Schizoproctus mollis, 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 : 120-122

Schizoproctus mollis sp. nov.

( Figs. 77 , 78 )

Type material. Holotype ♀ (MNHN-IU-2018-1982, dissected and mounted on a slide) from Cẚçna ẚntestẚnalẚs (Linnaeus, 1767) (MNHN-IT-2008-1886 = MNHN P1 / CIO/24 ); Locality and date unknown, MNHN-Saint Joseph coll.

Etymology. The specific name is from the Latin mçll (=soft), alluding to the weak exoskeleton of the new species.

Description of female. Body ( Fig. 77A ) dorsoventrally depressed, with soft exoskeleton; body length 1.94 mm. Anterior part of body gradually narrowing posteriorly, distinctly 5-segmented; last metasomite consisting of fused fourth and fifth pedigerous somites. Cephalosome 519×778 μm, with broadly rounded anterior margin. Posterior part of body consisting of genital somite and 3-segmented abdomen; genital and first 2 abdominal somites extremely soft, flexible. Genital apertures not seen. Caudal rami divergent; each ramus ( Fig. 77B ) about 130×72 μm, armed with 4 distal claws and 2 setae; lengths of claws 110, 115, 39, and 74 μm, respectively, from inner to outer.

Rostrum small, less than half length of first antennular segment, semicircular, slightly longer than wide. Antennule ( Fig. 77C ) 5-segmented, evenly tapering; articulation between first 2 segments indistinct; armature formula 10, 4, 2, 2, and 8. Antenna ( Fig. 77D ) consisting of coxa, basis, and 2-segmented endopod; proximal 3 segments unarmed; second endopodal segment about 4 times longer than wide (185×46 μm), as long as basis; armed with 8 spines; longest second outer spine on distal margin 123 μm long, 0.66 times as long as segment.

Labrum very weak, flexible. Mandible ( Fig. 77E ) with 3 teeth on coxal gnathobase; palp with 9 setae arranged as 3, 1, 1, 2, and 2. Maxillule ( Fig. 77F ) with 8 setae (including minute distalmost seta) on precoxal arthrite, 5 setae (2 inner and 3 outer) on basis, and 3 setae on endopod. Maxilla ( Fig. 77G ) 3-segmented with incomplete articulation between basis and endopod; armed with 2, 2, and 4 setae on proximal to distal segments. Maxilliped ( Fig. 77H ) 4-segmented; syncoxa unarmed; basis with 2 setae; first endopodal segment unarmed; second endopodal segment with 1 small seta; terminal claw longer than second endopodal segment.

Legs 1-4 ( Fig. 78 A-D) biramous with 1-segmented rami; coxa unarmed; basis with small outer seta. Exopods of legs 1-4 each with 6 slender spines. Seven setae on endopod of leg 1 comprising 1 unilaterally pinnate and 6 pinnate setae. Armature formula for legs 1-4 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-0	VI	7
Leg 2	0-0	1-0	VI	6
Leg 3	0-0	1-0	VI	4
Leg 4	0-0	0-0	VI	3

Leg 5 ( Fig. 78E ) large, lamellate, subcircular, wider than long, 463×504 μm, with 1 seta at outer distal corner and 1 minute setal vestige on middle of distal margin. Leg 6 not seen.

Male. Unknown.

Remarks. The setation of the endopods of legs 2-4 characterizes S. mçllẚs sp. nov. because the pattern of 6, 4, and 3 setae is unique within the genus ( Table 3 ). Schẚzçprçctus mçllẚs sp. nov. can be also distinguished from its congeners by the combination of a 3-segmented abdomen (shared only with S. vestẚtus and S. trẚpartẚtus sp. nov.), the possession of 4 claws and 2 setae on the caudal ramus (compared to 4 claws and 1 seta in S. vestẚtus, and 5 claws and 1 seta in S. trẚpartẚtus sp. nov.), and by having 2 setae on leg 5 (compared to 1 seta in S. vestẚtus and 4 setae in S. trẚpartẚtus sp. nov.).

Figures

FIG. 77. Schẚzçprçctus mçllẚs sp. nov., female. A, habitus, dorsal; B, caudal ramus; C, antennule; D, antenna; E, mandible; F, maxillule; G, maxilla; H, maxilliped. Scale bars: A, 0.2 mm; B-H, 0.05 mm.

FIG. 78. Schẚzçprçctus mçllẚs sp. nov., female. A, leg 1; B, leg 2; C, leg 3; D, leg 4; E, leg 5. Scale bars: A-D, 0.05 mm; E, 0.2 mm.