Nannopus robustus, Vakati & Lee, 2021

Vakati, Vinod & Lee, Wonchoel, 2021, - On- two- new- species- of- Nannopus- Brady, - 1880 - (Copepoda: - Harpacticoida Nannopodidae) - from-intertidal-mudflats-of-the-Korean-west-coast- (Yellow-Sea), Zootaxa 5051 (1), pp. 529-549 : 531-537

Nannopus robustus ­sp.­nov.

( Figs. 4–5 )

Type­ locality. Intertidal mudflat, St-8— Yeongheung-myeon , Ongjin-gun, Korea, Yellow Sea, 37°14’16.6”N 126°28’16.8”E ( Fig. 1 ) .

Type­ material. Holotype: 1 male adult in 70% ethanol (NIBRIV0000860821). Samples were collected by Vinod Vakati, 20 November 2013.

Etymology. The species epithet is derived from the Latin “robustus”, referring to the very strong and sturdy distal-most apical spine of P2 exp-2.

Description­ of­ male­(based­ on­ holotype).­ Body fusiform ( Fig. 4A–B ) narrow, total body length 461 μm, measured from tip of rostrum to posterior margin of caudal rami. Maximum width 138 μm, measured at posterior margin of cephalothorax. Body slightly slender, tapering posteriorly. Urosome/prosome length ratio 0.71 ( Fig. 4A ) and body length/width ratio about 3.3. Body ornamentation as in N. serratus (see Vakati & Lee 2017: 24, 27, Figs. 17A–F, 19A–D). Each urosomite with rows of slim setules ventrally as in N. serratus (see Vakati & Lee 2017: 24, Fig. 17F). Cephalothorax ( Fig. 4A ) bell-shaped, slightly narrow, comprising 36% of total body length, with a few paired sensilla and serrated posterior margin.

Rostrum as in N. serratus (see Vakati & Lee 2017: 23, Fig. 16C).

Prosome ( Fig. 4A–B ) 4-segmented, comprising cephalothorax and three subequal free pedigerous somites. P2-bearing somite with two long medial sensilla dorsally, posterior margins of prosomites serrated, and with few sensilla as figured.

Urosome ( Fig. 4A–B ) 5-segmented, comprising P5-bearing somite, genital double-somite, two free abdominal somites, and anal somite. Posterior margins of urosomites serrated dorsally and ventrally. Posterior margin of genital double-somite and following somite with pair of strong sensilla ventrally as in N. serratus (see Vakati & Lee 2017: 29, arrowed in Fig. 21B). Each somite with one transverse row of spinules along posterior margin ventrally. Genital double-somite as in N. serratus (see Vakati & Lee 2017: 29, Fig. 21B), clearly distinct dorsally and ventrally, with serrated dorsal posterior margin.

Anal somite ( Figs. 4A , 5A–C) almost as long as wide with unique pattern of surface ornamentation dorsally as in N. serratus , ventral surface with six spinules (see Vakati & Lee 2017: 29, Fig. 21C–D).

Caudal rami ( Fig. 5A–C ) square (dorsally) or sub-cylindrical (ventrally), almost as long as wide (in dorsal view), almost twice as long as wide (in ventral view), and with row of spinules along posteroventral margins. Caudal ramus bearing seven setae: seta I pinnate, shorter than ramus width, and located anterolaterally; seta II pinnate, almost as long as ramus length, and inserted anterolaterally midway along outer margin; seta III pinnate, as long as ramus length, and inserted anterolaterally midway along outer margin; seta IV bipinnate, 0.5 times as long as seta V, located at outer posterior margin and wide at proximal region; seta V strongest, bipinnate with proximal part heavily cylindrical and smooth (arrowed in Fig. 5A–C ), and located at inner posterior margin; seta VI naked, small, and located at inner posterior corner; seta VII slender, flexible, triarticulate, pinnate, located midway along inner margin.

Antennule, maxillule, maxilla, and maxilliped as in N. ganghwaensis (see Vakati et al. 2016: 218, Fig. 4A, D–F ).

Antenna, mandible, P1– P6 as in N. serratus (see Vakati & Lee 2017: 23, 25, 30, Figs. 16D–F, 18A, E, 22 B–D).

P2 ( Fig. 5D–E ) with smooth and short concave intercoxal sclerite (not illustrated). Praecoxa somewhat triangular and shorter than coxa. Coxa with one spinular row on anterior surface. Basis with one row of outer spinules on anterior surface, one row of distal spinules near insertion of exopod, and one row of distal spinules near insertion of endopod. Basal outer seta naked. Exopod 3-segmented, and all segments subequal in length. Each exopodal segment with robust outer spinules and without inner setules. Exp-2 without inner seta. Exp-1 to -2 with serrated outer spines, exp-3 outer spines smooth, and outer distal-most spine heavily robust (arrowed in Fig. 5D ), hook-shaped or recurved, and relatively longer. Endopod 2-segmented, both segments subequal in size, with one smooth outer distal spine and one pinnate inner distal seta.

Female. Unknown.

Figures

FIGURE­4.­Nannopus robustus sp.­nov. (holotype ♂). A, habitus, dorsal; B, habitus, lateral.

FIGURE­5.­Nannopus robustus sp.­nov. (holotype ♂). A, anal somite and caudal rami, dorsal (cylindrical shape arrowed); B, anal somite and caudal rami, ventral (cylindrical shape arrowed); C, anal somite and caudal ramus, lateral (cylindrical shape arrowed); D, P2 (recurved spine arrowed); E, P2 endopod.

FIGURE­1. Map showing the sampling localities and distribution of all valid Korean species identified and described so far. The black line between Stations 6a and 6b represents a man-made road with no gap for water entry from either side. Stations 1 to 15 refer to the study sites in Vakati et al. (2019), station 16 refers to the study site in Kim et al. (2017).