Nodoscarus rectus, 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 : 636-638

Nodoscarus rectus gen. et sp. nov.

( Fig. 433 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21455 ) , paratypes (2 intact ♀♀, MNHN-IU-2014-21456), and dissected paratypes (2 ♀♀, figured) from Aplidium sp., lobster wall, Mabul Island, Malaysia (04°14.53 Ń, 118°37.57 É), depth 17 m, 22 February 2004.

Etymology. The specific name is derived from the Latin rect (meaning “straight”) and refers to the linear body of the new species.

Descriptionoffemale. Body ( Fig. 433A ) elongate, vermiform, cylindrical, straight, and unsegmented. Body length 5.57 mm; body width 0.63 mm. Cephalosome ( Fig. 433B ) semicircular, slightly widerthan long, discernible from metasome by being narrower. Metasome entirely forming brood pouch, with parallel lateral margins. Urosome small, notarticulated from metasome, but defined from metasome by being narrower. Caudal rami ( Fig 433C ) small, about 1.5 timeslongerthan wide (48×33 μm): armed with several setae or setules, 2 setae near middle larger than others.

Rostrum ( Fig. 433D ) large, elongate, about 0.7 times as long as cephalosome, 2.3 times longer than wide (210×91 μm), with nearly parallel lateral margins in proximal two-fifths, abruptly narrowing and tapering in distal three-fifths; ventral surface ornamented with fine setules. Antennule ( Fig. 433E ) lobate, unsegmented, armed and ornamented with mix of setae and setules distally. Antenna ( Fig. 433F ) 3-segmented; coxa and basis unarmed; endopod about 3.1 timeslongerthan wide (59×19 μm); armedwith 5 smallsetae (arranged as 1, 2, and 2) plus small terminal claw, less than half length of endopod.

Labrum short and broad, unornamented, with convex lateral margins and slightly concave posterior margin. Mandible ( Fig. 433G ) lobate, bearing 9 setae. Maxillule ( Fig. 433H ) also lobate, bearing 9 setae (3 medial setae distinctly smaller than others). Maxilla ( Fig. 433I ) 3-segmented and armed with 4, 1, and 3 setae on first to third segments, respectively; articulation between second and third segments incomplete; 2 of 3 setae on third segment shorter but broad. Maxillipeds and legs absent.

Male. Unknown.

Remarks. Nodoscarus rectus gen. et sp. nov. is very similar to N. scutatus gen. et sp. nov. They both possess defined caudal rami and have the same numbers of setae on the mandible, maxillule, and maxilla. In particular, the shapes of the setae on the maxilla are alike in these two species. The differences between them are very slight, but are sufficient to allow us recognize them as distinct species. The main differences are: (1) the caudal rami are not articulated from the urosome and are 1.45 times longer than wide in N. rectus gen. et sp. nov. but are clearly defined from urosome and 1.13 times longer than wide in N. scutatus gen. et sp. nov.; (2) the rostrum is widest in the proximal 40% and abruptly narrowing and tapering in the distal 60% in N. rectus gen. et sp. nov. but it is slightly narrower in the proximal third, widest in middle, and tapering in the distal two-thirds in N. scutatus gen. et sp. nov.; (3) the mandible is uniramous in N. rectus gen. et sp. nov. but biramous in N. scutatus gen. et sp. nov.; and (4) all five observed specimens of N. rectus gen. et sp. nov. have straight bodies whereas the single specimen of N. scutatus gen. et sp. nov. has a curved body.

Figures

FIGURE 433. Nodoscarus rectus gen. et sp. nov., female. A, habitus, dorsal; B, cephalosome, ventral; C, caudal ramus; D, rostrum; E, antennule; F, antenna; G, mandible; H, maxillule; I, maxilla. Scale bars: A, 0.5 mm; B–D, 0.05 mm; C, E–I, 0.02 mm.