. 4C ) basis 1.4 × remaining articles combined, with numerous hair-like setae medially, 2 short simple and 4 long plumose setae mediodistally, numerous hair-like setae on lateral surface, 18 short simple and several hair-like setae laterally; ischium short, unarmed; merus 0.3 × basis, with 1 long plumose seta on medial distal surface, several hair-like and 4 short simple setae on lateral surface, a few hair-like and 1 short simple setae laterally; carpus 0.7 × merus, with 3 plumose and 4 plumo-microserrate setae medially, several hair-like setae on lateral surface, 1 short simple seta laterally; propodus 0.8 × carpus, with 2 microserrate, 10 plumo-microserrate, and 1 plumose setae medially, several hair-like setae on lateral surface, 2 long plumose setae laterally; dactylus 0.5 × propodus, with 1 long simple seta on lateral surface, 2 simple, 1 microserrate, and 1 stout microserrate setae terminally.

Maxilliped 3 (Fig. 4D ) basis 1.4 × remaining articles combined, with numerous hair-like setae medially, 2 plumose setae on medial distal corner, numerous hair-like setae on medial surface and lateral margin, 1 short simple seta with subterminal setules laterally; produced distally to border between merus and carpus, with 1 short simple and 14 plumose setae medially, 5 short simple setae with subterminal setules laterally; ischium 0.2 × basis, with several hair-like and 9 plumose setae medially; merus subequal to ischium, with several hair-like and 1 plumose setae medially; carpus 0.5 × merus, with 1 plumose seta medially; propodus 1.1 × carpus, with 1 short simple and 7 plumose setae medially, 1 short simple seta laterodistally; dactylus 0.8 × propodus, with a few hair-like setae medially, 1 short simple and 2 hair-like setae laterally, 5 microserrate setae terminally; exopod shorter than basis.

Pereopod 1 (Fig. 4E ) basis 0.9 × remaining articles combined, with numerous hair-like setae medially, 19 short simple setae on lateral surface, 2 complex pedunculate setae laterodistally, 1 short plumose seta on terminal point; ischium 0.1 × basis, with 1 complex pedunculate seta mediodistally; merus 1.7 × ischium, with 1 complex pedunculate seta mediodistally; carpus 1.6 × merus, with 1 short simple seta mediodistally; propodus subequal to carpus, with 6 simple setae medially; dactylus 0.9 × propodus, with 9 simple setae medially, 1 short simple and 2 simple setae terminally; exopod shorter than basis.

Pereopod 2 (Fig. 5A ) length 0.3 × basis of pereopod 1, basis fused with ischium, 0.6 × remaining articles combined, with 2 long plumose and 1 complex pedunculate setae medially, 3 complex pedunculate setae on lateral surface, 7 complex pedunculate setae and 1 short simple seta with subterminal setules laterally; merus 0.4 × basis, with 1 short simple seta with subterminal setules mediodistally, 1 short simple seta with subterminal setules lateroproximally; carpus 0.6 × merus, with 1 short simple seta with subterminal setules laterodistally; propodus 1.4 × carpus, with 1 short simple seta with subterminal setules mediodistally; dactylus 1.5 × propodus, with 1 short simple seta with subterminal setules and 1 broken seta medially, 1 simple seta with terminal setules laterally, 1 plumo-annulate seta, 1 long plumo-annulate seta with single subterminal setule, and 1 simple seta with terminal setules terminally.

Pereopod 3 (Fig. 5B ) basis 0.9 × remaining articles combined, with 5 complex pedunculate setae and 2 short simple setae with subterminal setules medially, 6 short simple setae with subterminal setules on lateral surface, 4 long plumose setae laterally; ischium 0.2 × basis, with 2 annulate setae laterodistally; merus 2.7 × ischium, with 2 short simple setae with subterminal setules medioproximally, 1 annulate seta laterally; carpus 0.7 × merus, with 3 annulate setae medially, 1 short simple seta with subterminal setules and 1 annulate seta laterally, 1 short simple and 2 long annulate setae on medial distal margin; propodus 0.7 × carpus, with 1 long annulate seta on medial distal corner, 1 complex pedunculate seta laterodistally; dactylus 0.4 × propodus, with 1 simple and 1 stout microserrate setae terminally.

Pereopod 4 (Fig. 5C ) basis 0.9 × remaining articles combined, with 1 plumose and 4 complex pedunculate setae medially, 8 plumose setae and 3 short simple setae with subterminal setules laterally; ischium 0.2 × basis, with 1 short simple seta with subterminal setules laterally, 2 annulate setae on distal margin; merus 2.3 × ischium, with 1 annulate seta laterodistally; carpus 0.7 × merus, with 3 long annulate setae and 1 short simple seta with subterminal setules medially, 1 short simple and 2 long annulate setae on medial distal corner, 1 annulate seta laterally; propodus 0.7 × carpus, with 1 long annulate and 1 complex pedunculate setae mediodistally; dactylus 0.4 × propodus, with 2 simple and 1 stout microserrate setae terminally.

