Lichomolgus brevicaudatus, Kim & Boxshall, 2021

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods associated with Ascidian hosts (Tunicata): Intramolgidae and Lichomolgidae, with descriptions of four new genera and 13 new species, Zootaxa 5013 (1), pp. 1-75 : 37-41

publication ID	https://doi.org/ 10.11646/zootaxa.5013.1.1
publication LSID	lsid:zoobank.org:pub:BBB1CB11-1AEA-4678-8F6C-B43B7F35E453
persistent identifier	https://treatment.plazi.org/id/8D4A87BF-FF9F-FFA6-FF19-FB1F9D78FC54
treatment provided by	Plazi
scientific name	Lichomolgus brevicaudatus
status	sp. nov.

Treatment

Lichomolgus brevicaudatus sp. nov.

( Figs. 23–25 View FIGURE 23 View FIGURE 24 View FIGURE 25 )

Type material. Holotype ♀ (MNHN-IU-2014-21600) and paratype ♂ (MNHN-IU-2014-21601), plus 1 ♀, 1 ♂ dissected paratypes (MNHN-IU-2014-21488) from molycarpa sp. MNHN-IT-2008-6805 (= MNHN S1 About MNHN / Pol.B /326); About 1 mile West of Murex resort, West of Manado , Sulawesi, Indonesia, OCDN A5 , Site MANADO 12, CRRF coll., 14 May 1993.

Etymology. The specific name is derived from the Latin brev (=short) and caud (=the tail), alluding to the short caudal rami of the new species.

Description of female. Body ( Fig. 23A View FIGURE 23 ) consisting of ovoid prosome and small urosome; body length 1.02 mm; prosome 670×473 μm. Cephalothorax with faint, indistinct dorsal suture line between cephalosome and first pedigerous somite. Urosome ( Fig. 23B View FIGURE 23 ) 5-segmented; fifth pedigerous somite 109 μm wide; genital double-somite subcircular, expanded, slightly longer than wide (175×153 μm); genital apertures positioned dorsolaterally, slightly posterior to middle of double-somite. Three free abdominal somites not ornamented, 48×64, 36×57, and 34×59 μm, respectively. Caudal ramus ( Fig. 23C View FIGURE 23 ) 1.15 times longer than wide (31×27 μm); armed with 6 setae, all setae located subdistally or distally; setae IV-VI pinnate, other 3 setae naked. Egg sac cylindrical, 538×182 μm; each egg about 65 μm in diameter.

Rostrum ( Fig. 23E View FIGURE 23 ) with broadly rounded posterior margin. Antennule ( Fig. 23F View FIGURE 23 ) slender, 298 μm long, 7-seg- mented; armature formula 4, 13, 6, 3, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setae naked. Antenna ( Fig. 23G View FIGURE 23 ) 4-segmented, with armature formula 1, 1, 4, and 4+3 claws; one of 4 setae on third segment (second endopodal segment) minute, setule-like; terminal segment about 2.0 times longer than wide (44×22 μm); 3 terminal claws consisting of 1 strong, shorter outer claw and 2 longer, annulated setiform inner claws; largest distal seta longer than terminal segment.

Labrum ( Fig. 23H View FIGURE 23 ) with broad median incision and broad hyaline fringe along inner margin of posterior lobes. Mandible ( Fig. 23I View FIGURE 23 ) slender, with elongate distal lash and spinule row along both margins of blade and lash. Maxillule ( Fig. 23J View FIGURE 23 ) truncate distally, with produced inner distal corner, armed with 2 apical setae and 1 minute, subapical inner seta. Maxilla ( Fig. 24A View FIGURE 24 ) consisting of unarmed syncoxa and basis with elongate distal lash and 3 setae; distal lash bearing row of long spinules along proximal half of outer margin; inner seta (seta I) bearing row of spinules along outer margin; anterior seta (seta II) stiff, knife-shaped; proximal seta (seta III) minute. Maxilliped ( Fig. 24B View FIGURE 24 ) 3-segmented; first segment unarmed; second segment with 2 small, equal setae subdistally; third segment attenuated, claw-like, with 1 small seta proximally.

