Demoixyscompressa, 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 : 549-551

Demoixyscompressa sp. nov.

( Figs. 367 , 368 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2009-5229 ) from Didemnum sp., (MNHN-IT-2018-10), ATIMOVATAE TA21, Banc Tozer, Madagascar (25°12’38’’S, 44°8’36’’E), depth 13-27 m, MNHN coll., 21 May 2010.

Etymology. The specific name alludes to the compressed body of the female of the new species.

Descriptionoffemale. Body ( Fig. 367A ) greatly expanded dorsally, slightly compressed, almost circular in lateral view, 1.54 mm in greatest diameter. Cephalosome small, discernible but incompletely defined from metasome. Metasome unsegmented, entire brood pouch containing developing eggs. Free urosome ( Fig. 367B ) broad, depressed, setulose, obscurely 3- segmented, stronglytapering posteriorly, widerthan long, comprising genital and 2 expressed abdominal somites. Caudalramus ( Fig. 367C ) notarticulated from anal somite, irregular in form, about twice as long as wide, flexed in middle, with broad proximal part and narrow distal part: armedwith 5 setae and ornamented with several setules.

	Protopod	Exopod	Endopod
Leg 1	0-0; 1-I	1-1; 8 (or 9)	0-1; 5
Leg 2	1-0	1-0; 5	0-0; 0

Rostrum longer than wide, tapering towards blunt apex. Antennule ( Fig. 367D ) 82 μmlong, obscurely 6- segmented, proximal two-thirds (first to third segments) broad and abruptly narrowing to distal third (fourth to sixth segments); armatureformula 3, 18, 6, 3, 2, and 9+aesthetasc; all setae small and naked. Antenna ( Fig. 367E ) stout, 3-segmented; coxa and basis unarmed; unsegmentedendopod about 3.1 timeslongerthan wide (55×18 μm) and about as long as basis: armed with 5 setae (grouped as 1, 2, and 2) plus short terminal claw, about quarter length of endopod.

Labrum missing. Mandible ( Fig. 367F ) comprising coxa and palp: medial margin of coxal gnathobase with 4 distal teeth and pectinate region proximally; proximal margin of gnathobase with 1 seta: basis with 1 broad seta onmedial margin; exopodwith 5 setae (4 large mediodistal setae and 1 short outer seta); endopod with 1 broad seta on first segment, 4 setae on second. Maxillule ( Fig. 367G ) with 7 setae on arthrite, 1 each on epipodite and basis, 4 on exopod, and 3 on endopod; endopod obscurely defined from basis; coxal endite absent. Maxilla ( Fig. 368A ) 4- segmented, comprising syncoxa, basis, and 2-segmented endopod; syncoxa with 4, 2, and 2 setae on first to third endites, respectively; basis with strong claw plus 2 unequal setae; first and second endopodal segments with 1 and 3 setae, respectively. Maxilliped ( Fig. 367H ) as unsegmented lobe bearing 2 setae distally and scattered setules on outer surface.

Legs 1–4 lacking inner coxal seta, ornamented with scattered setules on rami. Leg 1 ( Fig. 368B ) consisting of coxa, basis, and incompletely 2-segmented rami; inner distal spine on basis small, setiform. Legs 2–4 ( Fig. 368 C-E) degenerated; coxa and basis not defined. Rami of leg 2 and exopod of leg 3 obscurely 2-segmented. Exopod of leg 4 1-segmented. Endopods of legs 3 and 4 lobate and unarmed. Armature formula for legs 1–4 as follows:

Leg 3	1-0	0-0; 6	0
Leg 4	1-0	3	0

Leg 5 represented by posteroventral lobes on somite ( Fig. 367B ) tipped 1 smallseta.

Male. Unknown.

Remarks. Demoixys compressa sp. nov. seems to be closer to D. depressa sp. nov. than to its other congeners, because these two species share the possession of a 3- segmented antenna, 4 teeth on the coxalgnathobase of the mandible, 7 setae on the arthrite of the maxillule, and 9 setae on the exopod of leg 1. However, D. compressa sp. nov. exhibits some distinct differences from D. depressa sp. nov., for example: (1) the caudal ramus is armed with 5 setae (cf. apparently unarmed in D. depressa sp. nov.); (2) the endopod of the maxilla is 2-segmented (cf. unsegmented in D. depressa sp. nov.); (3) the maxilliped is armed with 2 setae as in the type species, D. chattoni and D. dialepta Illg & Dudley, 1961 (cf. 6 setaein D. depressa sp. nov.); (4) leg 1 bears an outer seta and an inner distal setaon the basis (cf. both of these setae are absent in D. depressa sp. nov.), and (5) leg 4 is present (cf. absentin D. depressa sp. nov.)

Figures

FIGURE 367. Demoixys compressa sp. nov., female. A, habitus, left; B, leg 5 and urosome, ventral; C, left caudal ramus, ventral; D, antennule; E, antenna; F, mandible; G, maxillule; H, maxilliped. Scale bars: A, 0.2 mm; B, 0.05 mm; C–H, 0.02 mm.

FIGURE 368. Demoixys compressa sp. nov., female. A, maxilla; B, leg 1; C, leg 2; D, leg 3; E, leg 4. Scale bars: 0.02 mm.