Doroixys acutirostris, 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 : 466-469

Doroixys acutirostris sp. nov.

( Figs. 308 , 309 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21361 ) and 1 paratype ♀ (dissected andmountedona slide, MNHN-IU-2014-21362) from Cystodytes sp. (MNHN-IT-2008-2621 = MNHNA 3/ CYS /135), CRRFOCDN 5119- X, the Philippines (09°31.02 Ń, 123°40.83 É), depth 10 m, 15 April 1997.

Etymology. The specific name is a combination of Latin words acut (= sharp) and rostr (= a beak), alluding to the acutely pointed rostrum.

Descriptionoffemale. Body ( Fig. 308A ) narrow, 1.27 mm long. Prosome 0.91 mm long. Dorsal cephalic shield bearing pair of slender, spiniform horn-like processes ( Fig. 308B ) posterolaterally. Metasome with 2 dorsal and lateral constrictions delimiting first, second, and fused third plus fourth pedigerous somites; region of fourth pedigerous somite longer than wide. Free urosome ( Fig. 308C ) graduallynarrowing posteriorly, 5-segmented: genital and 4 abdominalsomites 44×127, 57×115, 42×97, 40×84, and 52×74 μm, respectively. Abdominal somites ornamented with many scattered surface setules. Caudal ramus ( Fig. 308D ) about 4.0 timeslongerthan wide (75×19 μm): armed with 6 naked setae, 2 middle and 4 distal; 2 middle setae positioned at 40 and 53% of ramus length; setae small but at least as long as width of ramus at base.

Rostrum ( Fig. 308E, F ) well-developod, hook-like in lateral view ( Fig. 308A, E ), strongly tapering towards beak-like tip ( Fig. 308F ). Antennule ( Fig. 308G ) stout, 117 μmlong, 7-segmented; armatureformula 2, 13, 4, 4, 2, 3, and 12; second segment ornamented with several sensillae; all setae naked; aesthetascs apparently absent. Antenna ( Fig. 308H ) 4-segmented; proximal 3 segments unarmed; basis shorter than first endopodal segment; compound distal endopodal segment 2.7 times longerthan wide (38×14 μm), ornamented with few minute spinules on outer margin; armed with 5 small setae (arranged as 1, 2, and 2) plus strongly curved, hook-like terminal claw, as long as second endopodal segment.

Labrum ( Fig. 308I ) lacking defined posteromedian lobe, ornamented with fine setules on both sides of posterior margin; dense area of cuticle present posteromedially. Mandible ( Fig. 308J ) bearing 5 teeth on broad coxal gnathobase, 1 setaon basis, 5 setaeon exopod, and 1 and 6 setae on first and second endopodal segments, respectively; outer seta on exopod about one-third as long as other 4 setae; articulation between endopodal segments incomplete; outer seta on second endopodal segment small; largest mediodistal setaon second endopodal segment about twice as long as second longest seta on segment. Maxillule ( Fig. 308K ) armedwith 9 setaeon arthrite, 1 on epipodite; 1 on basis; 4 onexopodand 3 on endopod; coxal endite absent. Maxilla ( Fig. 309A ) 4- segmented; syncoxa with 4, 2, and 2 setae on first to third endites, respectively; basiswith slender, naked clawplus 2 setae (1 largeand 1 minute); endopod 2-segmentedwith 1 and 3 setae on first and second segments, respectively. Maxilliped ( Fig. 309B ) lobate, armed distally with 1 longer and 5 short setae, ornamented with spinules on outer surface.

Legs 1–4 with 3-segmented rami ( Fig. 309 C-E). Leg 3 same as leg 2 in armature. Inner coxal seta absent in all swimming legs. Innerdistalspineonbasisofleg 1 small, 13 μm long. All setaeon legs 2–4 naked, most bluntly tipped. Armature formula for legs 1–4 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-I	I-1; I-1; 2, 2, 3	0-1; 0-1; 1, 2, 3
Legs 2 & 30-0		1-0	1-0; 1-0; 3, 1, 50-0; 0-0; 0, 2, 3	50-0; 0-0; 0, 2, 3
Leg 4	0-0	1-0	1-0; 1-0; 2, 1, 50-0; 0-0; 0, 2, 2	50-0; 0-0; 0, 2, 2

Leg 5 ( Fig. 309F ) consistingof obscure protopod bearing 1 setaat outer distalcorner and tapering, sclerotized process representing exopod, bearing 1 seta on outer marginand 1 pointed dentiform process at tip.

Male. Unknown.

Remarks. In Doroixys acutirostris sp. nov. the endopods of legs 2 and 3 are 3-segmented and both are armed with 5 setae on the third segment, and the endopod of leg 4 is 3-segmented and armed with 4 setae on the third segment. This characteristic armature combination serves to differentiate the new species from all of its congeners. The possession of the beak-like rostrum and the distal position of all setae on the maxilliped seem to be additional diagnostic (autapomorphic) features.

Figures

FIGURE 308. Doroixys acutirostris sp. nov., female. A, habitus, right; B, posterolateral process of cephalic shield; C, leg 5 and urosome, ventral; D, right caudal ramus, ventral; E, rostrum, lateral; F, rostrum, ventral; G, antennule; H, antenna; I, labrum; J, mandible; K, maxillule. Scale bars: A, 0.1 mm; B, D–K, 0.02 mm; C, 0.05 mm.

FIGURE 309. Doroixys acutirostris sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 4; F, leg 5. Scale bars: 0.02 mm.