Nannopus minutus, Vakati, Vinod & Lee Wonchoel, 2017

Vakati, Vinod & Lee Wonchoel, 2017, Five new species of the genus Nannopus (Copepoda: Harpacticoida: Nannopodidae) from intertidal mudflats of the Korean West Coast (Yellow Sea), Zootaxa 4360 (1), pp. 1-66 : 6-10

publication ID	https://doi.org/ 10.11646/zootaxa.4360.1.1
publication LSID	lsid:zoobank.org:pub:D7ABA95B-5F41-42EB-94FA-1105489C5C34
DOI	https://doi.org/10.5281/zenodo.6024251
persistent identifier	https://treatment.plazi.org/id/8B0AA13A-FFA6-FFFD-A6C8-FF5DAD1DF8DA
treatment provided by	Plazi
scientific name	Nannopus minutus
status	sp. nov.

Treatment

Nannopus minutus sp. nov.

( Figs. 2–8 View FIGURE 2 View FIGURE 3 View FIGURE 5 View FIGURE6 View FIGURE 8 )

Type locality. Intertidal mudflat, Gilsang-myeon , Ganghwa Island, South Korea, Yellow Sea, 37°35'55.9"N 126°30'49.2"E ( Fig. 1A, B View FIGURE 1 ). GoogleMaps

Type material. Holotype: 1 female adult in 70% ethanol (NIBRIV0000753983). Allotype: 1 male adult in 70% ethanol (NIBRIV0000810831). Paratypes: 2 females dissected on 4 and 3 slides (NIBRIV0000810828 – 29),1 male dissected on 5 slides (NIBRIV0000810832); 2 females on an SEM stub (NIBRIV0000810830). All samples were collected by Vinod Vakati, 20 November 2013.

Etymology. The species epithet is derived from the Latin “ minutus ”, small, and alludes to the small size of the species (both sexes).

Description of female (based on holotype and paratypes). Body ( Fig. 2A, B View FIGURE 2 ) fusiform narrow, total body length ranged from 498 to 504 µm (mean = 500 µm, n = 3; holotype: 504 µm, measured from tip of rostrum to posterior margin of caudal rami). Maximum width ranged from 140 to 151 µm (mean 146 µm, n = 3; holotype: 140 µm, measured at posterior margin of cephalothorax). Boundary between prosome and urosome clearly visible, urosome/prosome length ratio 0.65, and body length/width ratio about 3.3. Body ornamentation ( Fig. 6A–D View FIGURE6 ) consisting of dorsal denticles, and horizontal row of setules. Cephalothorax ( Figs. 2A, B View FIGURE 2 , 6C View FIGURE6 ) anteriorly attenuated in dorsal view, almost as long as wide, comprising 29% of total body length, posterior margin serrated, with few paired sensilla, 1 row of sensilla, and 3 integumental windows (1 large medial posterior and 1 pair of small dorsolateral windows, arrowed in Fig. 6C View FIGURE6 ).

Rostrum ( Fig. 2C View FIGURE 2 ) prominent (not visible from dorsal view), deeply recurved downwards, fused to cephalothorax, anterior margin densely hirsute, and with pair of sensilla (not figured).

Prosome ( Fig. 2A View FIGURE 2 ) 4-segmented, comprising cephalothorax and 3 subequal pedigerous somites. P1-bearing somite fused to cephalothorax, posterior margin of free pedigerous somites serrated, and with row of sensilla posteriorly.

Urosome ( Figs. 2A, B View FIGURE 2 , 5A View FIGURE 5 , 6C View FIGURE6 ) tapering posteriorly, comprising P5-bearing somite, genital double-somite, 2 free abdominal somites and anal somite. Posterior margin of P5-bearing somite and first half of genital doublesomite serrated dorsally, second half of genital double-somite, fourth and fifth urosomites with posterior margin serrated dorsally and ventrally, each somite with sensilla dorsally except for penultimate somite and 1 row of spinules ventrally.

Genital double-somite ( Figs. 2A, B View FIGURE 2 , 5A View FIGURE 5 , 6C View FIGURE6 ) almost 1.7 times as wide as long (ventral view), completely fused ventrally, distinct dorsally and laterally, with serrated posterior margin dorsally, and smooth ventrally except for spinular row along posterior margin, and copulatory pore not visible (completely translucent).

Anal somite ( Figs. 5A–C View FIGURE 5 , 6C, D View FIGURE6 ) with well-developed operculum, covered with setules posteriorly, almost as long as wide, with pair of dorsal sensilla, and with 1 row of spinules on either side of somite ventrally.

