Pontoclausia cochleata, Lee & Chang & Kim, 2022

Lee, Jimin, Chang, Cheon Young & Kim, Il-Hoi, 2022, Symbiotic copepods (Cyclopoida and Siphonostomatoida) collected by light trap from Korea, ZooKeys 1115, pp. 1-71 : 1

Pontoclausia cochleata sp. nov.

Figs 7 , 8 , 9

Material examined.

Holotype ♀ (MABIK CR00250124) dissected and mounted on a slide, Site 22 (Yesong, Bogil Island, south coast, 34°08'11"N, 126°33'49"E), 26 Apr. 2021, leg. J. Lee and C. Y. Chang ; Paratype ♂ (MABIK CR00250125) dissected and mounted on a slide, Site 27 (Sepo, Chindo Island, southwest coast, 34°25'10.4"N, 126°05'39.0"E), 09 Jul. 2016, leg. J. Lee and C. Y. Chang.

Description.

Female. Body (Fig. 7A ) narrow, gradually narrowing from anterior to posterior. Body length 2.10 mm. Maximum width 523 μm across cephalothorax. Prosome 936 μm long, shorter than urosome, consisting of cephalothorax and second to fourth pedigerous somites. Cephalothorax wider than long, without dorsal suture line between cephalosome and first pedigerous somite. All prosomal somites with rounded lateral margins. Urosome six-segmented. Fifth pedigerous somite 340 μm wide. Genital somite ~ 1.8 × wider than long (170 × 304 μm), with convex lateral margins; genital aperture positioned dorsolaterally near middle of somite. Four abdominal somites unornamented, 160 × 220 μm, 152 × 200 μm, 130 × 174 μm, and 148 × 144 μm, respectively. Anal somite tapering distally. Caudal rami (Fig. 7B ) divergent; each ramus 4.9 × longer than wide (186 × 38 μm), gradually narrowed distally, armed with six stiff, naked setae (setae II-VII); seta II as long as ramus, positioned dorsolaterally at 34% region of ramus length; setae III to VII 136 μm, 83 μm, 532 μm, 38 μm, and 33 μm long, respectively; seta V much larger than other caudal setae, nearly 3.0 × longer than ramus.

Rostrum represented by spatulate anterior prominence of cephalothorax (Fig. 7A ). Antennule (Fig. 7C ) short, 190 μm long, five-segmented; armature formula 3, 24, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setae naked; aesthetascs tapering in distal part; first segment with few minute spinules on proximal anterior margin. Antenna (Fig. 7D ) three-segmented; first segment (coxobasis) longest, with one seta at inner distal corner and hair-like setules on outer margin; second segment (first endopodal segment) with one seta subdistally and two groups of spinules on inner surface; third segment (fused second and third endopodal segments) armed with one claw plus two setae on inner margin, four claws distally (outermost claw longest, bearing two minute spinules subdistally on inner margin), three setae on subdistal outer margin (middle one naked, but other two pinnate), and ornamented with three patches of spinules (two patches on outer side and one on proximal inner margin).

Labrum (Fig. 7E ) small, not covering mouthparts, with protuberance in middle of posterior margin and large, tapering, beak-like process on dorsal surface. Mandible (Fig. 7F ) unarmed but highly transformed; its distal part curved, tapering, scoop-like. Maxillule (Fig. 7G ) as foot-like lobe, distally expanded medially, armed with four setae (two outer ones longer than other two); broadened distal surface covered with numerous spinules. Maxilla (Fig. 7H ) two-segmented; proximal segment (syncoxa) unarmed, ~ twice longer than wide; distal segment (basis; Fig. 7I ) blunt, with two spinulose pads apically, armed with two small subdistal setae each on inner and outer margins. Maxilliped (Fig. 8A ) as unsegmented, tapering lobe tipped with one naked seta, ornamented with two subapical rows of setules (or spinules).

