Notoixys hirsuta, 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 : 515-517

Notoixys hirsuta gen. et sp. nov.

( Figs. 342 , 343 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21389 ) , paratypes (6 intact ♀♀, MNHN-IU-2014-21390), and dissected paratypes (2 ♀♀, figured) from Aplidium imbutum Monniot C. & Monniot F., 1983 , South Orkney Islands, Cruise876,Antarctic,“Islas Orcadas ”,(60°27.8’S, 46°23.1’W), depth 93-102 m, trawl, 16 February 1976.

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

Etymology. The specific name refers to the hirsute body of the new species.

Descriptionoffemale. Body ( Fig. 342A ) swollen, 1.20 mmlong. Prosome 0.91 mmlong; dorsalcephalic shield expanded ventrolaterally, surface densely setulose along ventral border, with paired acutely-pointed posterolateralhorn-likeprocesses ( Fig. 342B ). Metasome almost spherical, without trace of articulation, slightly longerthanwide. Freeurosome ( Fig. 342C ) 5-segmented: genital somite much wider than long: 4 abdominal somites setulose on ventral surface, 124×160, 67×127, 44×104, and 58×96 μm, respectively. Caudalramus ( Fig. 342D ) small, setulose, slightly tapering distally, about 2.0 times longer than wide (43×21 μm); caudal setae not discernible from setules.

Rostrum ( Fig. 342E ) about 1.2 timeslongerthan wide, densely covered with setules, tapering to blunt apex. Antennule ( Fig. 342F ) narrow, 147 μmlong, indistinctly 7-segmented; second to fourth segments each bearing 1 or 2 incomplete subdivisions on posterior surface; armature formula 2, 14, 8, 3+aesthetasc, 1, 4, and 5+aesthetasc. Antenna ( Fig. 342G ) 4-segmented; proximal 3 segments unarmed; terminal segment about 3.4 times longer than wide (57×17 μm) and distinctly longerthan first: armed with 9 setae (arranged as 1, 3, 2, and 3) plus small terminal claw, about 0.3 times as long as segment.

Labrum ( Fig. 342H ) withlarge posteromedian protuberance bearing setules along posterior margin. Mandible ( Fig. 342J ) with narrow coxalgnathobase bearing 6 unequalteeth on medial margin: basis with 1 seta onmedial margin: exopodwith 5 setae; outerdistalseta short, about half as long as adjacent seta: endopod with 1 and 6 setae on first and second segments, respectively. Maxillule ( Fig. 342I ) armedwith 6 setaeon arthrite, 1 on epipodite, 2 on basis, 4 onexopodand 3 on endopod; setae on endopod longer than those on exopod; arthrite ornamented with patch of setules on proximal medial margin. Maxilla ( Fig. 343A ) 5-segmented; syncoxa armed with 3, 1, 1, and 1 setae on first to fourth endites, respectively; basiswith 3 setae; first to third endopodal segments with 1, 1, and 3 setae respectively. Maxilliped ( Fig. 343B ) unsegmented, narrowing distally, armed with 3 setae distally.

Legs 1–4 ( Fig. 343 C-F) biramous; all setae on legs short and naked except pinnate inner coxal seta and outer seta on basis of leg 1. Leg 1 endopod distinctly 2- segmented; but segmentation of other rami of legs 1–4 obscure. Inner coxal seta present only in leg 1. Inner distal seta on basis of leg 1 smooth, 19 μm long. Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 342B ) represented by 2 small setae on posteroventral margin of somite, near base of free urosome.

Male. Unknown.

Remarks. Notoixys hirsuta gen. et sp. nov. possesses a seta-tipped coxal endite on the maxillule and has 3 setae on the third endopodal segment of the maxilla. Within the genus, both features are shared only with the type species, N. heardensis gen. et sp. nov. However, they can be distinguished by the number of setae on the second endopodal segment of the mandible (6 in D. hirsuta gen. etsp. nov. comparedto 5 in N. heardensis gen. et sp. nov.). The rami of legs 2–4 are also different: the exopods of legs 3 and 4 are armed with totals of 13 and 12 setae, respectively in N. hirsuta gen. et sp. nov., and the endopods are armed with 9 and 8 setae, respectively. In contrast, in all three congeners the numbers of these setae are lower, for example, with a maximum of 12 and 11, respectively, on the exopods of legs 3 and 4, and 6 setae on each endopod, as found in N. heardensis gen. et sp. nov.

Notoixys hirsuta gen. et sp. nov. has an inner coxal seta only on leg 1, as in N. planiceps gen. et sp. nov. (see below). However, unlike the latter species, N. hirsuta gen. et sp. nov. possesses more teeth on the medial margin of the mandibular coxal gnathobase, 2 setae (vs. 1 in N. planiceps gen. etsp. nov.) onthebasisof themaxillule, and has obscurely segmented rami on the posterior swimming legs, although there are more setae on these rami.

Figures

FIGURE 342. Notoixys hirsuta n gen. et sp. nov., female. A. habitus, right; B, cephalic horn; C, leg 5 and urosome, ventral; D, right caudal ramus, dorsal; E, rostrum; F, antennule; G, antenna; H, labrum; I, maxillule; J, mandible. Scale bars: A, C, 0.1 mm; B, D, F–J, 0.02 mm; E, 0.05 mm.

FIGURE 343. Notoixys hirsuta gen. et sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 3; F, leg 4. Scale bars: 0.02 mm.