Caudal rami ( Figs. 5A–C View FIGURE 5 , 6A, B View FIGURE6 ) cylindrical, with clear separation from anal somite, 1.3 (in dorsal view) and 2 (in ventral view) times as long as width. Ornamentation consisting of setules ( Fig. 6A, B View FIGURE6 ), and row of spinules along posterior margins dorsally and ventrally ( Fig. 5A, C View FIGURE 5 ). Caudal ramus bearing 7 setae: seta I naked, shorter than ramus width, located anterodorsally; seta II naked, almost as long as ramus width, inserted anterodorsally midway and close to inner margin; seta III bipinnate, almost as long as ramus length, and inserted anterolaterally midway along outer margin; seta IV bipinnate, 0.2 times as long as seta V, inflated, leaf-shaped, located distally, and dorsal to seta V; seta V longest, bipinnate, anterior part wide and smooth, located distally, and ventral to seta IV; seta VI small, and naked; seta VII triarticulate, naked, and located midway along inner margin.

Antennule ( Fig. 3A View FIGURE 3 ) 5-segmented, first and second segments strongest and widest, third segment with aesthetasc fused basally to 1 naked seta, fourth segment smallest, short and compact, and fifth segment with apical acrothek consisting of 1 slender aesthetasc fused basally to 2 long naked setae. All segments smooth except for spinular row on first and third segments. Armature formula: [1], 2-[6 + 3 pinnate], 3-[6 + (1 + ae)], 4-[1], 5-[8 + acrothek].

Antenna ( Fig. 3B View FIGURE 3 ) comprising allobasis and free 1-segmented endopod. Allobasis with 2 abexopodal pinnate setae. Free endopodal segment 1.8 times as long as wide, with long medial outer spinules, with some spinules on inner and outer distal corners, with 5 strong, rigid naked elements and 1 long naked (innermost element), relatively slender element. Exopod 1-segmented, small, as long as wide, and with 4 elements (1 sparsely bipinnate and 3 naked).

Mandible ( Fig. 3C View FIGURE 3 ) with well-developed gnathobasis, bearing several multicuspidate teeth distally, 1 small pinnate seta, and with 1 row of medial spinules near basis. Mandibular palp 1-segmented and incorporated into basis, armed with 4 bipinnate setae (1 basal, 2 exopodal and 1 endopodal), and 1 row of slender medial spinules.

Maxillule ( Fig. 3D View FIGURE 3 ) praecoxa with few outer spinules proximally. Praecoxal arthrite well developed with few spinules, 2 naked surface setae, 8 stout naked spines/setae, and 2 bipinnate lateral setae. Syncoxa with cylindrical coxal endite bearing 2 naked setae. Basis and rami fused, outer margin with few spinules, and with 8 setae [5 basal (3 naked, 1 pinnate, 1 unipinnate), 1 endopodal unipinnate, and 2 exopodal bipinnate setae].

Maxilla ( Fig. 3E View FIGURE 3 ) with large syncoxa bearing 1 row of outer spinules proximally, 2 subequal endites, and each with 3 elements fused to segment (2 spinulose and 1 slender naked). Allobasis into long naked curved claw with 1 accompanying naked seta. Endopod incorporated into basis, and represented by 2 naked setae.

Maxilliped ( Fig. 3F View FIGURE 3 ) comprising syncoxa, basis, and 2-segmented endopod. Syncoxa shorter than basis, with 1 short distal naked seta. Basis almost 2 times as long as width with longitudinal row of medial spinules. Endopod 2- segmented, distal segment with 1 strong curved claw ornamented with rigid spinules in distal half, and 2 naked accessory setae at proximal region.

P1–P4 (Fig. 4A–D) with smooth and short concave intercoxal sclerite (P2 and P3 illustrated). Praecoxa somewhat triangular and shorter than coxa, with 1 row of outer spinules. Coxa with 1 (P1, P2 and P3) or 2 (P4) spinular rows on anterior surface, and row of strong outer spinules (P2, P3 and P4). Basis with 1 row of strong outer spinules near insertion of exopod and 1 row of distal spinules near insertion of endopod. Basal outer seta naked (P1, P2 and P4) or bipinnate (P3), and inner spine (with few spinules) on P1. Exopod 3-segmented, and all segments subequal. Exp-1 to -3 with robust outer spinules. Exp-2 (P1) and exp-1 to -3 (P2, P3 and P4) with inner setules. Exp-2 (P1, P2, P3 and P4) with pinnate inner seta, and exp-3 (P1, P2, P3 and P4) with pinnate inner subdistal, distal and outer terminal setae. P4 exp-3 with 1 inner subdistal pectinate seta. Endopod 2-segmented in P1, P2 and P3 or 1-segmented in P4. Enp-1 to -2 (P1, P2 and P3) with robust outer spinules. Enp-1 to -2 (P1), enp- 2 (P2 and P3) with slender inner setules. All setae on P1–P4 endopods pinnate except for inner apical short seta on P4 endopod (Fig. 4D). Armature formula as follows:

