Acartia nadiensis, Lee, Seunghan, Soh, Ho Young & Lee, Wonchoel, 2019

Lee, Seunghan, Soh, Ho Young & Lee, Wonchoel, 2019, A new species in the genus Acartia Dana, 1846 (Crustacea, Copepoda, Calanoida, Acartiidae) from the South Pacific coastal waters of Nadi Bay, Fiji, ZooKeys 893, pp. 69-89 : 69

publication ID	https://dx.doi.org/10.3897/zookeys.893.38369
publication LSID	lsid:zoobank.org:pub:CE4FA51F-B90E-4893-9E5B-6A0498F33689
persistent identifier	https://treatment.plazi.org/id/6B2D92AF-5283-55D5-8C12-4ADE57FCB614
treatment provided by	ZooKeys by Pensoft
scientific name	Acartia nadiensis
status	sp. nov.

Treatment

Acartia nadiensis sp. nov. Figures 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8

Type locality.

Coastal water (17°45.848'S, 177°22.348'E), Nadi Bay, Fiji.

Materials examined.

All specimens have been deposited in the Marine Biodiversity Institute of Korea (MABIK). Holotype 1♀ (MABIK CR00246502) and Allotype 1♂ (MABIK CR00246503) undissected and preserved in 70% ethanol. Paratype: 2♀♀ (MABIK CR00246504-CR00246505) dissected on 13 and 10 slides, respectively; 2♂♂ (MABIK CR00246506-CR00246507) dissected on 14 and 8 slides, respectively; 10♀♀ (MABIK CR00246508-CR00246517) and 4♂♂ (MABIK CR00246518-CR00246521) undissected and preserved in 70% ethanol. 4♀♀ and 4♂♂ dried, mounted on stub, and coated with platinum for SEM. All specimens are from the type locality and were collected by S. Lee on 10 October 2013. The illustrations are based on the paratypes (♀, MABIK CR00246504; ♂, MABIK CR00246506).

Etymology.

The specific name refers to the type locality of Nadi bay, Fiji.

Description of female.

Total body length 975-1050 μm (mean ± SD = 1018 ± 26 μm, n = 10, holotype 1015 μm) as measured from anterior margin of cephalosome to posterior margin of the caudal rami. Body surface armed with some sensillae ( Fig. 1A View Figure 1 ). Prosome:urosome length ratio = 3.52:1.

Prosome 5-segmented ( Fig. 1A, B View Figure 1 ), cephalosome and first pedigerous somite completely separate; fourth and fifth pedigerous somite fused. Posterior corners of fifth pedigerous somite rounded, each with three spines. Rostral filaments thick and short ( Figs 2A View Figure 2 , 7A View Figure 7 ).

Urosome 3-segmented ( Figs 1 A–C View Figure 1 , 7 D–H View Figure 7 , 8A View Figure 8 ), genital double somite slightly swollen anterolaterally, with paired gonopores ventromedially, each gonopore covered with pointed operculum; first and second urosomites each with four spines on posterodorsal margin. Caudal rami bearing short hairs on lateral margin. Proportional lengths of urosomites and caudal rami as 38:23:17:22 = 100.

Antennule incompletely 18-segmented ( Fig. 2A, B View Figure 2 ), fourth to seventh segments partly fused on dorsal surface; ninth to eleventh segment each with one row of setules, twelfth segment with three rows of setules, thirteenth and seventeenth segment each with one row of setules; segmentation and setation patterns as follows: (1) I-[1], (2) II-VI-[5+ae], (3) VII-[1+ae], (4) VIII-XI-[4(1spiniform)+ae], (5) XII-[0], (6) XIII-[0], (7) XIV-XV-[2+ae], (8) XVI-[1+ae], (9) XVII-XVIII-[2+ae], (10) XIX-[1], (11) XX-[1], (12) XXI-[1+ae], (13) XXII-[1], (14) XXIII-[1], (15) XXIV-[2(1+1)], (16) XXV-[2(1+1)+ae], (17) XXVI-[2(1+1)], (18) XXVII-XXVIII-[4+ae].

Antenna ( Fig. 2C View Figure 2 ): coxa with seta; basis and first endopodal segment fused to form elongated allobasis bearing eight setae medially and one seta terminally along inner marin, and spinular row on distal area; second endopodal segment elongated, with seven setae, rows of spinules on lateral margin; third exopododal segment short, with seven setae. Exopod 4-segmented; setation formula 1, 2, 2, 3.

