Integrative description of Diosaccus koreanus sp. nov. (Hexanauplia, Harpacticoida, Miraciidae) and integrative information on further Korean species Author Lim, Byung-Jin Department of Taxonomy and Systematics, National Marine Biodiversity Institute of Korea, Seocheon 33662, Korea Author Bang, Hyun Woo Mokwon University, Daejeon, 35349, Korea https://orcid.org/0000-0002-9626-9762 Author Moon, Heejin Mokwon University, Daejeon, 35349, Korea Author Back, Jinwook Department of Taxonomy and Systematics, National Marine Biodiversity Institute of Korea, Seocheon 33662, Korea https://orcid.org/0000-0003-0285-1135 b.jinwook@gmail.com text ZooKeys 2020 927 1 35 http://dx.doi.org/10.3897/zookeys.927.49042 journal article http://dx.doi.org/10.3897/zookeys.927.49042 1313-2970-927-1 24272A94472E4F9C836F41D11E62C353 76BDE37F4FD3580F97704DD474B85663 Diosaccus koreanus sp. nov. Figs 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 Material examined. Holotype . Republic Of Korea ∙ Ulleungdo Island; 37°31'36.56"N , 130°49'41.77"E ; 25 July 2017; B. Jinwook leg.; hand net, 0.5 m ∙ 1 ♀ (MABIK CR00247255) was dissected on 14 slides (Table 1 ) ∙ GenBank accession number for COI sequence: MN996281. Paratypes . Republic Of Korea (Table 1 ) ∙ 1 ♂ (MABIK CR00247257) was dissected on 8 slides and observed ∙ 4 ♀♀ (MABIK CR00247256, CR00247258 - CR00247260) were preserved in 99% alcohol ∙ GenBank accession numbers: MN996277 to MN996280 ( COI ) and MT002900 to MT002902 ( 18SrRNA ). Description. Female. Body (Figs 1 , 2 ): Total length, from anterior margin of rostrum to posterior margin of caudal rami, 1135 μm ( N = 5, mean = 1133 μm ; Fig. 1 ); maximum width 340 μm , measured at distal cephalothorax; body cylindrical, not dorsoventrally depressed, and with minute dorsal sensilla; rostrum well developed, defined at base, trapezoid in shape, with round apex and 2 sensilla (Figs 1A , 2A ); cephalothorax sub-triangle with sensilla and smooth margin; second and third urosomites fully fused ventrally, but with transverse ridge on dorsal and lateral surfaces indicating original segmentation (Figs 1A, B , 6B ); anal operculum not well developed, with spinular tuft (Fig. 2D ). Figure 1. Diosaccus koreanus sp. nov., female A habitus, dorsal B habitus, lateral. Scale bars indicate length in µm . Figure 2. Diosaccus koreanus sp. nov., female A rostrum and antennule, dorsal B antenna C end of antennary endopod D caudal rami, dorsal E caudal rami, ventral. Scale bars indicate length in µm . Caudal rami (Fig. 2D, E ): Parallel, ca 1.5 times longer than maximum width, dorsal surface with small bumps; each ramus with 7 setae: seta I strong, pinnate; setae II bare on distal corner; seta III blunt spine; setae IV and V strong; seta VI pinnate; seta VII bare, triarticulate at base. A1 (Fig. 2A ): Slender, 8-segmented; seg-2 longest, ca 1.2 times as long as seg-3; seg-4 with sub-cylindrical pedestal armed with aesthetasc fused at base to 1 long bare seta; armature formula: 1-[1], 2-[11], 3-[9], 4-[3 + (1+ae)], 5-[2], 6-[4], 7-[4], 8-[3+acrothek]; apical acrothek of short aesthetasc fused basally to 2 bare setae. A2 (Fig. 2B, C ): 3-segmented, with coxa, allobasis, and free 1-segmented enp; coxa small and bare; allobasis without abexopodal seta; exp 1-segmented, with 2 lateral and 2 apical pinnate setae; free enp with 2 pinnate setae and 2 long spines laterally and with 1 bare seta, 2 spines, and 3 geniculate setae along distal margin. Mandible (Fig. 3A ): Gnathobase with several blunt teeth; palp basis with 2 inner pinnate setae; exp 