Schizoproctus pinguis, 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 : 126-131

Schizoproctus pinguis sp. nov.

( Figs. 81-84 )

Type material. Holotype ♀ (MNHN-IU-2018-1984), 1 ♀, and 2 ♂♂ intact paratypes (MNHN-IU-2018-1985) and 1 ♀, 1 ♂ paratypes (dissected, MNHN-IU-2014-17379) from Apl ẚdẚum hẚans (Monniot F. & Gail), 1978 (MNHN- IT-2008-445 = MNHN A1 / SID.B/16); East Kerguelen Is. , MD04 -BENTHOS cruise, R. V. “Marion Dufresne”, Stn CP 13 (49°32-33’S, 70°57’E), depth 149-155 m, Boury-Esnault coll., 22 February 1975.

Etymology. The name of the new species is derived from the Latin pẚngu meaning “stout” and refers to the stout body of the female.

Description of female. Body ( Fig. 81A ) stout, consisting of broader anterior and narrower posterior parts; body length 1.31 mm and maximum width 464 μm. Anterior part of body unsegmented, with parallel lateral margins and rounded anterior margin, showing vestiges of suture lines on dorsal surface. Fourth and fifth pedigerous somites not defined from each other; legs 4 and 5 positioned in same transverse plane. Posterior part of body ( Fig. 81B ) distinctly 5-segmented, consisting of genital and 4 abdominal somites. Genital somite about 110×243 μm; genital apertures large, positioned dorsally. Four abdominal somites 68×186, 57×166, 57×157, and 159×141 μm, respec- tively. Caudal rami divergent; each ramus ( Fig. 81C ) 77×50 μm, armed with 4 claws and 2 setae; lengths of claws 59, 54, 29, and 26 μm, respectively, from inner to outer.

Rostrum ( Fig. 81D ) small, semicircular, with 2 patches of spinules on ventral surface. Antennule ( Fig. 81E ) 5- segmented; first segment expanded, comprising about half length of entire limb; articulation between two terminal segments indistinct; armature formula 13, 4, 3, 4, and 7+aesthetasc. Antenna ( Fig. 81F ) 4-segmented; coxa, basis, and first endopodal segment unarmed; second endopodal segment 3.3 times longer than wide (100×30 μm), slightly longer than basis; armed with 8 armature elements (6 spines and 2 setae), spines shorter than width of segment; 2 setae (2 outer elements on distal margin) 52 μm long (outermost) and 86 μm.

Labrum ( Fig. 81G ) strongly tapering towards rounded posterior margin. Mandible ( Fig. 81H ) with 3 teeth on medial margin of coxal gnathobase; palp with 9 setae, as usual for genus. Maxillule ( Fig. 81I ) with 7 setae (third distal seta minute) on precoxal arthrite, 1 small seta representing coxal epipodite, 2 medial and 3 outer setae on basis, and 3 setae on endopod. Maxilla ( Fig. 81J ) 2-segmented; proximal segment with 2 large setae; distal segment with 6 setae, second distal seta vestigial. Maxilliped ( Fig. 82A ) robust, 4-segmented; syncoxa and basis each with 2 setae; first endopodal segment unarmed; second endopodal segment with 2 small setae subdistally; terminal claw bearing 2 denticles proximally and 2 subdistally.

Legs 1-3 ( Figs. 82 B-D) and leg 4 biramous with unsegmented rami. Leg 1 with defined coxa and basis, but protopod of legs 2-4 not segmented. Exopods and endopods subequal in length. Exopods each armed with 5 spines. All setae on endopods naked. Legs 3 and 4 with same structure. Armature formula for legs 1-4 as follows:

	Protopod	Exopod	Endopod
Leg 1	1-0	V	8
Leg 2	1-0	V	3
Legs 3 & 4	1-0	V	2

Leg 5 ( Fig 82E ) inserted into dorsal surface of body, lamellate, wider than long (239×333 μm), armed with 4 small setae, 2 (1 thick and 1 slender) positioned close to each other on ventrodistal margin. Leg 6 represented by 2 spinules on genital operculum.

