Doropygus adenensis, 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 : 339

Doropygus adenensis sp. nov.

( Fig. 224 , 225 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21314 ) from Molguloides monocarpa (Millar, 1959) (MNHN-IT-2008-5866 = MNHN S3/MOL.B/28), METEOR CRUISE 5, Gulf of Aden, “Meteor”, Stn 271 (12°56.7’ N.- 12°55.9’ N, 47°47.0’ E - 47°47.4’ E), depth 2276-2282 m, 14 March 1987 .

Etymology. The name of the type locality, Gulf of Aden, provides the name of the new species.

Descriptionoffemale. Body ( Fig. 224A ) relatively small, 2.45 mm long; prosome length 2.18 mm. Dorsal cephalic shield with indistinctly defined posterior border. First to fourth pedigerous somites separated from each otheronlyby weakdorsal constrictions. Fourthpedigerous somite forming spherical brood pouch, not longerthan wide. Freeurosome ( Fig. 224B ) small, 5-segmented. Caudal ramus ( Fig. 224C ) slender, about 6.0 times longer than wide (191×32 μm) and about 1.7 timeslongerthan anal somite; armed with 6 small setae; proximal and subdistal setae positioned at 33 and 93% of ramus length, respectively.

Rostrum ( Fig. 224D ) triangular, 93×103 μm, with bluntly rounded angles. Antennule ( Fig. 224E ) 220 μm long, 9-segmented; firstandsecondsegments expanded; armatureformula 3, 13, 3, 5, 3, 2, 2, 2, and 7+aesthetasc; allsetae nakedand thin.Antenna ( Fig. 224F ) 4-segmented; coxashortand unarmed; basis 86×38 μm, with 1 small seta distally and 1 large seta (59 μm long) plus 1 minute seta at outer distal corner (representing exopod); first endopodal segment 55×36 μm, with 1 seta subdistally on inner margin; compound distal endopodal segment about 4.1 times longer than wide (85×21 μm); armed with 10 setae arranged as 1, 3, 1, 2 and 3 (with 3 distal setae bluntly tipped) plus slender terminal claw 46 μm long.

Labrum ( Fig. 224G ) as in preceding species. Mandible ( Fig. 224H ) with coxa bearing 5 acute teeth on medial margin of gnathobase and 2 small setae and 1 dentiform process at proximal corner: basis with 1 seta subdistally onmedial margin; exopod armedwith 5 large setae, proximal seta slightly shorter; endopod armed with 4 and 10 setaeon first and second segments, respectively. Paragnath ( Fig. 225A ) truncated apically, with setules onmedial surface. Maxillule ( Fig. 224I ) armed asin D. gracilis sp. nov., with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 on medial margin of basis, 4 on exopod, and 3 on endopod. Maxilla ( Fig. 224J ) 5-segmented; syncoxa with 8 setae arranged as 3, 1, 2, and 2; basis with 3 setae, distal seta slightly less than half length of long middle seta; endopod with 1, 1, and 4 setae on first to third segments, respectively. Maxilliped ( Fig. 225B ) 2- segmented; first segment with 9 setae (4 proximal and 5 distal) and tuft of setules proximally; secondsegment narrow, tipped with 2 unequal setae.

Leg 1 ( Fig. 225C ) with 3-segmented rami; inner seta on coxa and outer seta on basis distinct, both pinnate; inner distal spine on basis 61 μm long; spines on exopod slender, that of first exopodal segment 68 μm long. Legs 2–4 each with 3-segmented exopod and 2-segmented endopod; inner seta on coxa pinnate and as long as that of leg 1; outersetaonbasis rudimentary. Armatureformula for legs 1–4 as in D. gracilis sp. nov.

Leg 5 ( Fig. 225F ) 2-segmented: protopod widerthan long, not articulated at base, with thin setaon outermargin and spinules on distal border; free exopodal segment, narrowing distally, about 2.8 timeslongerthan wide (88×32 μm), with 2 unequal setae distally, longer medial seta 33 μm, and 4 rows of minute spinules on dorsomedial surface.

Male. Unknown.

Remarks. Doropygus adenensis sp. nov. resembles D. gracilis sp. nov. in having a large exopodal seta located at the outer distal corner of the basis of the antenna. It can be distinguished from the latterspecies by its smaller body with a spherical brood pouch, its shorter caudal rami, the smaller, naked setae on the antennule, the possession of 5 large setae on the mandibular exopod (in contrast to 4 large setae and 1 vestigial seta in D. gracilis sp. nov.), and the possession of only 2 setae (without a small proximal seta) on the fourth endite of the syncoxa of the maxilla. These differences justify the establishment of the new species.

Group B (maxillule with 3 setae on exopod and endopod)

Figures

FIGURE 224. Doropygus adenensis sp. nov., female. A, habitus, right; B, urosome, ventral; C, right caudal ramus, ventral; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule; J, maxilla. Scale bars: A, 0.5 mm; B, 0.1 mm; C–J, 0.05 mm.

FIGURE 225. Doropygus adenensis sp. nov., female. A, paragnath; B, maxilliped; C, leg 1; D, leg 2; E, leg 4; F, leg 5. Scale bars: 0.05 mm.