Lichomolgella exigua, Lee & Kim, 2025

Lee, Jimin & Kim, Il-Hoi, 2025, Three new species of Lichomolgella Sars G. O., 1918 (Copepoda, Cyclopoida, Sabelliphilidae) associated with Bryozoa in Korea, ZooKeys 1244, pp. 195-211 : 195-211

publication ID	https://doi.org/10.3897/zookeys.1244.155561
publication LSID	lsid:zoobank.org:pub:8A6E974D-C606-4BA3-975D-F7AF60964756
DOI	https://doi.org/10.5281/zenodo.15856251
persistent identifier	https://treatment.plazi.org/id/4F717DA0-9BE9-5A5E-95F0-B491B52FE585
treatment provided by	ZooKeys by Pensoft
scientific name	Lichomolgella exigua
status	sp. nov.

Treatment

Lichomolgella exigua sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3

Type locality.

A tidal pool at northeastern tip of Yeongjong Island GoogleMaps (37°29'27"N, 126°35'00"E), Incheon, Korea.

Type material.

• Holotype (intact ♀; MABIK CR 00258577 ) and paratypes (intact 40 ♀♀, 7 ♂♂; MABIK CR 00258578 ) from washings of several colonies of the bryozoan Celleporina porosissima Harmer, 1957 , 19 April 2022, collected by I.-H. Kim GoogleMaps . Type material has been deposited in the Marine Biodiversity Institute of Korea ( MABIK), Seocheon, Korea. Dissected and figured specimens are kept in the collection of I.-H. Kim.

Etymology.

The specific name exigua is derived from the Latin exigu (small), referring to the small body size of the new species.

Description.

Female. Body (Fig. 1 A View Figure 1 ) small, cyclopiform. Body length 405 μm in figured specimen, 393–430 μm in other 10 measured specimens. Prosome occupying 70 % of body length. Cephalothorax 197 × 167 μm, ovoid, dorsoventrally deep, without dorsal suture line defining cephalosome and first pedigerous somite. Second to fourth pedigerous somites rapidly narrowing from anterior to posterior ones. Urosome (Fig. 1 B View Figure 1 ) 5 - segmented. Fifth pedigerous somite 30 μm wide. Genital double-somite distinctly longer than wide (50 × 38 μm), abruptly narrowing along posterior 15 % region; genital apertures positioned ventrolaterally (Figs 1 B View Figure 1 , 2 E View Figure 2 ), with large process bearing 2 very unequal setae. Three abdominal somites 10 × 28, 7 × 27, and 15 × 30 μm, respectively. Caudal ramus broad, 1.14 times longer than wide (16 × 14 μm), with 6 setae; two median terminal setae (setae IV and V) broadly flattened, tape-like; outer seta (seta II) positioned slightly distal to middle of outer margin.

Rostrum (Fig. 1 C View Figure 1 ) small, strongly tapering. Antennule (Fig. 1 D View Figure 1 ) short, 91 μm long, less than half length of cephalothorax, 7 - segmented; armature formula 3, 11, 6, 3, 4 + aesthetasc, 2 + aesthetasc, and 7 + aesthetasc; all setae naked. Antenna (Fig. 1 E View Figure 1 ) stout, 4 - segmented; armature formula 1, 1, 3 + claw, and 3 + 4 claws; second segment (first endopodal segment) 1.74 times longer than wide (33 × 19 μm), with pointed outer distal corner; third segment (second endopodal segment) small, armed with 1 claw and 3 setae; fourth segment 1.23 times longer than wide (16 × 13 μm), characteristically attached to slightly outer region of third segment, outermost one of 4 distal claws slender, setiform.

Labrum (Fig. 1 F View Figure 1 ) with rather elongated, divergent posterior lobes; each lobe bearing small denticle (indicated by an arrowhead) at proximal region of inner margin. Mandible (Fig. 1 G View Figure 1 ) with short inner margin, lacking inner notch; gnathobase with 1 large claw-like scale at outer proximal corner followed by denticulate convex margin, 1 row of more than 10 small spinules along midline of one surface, and smooth concave margin; distal region of gnathobase blunt, lamellated. Maxillule (Fig. 1 H View Figure 1 ) with 3 unequal, naked setae apically. Maxilla (Fig. 1 I View Figure 1 ) 2 - segmented; proximal segment (syncoxa) unarmed; distal segment (basis) distally with 4 teeth, distalmost one much smaller than proximal ones, and terminating in small, setule-like lash; inner seta (seta I) large, proximally broadened, with about 7 spinules along distal margin and several minute spinules along distal half of inner margin; seta II naked, slender; seta III absent. Maxilliped (Fig. 1 J View Figure 1 ) 3 - segmented; first segment narrow, unarmed; second segment as long as first, strongly inflated, with protruded inner margin bearing 2 naked setae, proximal seta larger than distal; third segment small, with 2 unequal, elongated spiniform processes and 1 proximal seta.