Mandible: ( Fig. 3A View Figure 3 ) coxa with well developed gnathobase bearing eleven teeth; basis with seta and row of setules on lateral and posterior margins; endopod 2-segmented, first endopodal segment with two setae, second segment with seven setae; exopod 5-segmented, setation formula as 1, 1, 1, 1, 2.

Maxillule: ( Fig. 3B View Figure 3 ) precoxa and coxa incompletely fused, praecoxal arthrite with eight setae; coxal endite with three setae; one short seta and eight long setae on coxal epipodite; basal endite with one seta; basal exite with one seta; 1-segment exopod with two setae laterally and five setae terminally; endopod absent.

Maxilla: ( Fig. 3C View Figure 3 ) precoxa and coxa incompletely fused, setation formula of endites 4, 2, 2, 3; basal endite with a seta and row of spinules on distal margin; endopod 3-segmented, with setation formula 2, 2, 3.

Maxilliped ( Fig. 3D View Figure 3 ) comprising syncoxa with six setae; basis with spiniform seta; endopod 2-segmented, first segment with three setae, second segment with two setae.

Legs 1-4 ( Fig. 4 A–D View Figure 4 ) biramous, each with 3-segmented exopod and 2-segmented endopod, and spinules along inner and outer margins as illustrated. Intercoxal sclerites well developed. Spine and setal formulae as follows:

P5 ( Figs 2D View Figure 2 , 7B, C View Figure 7 ) symmetrical, 3-segmented; basis ovate, with outer seta; exopod tapering, thick, bent at midlength, distal portion serrated, base slightly swollen.

Description of male.

Total body length 910-952 μm (mean ± SD = 931 ± 16 μm, n = 5, allotype 930 μm) measured from anterior margin of cephalosome to posterior margin of caudal rami. Body surface armed with some sensilla ( Fig. 5A, B View Figure 5 ). Prosome:urosome length ratio = 3.12:1.

Prosome ( Fig. 5A, B View Figure 5 ) 5-segmented. Rostral filaments thin ( Figs 5A, B View Figure 5 , 8B View Figure 8 ). Fifth prosomite with six spines on posterior margin.

Urosome ( Figs 6C, D View Figure 6 , 8 C–H View Figure 8 ) 5-segmented. Second urosomite with four spines on posterodorsal margin and two spines on posteroventral margin; pair of sensillae on dorsal surface. Third and fourth urosomites each with four spines on posterodorsal margin. Caudal rami bearing short hairs on lateral margin. Length proportions of urosomites to caudal rami as 16:31:21:7:12:14 = 100.

Left antennule 22-segmented ( Fig. 6A View Figure 6 ). Segmentation and setation pattern as follows: (1) I-[1], (2) II-VII-[3+ae], (3) VIII-[2], (4) IX-[1+ae], (5) X-[2(1spinifrom)], (6) XI-[2+ae], (7) XII-[0], (8) XIII-[0], (9) XIV-[2(1spiniform)+ae], (10) XV-[1], (11) XVI-[1+ae], (12) XVII-[1], (13) XVIII-[1+ae], (14) XIX-[1], (15) XX-[1], (16) XXI-[1+ae], (17) XXII-[1], (18) XXIII-[1], (19) XXIV-[2(1+1)], (20) XXV-[2(1+1)+ae], (21) XXVI-[2(1+1)], (22) XXVII-XXVIII-[4+ae]. Right antennule 18-segmented ( Fig. 6B View Figure 6 ), with geniculation with fourteenth and fifteenth segments. Segmentation and setation pattern as follows: (1) I-[1], (2) II-VII-[3+ae], (3) VIII-[2], (4) IX -[1+ae], (5) X-XI-[3(1spiniform)+ae], (6) XII-[0], (7) XIII-[0], (8) XIV-[2(1spiniform)+ae], (9) XV-[1], (10) XVI-[1+ae], (11) XVII-[1], (12) XVIII-[1+ae], (13) XIX-[1], (14) XX-[1], (15) XXI-XXIII-[3+ae], (16) XXIV-XXV-[4(2+2)+ae], (17) XXVI-[2(1+1)], (18) XXVII-XXVIII-[4+ae].

Other mouthparts and P1-P4 as in female. P5 asymmetrical ( Fig. 5C View Figure 5 ); intercoxal sclerite distinct. Left leg 4-segmented; basis armed with posterolateral seta and rounded lobe on posterior surface; exopod 2-segmented, exp-1 unarmed; exp-2 with hairs, and one spine with teeth on medial margin and one small spine distally. Right leg 5-segmented, basis armed with posterolateral seta. Exopod 3-segmented, exp-1 with long slender seta; exp-2 with oblong inner lobe bearing one spine on distal margin; exp-3 with one spine on medial margin and one spine distally.