Scolecodesrectus, Kim & Boxshall, 2020

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 605-608

Scolecodesrectus sp. nov.

( Figs. 408 , 409 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21438 ) from Boltenia hirta Monniot C. & Monniot F., 1977 (Type MNHN-IT-2008-1485 = MNHN S2/BOL.A/7), SW of Heard Island (55°49.5’S, 69°35.7’E), depth 4200-4225 m, MNHN coll., 11 April 1974.

Etymology. The name is derived from the Latin rect (=straight), alluding to the linear body of the female of the new species.

Descriptionoffemale. Body ( Fig. 408A ) elongate, cylindrical, straight, consisting of prosome and small unsegmented abdomen: bodylength 6.21 mm; maximum body width 0.86 mm in middle of prosome. Cephalosome ( Fig. 408B ) small, articulated from metasome, narrowing anteriorly. Metasome with 4 original pedigerous somites defined by incomplete dorsal sutures.Anteriorpart of body from rostrum tolevel of leg 4 occupying about 30% of total body length; legs 1–4 separated by equal intervals. Fourth pedigeroussomiteexpandedposteriorly, incorporatingfifth pedigerous somite and forming brood pouch. Copulatory pore positioned on posteroventral surface of incorporated genitalsomite. Abdomen ( Fig. 408C ) small, unsegmented, longerthan wide (216×180 μm), not articulated from prosome, inserted into posteroventral surface of prosome. Caudal rami ( Fig. 408D ) about 2.8 times longerthan wide (125×45 μm), tapering in distal half, ornamented with scattered papillae: armed with 6 smallsetae (2 outer lateral plus 4 distal and subdistal).

Rostrum ( Fig. 408B ) directed anteriorly, tapering. Antennule ( Fig. 408C ) unsegmented, consistingof greatly expanded, globular proximal part and narrow, digitiform distal part; armed with 4 setae on proximal part and about 8 setaeon distal part. Antenna ( Fig. 408F ) 3-segmented, consistingof short coxa, broad basis, and unsegmented endopod; basis slightly longerthan wide; endopod tapering, terminating in claw and bearing 1 outer and 4 inner smallsetae at base of claw.

Labrum ( Fig. 408G ) simple, with slightly produced mid-region of free posterior margin. Mandible with coxa represented by setulose lobe ( Fig. 408G ); palp forming rectangular lobe ( Fig. 408H ) bearing 3 large naked setae distally on medial margin and 3 small pinnate setae plus 1 pointed, setiform process on distal margin. Maxillule ( Fig. 408I ) lobate, bearing 7 pinnate setae (3 large setae on medial margin and 4 smaller, apical or subapical setae). Maxilla ( Fig. 408A ) lobate, unsegmented, armed distally with 3 naked setae. Maxilliped absent.

Legs 1–4 ( Fig. 409 B-E) biramous, each consisting of unsegmented protopod, 2-segmented exopod and 1- segmented endopod. Protopods armed with outer seta (derived from basis) only. Both rami obscurely defined from protopod; all setae naked, most spiniform, short but thick, with nipple-like tip. Armature formula for legs 1–4 as follows:

	Protopod	Exopod	Endopod
Leg 1	1-0	1-0; 8	7 or 8
Leg 2	1-0	1-0; 11	10 or 11
Leg 3	1-0	1-0; 11	10
Leg 4	1-0	1-0; 11 or 12	10 or 13
Leg 5	absent.

Male. Unknown.

Remarks. Scolecodes rectus sp. nov. shares the possession of 2-segmented exopods on legs 1–4 only with S. pugetensis sp. nov. Thischaracterstate distinguishesthe new species from the type species, S. huntsmani . It differs from S. pugetensis sp. nov. as follows: the abdomen is longer than wide (vs. as long as wide in S. pugetensis sp. nov.), the mandible carries a setiform apical process in addition to 6 setae (vs. no setiform process in S. pugetensis sp. nov.), the maxillule is armed with 7 setae (vs. 6 setae in S. pugetensis sp. nov.), the maxilla is armed with 3 setae (vs. 4 setae in S. pugetensis sp. nov.), and the rami of legs 1–4 are armed with fewer setae.

Figures

FIGURE 408. Scolecodes rectus sp. nov., female. A, habitus, right; B, anterior part of prosome, dorsal; C, urosome, ventral; D, right caudal ramus, ventral; E, antennule; F, antenna; G, labrum and paragnaths; H, mandible; I, maxillule. Scale bars: A, 1 mm; B, C, 0.1 mm; D–I, 0.02 mm.

FIGURE 409. Scolecodes rectus sp. nov., female. A, maxilla; B, leg 1; C, leg 2; D, leg 3; E, leg 4. Scale bars: A, 0.02 mm; B–E, 0.05 mm.