Legs 1-4 (Fig. 8B-E ) biramous, with three-segmented rami; both rami of each leg slender, almost equal in length. Coxa lacking inner seta but ornamented with spinules on outer distal corner. Basis with spinules on distal margin between rami; outer seta long, naked. Terminal spine on third exopodal segment of legs 1-4 characteristically unequally bifurcate at tip. Armature formula for legs 1-4 as follows:

Leg 5 (Fig. 8F ) two-segmented; proximal segment (protopod) articulated from somite, armed with one dorsodistal seta of 180 μm long. Distal segment (exopod) 1.4 × longer than wide (114 × 82 μm), armed with four slender setae, single on inner margin and three on distal margin; inner margin seta 170 μm long; three distal setae 252, 180, and 261 μm long respectively from inner to outer. All setae on leg 5 finely spinulose (or with minute setules). Leg 6 probably represented by single minute seta on genital operculum.

Male. Body form (Fig. 9A ) as in female. Body length 1.36 mm. Urosome (Fig. 9B ) six-segmented, as in female. Genital somite rectangular, wider than long (158 × 224 μm), as wide as fifth pedigerous somite, gradually broadened distally; genital opercula indistinct, positioned at outer distal corners. Four abdominal somites 106 × 178 μm, 97 × 150 μm, 82 × 127 μm, 97 × 103 μm, respectively. Caudal ramus (Fig. 9C ) 4.32 × longer than wide (121 × 28 μm), armed as in female.

Rostrum as in female. Antennule and antenna segmented and armed as in female. Labrum, mandible, maxillule, and maxilla also as in female. Maxilliped (Fig. 9D ) four-segmented; first segment (syncoxa) wider than long, unarmed; second segment (basis) gradually broadened distally, armed with two unequal setae, one of them rudimentary, on subdistal inner margin, ornamented with two patches of scale-like spinules; short third segment (first endopodal segment) unarmed; terminal segment as long, arched hook bearing two simple setae proximally.

Leg 1 (Fig. 9E ) with three-segmented exopod and two-segmented endopod; compound distal endopodal segment (Fig. 9F ) armed with two spines plus five setae (formula I, 2, I, 3). Legs 2-4 as in female. Leg 5 also as in female; exopodal segment 1.5 × longer than wide (68 × 44 μm). Leg 6 not seen.

Etymology.

The specific name cochleata is derived from the Latin cochl (a spoon), alluding to the spoon-like mandible of the new species.

Remarks.

With the three-segmented rami of legs 1-4, the inner distal spine on the basis of leg 1, and the laterally positioned leg 5, the new species apparently belongs to the genus Pontoclausia which contains five known species ( Ho and Kim 2003). Within the genus Pontoclausia cochleata sp. nov. may be clearly defined from other species by its three unique features: (1) the mandible is unarmed, with a scoop-like distal part, rather than armed with one or two armature elements as in congeners; (2) the maxilliped is unsegmented and tipped with one seta, rather than segmented and unarmed as in congeners; and (3) the third exopodal segment of leg 1 is armed with eight armature elements (formula III, I, 4), rather than six or seven elements as in congeners. It is remarkable that the form of the mandible of the new species is very unusual for the Clausiidae . Nevertheless, we have refrained from establishing a new genus, since other features of mouthparts and legs are as usual for the genera within Clausiidae .

Figures

Figure 7. Pontoclausia cochleata sp. nov., female A habitus, dorsal B caudal rami, dorsal C antennule D antenna E labrum F mandible G maxillule H maxilla I distal segment of maxilla. Scale bars: 0.2 mm (A); 0.05 mm (B, C); 0.02 mm (D-I).

Figure 8. Pontoclausia cochleata sp. nov., female A maxilliped B leg 1 C leg 2 D leg 3 E leg 4 F leg 5. Scale bars: 0.02 mm (A); 0.05 mm (B-E); 0.1 mm (F).

Figure 9. Pontoclausia cochleata sp. nov., male A habitus, dorsal B urosome, dorsal C left caudal ramus, dorsal D maxilliped E leg 1 F distal part of endopod of leg 1. Scale bars: 0.1 mm (A); 0.05 mm (B, C); 0.02 mm (D, F); 0.05 mm (E).