Eupolymniphilus foliatus, 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

Eupolymniphilus foliatus sp. nov.

Figs 22 , 23 , 24

Material examined.

Holotype ♀ (MABIK CR00250130) and paratype ♂ dissected and mounted on a slide, and intact paratypes 2 ♂♂ (MABIK CR00250122) preserved in 90% alcohol, Site 2 ( Namyang , Ulleung Island, Sea of Japan, 37°28'01.3"N, 130°50'01.4"E), 01 Jul. 2021, leg. J. G. Kim. Dissected paratype (♂) is retained in the collection of I.-H. Kim.

Description.

Female. Body (Fig. 22A ) moderately broad. Body length 1.44 mm. Prosome 840 × 586 μm, fusiform. Cephalothorax with dorsal suture line delimiting cephalosome and first pedigerous somite. Second to fourth pedigerous somites bearing angular posterolateral corners. Urosome (Fig. 22B ) five-segmented. Fifth pedigerous somite expanded laterally, wider than genital double-somite, with sleeve-like, pronounced posterolateral corners. Genital double-somite longer than wide (210 × 184 μm), with convex lateral margins, widest at 45% region of double-somite. Three free abdominal somites 59 × 106 μm, 45 × 95 μm, and 80 × 91 μm, respectively. Anal somite unornamented, lacking any spinules. Caudal ramus (Fig. 22C ) 3.33 × longer than wide (130 × 39 μm), ~ 1.6 × longer than anal somite, armed with six setae; seta II slightly expanded along proximal third, positioned dorsally at 56% region of ramus length.; setae IV-VI pinnate, other setae naked.

Rostrum (Fig. 22D ) well-developed, slightly wider than long, with blunt apex. Antennule (Fig. 22E ) 340 μm long, seven-segmented; first and second segments broader than distal segments; armature formula 4, 13, 6, 3, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setae naked; third and terminal segments equally short. Antenna (Fig. 22F ) four-segmented; armature formula 1, 1, 3+claw, and 4+3 claws; terminal segment (third endopodal segment) 2.65 × longer than wide (61 × 23 μm); claws on third and terminal segments slender, setiform; apical seta on terminal segment distinctly longer than other setae on same segment; innermost of three claws on terminal segment shorter than others.

Labrum (Fig. 22G ) with distinctly defined, divergent posterolateral lobes and broad posteromedian incision. Mandible (Fig. 22H ) with gnathobase bearing finely denticulate convex outer margin, ~ 15 unequal spinules along concave inner margin, and distal lash fringed with wrinkled membrane along outer margin and narrow membrane along inner margin; inner proximal region of gnathobase lacking notch; outer proximal region of blade with one small, indistinct scale. Maxillule (Fig. 22I ) lobate, with one expanded, leaf-like, modified seta on inner margin and three (one longer and two shorter) apical setae. Maxilla (Fig. 22J ) two-segmented; proximal segment (syncoxa) unarmed; distal segment (basis) distally with five spinules followed by three larger spinules and slender, spinulose lash, and armed with three setae (seta I-III); seta I (inner seta) large, spinulose along distal (outer) margin; seta II (anterior seta) slightly broadened, with acute distal tip; seta III (outer proximal seta) rudimentary. Maxilliped (Fig. 23A ) three-segmented; first segment unarmed; second segment with two unequal setae subdistally; third segment narrow, pointed distally, with one small, subdistal seta.

Legs 1-4 (Fig. 23B-D ) biramous with three-segmented rami; outer seta on basis small, naked. Inner coxal seta of all swimming legs well-developed, pinnate. Armature formula for legs 1-4 as follows:

Leg 5 (Fig. 23F ) consisting of one small dorsolateral seta on fifth pedigerous somite and exopod; exopodal segment small, 1.59 × longer than wide (46 × 29 μm), widest at proximal third, narrowing distally, armed with one seta (60 μm long) and one elongate compound spine (117 μm long). Leg 6 (Fig. 23F ) represented two small setae and single denticle on genital operculum

Male. Body (Fig. 24A ) narrower and smaller than that of female. Body length 847 μm in dissected paratype (length range 782-847 μm). Prosome 495 × 287 μm. Urosome (Fig. 24B ) six-segmented. Fifth pedigerous somite 109 μm wide, lacking posterolateral sleeve-like extension seen in female. Genital somite subquadrate, 127 × 124 μm, with rounded anterolateral corners and pointed posterolateral corners; genital operculum with pointed apex. Four abdominal somites 36 × 60 μm, 29 × 55 μm, 22 × 51 μm, and 36 × 56 μm, respectively. Caudal ramus 2.40 × longer than wide (60 × 25 μm), armed as in female.