1-segmented with 2 pinnate distal setae; enp with 2 lateral and 6 distal setae. Maxillule (Fig. 3B, C ): Praecoxa trapezoidal in shape, without ornamentation; arthrite well developed, with 2 juxtaposed setae near midpoint of anterior surface, 4 strong teeth-like spines and 3 tuft spines along distal margin; coxa fused with cylindrical endite, with 1 pinnate seta; basis fused with endite, with 1 bare and 5 pinnate setae; exp 1-segmented, with 2 pinnate setae distally; enp 1-segmented, with 4 pinnate setae along distal margin. Maxilla (Fig. 3D ): Syncoxa with 2 endites; proximal endite with 2 strong spines and 1 bare seta among distal margin; second endite with 1 strong spine, 1 bare seta, and 1 tuft-like seta; allobasis developed into cylindrical process, with 2 strong spines and 2 bare setae; enp 1-segmented, with 2 bare and 3 pinnate setae. Mxp (Fig. 3E ): 4-segmented, with syncoxa, basis, and 2-segmented enp; syncoxa with 2 pinnate setae distally; basis elongate and robust, with 2 small bare setae (Fig. 3E , arrow) and roughly ornamented with rows of spinules along inner margin; enp-1 with 1 bare and 1 pinnate setae; enp-2 forming strong claw ornamented with row of spinules among inner proximal half. Figure 3. Diosaccus koreanus sp. nov., female A mandible B maxillule C shape of elements in praecoxal arthrite of maxillule D maxilla E maxilliped. Scale bars indicate length in µm . Swimming legs (Figs 4 , 5 ): Biramous; P1-P4 with coxa, basis, and 3-segmented exp and enp; each ramus ornamented with setules or spinules along outer margins as figured.3 P1 (Fig. 4A, B ): Coxa ornamented with inner spinules; basis with 1 outer and 1 inner pinnate setae; exp-1 with 1 outer spine; exp-2 with 1 outer spine and 1 inner pinnate seta; exp-3 with 3 spines and 1 bare seta; enp-1 ornamented with row of spinules on inner proximal half, ca 2 times longer than exp, with 1 pinnate seta; enp-2 with 1 small bare seta on inner distal corner, enp-3 with 2 strong spines distally and 1 bare seta near inner distal corner. P2 (Fig. 4C ): Coxa ornamented with row of spinules on outer margin; basis with 1 outer bare seta near distal corner; exp-1 with 1 outer spine, ornamented with a row of long setules along inner margin; exp-2 with 1 outer spine and 1 inner pinnate seta, ornamented with row of setules along outer margin; exp-3 with 2 outer spines and 2 apical and 2 inner pinnate setae; enp-1 with 1 inner pinnate seta, ornamented with long setules along outer margin; enp-2 with 2 pinnate inner setae; enp-3 with 1 outer, 2 distal, and 1 inner pinnate setae. P3-P4 (Fig. 5A, B ): Coxa ornamented with rows of spinules on outer margin; basis with 1 outer bare seta near distal corner; exp-1 with 1 outer spine, ornamented with row of long setules along inner margin; exp-2 with 1 outer spine and 1 inner pinnate seta, ornamented with row of spinules along outer margin; exp-3 with 3 outer spines, 2 apical and 3 inner pinnate setae; enp-1 with 1 inner seta, ornamented with long setules among outer margin; enp-2 with 2 inner pinnate setae [P3] or 1 inner pinnate seta [P4]; enp-3 with 1 outer spine, 2 apical pinnate and 2 inner pinnate setae. Figure 4. Diosaccus koreanus sp. nov., female A first thoracopod B middle and distal endopods of first thoracopod C second thoracopod. Scale bars indicate length in µm . Figure 5. Diosaccus koreanus sp. nov., female A third thoracopod B fourth thoracopod. Scale bars indicate length in µm . Armature formulae as follows:
- Exopod Endopod
P1 0.1.112 1.1.120
P2 0.1.222 1.2.121
P3 0.1.323 1.2.221
P4 0.1.323 1.1.221