Pereopod 5 (Fig. 5D ) basis subequal to remaining articles combined, with 3 long plumose, 9 plumose, 2 complex pedunculate setae, and 2 short simple setae with subterminal setules; ischium 0.2 × basis, with 1 short simple and 2 annulate setae laterodistally; merus 2.0 × ischium, with 1 annulate seta laterally; carpus 0.6 × merus, with 4 annulate setae medially, 1 annulate seta laterally; propodus 0.8 × carpus, with 1 long annulate seta on medial distal corner; dactylus 0.3 × propodus, with 2 simple and 1 stout microserrate setae terminally.

Uropod (Fig. 5E ) peduncle 0.4 × pleotelson, with 9-10 plumose, 14-16 stout short simple, and 35-40 microserrate setae medially. Endopod uniarticulate, 3.2 × peduncle, with 21 plumose, 77 plumo-microserrate, and 3 stout short simple setae medially, tip with setulate seta. Exopod biarticulated, subequal to endopod, article 1 unarmed; article 2 with 23 plumose setae medially, 21 plumose setae laterally, 1 simple seta distally, tip with 2 curved setulate setae.

Remarks.

This new species resembles Eocuma amakusense Gamô, 1967, E. hilgendorfi Marcusen, 1894, and E. latum Calman, 1907 in having a pair of well-developed dorso-lateral carinae on the flat carapace and similar setae pattern on the telson. Eocuma orbiculatum sp. nov., however, is easily distinguished from its congeners by the pattern of dorso-lateral carina and lacking lateral horns on the carapace. This difference also applies when considering growth, geographical distribution and individual variations (Table 1 ). Comparison between the species was done assuming that E. orbiculatum sp. n and E. cf. hilgendorfi (by Park et al. 1998) subadult male was the same species, since information of E. hilgendorfi adult male was not suggested in previous studies. Eocuma orbiculatum sp. n is distinguished from the specimen of Park et al. (1998) by the combination of the following features ( E. cf. hilgendorfi condition in parentheses): 1) a pair of dorso-lateral carinae from near the near apices of the antero-lateral horns extending to approximately 0.8 of the carapace length (vs. from ocular lobe to the posterior margin of carapace); 2) carapace without lateral horn (vs. with lateral horns); 3) basis of pereopod 1 with 19 short simple setae on ventral surface (vs. without short simple seta); 4) carpus of pereopod 1.6 × merus length (vs. 2.3 × merus length); 5) medial margin of uropod peduncle and endopod with plumose, stout short simple, and microserrate setae (vs. with plumose setae on endopod, with plumose setae and 3 spaced teeth on exopod); 6) uropod exopod with plumose setae laterally (vs. without seta). Even considering growth and individual variations, many differences were found in carapace shape, carpus length, and setal pattern of the telson. In addition, E. cf. hilgendorfi (by Park et al. 1998) is considered to be a different species, as it shows many morphological differences from E. hilgendorfi reported by Zimmer (1903). Additional samples shall be obtained and identified.

Etymology.

The new species name orbiculatum is a Latin word, meaning ‘round’, alluding to the absence of a horn on the lateral margin of the carapace and the round appearance of the carapace in dorsal view.

Distribution.

The new species was collected in Hangdong Port, Sedong-ri, Wando-gun, Jeollanam-do, Korea, muddy bottom, 2-5 m depth.

Key to the Korean Eocuma species

Figures

Figure 1. Eocuma orbiculatum sp. nov., holotype, adult male, 11.92 mm. A Lateral view B cephalothorax, dorsal view. Scale bars: 1.0 mm (A, B).

Figure 2. Eocuma orbiculatum sp. nov., holotype, adult male, 11.92 mm. A Habitus, lateral view B cephalothorax, dorsal view C cephalothorax, ventral view D antenna 1 E antenna 2 F left mandible G right mandible H maxilla 1. Scale bars: 1.0 mm (A-C), 0.2 mm (D), 0.1 mm (C, E, F), 0.05 mm (G).

Figure 3. Eocuma orbiculatum sp. nov., holotype, adult male, 11.92 mm. A, B Carapace, dorsal view. Scale bar: 250 μm (A), 125 μm (B).

Figure 4. Eocuma orbiculatum sp. nov., holotype, adult male, 11.92 mm. A Maxilla 2 B maxilliped 1 C maxilliped 2 D maxilliped 3 E pereopod 1. Scale bars: 0.3 mm (D, E), 0.2 mm (C), 0.1 mm (A, B).

Figure 5. Eocuma orbiculatum sp. nov., holotype, adult male, 11.92 mm. A Pereopod 2 B pereopod 3 C pereopod 4 D pereopod 5 E pleotelson. Scale bars: 0.3 mm (E), 0.2 mm (B-D), 0.1 mm (A).