Rostrum as in female. Antennule as in female, but with three additional aesthetascs at places of dark circles in Fig. 21E . Antenna, labrum, mandible as in female. Maxillule (Fig. 24C ) with less expanded inner margin seta. Maxilla as in female. Maxilliped (Fig. 24D ) consisting of three segments and terminal claw; first segment with one large tubercle at inner subdistal region; second segment with two unequal setae and one longitudinal row of spinules; small third segment unarmed; terminal claw elongate, as long as three segments, arched, bearing one setule and one large, slightly undulated seta proximally.

Legs 1-5 as in female. Leg 6 represented by two small setae on genital operculum (Fig. 24B ).

Etymology.

The specific name of the new species is from Latin foli (a leaf), alluding to the leaf-like inner seta of the maxillule.

Remarks.

Differences between species of Eupolymniphilus are slight. However, E. foliatus sp. nov. can be differentiated from its congeners by the key character, the leaf-like modified inner seta of the maxillule. This seta in other species of the genus is known to be simple and slender. Another characteristic feature of the new species is the presence of thick membranes on the distal part of the mandibular lash.

The length-to-width ratio of the caudal ramus in Eupolymniphilus is somewhat variable among congeneric species. In the female, it is 3.5:1 in E. finmarchicus (Scott T., 1903) according to the illustration of G. O. Sars (1918), ~ 10:1 in E. tenuicaudis (G. O. Sars, 1918), 1.50:1 in E. orientalis Kim, 2006, 1.03:1 in E. brevicaudatus Kim, 2009, 2.69:1 in E. occidentalis Kim, 2009, and 3.05:1 in E. mediterraneus Costanzo, Brugnano & Zagami, 2013. Thus, E. foliatus sp. nov., in which the caudal ramus is 3.33 × longer than wide, is comparable to the three species, E. finmarchicus , E. occidentalis , and E. mediterraneus . Furthermore, they differ from the new species, as follows: E. finmarchicus has five setae on the first segment of the antennule ( Bocquet et al. 1963), and the mandible lacks any outer scale; E. occidentalis has acutely pointed posterolateral corners on the second pedigerous somite (cf. with blunt posterolateral corners in E. foliatus sp. nov.), seven aesthetascs on the male antennule (cf. six aesthetascs in E. foliatus sp. nov.), and a shorter terminal segment of the antenna which is 1.92 × longer than wide according to Kim (2009) (cf. 2.65 × longer than wide in E. foliatus sp. nov.); and E. mediterraneus has a small body size, 0.75 mm in the female, and the terminal segment of the antenna bears four claws ( Costanzo et al. 2013) (cf. three claws in E. foliatus sp. nov.).

Figures

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).

Figure 22. Eupolymniphilus foliatus sp. nov., female A habitus, dorsal B urosome, dorsal C left caudal ramus, dorsal D rostrum E antennule F antenna G labrum H mandible I maxillule J maxilla. Scale bars: 0.2 mm (A); 0.1 mm (B); 0.05 mm (C-G); 0.02 mm (H-J).

Figure 23. Eupolymniphilus foliatus sp. nov., female A maxilliped B leg 1 C leg 2 D third endopodal segment of leg 3 E leg 4 F left leg 5 and genital aperture. Scale bars: 0.02 mm (A); 0.05 mm (B-F).

Figure 24. Eupolymniphilus foliatus sp. nov., male A habitus, dorsal B urosome, dorsal C maxillule D maxilliped. Scale bars: 0.1 mm (A); 0.05 mm (B); 0.02 mm (C, D).