Nodoscarus scutatus, 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 : 636

Nodoscarus scutatus gen. et sp. nov.

( Figs. 431 , 432 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21454 ) from Aplidium lobatum Savigny, 1816 (MNHN-IT-2008-488 = MNHNA1/APL B/403), Ardoukoba, Djibouti, Monniot coll., October 1996.

Etymology. The specific name is derived from the Latin scut (=a shield) and refers to the shield-shaped rostrum of the new species.

Description of female. Body ( Fig. 431A ) vermiform, elongate, unsegmented, and curved. Body length 5.23 mm; body width 0.63 mm across widest region in middle. Cephalosome ( Fig. 431B, C ) defined from metasome by margins of cephalic shield, narrower than metasome. Posterior part of body bearing copulatory pore on ventral surface ( Fig. 431D ) and short, transverse dorsal slit (posterior part of body in Fig. 431A distorted) representing vestige of articulation between prosome and urosome. Caudal rami ( Fig. 431D, E ) present, slightly longerthan wide (43×38 μm), incompletely articulated from abdomen, graduallynarrowing distally; armedwith 6 unequal caudal setae, all shorter than width of ramus at base, proximalmost seta longest.

Rostrum ( Fig. 431G, H ) large, shield-shaped, about twice as long as wide (231×119 μm), widest in middle; lateral margins parallel in proximal third, tapering and setulose in distal two-thirds.Antennule ( Fig. 431H ) small, lobate, subcircular, with mix of setae and setules on distal and posterior surfaces. Antenna ( Fig. 431I ) 3-segmented; coxa and basis unarmed; unsegmented endopod about 3.7 times longer than wide (62×17 μm), slightly shorter than basis: armedwith 7 setae (arranged as 3, 2, and 2) plus slender terminal claw, about half as long as endopod.

Labrum ( Fig.431J ) rather large, smooth, withrounded posterior margin. Mandible ( Fig. 432A ) represented by biramous palp, armed with 4 setae on outer ramus (exopod) and 5 setae on inner ramus (endopod). Maxillule ( Fig. 432B ) as unsegmented lobe, fan-like and armed with 9 broad setae, 2 on medial margin smaller than others. Maxilla ( Fig. 432C ) incompletely 3-segmented and armed with 4, 1, and 3 setae on first to third segments, respectively. All setae on mandible, maxillule and maxilla pinnate. Maxillipeds and legs absent.

Male. Unknown.

Remarks. The maxilla of N. scutatus gen. et sp. nov. is 3-segmented and armed with 4, 1, and 3 setae on the firsttothird segments, respectively, asin N. bretoni gen. etsp. nov. However, N. scutatus gen. etsp. nov. differs in the possession of defined caudal rami, in the presence of 9 setae on the mandible (vs. 10 setae in N. bretoni gen. et sp. nov.), and of 9 setae on the maxillule (vs. 10 setae in N. bretoni gen. et sp. nov.). As an additional difference between the two species, the antennule of N. bretoni gen. et sp. nov. is strongly tapering and has partial articulations dorsally, whereas that of N. scutatus gen. et sp. nov. is globular and lacks any trace of an articulation.

It is notable that N. scutatus gen. et sp. nov. and N. curvus gen. et sp. nov. share the same species of ascidian host, Aplidium lobatum , but the former copepod species was collected from New Caledonia, while the latter came from off Djibouti in the Red Sea.

Figures

FIGURE 431. Nodoscarus scutatus gen. et sp. nov., female. A, habitus, right; B, cephalosome, right; C, cephalosome, dorsal; D, posterior end of body, ventrolateral; E, caudal ramus; F, cephalosome, ventral; G, rostrum; H, antennule; I, antenna; J, labrum and mouthparts in situ. Scale bars: A. 0.5 mm; B–D, F, G, 0.1 mm; E, I, 0.02 mm; H, J, 0.05 mm.

FIGURE 432. Nodoscarus scutatus gen. et sp. nov., female. A, mandible; B, maxillule; C, maxilla. Scale bars: 0.02 mm.