Thoracodelphys caledonica, 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 : 435-438

Thoracodelphys caledonica sp. nov.

( Figs. 288 , 289 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21352 ) , paratypes (4 intact ♀♀, MNHN-IU-2014-21353), and dissected paratypes (2 ♀♀, figured) from Symplegma brakenhielmi (Michaelsen, 1904) , Quai des Scientifique, Noumea, New Caledonia, Monniot coll., 24 March 1987.

Additionalmaterial. 6 ♀♀ (MNHN-IU-2018-1883) from S. brakenhielmi , Port de Noumea, New Caledonia.

Etymology. This species is named after the type locality, New Caledonia.

Descriptionoffemale. Body ( Fig. 288A, B ) 1.65 mm long; prosome 1.25 mmlong, slightlydepressed, 594 μm in greatest width, 558 μm in greatest dorsoventral depth. Cephalosome weakly defined; metasome unsegmented, but with 3 faint, transverse wrinkles mid-dorsally. Free urosome ( Fig. 288C ) slender, 5-segmented: genital and 4 abdominalsomites 64×180, 100×147, 82×145, 73×136, and 60×110 μm, respectively. Anal somite with broad posteromedian incision. Caudalramus ( Fig. 288D ) slender, about 5.1 timeslongerthan wide (118×23 μm), narrowing distally: armed with 2 setae and 4 distal spines; 2 setae located at 33 and 73% of ramus length, shorter than width of ramus at base; 4 distal spines straight, innermost longest 23 μm, and outermost shortest 14 μm.

Rostrum ( Fig. 288E ) short, muchwiderthanlong, withrounded apex. Antennule ( Fig. 288F ) small, strongly tapering, 130 μm long, 8-segmented; articulation between second and third segments obscure; articulation between 2 terminal segments incomplete; armature formula 3, 16, 5+aesthetasc, 4+aesthetasc, 1, 2, 2+aesthetasc, and 7+aesthetasc; all setae naked; longest seta on first segment shorter than entire antennule. Antenna ( Fig. 288G ) 4- segmented; coxashortand unarmed; basis 41×30 μm, with 1 small seta distally; first endopodal segment 48×32 μm, unarmed; compounddistalendopodal segment about 2.9 times longer than wide (57×20 μm): armed with 6 setae arranged as 3, 1, and 2 (2 distal setae bluntly tipped) plus terminal claw 33 μm long, 0.58 times as long as segment.

Labrum ( Fig. 288H ) with conical posteromedian lobe; posteriormargin setulose. Mandible ( Fig. 288I ) with 5 teethand 1 smallsetaoncoxalgnathobase, distalmost tooth acutely pointed: basis with 1 seta subdistally on medial margin and narrow crescent of surface membrane near base of seta; exopod armed with 5 setae; 4 proximal setae equal in length, distal seta small, less than half length of proximal setae; endopod with 2 and 5 setae on firstandsecondsegments, respectively. Maxillule ( Fig. 288J ) with 8 setae on arthrite, 1 blunt seta on coxal endite, 2 unequal setae on epipodite, 3 setae onmedial margin of basis (proximal seta about one-thirdlength of distalsetae); exopod and endopod with 3 and 2 setae, respectively. Maxilla ( Fig. 289B ) 5-segmented and armed as in T. longiseta sp. nov. Maxilliped ( Fig. 289A ) unsegmented, armed with 8 medial and 1 outer subdistal setae.

Legs 1–4 ( Fig. 289 C-F) each with 3-segmented exopod and 2-segmented endopod; coxa lacking inner seta. Innerdistalspineonbasisofleg 1 spinulose, 37 μm long, extending to middle of second endopodal segment. First exopodal segment of legs 2–4 with blunt, spinulose anterodistal protrusion. Second exopodal segment of legs 2–4 with bifurcate anterodistal process. First and second exopodal segments of legs 3 and 4 lacking inner seta. Outer and distalsetae on exopods of legs 2–4 naked and attenuated. Armature formula for legs 1–4 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-I	I-1; 1-1; 3, 1, 4	0-0; 1, 2, 3
Leg 2	0-0	1-0	1-1; 1-1; 3, 1, 5	0-1; 1, 2, 5
Leg 3	0-0	1-0	1-0; 1-0; 2, 1, 5	0-1; 1, 2, 5
Leg 4	0-0	1-0	1-0; 1-0; 2, 1, 5	0-0; 1, 2, 1

Leg 5 ( Fig. 289G ) rudimentary, consistingof protopod represented by small lobe bearing 1 seta and strongly tapering free exopodal segment 16×31 μm, articulated from protopod, tipped with 2 setae; inner seta 10 μm long, outer seta 32 μm.

Male. Unknown.

Remarks. In known species of Thoracodelphys the first exopodal segments of legs 2–4 usually bear a simple pointed or bifurcate, spiniform anterodistal process. Thoracodelphys caladonica sp. nov. and T. tertius sp. nov. are exceptions because these segments bear only a blunt protrusion in both of these species. Thoracodelphys tertius sp. nov. has 8 (7+1) setae on the maxilliped and an outer spine (rather than an outer seta) on the first exopodal segment of legs 2–4, and is, therefore, readily distinguishable from T. caledonica sp. nov. In addition, T. caledonica sp. nov. lacks an inner seta on the second exopodal segment of leg 3, a unique loss within the genus.

Figures

FIGURE 288. Thoracodelphys caledonica sp. nov., female. A, habitus, right; B, habitus, dorsal; C, urosome, ventral; D, right caudal ramus, ventral; E, rostrum; F, antennule; G, antenna; H, labrum; I, mandible; J, maxillule. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D–J, 0.02 mm.

FIGURE 289. Thoracodelphys caledonica sp. nov., female. A, maxilliped; B, maxilla; C, leg 1; D, leg 2; E, leg 3; F, leg 4; G, leg 5. Scale bars: A, B, G, 0.02 mm; C–F, 0.05 mm.