P5 (Fig. 6C ): Defined at supporting somite; each side of endopodal lobe separated, with 6 spine-like setae; exp with 6 setae, second inner element longest. P6 (Fig. 6A, B ): Fused with supporting somite, with 3 bare setae, innermost seta longest. Figure 6. Diosaccus koreanus sp. nov., female A sixth thoracopod and genital field B urosomites, ventral C fifth thoracopod. Scale bars indicate length in µm . Male. Body (Fig. 7A ): Total length, from anterior margin of rostrum to posterior margin of caudal rami, 880 μm ; maximum width 262 μm , measured at distal cephalothorax; general body shape, ornamentation, and sensilla pattern almost identical to those of female, but with sexual dimorphisms observed in A1, P1, P2, P5, P6, and genital somites. Figure 7. Diosaccus koreanus sp. nov., male A habitus, dorsal B caudal rami, dorsal C urosomites, lateral D fifth thoracopod E sixth thoracopod. Scale bars indicate length in µm . A1 (Fig. 8C, D ): Subchirocer 10-segmented, robust; seg-3 with aesthetasc fused at base to 1 bare seta; seg-5 swollen, with aesthetasc fused at base to 1 bare seta; armature formula: 1-[1], 2-[10], 3- [4+(1+ae)], 4-[2], 5-[4+(1+ae)], 6-[2 bare], 7-[1], 8-[1], 9-[4], 10-[5+(1+ae)]. P1 (Fig. 8A ): General shape of P1 similar to that of female, except basis; basis with 1 outer pinnate seta and 1 wrinkled process near base of outer seta. P2 (Fig. 8B ): Enp 2-segmented; enp-1 with 1 inner bare seta and ornamented with row of long setules along outer margin; enp-2 with 1 inner bare seta on small disk (Fig. 8B , arrow) of which middle inner edge and 1 longest bare seta, 3 pinnate inner setae, and 1 strong spinulose seta apically. Figure 8. Diosaccus koreanus sp. nov., male A base of first thoracopod B second thoracopod C antennule D antennule segments 3-6. Scale bars indicate length in µm . P5 (Fig. 7D ): Fused medially; plate of benp fused each side; basal part with 1 bare seta; endopodal lobe with 2 spinulose pinnate setae; exp fused at base, with 3 spinulose setae and 1 bare seta. P6 (Fig. 7E ): Fused at base, with 2 bare and 1 spinulose setae. Etymology. Species name refers to the type locality (i.e., Republic of Korea). DNA sequences. In regards to pairwise distances (Tamura-Nei distance) among the 582-bp COI sequences, D. koreanus sp. nov. exhibited intra-specific variation of 0-2.28%, and inter-specific distances of 19.42-22.34% were observed among all three Diosaccus species (Table 3 ). In regards to the 18SrRNA sequences, intra- and inter-specific variations of 0% and 1.46-8.55% were observed (Table 4 ). Table 3. Pairwise distances (Tamura-Nei distance) between COI sequences from species in genus Diosaccus . Numbers in parentheses indicate the Genbank accession numbers.
- - 1 2 3 4 5 6 7 8
1 D. koreanus sp. nov. (CR00247255, CR00247258) - - - - - - - -
2 D. koreanus sp. nov. (CR00247256) 1.52 - - - - - - -
3 D. koreanus sp. nov. (CR00247257 CR00247260) 0.91 0.91 - - - - - -
4 D. koreanus sp. nov. (CR00247259) 2.28 1.67 1.67 - - - - -
5 D. ezoensis (KR049013) 19.93 20.62 20.62 20.79 - - - -
6 D. spinatus (MH242730) 20.36 21.28 21.28 22.04 19.76 - - -
7 D. spinatus (MH242731) 20.67 21.59 21.59 22.34 19.42 1.06 - -
8 D. spinatus (HQ966504) 20.06 20.97 20.97 21.73 19.93 1.06 0.61 -
Table 4. Pairwise distances (Tamura-Nei distance) based on 1,756 bp between 18SrRNA sequences from species in genus Diosaccus .
- Species (Genbank accession number) 1 2 3
1 Diosaccus koreanus sp. nov (MT002900 - MT002902) - - -
2 D. ezoensis (KR048740) 1.46 - -
3 Diosaccus sp. (EU380290) 7.24 8.55 -