Schizoproctus magnus 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 magnus

description: Schizoproctus magnus sp. nov.   
(Figs. 65, 66)  
 Type material. Holotype ♀ (MNHN-IU-2018-1976, dissected and mounted on 2 slides) from myura bçuvetensẚs Michaelsen, 1904 (MNHN-IT-2008-7430 = MNHN S2 / PYU/450); Antarctic, Terre Adélie, CEAMARC cruise, RV “Aurore Australis”, Stn 31EV268 (66°35´S, 145°01´E), depth 429-451 m, IPEV-AAD-MNHN coll., 03 January 2008.   
 Etymology. The specific name is derived from the Latin magn (=large), referring to the large body size.   
 Description of female. Body (Fig. 65A, B) large, slender, 4.88 mm long; maximum width 1.03 mm. Anterior part of body unsegmented, with weak constriction dorsally and laterally between cephalosome and remaining part; legs 5 directed laterally, perpendicular to body axis. Posterior part of body narrower and slightly shorter than anterior part, not articulated from anterior part, gradually narrowing posteriorly, consisting of genital and abdomen of 6 annulations; annulations indistinct or separated by constrictions. Caudal ramus (Fig. 65C) as long as wide (120×120 μm), armed with 4 claws and 2 small setae; claws shorter than ramus, 2 shorter, outer distal claws bluntly tipped, 1 rudimentary.   
Rostrum (Fig. 65D) small, semicircular with rounded apex. Antennule (Fig. 65D) 417 μm long, 5-segmented; armature formula 12, 6, 3, 4, and 7; first segment much broader than other segments; setae small, much shorter than width of first segment. Left antenna (Fig. 65E) 4-segmented; coxa, basis, and first endopodal segment unarmed; second endopodal segment about 3.3 times longer than wide (92×28 μm), slightly shorter than basis, armed with 8 bluntly tipped, smooth setae. Right antenna as for left, but second inner seta on distal margin of second endopodal segment (Fig. 65F) longer than that of left antenna.  
Labrum weak, semicircular, with rounded posterior margin. Mandible (Fig. 65G) with 3 teeth on coxal gnathobase, distalmost tooth finely spinulose along proximal margin; palp with 9 setae arranged as 3, 1, 1, 2, and 2. Maxillule (Fig. 65H) consisting of precoxa and palp: precoxa with 7 setae on medial margin and 1 rudimentary seta distally; proximalmost seta specialized, tipped with pinnate setule; palp consisting of coxa, basis, and endopod, with 1 small seta on coxal epipodite, 2 medial and 3 (proximal 1 naked and weak) outer setae on basis; endopod articulated from basis, with 3 setae on distal margin. Maxilla (Fig. 65I) 2-segmented; first segment with 3 setae; second segment with bilobed tubercles on outer margin and 6 setae, distal seta naked and accompanied by minute tubercle (setal vestige) near base. Maxilliped (Fig. 66A) 4-segmented; syncoxa longer than wide, with 2 small setae on inner side; basis much shorter than syncoxa, with 2 small setae; first endopodal segment short and unarmed; second endopodal segment with 1 small seta on inner margin; terminal claw smooth, shorter than second endopodal segment.  
Legs 1-4 (Fig. 66 B-E) biramous with 1-segmented exopods and endopods; coxa and basis indistinctly defined from or fused with each other; coxa unarmed; coxa of leg 1 with large tubercle on inner side (Fig. 66B). Basis with numerous minute spinules on anterior surface. Legs 1 and 2 with small outer seta on basis, but legs 3 and 4 with unarmed basis. Exopods longer than endopods. Spines on exopods rod-shaped, roundly tipped, gradually becoming longer from proximal to distal, but inner subdistal spine rudimentary. Legs 3 and 4 not different from each other. Armature formula for legs 1-4 as follows:  
     Coxa  Basis  Exopod  Endopod      Leg 1  0-0  1-0  VI, 1  8      Leg 2  0-0  1-0  VI, 1  9      Legs 3 & 4  0-0  0-0  VI, 1  7      
Leg 5 (Fig. 66F) elongate, tapering distally, as long as body width (1.00× 0.34 mm), directed dorsolaterally; armed with 4 rudimentary setae (1 at proximal third, 1 at distal third, and 2 distally). Leg 6 (Fig. 66G) represented by 1 spinule, 1 spinule-like process, and 1 small setule on genital operculum.  
 Male. Unknown.   
 Remarks. Schẚzçprçctus magnus sp. nov. is readily recognizable by having an abdomen of 6 annulations, although the separation of the annulations is incomplete, and by the characteristic leg 5 which is elongate, tapering, and dorsolaterally directed. The combination of setal numbers on the endopods of legs 1-4 (8-9-7-7) of the new species is unique within the genus (Table 3).
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 104, DOI: 10.11646/zootaxa.4978.1.1, http://zenodo.org/record/4820443