Notoixys, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 510-512

Notoixys gen. nov.

Diagnosis. Body inflated, usually with unsegmented, globular metasome. Dorsal cephalic shield expanded ventrolaterally, with paired horn-like processes posterolaterally. Fifth pedigerous somitecompletely fused with fourth. Free urosome 5-segmented. Caudal setae small or absent. Rostrum well-developed.Antennule 7- to 10-segmented. Antenna 4-segmentedwith 2-segmented endopod bearingsmallterminal claw. Mandiblewith coxal gnathobase bearing narrow medial cutting margin; armed with 1 seta on basis, 5 setae on exopod, 1 seta on first endopodal segment, and 4 to 7 setaeon second. Maxillule armedwith 5 or 6 setaeon arthrite, 1 setaon epipodite, 1 or 2 setaeon basis, 4 setaeon exopod, and 3 setaeon endopod; coxal endite absent. Maxilla 5-segmented with 3-segmented endopod; syncoxa bearing 4 endites; basis with 3 setae (or 2 setae plus claw). Maxilliped as unsegmented lobe bearing 3 to 5 setae. Legs 1–4 biramous; segmentation of rami frequently incompletely expressed. Inner coxal seta present at least in leg 1. Leg 1 with inner distal element on basis; exopod 3-segmented, with inner seta on first and second segments, and 7 or 8 setae on third segment. Leg 2 exopod 3-segmented, with inner seta on first and second segments. Exopods of legs 3 and 4 usually with inner seta on first or second, or both segments. Endopods of legs 2–4 usually with inner seta on first or second, or both segments. Leg 5 rudimentary or absent.

Type species. Notoixys heardensis gen. et sp. nov. by original designation.

Other included species. Notoixys hirsuta gen. et sp. nov., N. ovata gen. et sp. nov. and Notoixys planiceps gen. etsp. nov.

Etymology. The generic name is derived from the combination of noto (=”south” in Greek) and - ixys, the ending of several existing genera of the Notodelphyidae . The name alludes to the zoogeographic distribution of the new genus in the Antarctic or Southern Ocean.

Remarks. Notoixys gen. nov. can be distinguished from Loboixys and Doroixys by the more complex state of the armature on the oral appendages and swimming legs. Unlike the latter two genera, Notoixys gen. nov. has a 3-segmented endopod in the maxilla (cf. 2-segmented in Doroixys and 1- or 2-segmented in Loboixys ), and anarrow cutting edge on the coxal gnathobase in the mandible (vs. broad medial margin in Doroixys and Loboixys ). It also differs from Loboixys in having an inner seta on the first and second exopodal segments of legs 1 and 2, whereas setae on these segments are lacking in Loboixys . It also differs from Doroixys in having an inner seta on the proximal segment(s) of endopods of legs 2–4 (vs. lacking in Doroixys ) and it lacks a tapering (exopodal) process on leg 5 which is present in Doroixys .

The four species of Notoixys gen. nov. described in the present work live in association with compound ascidians of the genus Aplidium in the Antarctic Ocean.