Antarctomolgus, 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 : 47-48

Antarctomolgus gen. nov.

Diagnosis. Lichomolgidae . Body cyclopiform. Urosome 5-segmented in female, 6-segmented in male. Caudal ramus with 6 setae; 2 median terminal setae (setae IV and V) flattened, tape-like. Rostrum distinct. Antennule 7-segmented, with armature formula 3, 10, 5, 3, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc in female. Male antennule with 3 additional aesthetascs: 2 on second segment and 1 on fourth. Antenna 4-segmented; third segment (second endopodal segment) with 1 setiform claw and 3 setae; terminal segment with 4 claws and 3 setae. Mandible with elongate distal lash and 1 spine on outer side at base of blade. Maxillule with 4 setae. Maxilla consisting of syncoxa and basis; basis with elongate, spinulose distal lash and 3 setae; inner seta (seta I) large. Maxilliped 3-segmented in female and 4 segmented (fourth segment as claw) in male, as in iẚchomolgus. Legs 1-4 biramous, with 3-segmented rami. Third endopodal segment of leg 1 armed with 1 spine and 5 setae (formula I, 1, 4) in female and with 2 spines and 4 setae (formula I, I, 4) in male. Third exopodal segment of leg 3 armed with 3 spines and 5 setae (formula II, I, 5). Third endopodal segment of leg 4 armed with 3 spines. Armature formula for legs 1-4 of female 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 consisting of dorsolateral seta on fifth pedigerous somite and 1-segmented free exopod armed with 1 spine and 1 seta distally. Leg 6 represented by 2 setae and 1 denticle on genital operculum.

Type species. Antarctomolgus molgulae gen. et sp. nov. by original designation.

Etymology. The new name combines the Antarctic, the region from which the type species was collected and – molgus, a common suffix of lichomolgid genera. Gender masculine.

Remarks. In the Lichomolgidae eight genera have a 3-segmented endopod of leg 4, as in Antarctomolgus gen. nov. These eight genera are aẚogenella Stock, 1968, aẚogenẚdẚum Edwards, 1891, eenẚcoxẚphẚum, eerrmannella Canu, 1891, iẚchomolgẚdẚum, Modẚolẚcola Aurivillius, 1882, mrotomolgus, and mterẚoẚdẚcola. Of these, eenẚcox- ẚphẚum has a single spine on the third endopodal segment of leg 4 (armature formula for the endopod 0-1; 0-1; 0, I, 0) and almost all species of the remaining six genera have two spines on the third endopodal segment (armature formula 0-1; 0-1; 0, II, 0), except a single species of eerrmannella, e. panopeae (Illg, 1949), which bears 3 spines on the same segment (armature formula 0-1; 0-1; I, II, 0), as in Antarctomolgus molgulae gen. et sp. nov. Humes & Stock (1973) mentioned that the future discovery of similarly armed species would indicate generic separation of e. panopeae from the genus eerrmannella. eerrmannella consists of 28 known species ( Boxshall & Halsey, 2004; Kim & Sato, 2010; Varela, 2011), all of which are associated with bivalve molluscs ( Humes & Stock, 1972; 1973; Humes & Boxshall, 1996) K

Antarctomolgus molgulae gen. nov. et sp. nov. cannot be assigned to eerrmannella due to three important differences. Firstly, the terminal segment of the antenna of the new genus has 4 slender claws, in contrast to 1 strong claw and 1 or 2 setiform claws in eerrmannella ( Humes & Stock, 1973; Humes & Boxshall, 1996). Secondly, the third exopodal segment of leg 3 is armed with 3 spines and 5 setae (formula II, I, 5), compared to 4 spines and 5 setae (formula III, I, 5) in eerrmannella. Thirdly, the mandible of Antarctomolgus molgulae gen. et sp. nov. has a spiniform outer scale, which is lacking in eerrmannella. In the Lichomolgidae the presence of the outer scale on the mandible has been reported only in the genera Botulosoma , Zygomolgus and keomenẚcola Avdeev & Avdeev, 1991 ( Boxshall & Halsey, 2004), although the latter genus appears to belong to the family Anthessiidae since it possesses a distal aesthetasc on the fourth antennular segment. On the basis of this evidence, Antarctomolgus gen. nov. is established to accommodate AK molgulae gen. et sp. nov.