Vaoda depressa, 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 : 416-420

Vaoda depressa gen. et sp. nov.

( Figs. 275–277 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21342 ) , paratypes (intact, 3 ♀♀, 1 ♂, MNHN-IU-2014- 21343), and dissected paratypes (2 ♀♀, 1 ♂, figured) from Herdmania mauritiana (Drasche, 1884) (MNHN-IT-2008-4577 = MNHNS 2/ HER /17), CRRFCRCHO 3497- L, Davao, the Philippines (07°05.89’N, 125°47.58’E), depth 8 m, 02 April 1996.

Etymology. The specific name refers to the strongly depressed body.

Descriptionoffemale. Body ( Fig. 275A ) extremely dorsoventrally flattened: bodylength 1.36 mm. Prosome 5-segmented, with parallel lateral margins. Dorsal cephalic shield semicircular, 260×490 μm, with concave posterior margin and rounded posterolateral corners. First pedigerous somite short and narrow, without epimera; second and third pedigerous somites short, 90×500 and 125×510 μm, respectively, each with well-developed epimera. Fourthpedigerous somite forming brood pouch, 590×535 μm, with weakly convex lateral margins and slightly concave posterior margin. Free urosome ( Fig. 275B ) narrow, 5-segmented; genital somite about 75×112 μm, with convex lateral margins; 4 abdominal somites 53×80. 67×73, 50×64, and 35×58 μm, respectively. Anal somite with deep posteromedian incision. Caudal ramus ( Fig. 275C ) about 4.1 timeslongerthan wide (95×23 μm) and 2.7 times longer than anal somite, terminating in hook-like process: armed with 6 setae (2 proximal and 4 distal), all setae naked, subequal in length, about threequarters as long as ramus; 2 proximal setae positioned together at 28% of ramus length.

Rostrum ( Fig. 275D ) plate-like, subrectangular, wider than long (85×127 μm), well-defined at base, with slightly convex lateral and distal margins. Antennule ( Fig. 275E ) ratherslender, 240 μmlong, 9-segmented; articulation between fifth and sixth segments faint; armatureformula 3, 17, 6, 4+aesthetasc, 5, 3+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; 2 pinnate setaeonfirst segment, 1 each on fifth and sixth, all other setae naked. Antenna ( Fig. 275F ) slender, 4-segmented; coxa unarmed; basis 53×26 μm, with pair of minute setal vestiges at outer distal corner; first endopodal segment unarmed, 50×27 μm; compound distal endopodal segment about 4.6 times longerthanwide (82×18 μm); armedwith 10 smallsetae (arranged as 1, 1, 2, 1, 2, and 3) plus small terminal claw, about 25 μm long, 0.3 times as long as segment.

Labrum ( Fig. 276A ) simple, with narrow posterior margin bearing tuft of setules on each side. Mandible ( Fig. 275G ) bearing 5 pointed teeth on narrow coxal gnathobase; distalmost tooth accompanied on distal margin with spinule-like, minute subsidiary tooth: basis with 1 seta subdistally and fine spinules distally on medial margin; exopod elongate, armedwith 3 subequal, short setae proximally and 1 large distal seta (more than twice length of proximal setae); endopod 2-segmented; first segment with 3 setae and fine spinules at mediodistally; second segment with 7 setae, second and third outer setae on distal margin longer than other endopodal setae. Maxillule ( Fig. 275H ) with 9 setae on arthrite, 1 on coxal endite and 2 on epipodite; exopod and endopod fused with basis; exopod demarcated from fused endopod and basis by incision, armedwith 3 setae distally; fusedendopod and basis with 5 setae, 3 on endopodal part and remaining 2 on basis part. Maxilla ( Fig. 276B ) 3-segmented, comprising syncoxa, basis, and 1-segmented endopod; syncoxawith 8 setae arranged as 3, 1, 2, and 2 on first to fourth endites, respectively; basis with 2 setae, distal seta slender, naked, about half length of proximal seta; endopod with 3 setae, smallest seta naked. Maxilliped ( Fig. 276C ) unsegmented but with shallow constriction subdistally on medial side, armed with 7 setae (3 proximal and 4 distal) onmedial margin and 2 larger setae distally.

