Rhyncholagena cuspis, Yeom & Lee, 2023

Yeom, Jisu & Lee, Wonchoel, 2023, A new species of Rhyncholagena Lang, 1944 (Copepoda, Harpacticoida, Miraciidae) from Palau, ZooKeys 1180, pp. 181-199 : 181

Rhyncholagena cuspis sp. nov.

Figs 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10

Type locality.

St.1-Shark City (7°16'04.2"N, 134°11'11.4"E) and St.2-Blue Corner (7°08'04.0"N, 134°13'13.5"E) diving sites in west coast of Palau on 19-20 October 2018 and 22-26 January 2019, collected by Wonchoel Lee, Eunha Choi and Jisu Yeom. Sediment type: sand. Depth: 15 m.

Type material.

Holotype: Palau • ♀; Koror, Shark City diving site; 7°16'04.2"N, 134°11'11.4"E, depth 15 m, 20 Oct 2018; W. Lee leg.; SCUBA diving; GenBank: OR252612, OR257802; MABIKCR00254070. Allotype: Palau • ♂; same collection data as for holotype; GenBank: OR252613, OR257803; MABIKCR00254071. Paratypes: Palau • ♀; Peleliu, Blue Corner diving site; 7°08'04.0"N, 134°13'13.5"E, depth 15 m, 22 Jan 2019; W. Lee, E. Choi, J. Yeom leg.; SCUBA diving; MABIKCR00254072 • ♀,♂; Peleliu, Blue Corner diving site; 7°08'04.0"N, 134°13'13.5"E, depth 15 m, 19 Oct 2018; W. Lee leg.; SCUBA diving; MABIKCR00254073, MABIKCR00254074 • ♀,♂; Koror, Shark City diving site; 7°16'04.2"N, 134°11'11.4"E, depth 15 m, 26 Jan 2019; W. Lee, E. Choi, J. Yeom leg.; SCUBA diving; MABIKCR00254075, MABIKCR00254076 • 2♀,5♂; same collection data as for holotype; MABIKCR00254077.

Description.

Female. Total body length 593 µm (n = 4) (Fig. 2A ); body slender, cylindrical, slightly tapering distally. Rostrum (Figs 2A, B , 3A ) prominent, triangular flask-shaped, tapering distally, reaching second antennular segment, defined at base; with two small sensilla. Cephalothorax bell-shaped (Fig. 8A ). Anal somite (Figs 2 , 9 ) with row of spinules along ventral distal margin and long lateral spinous process distally, 1.5 times longer than caudal ramus; Anal operculum well developed, semicircular.

Caudal ramus (Figs 2A, B , 9 ). Approximately 1.2 times as long as greatest width, armed with spinules on the lateral ventral surface and the inner dorsal surface. Each ramus armed with seven setae; seta I and seta II located the medial of the lateral margin, seta I bare, seta II short, seta III bare and located near seta I and seta II on the lateral margin; seta IV well developed, bipinnate, seta IV more than half as long as seta V, seta V as long as urosome; both terminal caudal setae with fractured plane; seta VI bare, located on inner distal corner; seta VII, bare, located on dorsal surface of caudal ramus.

A1 (Fig. 3A ). Eight-segmented, slender; seg-2 about 2.5 times as long as broad and slightly longer than seg-1; seg-4 twice as long as seg-3. Armature formula (segment-[number of seta/setae]): 1-[1 bare], 2-[8 bare + 2 pinnate], 3-[7 bare], 4-[4 bare + aesthetasc], 5-[2 bare], 6-[2 bare], 7-[4 bare], 8-[5 bare + acrothek]. Aesthetasc on seg-4 fused basally with adjacent seta and about twice as long as distal four segments combined. Apical acrothek consisting of aesthetasc and two bare setae.

A2 (Fig. 4A ). Basis short, squarish, unarmed. Endopod two-segmented, enp-2 with two spiniform setae laterally, four geniculate setae and three bare setae terminally. Exopod (Fig. 8B ) two-segmented, exp-1 with the long pinnate seta; exp-2 with two pinnate setae laterally, pinnate seta and small bare seta distally.

Mandible (Fig. 4B ). Gnathobase bearing chitinous projection on surface; basis with setules bearing three bare setae and one pinnate seta; exopod two-segmented, exp-1 with seta, exp-2 with two setae; endopod bearing two setae on proximal lobe and seven terminal setae.

Maxillule (Fig. 4C ). Praecoxal arthrite bearing six elements distally with two pinnate spines, two bare setae laterally and two bare setae on surface; coxa with two bare setae; basis with six bare setae; endopod bearing four bare setae; exopod bearing two plumose setae.

Maxilla (Fig. 4D ). Three endites of syncoxa with two, two and three setae, proximal to distal, respectively; allobasis transformed to thick pinnate claw bearing bare seta, two thin setae and short seta on surface; uniarticulated endopod with six bare setae.

Maxilliped (Fig. 4E ). Subchelate; syncoxa with three pinnate setae and row of setules; basis with row of setules on surface, three times as long as broad, bearing two bare setae; endopod elongate, with strong claw and two bare setae.

In P1-P4, all rami three-segmented and coxa ornamented with several rows of spinules. Armature formula of the new species as follows:

P1 (Fig. 5A ). Basis with outer ornamented seta, inner margin with setules and armed with bipinnate spine. Exp-1 inner margin bare, exp-1 and exp-2 with bipinnate outer spine and ornamented with spinules along outer margin, exp-2 inner margin with setules and bare inner seta; exp-3 with three outer spines and two geniculate setae distally. Enp-1 much longer than exopod, about 6.2 times longer than wide, with inner pinnate seta distally, which almost reaches the end of enp-3, inner margin ornamented with setules; enp-2 small and bare; enp-3 as long as enp-2, outer margin ornamented with spinules, bearing slender bare seta at inner distal edge, long seta and unipinnate claw-like spine apically.