Legs 1-3 with 3-segmented rami. Outer spines on exopod of leg 1 ( Fig. 24C View FIGURE 24 ) serrate along proximal margin. Leg 3 same as leg 2 ( Fig. 24D View FIGURE 24 ) except third endopodal segment bearing 3 spines and 2 setae ( Fig. 24E View FIGURE 24 ). Leg 4 ( Fig. 24F View FIGURE 24 ) with 3-segmented exopod and 2-segmented endopod; distal endopodal segment 50×22 μm, with 1 dentiform process on outer margin; 2 terminal spines 18 μm (outer) and 49 μm (inner). Armature formula as in i. papuensẚs sp. nov.

Leg 5 exopodal segment ( Fig. 24G View FIGURE 24 ) subquadrate, 28×16 μm, about 1.75 times as long as wide, with 2 setae dis- tally; outer seta 75 μm, inner seta 35 μm. Leg 6 ( Fig. 24H View FIGURE 24 ) represented by 1 pinnate and 1 naked seta and 1 denticle on genital operculum.

Description of male. Body ( Fig. 25A View FIGURE 25 ) similar in form to that of female. Body length 785 μm long; prosome 509×345 μm. Dorsal suture line distinct between cephalosome and first pedigerous somite. Urosome ( Fig. 25B View FIGURE 25 ) 6- segmented; fifth pedigerous somite 79 μm wide, with small tubercle on ventral surface; genital somite subcircular, 130×144 μm. Four abdominal somites 32×55, 29×52, 26×53, and 21×52 μm, respectively. Caudal ramus as long as wide (25×25 μm), armed as in female.

Rostrum as in female. Antennule also as in female, without additional aesthetascs. Antenna as in female, but all 4 setae on second endopodal segment distinct, subequal in length.

Labrum, mandible, maxillule and maxilla as in female. Maxilliped ( Fig. 25C View FIGURE 25 ) 4-segmented; second segment with 3 longitudinal rows of spinules and 2 setae on inner surface, distal seta modified to digitiform element tipped with setule; terminal segment as long claw bearing 1 small and 1 large seta proximally.

Legs 1–4 as in female. Leg 5 ( Fig. 25D View FIGURE 25 ) exopod 21×15 μm, with convex outer margin; armed with 2 setae distally; outer seta 56 μm, inner seta 32 μm. Leg 6 ( Fig. 25B View FIGURE 25 ) represented by 2 equal, naked setae on genital oper- culum.

Remarks. iẚchomolgus brevẚcaudatus sp. nov. has short caudal rami, with a length/width ratio of 1.15: 1 in the female. Similarly short caudal rami with a ratio of less than 1.5:1 are found in five congeners: i. eganae Gotto, 1975, i. fusẚformẚs Kim I.H., 2009, i. ẚndẚcus, i. nakaẚẚ Matsuzaki & Ogawa, 1989, and i. pectẚnatus Moon & Kim I.H., 2011.

iẚchomolgus fusẚformẚs, i. nakaẚẚ and i. pectẚnatus each have 1 spine and 1 seta (rather than 2 setae as in the new species) on the exopod of leg 5, and i. ẚndẚcus lacks a dentiform process (present in the new species) on the outer margin of the distal endopodal segment of leg 4. Therefore iK brevẚcaudatus sp. nov. is easily distinguishable from these four species

The new species is similar to i. eganae which is associated with the ascidian Cnemẚdocarpa radẚcosa (Herdman, 1882) (as Cnemẚdocarpa etherẚdgẚẚ Hartmeyer) in Australia ( Gotto, 1975). The form of the genital doublesomite is particularly similar in these two species, but marked differences can be seen in the exopods of leg 5 of both sexes, and in the male maxilliped. The inner margin of the exopodal segment of female leg 5 is smooth in the new species but has a pointed process in i. eganae, and the exopodal segment of male leg 5 is inflated in the middle in the new species but gradually broadening in i. eganae (as described and illustrated by Gotto, 1975). In the male maxilliped, the second segment has one simple seta and 1 specialized seta in the new species but only a simple seta in i. eganae.