Leg 1 ( Fig. 276D ) with 3-segmented rami. Inner coxal seta large, broad proximally, extending beyond distal tip of endopod.Basiswith rudimentaryoutersetaandfine spinules on medial margin and at base of inner distal spine. Inner distal spine on basis 23 μm long, slightly longer than first endopodal segment. Inner seta on first endopodal segment rudimentary, setule-like. Legs 2–4 ( Figs. 276E, F ) with 3- segmented exopods and 2-segmented endopods: rami equal in length. Coxa of leg 3 lacking inner seta. Outer seta on basis larger than that of leg 1. Exopodal and compound second endopodal segments ornamented with spinules on outer and distal margins, mainly at bases of outer and distal setae. First segments of both rami of leg 4 lacking inner seta. Armature formula for legs 1–4 as follows:

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

Leg 5 ( Fig. 276G ) small, slender; protopod slightly longer than wide, not articulated at base, armed with 1 naked seta at outer distal corner; free exopodal segment fusiform, 26×10 μm, armed with 2 naked setae distally; outer seta 29 μm, inner seta 55 μm.

Descriptionofmale. Body ( Fig. 277A ) muchsmaller and narrower than female, slightly depressed: body length 0.77 mm. Prosome fusiform, 436×264 μm: firstpedigerous somite much shorter and narrower than other prosomites; second to fourth pedigerous somites subequal in length, each with concave posterior margin. Urosome ( Fig. 277B ) 6-segmented. Fifth pedigerous somite clearly articulated from prosome, wider than genital somite. Genital somite 68×121 μm, narrowing posteriorly; abdomen narrowing posteriorly, somites 60×70, 67×52, 45×42, and 27×32 μm, respectively. Caudal ramus ( Fig. 277C ) 3.7 times longer than wide (52×14 μm), armed as in female.

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

Rostrum large, directed anteriorly ( Fig. 277A ), 68×95 μm. Antennule and antenna as in female. Mandible ( Fig. 277D ) differing from that of female in having 1 small seta on proximal margin of gnathobase and 5 subequal setae on exopod. Labrum, maxillule and maxilla as in female. Maxilliped armed with 5 medial (2 proximal+3 distal) and 2 apical setae.

Legs 1–4 as female. Leg 5 ( Fig. 277E ) consisting of short, broad protopod with seta at outer distal corner and free exopodal segment about 3.1 times longer than wide (28×9 μm), armed with 2 unequal setae distally, ornamented with 3 groups of minute spinules on medial side. Leg 6 ( Fig. 277E ) represented by 3 small setae on distal margin of genital operculum.

Remarks. The body form of the new species is superficially similar to some species of Notodelphys and Paranotodelphys , but differs fundamentally from these genera in the morphology of the maxillule (with both rami fused to the basis in Vaoda gen. nov.), the maxilla (with an unsegmented endopod in Vaoda gen. nov.), the unsegmented, lobate maxilliped in Vaoda gen. nov., and in the reduced segmentation and setation of legs 2–4.

Figures

FIGURE 275. Vaoda depressa gen. et sp. nov., female. A, habitus, dorsal; B, urosome, ventral; C, right caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, mandible; H, maxillule. Scale bars: A, 0.2 mm; B, D, 0.05 mm; C, E–H, 0.02 mm.

FIGURE 276. Vaoda depressa gen. et sp. nov., female. A, labrum; 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 277. Vaoda depressa gen. et sp. nov., male. A, habitus, dorsal; B, urosome, ventral; C, right caudal ramus, lateral; D, mandible; E, legs 5 and 6, ventral. Scale bars: A, 0.1 mm; B, 0.05 mm; C–E, 0.02 mm.