Doropygus corsu, 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 : 385-388

Doropygus corsu sp. nov.

( Figs. 255 , 256 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21327 ) anddissectedparatype (♀, figured) from Molgula amesophleba (Codreanu & Mack-Fira, 1956) , Porto Vecchio, Corsica, Monniot coll.

Etymology. The specific name means pertaining to Corsica in the Mediterranean.

Descriptionoffemale. Body ( Fig. 255A ) 2.90 mm long. Prosome 2.04 mm long, gradually increasing in widthposteriorly, withgentlyarcheddorsal margin. Dorsal cephalic shield well-defined posteriorly and expanded ventrolaterally. Metasomeincompletely 4-segmented. Fourthpedigerous somite forming brood pouch about 1.5 times longerthan wide in lateral view, with rounded posteriormargin. Freeurosome 5-segmented. Caudal ramus ( Fig. 255B ) 3.8 timeslongerthan wide (261×69 μm) and about 1.5 times longerthan anal somite, gradually narrowing distally: armed with 6 smallsetae; setae at most half width of ramus at base; 2 proximal setae located at 30 and 69% of ramus length.

Rostrum short and semicircular. Antennule ( Fig. 255C ) about310 μmlong,9-segmented, tapering;armature formula 3, 16, 5, 4+aesthetasc, 3, 2, 2, 2+aesthetasc, and 7+aesthetasc; all setae naked and typically short. Antenna ( Fig. 255D ) slender, 4-segmented, including unarmed coxa; basis 84×36 μm with 1 smallseta distally; first endopodal segment 65×37 μm, with 1 smallseta subdistally; compound distal endopodal segment about 4.2 times longer than wide (93×22 μm); armed with 2 setae subdistally plusterminal claw 62 μm long, 0.67 times as long as segment, with 1 blunt seta proximally.

Labrum ( Fig. 255E ) densely ornamented with setules along posterior margin; posteromedian lobe linguiform and densely setulose. Mandible ( Fig. 255F ) similar to that of D. pulex ; exopod armed with 4 large setae; first endopodal segment armed with 4 setae and ornamented with curved row of fine spinules on ventral surface; second endopodal segment with 9 setae. Maxillule ( Fig. 255G ) with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 on exopod, and 2 on endopod; seta on coxal endite broad, twice as long as wide, pointed at tip; outer seta on exopod with blunt tip. Maxilla ( Fig. 56H ) as in D. pulex , armed with 9 setae on syncoxa, 3 on basis, and 1, 1, and 3 on first to third endopodal segments, respectively. Maxilliped ( Fig. 255I ) with short trace of articulation mediodistally, armed with 9 setae medially and 2 setae apically.

Leg 1 ( Fig. 256A ) with 3-segmented rami. Outer seta on basis naked, flagellate distally. Inner distal spine on basis 59 μm long, extending tomiddleof secondendopodal segment. Outer spines on exopod fringed with membrane along both margins. Legs 2–4 with 3-segmented exopods and 2-segmented endopods; exopods and endopods subequal in length ( Fig. 256B, C ). Inner coxal seta of leg 4 smaller than that of legs 1–3, but pinnate as inlegs 1–3. Outer setae on exopods and distal setae on both rami naked. Armature formula for legs 1–4 as follows:

Coxa Basis Exopod			Endopod
Leg 1 0-1 Legs 2 & 30-1 Leg 4 0-1	1-I 1-0 1-0	I-1; I-1; III, I, 4 1-1; 1-1; 3, 1, 5 1-1; 1-1; 2, 1, 5	0-1; 0-1; 1, 2, 3 0-1; 1, 3, 4 0-1; 1, 3, 2

Leg 5 ( Fig. 255J ) similartothatof D. pulex ; protopod with 1 outer seta and distal row of spinules; free exopodal segment about 3.6 times longer than wide (154×43 μm), with rounded distal margin, armed with 1 spine and 1 seta distally; ornamented with 3 rows of fine spinules on dorsomedial surface.

Male. Unknown.

Remarks. There are two species in Doropygus which have a combination of 3 setae on the exopod and 2 setae on the endopod of the maxillule: D. reductus Stock, 1970 known from the West Indies ( Stock, 1970) and D. schellenbergi Illg, 1958 known from off the Atlantic coast of Georgia, United States of America ( Illg, 1958). As Stock (1970) illustrated, D. reductus has a Notodelphys - like body form, 2 and 8 setae, respectively, on the first and secondendopodal segments of the mandible, a blunt, bulbous seta on the coxal endite of the maxillule, 9 setae on the maxilliped (8 medial and 1 outer subdistal), a 2- segmented endopod of leg 1, and 2 large setae distally on the free exopodal segment of leg 5. In all these features D. reductus clearly differs from D. corsu sp. nov., as described above.

The armature of the mandible and maxilliped of D. schellenbergi are uncertain, because in its original description this species was said to have 4 and 7 setae, respectively, on the first and second endopodal segments of the mandible, and 8 setae on the medial margin of the maxilliped. However, the accompanying illustrations show 3 and 9 setae on the mandibular endopod and 7 setae on the medial margin of the maxilliped. This inconsistency makes comparisons problematic, however, in D. schellenbergi the free exopodal segment of leg 5 tapers in the distal quarter, as described and illustrated by Illg (1958). Using this character, D. schellenbergi is easy to separate from D. corsu sp. nov.

Figures

FIGURE 56. Notodelphyopsis gemina sp. nov., female.A, antenna; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, leg 4; G, leg 5. Scale bars: A, D–F, 0.05 mm; B, C, G, 0.02 mm.

FIGURE 255. Doropygus corsu sp. nov., female. A, habitus, right; B, left caudal ramus, lateral; C, antennule; D, antenna; E, labrum; F, mandible; G, maxillule; H, maxilla; I, maxilliped; J, leg 5. Scale bars: A, 0.5 mm; B–J, 0.05 mm.

FIGURE 256. Doropygus corsu sp. nov., female. A, leg 1; B, leg 2; C, leg 4. Scale bars: 0.1 mm.