Borixys, 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 : 523

Borixys gen. nov.

Diagnosis. Body inflated. Dorsal cephalic shield lacking posterolateralhorn-like processes. Freeurosome 5- segmented. Caudal rami setulose; caudal setae obscure. Rostrum well-developed. Antennule 7-segmented, tapering. Antenna 4-segmented, consistingof coxa, basis, and 2-segmented endopod with small terminal claw. Mandible with large coxal gnathobase bearing 5 teeth; palparmedwith 1 setaon basis, 5 on exopod, 1 on first endopodal segment and 7 on second. Maxillule with 9 setae on arthrite, 1 each on epipodite and basis, 4 onexopodand 3 on endopod. Maxilla 4-segmented with 4, 1, and 2 setae on first to third endites of syncoxa, strong claw plus 2 setae on basis, 1 and 3 setae on first and secondendopodal segments, respectively. Maxilliped as unsegmented lobe bearing several setae. Legs 1–4 biramous with 2-segmented protopods and 3-segmented rami. Leg 5 represented by outer protopodal seta and inner lobe bearing exopodal seta.

Typeandonly species. Borixyssimplex ( Marchenkov & Boxshall, 2004) comb. nov. (originally as Doroixys simplex ), by original designation.

Etymology. The name is derived from the Greek boreios (=northern) and refersto the known distribution of the type species in the North Pacific. Gender feminine.

Remarks. There were only three species in the genus Doroixys at the time Marchenkov & Boxshall (2004) described D. simplex . The addition of multiple new species to this genus in the present work allows generic boundaries to be re-assessed and we consider that it is necessary to place D. simplex in a separate genus. We establish Borixys gen. nov. to accommodate D. simplex as type species, and the new genus can be differentiated from Doroixys by the absence of the paired horn-likeprocesses on the posterolateral corners of the dorsal cephalic shield, by the reduction of leg 5 to single protopodal and exopodal setae each carried on a small, ill-defined lobe, and by the presence of the inner setaon the first and second exopodal segments of legs 2–4. The new genus differs from Prodoroixys gen. nov. by the lack of the coxal endite on the maxillule (cf. present and armed with a single seta in the latter), by the presence of a single setaon the maxillular basis (cf. 2 setae in Prodoroixys gen. nov.), and by the 2-segmented endopod of the maxilla (cf. 3-segmented in Prodoroixys gen. nov.). The new genus differs from Notoixys gen. nov. by the presence of 5 teeth on the broad coxalgnathobase of the mandible (cf. a narrow coxalgnathobase in Notoixys gen. nov.), by the 2-segmented endopod of the maxilla (cf. 3-segmented in Notoixys gen. nov.), and by the absence of the horn-like processes on the dorsal cephalic shield. Finally, the new genus differs from Loboixys by the 4-segmented antenna (cf. 3-segmented in Loboixys ), by the possession of 5 setaeon the maxilliped (cf. 6 setae in Loboixys ), and by the possession of the inner setaon the first and second exopodal segments of legs 2–4 (cf. inner seta absent in legs 2–4 in Loboixys ).

Borixys simplex displays a unique feature in this cluster of genera in retaining an inner coxal seta on leg 4. None of these other genera has an inner coxal seta on leg 4 but we don’t yet know whether this character state is significant at the generic level.