Loboixys tetramera, 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 : 539

Loboixys tetramera sp. nov.

( Figs. 359 , 360 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21403 ) from Trididemnum cyclops Michaelsen, 1921 , New Caledonia, Récif Néokumbi ext, Stn NC30, depth 20-30m, Monniot coll., 09 March 1987.

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-1	1-0; 1, 1, 3	0-1; 1, 2, 2
Leg 2	0-0	1-0	1-0; 1-0; 3, 1, 5	0-0; 1, 2, 1
Leg 3	0-0	1-0	1-0; 3, 1, 5	0-0; 1, 2, 1
Leg 4	0-0	1-0	1-0; 2, 1, 5	0-0; 0, 2, 1
Leg 5	absent ( Fig. 359C ).

Etymology. The name is derived from the Greek tetr (=four) and mero (=part), alluding to the four-segmented urosome of the new species.

Descriptionoffemale. Body ( Fig. 359A, B ) highly transformed, globular, about 2.0 mm long along body axis. Bodysurface smooth. Prosome curved ventrally; dorsal cephalic shield lacking posterolateral horn-like processes. Metasome 4-segmented; fourth pedigeroussomite nearly spherical, 1.15 mm in dimeter, consisting of narrower dorsal and broad ventral zones indented ventrally. Free urosome ( Fig. 359C ) small, tapering, inserted into indented ventral surface of brood pouch, 4-segmented, consisting of genital and 3 abdominal somites measuring 68×330, 68×227, 50×197, and 105×175 μm, respectively. Caudalramus ( Fig. 359C ) narrowing distally, about 2.3 times longerthan wide (100×47 μm) and slightly shorter than anal somite: armed with 4 small setae only (1 outer lateral and 3 distal).

Rostrum ( Fig. 359D ) bulbous, ornamented with long setules along distal margin. Antennule ( Fig. 359D ) small, tapering, abruptly narrowing in distal third, 85 μm long, unsegmented and apparently unarmed, but ornamented with many setules. Antenna ( Fig. 359E ) 3-segmented; coxa and basis unarmed; unsegmented endopod about 3.7 times longer than wide (63×17 μm) and about 0.8 times as long as basis: armed with 5 small setae (arranged as 1, 2, and 2) plus small terminal claw, about 0.35 times as long as endopod.

Labrum ( Fig. 359F ) with broad, straight posterior margin covered with fine setules. Mandible ( Fig. 359G ) with 6 acute teeth, including smaller distalmost tooth, and 1 smallsetaoncoxalgnathobase; palparmedwith 1 setaon basis, 5 equal setae on exopod, and 5 setae on endopod (1 on first and 4 on second segment). Maxillule ( Fig. 359H ) armed with 6 setae on arthrite, 1 on basis, 4 on exopod and 3 on endopod; coxa lacking endite and epipodite. Maxilla ( Fig. 360A ) 4-segmented, strongly flexed between syncoxa and basis; syncoxa with 4 (including 1 minute seta), 2, and 2 setae on first to third endites, respectively; basis with 2 small setae; first endopodal segment with 1 thick seta, second segment with 1 thick, spiniform seta and 2 small setae. Maxilliped ( Fig. 359I ) as unsegmented lobe bearing 6 setae and scattered fine spinules.

Legs 1–4 ( Fig. 360 B-E) biramous: protopod 2- segmented in legs 1–3, unsegmented and obscurely defined at base in leg 4. Inner coxal seta absent in legs 1–4. Endopods of these legs 2–segmented, shorter than exopods. Exopods of legs 1–3 incompletely segmented. Leg 4 with distinctly 2-segmented rami; endopod much reduced in size. All setae naked and short. Armature formula for legs 1–4 as follows:

Male. Unknown.

Remarks. Loboixys tetramera sp. nov. is unique within the genus in having a 4-segmented urosome and in lacking leg 5. Additional diagnostic features include: the antennule is small, unsegmented, andornamented only with setules, without identifiable setae, the coxal gnathobase of the mandible is armed with 6 teeth, and the swimming legs are armed with the fewest setae of any species within the genus, i.e., the endopods of legs 1–4 carry 6, 4, 4, and 3 setae, respectively. These features allow us to differentiate L. tetramera sp. nov. from its congeners.

Figures

FIGURE 359. Loboixys tetramera sp. nov., female. A, habitus, dorsal; B, habitus, right; C, urosome, ventral; D, rostrum and antennule; E, antenna; F, labrum; G, mandible; H, maxillule; I, maxilliped. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D–I, 0.02 mm.

FIGURE 360. Loboixys tetramera sp. nov., female. A, maxilla; B, leg 1; C, leg 2; D, leg 3; E, leg 4. Scale bars: 0.02 mm.