Description of male. Body ( Fig. 83A ) narrow, distinctly segmented, consisting of well-defined prosome and urosome: body length 797 μm and maximum width 249 μm. Prosome 497 μm long, consisting of cephalothorax and 3 free pedigerous somites. Cephalothorax 278 μm long, with dorsal suture line between cephalosome and first pedigerous somite. Urosome ( Fig. 83B ) 5-segmented; fifth pedigerous somite 79 μm wide; genital somite 90×89 μm, with well-developed genital opercula. Three abdominal somites 38×58, 27×50, and 73×44 μm, respectively; anal somite with row of minute spinules on ventral surface near base of caudal rami. Caudal ramus 2.6 times longer than wide (52×20 μm); setation uncertain due to damage.

Rostrum narrower than that of female. Antennule ( Fig. 83C ) 4-segmented; first segment with 5 setae and numerous (more than 130) aesthetascs; second segment with 15 setae or aesthetascs (setae difficult to distinguish from aesthetascs); third segment with 3 setae and 1 broad aesthetasc; terminal segment with 6 setae and 4 aesthetascs (including 2 broad ones). Antenna as in female.

Labrum missing. Mouthparts extremely small, feeble and transparent. Mandible ( Fig. 83D ) consisting of coxa and palp; coxa small, stellate, bearing 3 teeth and several minute spinules; palp elongate, trifurcate (or with 3 setae) distally. Maxillule ( Fig. 83E ) bilobed; longer lobe tipped with 2 setae and shorter lobe with 3 setae. Maxilla ( Fig. 83F ) unequally bilobate, with short tapering lobe and elongated lobe bearing 4 setae and seta-like distal part. Maxilliped as in female but more slender.

Legs 1-4 ( Figs. 83G, H , 84A, B ) biramous with well-defined coxa and basis. Legs 1 and 2 with unarmed coxa, but coxa of legs 3 and 4 each with inner seta. Basis of legs 1-4 with small outer seta. Exopods 3-segmented in legs 1-4, distinctly longer than endopods. Endopods incompletely 2-segmented (articulation only on posterior surface) in leg 1, 3-segmented in legs 2 and 3, and 2-segmented in leg 4. Distal segment of leg 1 endopod with 2 minute, hardly visible setae. Armature formula for legs 1-4 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-0	I-0; I-1; III, I, 4	0-1; 2
Leg 2	0-0	1-0	I-0; I-1; III, I, 5	0-1; 0-2; I, 3
Leg 3	0-1	1-0	I-0; I-1; III, I, 5	0-1; 0-2; I, 2
Leg 4	0-1	1-0	I-0; I-1; III, I, 5	0-1; I, 4

Leg 5 ( Fig. 83B ) consisting of outer seta on fifth pedigerous somite and small, free exopodal segment bearing

2 setae distally. Leg 6 ( Fig. 83B ) represented by 2 setae on genital operculum

Remarks. Schẚzçprçctus pẚnguẚs sp. nov. resembles S. fẚjẚensẚs sp. nov. in sharing the same armature formula (8, 3, 2, and 2) for the endopods of legs 1-4 but differs from the latter in many other respects. For example, the coxal gnathobase of the mandible of S. pẚnguẚs sp. nov. is not specialized as in S. fẚjẚensẚs sp. nov., the exopods of legs 1-4 are armed with 5 spines (cf. 6 spines in S. fẚjẚensẚs sp. nov.), and leg 5 is wider than long (cf. longer than wide in S. fẚjẚensẚs sp. nov.).

Schẚzçprçctus pẚnguẚs sp. nov. shares some character states with S. vestẚtus, such as the setation of the exopods of legs 1-4, which bear 5 spines in both species. However, SK vestẚtus differs from S. pẚnguẚs sp. nov. in having a larger body, 7 mm long according to Aurivillius (1885) or 6.1 mm according to Sars (1921), a 5-segmented abdomen, and in being armed with spines on the endopods of legs 1, 2, and 4 (leg 3 is unknown).

Numerous diatom frustules were observed in the gut of the examined female specimens of S. pẚnguẚs sp. nov. The atrophied mouthparts of the male suggest that the adult is a non-feeding stage.

