Cystixys globosa, 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 : 524-527

Cystixys globosa gen. et sp. nov.

( Fig. 348–350 )

Typematerial. Holotype (intact ♀, MNHN-IU-2009- 2469 ) , paratypes (2 intact ♀♀, MNHN-IU-2014-21394), and dissected paratypes (2 ♀♀, figured), each from membranous cyst in globular gall in Eudistoma illotum (Sluiter, 1898) (MNHN-IT-2008-XXXX = MNHNA 3 EUD 353), south of Madagascar (25°02.8 Ś, 46°59.3 É), depth 22 m, MNHN coll., 01 May 2010.

Etymology. The name alludes to the globose body of the new species.

Descriptionoffemale. Body ( Fig. 348A, B ) inflated, almost spherical, slightly longer than wide, 1.01 mm in greatest diameter. Cephalosome and urosome facing each other on ventral side of brood pouch. Dorsal cephalic shield ( Fig.348D ) withpairedhorn-likeprocesses laterally ( Fig. 348D, E ). Metasome unsegmented, entire metasome forming brood pouch. Free urosome ( Fig. 348C ) curved ventrally, stout, 5-segmented. Caudal rami ( Fig. 348F ) small, shorter than anal somite, about 1.6 times longer than wide (31×20 μm), setulose: armed with 6 setae, but setae difficult to distinguish from setules.

Rostrum ( Fig. 348D, G ) evenly tapering, longer than wide, ornamented with numerous setules. Antennule ( Fig. 348H ) 108 μm long, 7-segmented; second and third segments with traces of 1 and 3 sutures on posterior side, respectively, and terminal segment with trace of suture on anterior side; armature formula 2, 22, 11, 3, 2, 3, and 11+aesthetasc. Antenna ( Fig. 348I ) 4-segmented; proximal 3 segments stout, unarmed; terminal segment (second endopodal segment) about 3.1 times longer than wide (52×17 μm) and longer than first endopodal segment; armedwith 5 setae (arranged as 1, 2, and 2) plus small terminal claw, less than third of length of segment.

Labrum ( Fig. 349A ) short, unornamented, tapering towards thin, soft distal part. Mandible ( Fig. 349B ) with narrowcoxalgnathobasebearing1distaltoothandproximal pectinate region on medial (cutting) margin: basis with 1 medial seta; exopod with 4 large medial and 1 small outer seta (less than third length of adjacent seta): endopod with 1 and 4 setae on first and second segments, respectively; seta on first segment markedly broadened; proportional lengths of setae on second segment 7:10:17:10 from medial to outer. Maxillule ( Fig. 349C ) armed with 3 setae on arthrite, 1 each on epipodite and basis, 4 on exopod and 3 (1 short medial and 2 longer distal) on endopod. Maxilla ( Fig. 349D ) 4-segmented; syncoxawith 2 setae on each of first to third endites; basiswith 2 setae, one spiniform, spinulose; endopod small, with 1 and 3 setae on first and second segments, respectively; setaon first endopodal segment and 1 seta on second extremely large (about twice as long as entire maxilla). Maxilliped ( Fig. 349E ) small, unsegmented, armedwith 2 setae distally; ornamented with few setules on outer margin.

Legs 1–4 ( Figs. 349F, G , 350A, B ) with 3-segmented rami; coxa short or absent; intercoxal sclerite and inner coxal seta absent. Inner distal spine on basis of leg 1 large, 28 μm long. Inner setaon first endopodal segment broad. Endopods of legs 2–4 small, about half as long as exopods. Second endopodal segment of leg 2 and first and second endopodal segments of leg 3 with variable setation; setae indicated by arrowheads in Fig. 349G and 350Amay be present or absent.Armature formula for legs 1–4 as follows:

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

Leg 2	0-0	1-0	1-1; 1-1; 3, 1, 5	0-0; 0-1 (or 0-2);
				1, 2, 3
Leg 3	0-0	1-0	1-1; 1-1; 3, 1, 5	0-1 (or 0-0); 0-1
				(or 0-2); 1, 2, 3
Leg 4	0-0	1-0	1-1; 1-1; 2, 1, 5	0-1; 0-2; 1, 2, 2

Leg 5 ( Fig. 350C, D ) positioned on posteroventral margin of somite and represented by outer protopodal seta and irregular inner (exopodal) process bearing 1 seta on outer margin.

Male. Unknown.

Remarks. The specimens of this species were each enclosed within a membranous cyst and each cyst was located within a gall formed in the branchial tissue of the host.

Figures

FIGURE 348. Cystixys globosa gen. et sp. nov., female. A, habitus, left; B, habitus, ventral; C, urosome, left; D, cephalic shield, frontal; E, cephalic horn; F, caudal rami, dorsal; G, rostrum; H, antennule; I, antenna. Scale bars: A, B, 0.2 mm; C, 0.05 mm; D, 0.1 mm; E–I, 0.02 mm.

FIGURE 349. Cystixys globosa gen. et sp. nov., female. A, labrum; B, mandible; C, maxillule; D, maxilla; E, maxilliped; F, leg 1 (marked seta absent in some specimens); G, leg 2. Scale bars: 0.02 mm.

FIGURE 350. Cystixys globosa gen. et sp. nov., female. A, leg 3 (marked seta absent in some specimens); B, leg 4; C, right leg 5, ventral; D, left leg 5, ventral. Scale bars: 0.02 mm.