Pseudanthessius linguifer, 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

Pseudanthessius linguifer sp. nov.

Figs 20 , 21

Material examined.

Holotype ♀ (MABIK CR00250120) and intact paratypes 3 ♀♀ (MABIK CR00250121) preserved in 90% alcohol, and paratype ♀ dissected and mounted on a slide, Site 22 ( Yesong , Bogil Island, south coast, 34°08'11"N, 126°33'49"E), 31 May 2021, leg. J. Lee; ♀ dissected and mounted on a slide, Site 23 (Haenam, south coast, 34°17'57"N, 126°31'50"E), 24 Apr. 2021, leg. J. Lee and C. Y. Chang. Dissected specimens are retained in the collection of I.-H. Kim.

Description.

Female. Body (Fig. 20A ) narrow. Body length of dissected and figured paratype 1.23 mm (length range 1.17-1.32 mm, holotype 1.19 mm). Maximum width 385 μm across cephalothorax. Prosome 727 μm long. Cephalothorax 463 μm long, distinctly longer than wide, with weak dorsal suture line delimiting cephalosome and first pedigerous somite. Fourth pedigerous somite with point near posterolateral corners; other prosomal somites with rounded corners. Urosome (Fig. 20B ) shorter than prosome, five-segmented. Fifth pedigerous somite 102 μm wide. Genital double-somite ~ 1.5 × longer than wide (182 × 123 μm), consisting of narrow anterior 17%, inflated middle 49%, and narrow posterior 34%; dorsally covered by brownish sticky material; genital apertures characteristically positioned ventrolaterally (Fig. 21G ) at 45% region of double-somite length; broader middle region bearing linguiform process dorsolaterally, posterior to each genital aperture (Fig. 20C ); narrow posterior region with four horizontal membranous flanges (Fig. 20C ) on dorsal surface, anterior one short, curved. Three free abdominal somites 45 × 49 μm, 25 × 44 μm, and 56 × 42 μm, respectively. Anal somite with minute spinules along posteroventral margin. Caudal ramus (Fig. 20D ) elongate, 10 × longer than wide (155 × 15.5 μm), 2.77 × longer than anal somite, armed with six setae (seta II-VII); seta II (outer lateral seta) positioned at 78% length of ramus; setae IV-VI pinnate, other three setae naked.

Rostrum (Fig. 20E ) tapering, as long as wide, abruptly narrowed subdistally, with round apex. Antennule (Fig. 20F ) 295 μm long, seven-segmented; armature formula 4, 13, 6, 3, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setae thin, naked; aesthetascs also thin, setiform. Antenna (Fig. 20G ) four-segmented; first segment (coxobasis) with one seta inner distally; second segment (first endopodal segment) with one seta on inner margin and fine spinules along outer margin; third segment short, armed with one slender claw and two setae; terminal segment 3.28 × long than wide (77 × 23 μm), armed with four slender claws (inner and outer claws longer than middle two) plus three setae, and ornamented with fine spinules along outer margin.

Labrum (Fig. 20H ) with long, divergent posterolateral lobes, with deep median incision; each lobe with angle on inner margin; posterior margin of lobes fringed with membrane. Mandible (Fig. 20I ) with one large, tooth-like outer scale; gnathobase tapering, with row of minute spinules along inner margin, terminating in long, thin lash. Maxillule (Fig. 20J ) with four unequal setae (three apical and one on inner margin) and one blunt tubercle on outer margin; middle of three distal setae larger than other two. Maxilla (Fig. 21A ) two-segmented; proximal segment (syncoxa) unarmed; distal segment (basis) with extremely long distal lash and armed with two setae (setae I & II); distal lash longer than remaining part maxilla, bearing one large claw-like process proximally, spinulose along convex outer margin; seta I large, slightly longer than half length of distal lash, spinulose along both margins; seta II unequally bifurcate at tip, with setiform outer furca and spinule-like inner furca; seta III absent. Maxilliped (Fig. 21B ) three-segmented; first segment (syncoxa) longest but unarmed; second segment (basis) armed with two very unequal setae (proximal seta large, spiniform, longer than width of segment, more than 4 × as long as small distal seta), and ornamented with several longitudinal rows of fine spinules on inner surface; small third segment (endopod) tapering, claw-like, proximally with one spine and one small seta.

Legs 1-4 (Fig. 21C-F ) biramous. Legs 1-3 with three-segmented rami. Leg 4 with three-segmented exopod and one-segmented endopod. Inner coxal seta well-developed, pinnate in legs 1-4. Outer seta on basis thin, naked. Distal process between two distal spines on third endopodal segment of leg 2 blunt, slightly swollen. Three inner distal setae on third exopodal segment of legs 2 and 3 naked. Endopodal segment of leg 4 setulose on inner and outer margins, 2.6 × longer than wide (68 × 26 μm), bearing angle on outer margin; two distal spines 82 (inner) and 61 μm long (outer). Armature formula for legs 1-4 as follows:

Leg 5 (Fig. 21G ) represented by one spine and two setae on lateral surface of fifth pedigerous somite. Leg 6 (Fig. 21G ) represented on two setae on genital operculum; anterior seta thin, weakly pinnate; posterior seta naked, proximally broadened.

Male. Unknown.

Etymology.

The specific name of the new species linguifer is derived from Latins lingu (the tongue) and fer (bear), referring to the presence of the tongue-like dorsolateral processes on the genital double-somite.

Remarks.

The most conspicuous feature of Pseudanthessius linguifer sp. nov. is its elongate caudal rami, which are 10 × longer than wide. Such long caudal rami are exhibited by four congeners: P. concinnus Thompson & Scott, 1903, P. dubius Sars, 1918, P. thorelli (Brady & Robertson, 1875), and P. stenosus Kim & Hong, 2014. All of the other species in the genus have shorter caudal rami, at most 8.5 × longer than wide, as in P. deficiens Stock, Humes & Gooding, 1964 ( Stock et al. 1964). Pseudanthessius linguifer sp. nov. differs from P. concinnus in having a large outer scale on the mandible (cf. the scale absent in P. concinnus ) and two distal spines on the endopod of leg 4 (cf. one spine plus one seta in P. concinnus ); from P. dubius in having the five-segmented urosome in the female (cf. four-segmented female urosome in P. dubius ) and four distal claws on the antenna (cf. a single large claw in P. dubius ); and from P. thorelli in having one spine plus one seta on the exopod of female leg 5 (cf. two setae in P. thorelli ). Pseudanthessius linguifer sp. nov. resembles P. stenosus which is known from Thailand ( Kim and Hong 2014) in many morphological aspects, in particular, the possession of the spinules-covered second segment (basis) of the female maxilliped and the bifurcate anterior seta (seta II) on the basis of the maxilla. However, the new species is distinguishable from P. stenosus and other congeners by its other outstanding features, such as the presence of the tongue-like dorsolateral processes on the genital double-somite, the extremely long distal lash of the maxilla, and the ventrolateral position of the genital apertures.

Figures

Figure 20. Pseudanthessius linguifer sp. nov., female A habitus, dorsal B urosome, dorsal C proximal somites of urosome, dorsal D left caudal ramus, dorsal E rostrum F antennule G antenna H labrum I mandible J maxillule. Scale bars: 0.2 mm (A); 0.05 mm (B- D, F, G); 0.02 mm (E, H-J).

Figure 21. Pseudanthessius linguifer sp. nov., female A maxilla B maxilliped C leg 1 D leg 2 E third endopodal segment of leg 3 F leg 4 G leg 5 and genital aperture, dorsal. Scale bars: 0.02 mm (A, B); 0.05 mm (C-G).