Notoixys heardensis, 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 : 512-515

Notoixys heardensis gen. et sp. nov.

( Figs. 340 , 341 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21387 ) , paratypes (3 intact ♀♀, MNHN-IU-2014-21388), and dissected paratypes (2 ♀♀, figured) from branchial chamber of Aplidiumacropodium Monniot F. & Gaill, 1978 (MNHN-IT-2008-155 = MNHNA 1/ APL.B/111), Heard Island, Antarctic Ocean, ”Marion Dufresne”, 52°59.4’S, 73°38’E, depth 90 m, 08 April 1974, MNHN coll.

Etymology. The new species is named after the type locality, Heard Island in the Antarctic.

Descriptionoffemale. Body ( Fig. 340A ) swollen, 1.80 mmlong. Prosome 1.72 mmlong; dorsalcephalic shield expanded ventrolaterally, well-defined from metasome, bearing paired, tapering horn-like processes ( Fig. 340D ) posterolaterally. Metasome globular, unsegmented, with thin exoskeleton; fifth pedigerous somite completely fused with fourth. Freeurosome ( Fig. 340B ) stout, tapering, 5-segmented. Anal somite and caudal rami setulose. Caudal ramus ( Fig. 340C ) about 1.7 times longerthan wide (74×44 μm), withrounded distal margin; caudal setae not discernible from setules.

Rostrum ( Fig. 340E ) large, elongate, twice as long as wide, constricted at proximal 20%, widest at proximal third, tapering in distal two-thirds towards blunt apex; surface ornamented with setules. Antennule ( Fig. 340F ) indistinctly 10-segmented; proximal 2 segments much broader than following segments; terminal segment subdivided by indistinct articulation on one surface; firstandsecondsegments armedwith 3 and 17 setae, respectively; armature uncertain for remaining segments. Antenna ( Fig. 340G ) 4-segmented, with 2-segmented endopod; coxa, basis, and first endopodal segment unarmed; compound distal endopodal segment about 2.8 timeslongerthan wide (47×17 μm): armed with 9 small setae (arranged as 1, 1, 2, 2, and 3) plus slender terminal claw, half as long as segment.

Labrum not examined. Mandible ( Fig. 340H ) with narrow medial margin on coxal gnathobase, bearing 7 teeth of irregular sizes: basis with large medial seta: exopod with 5 setae, outer distal seta much smaller than other 4 (about one-third as long as adjacent seta): endopod incompletely articulated from basis, armed with 1 and 5 setaeon first and secondsegments, respectively. Maxillule ( Fig. 340I ) with 5 setaeon arthrite, 1 on epipodite, 2 on basis, 4 on exopod and 3 on endopod; coxal endite absent. Maxilla ( Fig. 340J ) 5-segmented; syncoxawith 3, 1, 2, and 2 setae on first to fourth endites, respectively; basis with 3 unequal setae; endopodwith 1, 1, and 3 setaeon first tothird segments, respectively; setae on thirdsegment very unequal in size. Maxilliped ( Fig. 341A ) as small lobe bearing 3 equal setae distally.

Legs 1–3 ( Fig. 341 B-D) with 3-segmented rami. Legs 3 and 4 smaller than legs 1 and 2. Leg 4 ( Fig. 341E ) with 3-segmented exopod and 2-segmented endopod; second endopodal segment subdivided by lateral constriction. Endopods shorter than exopods in legs 1–4. Inner coxal seta present in legs 1 and 2, absent in legs 3 and 4. Inner distal spine on basis of leg 1 small, smooth, 13 μm long. First exopodal segments of legs 3 and 4 lacking inner seta. All setae on legs 1–4 short and naked, except large pinnate inner coxal seta of leg 1. Armature formula for legs 1–4 as follows:

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

Leg 5 ( Fig. 340B ) represented by 2 posteroventral papillae on somite, each papilla tipped with 1 small seta.

Male. Unknown.

Remarks. The salient character states of the type species Notoixys heardensis gen. et sp. nov. are the possession of 5 setae on the second endopodal segment of the mandible and 5 on the maxillular arthrite whereas its congeners have 6 setae in both positions. The setation of legs 2–4 of N. heardensis gen. et sp. nov. is quite different from all other congeners. Thetype species has an inner coxal seta on both legs 1 and 2, which is shared only with N. ovata gen. etsp. nov. (see below).

Figures

FIGURE 340. Notoixys heardensis gen. et sp. nov., female. A, habitus, right; B, leg 5 and urosome, ventral; C, right caudal ramus, dorsal; D, cephalic horn; E, rostrum; F, antennule; G, antenna; H, mandible; I, maxillule; J, maxilla. Scale bars: A, 0.2 mm; B, C, E, 0.05 mm; D, F–J, 0.02 mm.

FIGURE 341. Notoixys heardensis gen. et sp. nov., female. A, maxilliped; B, leg 1; C, leg 2; D, leg 3; E, leg 4. Scale bars: 0.02 mm.