Nodoscarus latirostris, 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 : 638-642

Nodoscarus latirostris gen. et sp. nov.

( Fig. 434 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21457 ) from Cystodytes violatinctus Monniot, F., 1988 , Grand Terre, Canal Woodin , New Caledonia, depth 3 m, Monniot coll., 18 September 1985.

Etymology. The specific name is derived from the Latin lat (=wide) and rostr (=snout), referring to the broad rostrum of the new species.

Description of female. Body ( Fig. 434A ) vermiform, cylindrical, unsegmented, taperinganteriorly and posteriorly. No traces of division of cephalosome, metasome, and urosome present. Posterior half of body recurved ventrally. Body length 5.54 mm; body width 1.03 mm at widest region in middle. Body surface ornamented withdensecoveringof finesetulesanteriorlybutbecoming more sparse posteriorly. Posterodorsal region lacking any trace of transverse vestigial suture delimiting prosome from abdomen. Posterior margin of body bilobed, with median (anal) incision ( Fig. 434C ). Caudal rami fully incorporated into posterior margin; caudal setae lacking.

Rostrum ( Fig. 434B, D ) roughly quadrangular in ventral view, setulose, wider than long, with straight posteriormargin and slightly convex lateral margins; both posterolateral corners rounded. Antennule ( Fig. 434E ) lobate, shorter than rostrum, unsegmented, setulose but lacking setae. Antenna ( Fig. 434F ) 3-segmented, first segment (coxa) obscure; basis unarmed; endopod about 2.2 times longer than wide (41×18 μm) and 0.7 times longerthan basis: armedwith 7 smallsetae (arranged as 2, 2, and 3) plus terminal claw half as long as endopod.

Labrum ( Fig. 434G ) with slightly concave posterior margin and convex lateral margins; ornamented with scattered setules on ventral surface. Mandible ( Fig. 434H ) lobate, unsegmented, armedwith 9 setae (1 medial, 1 medial subdistal, 3 distal, and 4 outer); all setae naked. Maxillule ( Fig. 434I ) lobate with 9 pinnate setae increasing in length from inner to outer. Maxilla ( Fig. 434J ) distinctly 3-segmented, armedwith 2, 2, and 3 setae on first to third segments, respectively; all setae weakly pinnate. Maxillipeds and legs absent.

Male. Unknown.

Remarks. In Nodoscarus gen. nov. the setation of the maxilla appears to vary according to species. In N. latirostris gen. et sp. nov. the maxilla is 3-segmented and armed with 2, 2, and 3 setae on the first to third segments, respectively. This setation pattern is unique within the genus, because in the four other congeners with a 3- segmented maxilla the setation pattern is 4, 1, and 3 (in N. bretoni gen. etsp. nov., N. scutatus gen. etsp. nov., and N. rectus gen. etsp. nov.), or 2, 1, and 4 (in N. curvus gen. etsp. nov.).

The form of the rostrum of N. latirostris , which is quadrangular in ventral view and wider than long, also serves to characterise this new species, considering that the rostrum of its congeners are typically longer than wide, or tapering with a rounded apex.

Figures

FIGURE 434. Nodoscarus latirostris gen. et sp. nov., female. A, habitus, right; B, cephalic region, right; C, posterior end of body, ventral; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule; J, maxilla. Scale bars: A, 1 mm; B, C, 0.1 mm; D–F, 0.02 mm; G, 0.05 mm; H–J, 0.01 mm.