Schizoproctus oligomerus, Kim & Boxshall, 2021

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, Zootaxa 1, pp. 1-286 : 118

publication ID	https://doi.org/ 10.11646/zootaxa.4978.1.1
publication LSID	lsid:zoobank.org:pub:9C7C1723-73EB-4FBE-A47A-54627DEB8F93
DOI	https://doi.org/10.5281/zenodo.5047121
persistent identifier	https://treatment.plazi.org/id/3729879B-FF90-FF82-FA93-FEA1D1831AAF
treatment provided by	Plazi
scientific name	Schizoproctus oligomerus
status	sp. nov.

Treatment

Schizoproctus oligomerus sp. nov.

( Figs. 75 View FIG , 76 View FIG )

Type material. Holotype ♀ (MNHN-IU-2018-1981, dissected and mounted on a slide) from mareugyrẚçẚdes chardyẚ Monniot C. & Monniot F., 1977; Gulf of Gascogne, BIOGAS 6 cruise, RV “Jean Charcot”, Stn CP 10 (47°30’N, 09°04’W), depth 2878 m, Station Marine d’Endoume coll., 21 October 1974. GoogleMaps

Etymology. The specific name is from Greek çlẚgç (=few) and merçus (=parted), referring to the oligomeric body.

Description of female. Body ( Fig. 75A View FIG ) poorly segmented; 2.50 mm long; maximum width 0.81 mm. Anterior part of body divisible by incomplete suture into cephalosome and unsegmented metasome incorporating fifth pedigerous somite. Posterior part of body ( Fig. 75B View FIG ) consisting of genital somite and unsegmented abdomen. Genital somite not articulated from anterior part, much wider than long, 409 μm wide; genital apertures located dorsally. Abdomen distinctly narrower than genital somite, about 800×259 μm, obscurely articulated from genital somite, unsegmented but with 3 indistinct transverse surface wrinkles. Caudal ramus ( Fig. 75C View FIG ) wider than long (98×103 μm), lamellate: armed with 5 spiniform claws and 1 small seta; claws straight, outer 4 claws fringed with narrow membrane along both margins, 67, 121, 150, 112, and 45 μm long from inner (dorsal) to outer (ventral).

Rostrum absent. Antennule ( Fig. 75D View FIG ) short, 5-segmented; first segment markedly broadened; armature formula 12, 5, 2, 4, and 7+aesthetasc; all setae shorter than width of first segment. Antenna ( Fig. 75E View FIG ) 4-segmented, consisting of coxa, basis, and 2-segmented endopod; proximal 3 segments unarmed; second endopodal segment about 3.4 times longer than wide (182×54 μm); armed with 8 spines (4 inner and 4 distal); proximal 2 spines on inner margin shorter than width of segment, all other spines longer than width of segment; second outer spine on distal margin longest, 130 μm.

Labrum ( Fig. 75F View FIG ) wider than long, with large posteromedian protuberance bearing 4 rows of minute spinules on surface. Mandible ( Fig. 75G View FIG ) with 3 teeth on coxal gnathobase; palp with 8 setae. Maxillule ( Fig. 75H View FIG ) with 8 setae (including 2 small distal setae) on precoxal arthrite, 1 small seta on coxal epipodite, 5 setae on basis (2 on medial and 3 on outer margins) and 3 setae on endopod. Maxilla ( Fig. 75I View FIG ) 3-segmented with 2, 3, and 4 setae respectively on first to third segments; 2 of 4 setae on third segment small, setule-like. Maxilliped ( Fig. 75J View FIG ) 4-segmented; syncoxa and basis broad, each with 2 setae; first endopodal segment short and unarmed; second endopodal segment with 2 minute setae; terminal claw longer than second endopodal segment, with 1 small denticle proximally on inner margin.

Legs 1-4 biramous with 1-segmented rami ( Fig. 76A, B View FIG ); coxa unarmed; basis with 1 small outer seta and ornamented with inner patch of minute spinules on anterior surface; all exopods with 6 slender spines and 1 rudimentary inner subdistal seta. Distalmost spine on exopods much longer than other spines, at least twice as long as adjacent seta. Armature formula for legs 1-4 as follows:

	Coxa	Basis	Exopod	Endopod
Legs 1 & 2	0-0	1-0	VI, 1	7
Legs 3 & 4	0-0	1-0	VI, 1	6

Leg 5 ( Fig. 76C View FIG ) lamellate, about 564×542 μm, with rounded distal margin and 2 small setae distally (1 minute).

Leg 6 represented by 1 spinule and 1 spinule-like process on genital operculum.

Male. Unknown.

Remarks. The diagnostic features of S. çlẚgçmerus sp. nov. include: (1) the abdomen is unsegmented (a unique feature); (2) the caudal ramus is armed with 5 claws and 1 seta (shared only with S. bẚsetatus sp. nov. and S. trẚpartẚtus sp. nov.); and (3) the armature of the endopods of legs 1-4 is 7, 7, 6, and 6 setae (a unique combination, see Table 3 View TABLE 3 ). The combination of these three features serves to distinguish S. çlẚgçmerus sp. nov. from all congeneric species.