Chilodelphys cerasta, 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 : 648-650

Chilodelphys cerasta gen. et sp. nov.

( Fig. 440 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21464 ) anddissectedparatype (♀, figured) from Didemnum cuculliferum (Sluiter, 1909) , south lagoon, New Caledonia, depth 10- 40 m. Monniot coll., 1985.

Etymology. The specific name is derived from the Greek cerast (=horned) referring to the presence of the horn-like leg 5.

Description of female. Body maggot-shaped ( Fig. 440A, B ), slightly arched ventrally, divisible into cephalosome, metasome, and urosome. Bodylength 1.75 mm; maximum body width 0.54 mm across middle of metasome. Cephalosome incompletely articulated from metasome, with expanded ventral region. Metasome subdivided by 2 constrictions into 3 parts; middle part widest; posterior part longest and bearing transformed leg 5 posteroventrally ( Fig. 440E, F ). Body surface covered with numerous fine spinules. Free urosome ( Fig. 440F, G ) directed posteroventrally, small, about 200 μm long, indistinctly 2-segmented, consistingof genitalsomite and abdomen. Abdomen about twice as long as genital somite, ornamented with scattered fine spinules on surface. Caudal rami about 1.8 times longer than wide (86×48 μm), incompletely articulated from abdomen; ornamented with scattered fine spinules on surface, and bearing 1 smallseta dorsally.

Rostrum ( Fig. 440D ) broad, stronglytapering towardsroundedapex. Antennule ( Fig. 440G ) tapering, 2-segmented, 170 μm long, curved dorsally, covered with fine spinules and papillae; first segment lacking setae; second segment occupying 23% of total antennule length, armed with 7 small setae of unequal lengths, longest seta aslongas segment. Antenna ( Fig. 440H ) 3-segmented, including short unarmed coxa; unarmed basis; slender unsegmentedendopod about 3.5 timeslongerthan wide (56×16 μm), as long as basis; armed with 2 subdistal and 2 distal setae plus very small terminal claw, about 0.2 times as long as endopod.

Labrum ( Fig. 440C, D ) as ventrally protruding, setulecovered lobe. Mouthparts absent, but 3 pairs of large ventral lobes present in oral region; each lobe densely covered with setules distally and fine spinules proximally; middle lobe protruding ventrally. Mouth not discernible.

Legs 1–4 absent. Leg 5 ( Fig. 440E, F ) positioned on posteroventral surface of metasome, transformed into horn-like, pointed process bearing 1 minute seta proximally on outer margin.

Male. Unknown.

Remarks. The three pairs of swellings in the oral region may represent vestiges of the mouthparts but no evidence is currently available to support this interpretation.

Figures

FIGURE 440. Chilodelphys cerasta gen. et sp. nov., female. A, habitus, dorsal; B, habitus, right; C, cephalic region, right; D, cephalic region, ventral; E, urosome, right; F, urosome, ventral; G, antennule; H, antenna. Scale bars: A, B, 1 mm; C–F, 0.1 mm; G, H, 0.02 mm.