P2 (Fig. 5B ). Basis with setules distally and outer ornamented seta. Both exp-1 and exp-2 with inner plumose seta, inner margin ornamented with setules, bipinnate outer spine and outer margin ornamented with spinules; exp-3 with two plumose inner setae, long plumose seta at inner terminal, long spiniform seta with plumose inner side and pinnate outer side at outer terminal and three outer spines, proximal outer margin ornamented with spinules. Endopod as long as exopod, enp-1 with plumose inner seta; enp-2 with two plumose inner setae; enp-3 with pinnate inner seta, two setae distally and spine at outer distal corner, outer margin of endopod segments ornamented with spinules.

P3 (Fig. 6A ). Basis with bare outer seta. Both exp-1 and exp-2 with inner seta and outer margin ornamented with spinules; exp-3 with two long inner setae, long plumose seta and long pinnate seta at inner terminal and three outer pinnate spines, proximal outer margin ornamented with spinules. Endopod as long as exopod, both enp-1 and enp-2 with plumose inner seta; enp-3 with three plumose inner setae, two setae distally and short spine at outer distal corner; outer margin of endopod segments ornamented with spinules.

P4 (Fig. 6B ). Basis with bare outer seta. Exp-1 with bare inner seta; exp-2 with plumose inner seta, inner margin ornamented with setules; exp-3 with two long setae and short seta on inner margin, long plumose seta and long seta with plumose inner side and pinnate outer side at distal and three outer spines, outer margin of exopod ornamented with spinules. Endopod shorter than exopod, both enp-1 and enp-2 with plumose inner seta; enp-3 with two plumose inner setae, two setae distally and spine at outer distal corner, outer margin of endopod segments ornamented with spinules.

P5 (Fig. 7A ). Baseoendopod and exopod distinct, baseoendopod with long, slender and bare basal seta; endopodal lobe bearing three inner pinnate spines and two distal pinnate spines. Exopod elongated, 3.6 times longer than wide, with incision between the apical setae, with setules along inner margin and spinules along outer margins, bearing six bare setae.

Genital area as in Fig. 7B . P6 with two long setae and short pinnate spiniform seta. Genital double-somite with epicopulatory bulb.

Male. Body (Fig. 2C ) 502 µm (n = 3) in length, smaller and more slender than female. Sexual dimorphism shown in A1, P1, P2, P5 and P6.

A1 (Fig. 3B ). Subchirocer, 11-segmented. Armature formula: 1-[1 bare], 2-[9 bare + 1 pinnate], 3-[6 bare], 4-[1 bare + 1 pinnate], 5-[4 bare + aesthetasc], 6-[1 bare], 7-[1 bare], 8-[0], 9-[1 bare], 10-[3 bare], 11-[4+1 acrothek].

P1 basis (Fig. 5C ) with claw-like spine and inner margin with bifid protrusion.

P2 endopod (Figs 5D , 10A ). Two-segmented, outer margin ornamented with setules; enp-1 with pinnate inner seta; enp-2 modified, bearing three inner setae, terminal seta, outer distal curved thick spine.

P5 (Figs 7C , 10B ). Baseoendopod and exp distinct; endopodal lobe ornamented with spinules at outer margin, armed with two spines. Exp with five setae in total, including bipinnate inner seta, long distal bare seta and three bare outer setae, outer margin ornamented with setules.

P6 (Figs 7C , 10B ) represented by short inner seta and two long bare setae on outer distal corner of genital operculum.

Etymology.

The scientific name is derived from the Latin Rhyncholagena cuspis (meaning a point), alluding to the spinous process on the anal somite.

DNA-barcode.

The 18S rRNA sequences [female: 1,691 base pairs (bp) (OR257802); male: 1,775 bp (OR257803)] and the mtCOI sequences [female: 641 bp (OR252612); male: 573 bp (OR252613)] were successfully amplified from the two specimens of the new species. These sequences were submitted to GenBank.

Figures

Figure 2. Rhyncholagena cuspis sp. nov. Female A habitus, dorsal B habitus, lateral. Male C habitus, dorsal. Scale bar: 100 μm.

Figure 3. Rhyncholagena cuspis sp. nov. Female A A 1 and rostrum, dorsal. Male B A 1 and segments (3 rd and 5 th segment), rostrum, dorsal. Scale bar: 10 μm.

Figure 4. Rhyncholagena cuspis sp. nov. A A 2 B mandible C maxillule D maxilla E maxilliped. Scale bars: 10 μm.

Figure 5. Rhyncholagena cuspis sp. nov. Female A P 1 B P 2. Male C P 1 basis D P 2 endopod. Scale bar: 30 μm.

Figure 6. Rhyncholagena cuspis sp. nov. A P 3 B P 4. Scale bar: 30 μm.

Figure 7. Rhyncholagena cuspis sp. nov. Female A P 5 B genital field and P 6. Male C P 5 and P 6. Scale bar: 30 μm.

Figure 8. Rhyncholagena cuspis sp. nov. SEM photographs A mouth parts B A 2 exopod. Scale bars: 10 μm.

Figure 9. Rhyncholagena cuspis sp. nov. SEM photographs A anal somite and caudal rami, dorsal B caudal ramus, lateral C anal somite and caudal rami, ventral. Scale bars: 10 μm.

Figure 10. Rhyncholagena cuspis sp. nov. SEM photographs. Male A P 2 B P 5 and P 6. Scale bars: 10 μm.