Genus Haplostomides Chatton & Harant, 1924

Diagnosis. Female: Body vermiform, unsegmented or incompletely segmented, indistinctly divisible into cephalosome, metasome, and genitoabdomen. Caudal rami usually fused with abdomen, armed with 1 terminal spine and 1 to 4 setae. Rostrum weakly developed. Antennule small, 1- to 5-segmented. Antenna 2- or 3-segmented; terminal segment (endopod) armed with 2 to 4 spines. Labrum simple. Mandible 1- or 2-segmented, with 2 or 3 setae on distal segment, rarely with 1 seta on proximal segment; mandible with rudimentary gnathobase in some species. Maxillule typically 2-segmented, consisting of precoxa and palp, bearing 2 to 5 setae on medial margin of precoxa and 4 to 6 setae on palp. Maxilla as small lobe bearing 2 to 4 setae. Maxilliped consisting of coxa, basis, and 2- segmented endopod plus small terminal claw. Legs 1-4 consisting of unsegmented protopod, exopod, and endopod. Protopods with or without outer margin seta. Exopods with 1 seta and 2 to 5 spines; 2 distal spines occasionally fused at base to form bifurcate spine. Endopods lobate, unarmed, sometimes vestigial. Leg 5 reduced to small lobe bearing 2 to 4 setae.

Male (based on eaplçstçmẚdes scçttẚ Chatton & Harant, 1924): Body cyclopiform, distinctly segmented, consisting of cephalosome, 4-segmented metasome, and 6-segmented urosome. Caudal ramus with 5 setae. Antennule 4-segmented, with numerous aesthetascs on first segment. Antenna 3-segmented, similar to that of female. Mandible, maxillule, and maxilla degenerated. Maxilliped similar to that of female. Legs 1-4 biramous. Leg 1 with 3-segmented exopod and transformed 1-segmented endopod. Legs 2 and 3 with 3-segmented rami. Leg 4 with 3- segmented exopod and 2-segmented endopod. Inner coxal seta absent in legs 1 and 2, but present in legs 3 and 4. Armature formula for legs 1-4 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-0	I-0; I-0; III, I, 4	II, 6
Leg 2	0-0	1-0	I-0; I-1; II, I, 5	0-1; 0-2; 0, II, 3
Leg 3	0-1	1-0	I-0; I-1; II, I, 5	0-1; 0-2; 0, II, 2
Leg 4	0-1	1-0	I-0; I-1; II, I, 5	0-1; 0, II, 3

Leg 5 consisting of obscure protopod bearing 1 seta and free exopodal segment bearing 2 setae. Leg 6 represented by 2 setae on distal margin of genital operculum.

Type species. eaplçstçmẚdes scçttẚ Chatton & Harant, 1924, by original designation.

Remarks. Marchenkov & Boxshall (2003) mentioned that species of eaplçstçmẚdes differ from one another in details of the antennae, mandibles, maxillules and maxillae, and other limbs have little taxonomic value at the species level. Key character states of the ten known and the three new species described below are summarized in Table 4 .

Figures

FIG. 81. Schẚzçprçctus pẚnguẚs sp. nov., female. A, habitus, dorsal; B, posterior part of body, dorsal; C, caudal ramus; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule; J, maxilla. Scale bars: A, B, 0.1 mm; C, D, I, 0.02 mm; E-H, J, 0.05 mm.

FIG. 82. Schẚzçprçctus pẚnguẚs sp. nov., female.A, maxilliped; B, leg 1; C, leg 2; D, leg 3; E, leg 5. Scale bars: A-D, 0.05 mm; E, 0.1 mm.

FIG. 83. Schẚzçprçctus pẚnguẚs sp. nov., male. A, habitus, dorsal; B, urosome, ventral; C, antennule; D, mandible; E, maxillule; F, maxilla; G, leg 1; H, leg 2. Scale bars: A, 0.1 mm; B, G, H, 0.05 mm; C, D, F, 0.02 mm; E, 0.1 mm.

FIG. 84. Schẚzçprçctus pẚnguẚs sp. nov., male. A, leg 3; B, leg 4. Scale bars: 0.05 mm.