Antarctomolgus molgulae, 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 : 48-52

Antarctomolgus molgulae gen. et sp. nov.

( Figs. 30–32 )

Type material. Holotype ♀ (MNHN-IU-2009-5724) and paratypes (1 ♀, 8 ♂♂, MNHN-IU-2014-21604) plus 1 ♀ and 1 ♂ dissected paratypes (MNHN-IU-2014-21490) from Molgula pedunculata (Herdman, 1881) MNHN-IT- 2008-5697 (= MNHN S3 /MOL A/389): Antarctic, 65°29´S, 139°24´E, CEAMARC Expedition, Terre Adélie , RV “ Aurora Australis”, Stn 86EEV518, depth 781-835 m, IPEV-AAD-MNHN coll. 16 January 2008.

Etymology. The generic name of the ascidian host provides the name of the new species.

Description of female. Body ( Fig. 30A ) moderately broad. Body length of dissected specimen 1.57 μm (other 2 specimens 1.56 and 1.60 mm); prosome ovoid, 972×658 μm. Dorsal suture line between cephalosome and first pedigerous somite indistinct. Epimera of second pedigerous somite with slightly extended posterolateral corners. Urosome ( Fig. 30B ) 5-segmented; fifth pedigerous somite 183 μm wide; genital double-somite 212×190 μm, wid- est in middle, with laterally expanded anterior two-thirds and narrower posterior third; genital apertures positioned dorsolaterally, slightly anterior to middle. Three free abdominal somites 61×100, 48×92, and 77×89 μm, respec- tively. Genital double-somite and first 2 abdominal somites each bearing narrow membranous fringe along posterior border. Caudal ramus ( Fig. 30C ) broad, about 3.3 times longer than wide (137×41 μm); armed with 6 naked setae; outer lateral seta located about at 70% of ramus length; 2 mid-terminal setae (setae IV and V) flattened, tape-like.

Rostrum ( Fig. 30D ) tapering towards rounded apex. Antennule ( Fig. 30E ) 406 μm long, 7-segmented; armature formula 3, 10, 5, 3, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setae naked. Antenna ( Fig. 30F ) 4-segmented; armature formula 1, 1, 3+claw, and 3+4 claws; claw on third segment (second endopodal segment) thin, setiform; terminal segment about 1.8 times longer than wide (77×42 μm), second and terminal segments ornamented with fine spinules along outer margin; 4 terminal claws unequal in length, inner 2 setiform.

Labrum ( Fig. 30G ) deeply incised, with convex lateral margins; posterior lobes with straight lateral margins and convex, sloping inner margins. Mandible ( Fig. 30H ) with 1 slender spine-like scale on convex side at base of blade; broadened blade with elongate, slender distal lash, finely serrate along outer margin and setulose on inner margin. Maxillule ( Fig. 30I ) broadening distally, with oblique distal margin bearing 4 naked setae. Maxilla ( Fig. 31A ) consisting of syncoxa and basis; syncoxa unarmed; basis with elongate distal lash bearing long spinules along outer margin, and armed with 3 setae; inner seta (seta I) about half as long as distal lash, bearing row of spinules along outer margin; anterior seta (seta II) slightly broadened along proximal half; proximal seta (seta III) minute. Maxilliped ( Fig. 31B ) 3-segmented; first segment unarmed; second segment with 2 equal setae at distal third of inner side; third segment acutely pointed, bearing 1 small seta proximally.

Legs 1–4 ( Figs. 31C–E , 32A ) with 3-segmented rami. Inner coxal setae distinct, pinnate. Outer seta on basis of legs 1-4 naked. Third exopodal segment of legs 3 and 4 armed with 3 spines and 5 setae. Leg 4 ( Fig. 32A ) endopod as long as exopod; third endopodal segment armed with 1 small outer spine and 2 larger distal spines. Armature formula for legs 1–4 as follows:

Coxa Basis Exopod Endopod

Leg 1: 0-1 1-0 I-0; I-1; III, I, 4 0-1; 0-1; I, 1, 4

Leg 2: 0-1 1-0 I-0; I-1; III, I, 5 0-1; 0-2; I, II, 3

Leg 3: 0-1 1-0 I-0; I-1; II, I, 5 0-1; 0-2; I, II, 2

Leg 4: 0-1 1-0 I-0; I-1; II, I, 5 0-1; 0-1; I, II, 0

Leg 5 ( Fig. 30B ) consisting of dorsolateral seta on fifth pedigerous somite and free exopod; exopodal segment ( Fig. 31F ) elongate, about 3.2 times longer than wide (97×30 μm), distally with 1 dentiform process, and armed with 1 naked, wrinkled seta (78 μm long) and 1 spine (45 μm long) with membranous flanges bilaterally. Leg 6 ( Fig. 31G ) represented by 2 naked setae and 1 denticle on genital operculum.

Description of male. Body ( Fig. 32B ) narrower than that of female; body length 1.35 mm. Prosome 764×445 μm; lateral margins of cephalothorax nearly parallel. Urosome ( Fig. 32C ) 6-segmented; fifth pedigerous somite nar- row, 135 μm wide; genital somite subcircular, 261×241 μm. Four abdominal somites unornamented, 48×79, 46×73, 38×67, and 62×77 μm, respectively. Caudal ramus broad, about 2.8 times longer than wide (108×38 μm), armed as in female.

Rostrum as in female. Antennule with 3 short, additional aesthetascs: 2 on second segment and 1 on fourth, as indicated by dots in Fig. 30E . Antenna as in female.

Labrum, mandible, maxillule, and maxilla as in female. Maxilliped ( Fig. 32D ) 4-segmented; first segment unarmed, with convex swellings along inner margin and convex outer margin; second segment with spinules on inner side and 2 equal setae near roundly produced part of inner margin; small third segment unarmed; fourth segment as slender, elongate, arched claw bearing 2 unequal, naked setae proximally.

Leg 1 ( Fig. 32E ) with third endopodal segment armed with 2 spines and 4 setae (armature formula I, I, 4); outer spine smooth, but distal spine with membranous flanges. Legs 2–4 as in female.

Leg 5 similar to that of female; exopodal segment ( Fig. 32F ) about 3.0 times longer than wide (63×21 μm). Leg 6 ( Fig. 32C ) represented by 2 small setae and 1 denticle on genital operculum.

Remarks. The host ascidian Molgula pedunculata serves as host to four other species of copepods from the Monniot collection: Archẚnotodelphys antarctẚcus Kim & Boxshall, 2020, Bonnẚerẚlla tahẚtẚensẚs Kim & Boxshall, 2020, aoropygus tuberculatus Kim & Boxshall, 2020, and aK kerguelensẚs Schellenberg, 1922 ( Kim & Boxshall, 2020a, b).

Figures

FIGURE 30. Antarctomolgus molgulae gen. et sp. nov., female. A, habitus, dorsal; B, urosome, dorsal; C, right caudal ramus, dorsal; D, rostral area; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule. Scale bars: A, 0.2 mm; B, 0.1 mm; C–G, 0.05 mm; H, I, 0.02 mm.

FIGURE 31. Antarctomolgus molgulae gen. et sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 3; F, exopod of leg 5; G, left genital aperture, dorsal. Scale bars: A, F, G, 0.02 mm; B–E, 0.05 mm.

FIGURE 32. Antarctomolgus molgulae gen. et sp. nov., female. A, leg 4. Male: B, habitus, dorsal; C, urosome, ventral; D, maxilliped; E, leg 1; F, exopod of leg 5. Scale bars: A, D, E, 0.05 mm; B, 0.2 mm; C, 0.1 mm; F, 0.02 mm.