Legs 1–3 (Fig. 2 A – C View Figure 2 ) each with 3 - segmented exopod and 2 - segmented endopod. Leg 4 (Fig. 2 D View Figure 2 ) with 3 - segmented exopod and 1 - segmented endopod. Spines on rami large, distinctly serrate. Third exopodal segment of legs 3 and 4 armed with 3 spines and 5 setae (formula II, I, 5). Leg 4 lacking inner coxal seta; endopodal segment 1.8 times longer than wide (18 × 10 μm), with denticle-like process at inner distal corner; 2 distal spines 13 (outer) and 19 μm (inner). Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 2 E View Figure 2 ) consisting of 1 small dorsolateral seta on fifth pedigerous somite and small exopod; exopodal segment 11 × 6 μm, with 1 small denticle-like processes distally and armed with 2 distal setae; outer seta 31 μm long, inner seta short, spiniform, 8 μm long. Leg 6 (Fig. 2 E View Figure 2 ) represented by digitiform process in genital aperture, bearing 1 small outer setule and 1 large distal seta of 33 μm long, latter seta extending to posterior margin of anal somite, pinnate along its distal third.

Male. Body (Fig. 3 A View Figure 3 ) similar to that of female but narrower. Body length 376 μm. Cephalothorax 185 × 138 μm. Urosome (Fig. 3 B View Figure 3 ) 6 - segmented. Genital somite 1.2 times longer than wide (51 × 42 μm), with slightly convex lateral margins and slightly concave dorsodistal margin. Caudal ramus 1.25 times longer than wide (15 × 12 μm), armed as in female.

Rostrum as in female. Antennule with 3 additional aesthetascs, 2 on second segment and 1 on fourth segment, as indicated by dark circles in Fig. 1 D View Figure 1 . Antenna as in female, lacking additional ornamentation.

Labrum, mandible, maxillule, and maxilla as in female. Maxilliped (Fig. 3 C View Figure 3 ) consisting of 3 segments and terminal claw; first segment unarmed; second segment (basis) with blunt protrusion at proximal region, 2 equally small, naked setae and row of spinules along inner margin; third segment small and unarmed; terminal claw elongate, arched, proximally bearing 1 large, naked seta and on opposite side 1 small setule.

Legs 1–4 as in female. Leg 5 (Fig. 3 B View Figure 3 ) also as in female; exopodal segment (Fig. 3 D View Figure 3 ) 11 × 7 μm; lengths of 2 distal setae 8 (inner) and 30 μm (outer). Leg 6 (Fig. 3 B View Figure 3 ) represented by 1 large seta, 1 setule and 1 small denticle on genital operculum.

Remarks.

While describing Lichomolgella isseli, Gallingani (1952) stated that no noteworthy differences were found in appendages between this species and the type species of the genus, L. pusilla , except for the antennule and antenna. According to her, L. isseli differed from L. pusilla in proportional lengths of segments of the antennule and the long second segment of the antenna. However, she did not provide specific measurements for these appendage segments. In addition, the antennule illustrated in that paper does not exhibit any taxonomic significance. However, in the illustration of the antenna, the second segment (first endopodal segment) is elongated, and Humes and Stock (1973) measured this segment as being 3.5 times longer than wide, a characteristic that allowed them to differentiate L. isseli from L. pusilla .

Lichomolgella exigua sp. nov. can be clearly distinguished from the two existing species, as the endopods of legs 1–3 of the new species are all two-segmented, in contrast to the three-segmented condition in L. pusilla and L. isseli . In the forms of the antenna and genital double-somite, L. exigua sp. nov. is more similar to L. pusilla than to L. isseli , but still exhibits several differences from the former: (1) the fourth segment of the antenna is armed with four claws and three setae (vs one claw and five setae in L. pusilla ); (2) the mandible is bluntly terminated (vs distally attenuated in L. pusilla ); and (3) the third segment of the female maxilliped bears two spiniform processes and one seta (vs one spiniform process and one seta in L. pusilla ). These and other differences between species are summarized in Table 1 View Table 1 .