Schizoproctus oligomerus Kim & Boxshall 2021, sp. nov.
Creators: name: Kim, Il-Hoi
name: Boxshall, Geoff A.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Maxillopoda
Cyclopoida
Ascidicolidae
Schizoproctus
Schizoproctus oligomerus

description: Schizoproctus oligomerus sp. nov.   
(Figs. 75, 76)  
 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.   
 Etymology. The specific name is from Greek çlẚgç (=few) and merçus (=parted), referring to the oligomeric body.   
 Description of female. Body (Fig. 75A) 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) 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) 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) 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) 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) wider than long, with large posteromedian protuberance bearing 4 rows of minute spinules on surface. Mandible (Fig. 75G) with 3 teeth on coxal gnathobase; palp with 8 setae. Maxillule (Fig. 75H) 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) 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) 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); 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) 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). The combination of these three features serves to distinguish S. çlẚgçmerus sp. nov. from all congeneric species.
description: Published as part of Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, pp. 1-286 in Zootaxa 1 on page 118, DOI: 10.11646/zootaxa.4978.1.1, http://zenodo.org/record/4820443