P5 ( Fig. 5D View FIGURE 5 ) with separate baseoendopod and exopod. Baseoendopod transversely elongated, with inner spinules on endopodal lobe and close to exopod, with 2 pectinate and 2 pinnate setae. Exopod squarish, almost as long as wide, with 5 elements (innermost element longest, bipinnate, and fused to segment, medial 2 setae pinnate and outermost 2 setae naked).

P6 ( Fig. 5A, E View FIGURE 5 ) with 1 small flap bearing 1 small pinnate seta.

Description of male (based on allotype and paratypes). Body (Fig. 7A) as in female except for total body length ranged from 428 to 434 µm (mean = 431 µm, n = 2; allotype: 428 µm, measured from tip of rostrum to posterior margin of caudal rami). Maximum width ranged from 118 to 123 µm (mean 120 µm, n = 2; allotype: 118 µm, measured at posterior margin of cephalothorax). Urosome/prosome ratio about 0.7, and body length/width ratio about 3.5. Cephalothorax (Fig. 7A) without integumental windows. Body ornamentation (not illustrated), rostrum (Fig.7A), antenna (not illustrated), mouth parts (not illustrated), P1 and P4 (not illustrated) as in female.

Prosome 4-segmented (Fig. 7A), comprising cephalothorax (bearing first pedigerous somite), and 3 free somites. Posterior margin of prosomites serrated and with sensilla as in female.

Urosome 6-segmented (Fig. 7A, B), comprising P5-bearing somite, genital somite and 3 free abdominal somites and anal somite. Posterior margin of urosomites serrated except for anal somite and with sensilla as in female, P6-bearing somite and urosomite 3 to 5 with longitudinal row of spinules close to posterior margin ventrally.

Genital somite (Fig. 7A, B) homologous to anterior part of genital double-somite in female. P6-bearing somite and third urosomite well segmented ventrally, 3.3 times as wide as long in ventral view, and with 1 spermatophore located on right side extending from posterior part of P4-bearing somite to posterior part of genital somite.

FIGURE 4. Nannopus minutus sp. nov., line drawings, A–B, paratype ♀ 1; C–D, paratype ♀ 2: A, P1; B, P2; C, P3; D, P4; E– F, P2 and P3 intercoxal sclerite.

Anal somite (Fig. 7A) as in female except for anal operculum deeply protruded downwards.

Caudal rami (Fig. 7A–D) as in female except for small inner projection (arrowed in Fig. 7B). Seta IV 0.4 times as long as seta V, but twice as long as one in female, seta V anterior part as in female, and posterior part more flexible than in female.

Antennule ( Fig. 8E View FIGURE 8 ) chirocer, 7-segmented, with strong geniculation between segments 5 and 7. Segment 1 with 1 row of spinules along inner margin. Segment 2 longer than segment 1. Segment 4 represented by 1 small sclerite located posteriorly, with 1 seta. Armature formula as follows: 1-[1], 2-[6 + 3 pinnate], 3-[3], 4-[1], 5-[6], 6- [9(1 + ae)], 7-[7 + acrothek]. Apical acrothek consisting of 1 minute aesthetasc and 2 naked setae.

P2–P3 ( Fig. 8A, B View FIGURE 8 ) almost as in female except for P3 praecoxa without spinular row. P2 coxa with only 1 spinular row along anterior surface. Exopod 3-segmented, P2 exp-1 with pinnate outer spine, and exp-2 inner seta extremely smaller than in female (arrowed in Fig. 8A View FIGURE 8 ). Endopod 2-segmented, P3 enp-2 inner seta extremely short and naked (arrowed in Fig. 8B View FIGURE 8 ), and outer spine fused to segment forming sharp and naked apophysis (arrowed in Fig. 8B View FIGURE 8 ).

P5 ( Fig. 8C View FIGURE 8 ) fused with somite, exopod and baseoendopod fused, and both baseoendopods confluent. Baseoendopod with distal spinules, and outer basal bipinnate seta. Endopodal lobe with 2 sub-equal pectinate and 2 bipinnate setae. Exopodal lobe with 5 elements (3 bipinnate and 2 naked, and outer naked seta smallest).

P6 (Figs. 7B, 8D) asymmetrical, only right flap functional, and with row of spinules distally. Each P6 with 3 bipinnate setae, medial element longest, and each seta arising from cylindrical peduncle.