Loboixyssibogae, 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 : 528-530

Loboixyssibogae sp. nov.

( Figs. 351 , 352 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21395 ) , paratypes (9 intact ♀♀, MNHN-IU-2014-21396), and dissected paratypes (3 ♀♀, figured) from Diplosoma sp., south coast of Timor, Siboga Stn 296 (10°14’S, 124°5.5’ E), depth 8-36 m, 24-26 January 1900.

Etymology. This species is named after the “Siboga Expedition” during which the type specimens were collected.

Description of female. Body ( Fig. 351A ) of ovigerous adult extremely swollen. Smaller young adult ( Fig. 351B ) stout, but not as swollen. Body surface densely ornamented with minute setules. Prosome of ovigerous adult 1.57 mm long; dorsal cephalic shield bearing acutely pointed, paired horn-like processes posterolaterally ( Fig. 351C ). Metasome with 2 or 3 dorsal constrictions, marking original articulations between somites; fourth pedigeroussomite (or fusedthirdand fourthpedigerous somites) greatly expanded, almost spherical, forming brood pouch. Free urosome ( Fig. 351D ) small, inserted into ventral surface of prosome, 5- segmented, but posterior articulations indistinct. Genital somite 49×193 μm; abdominal somites covered with minutesetules, 36×167, 58×149, 33×138, and 73×135 μm, respectively. Caudalramus ( Fig. 351E ) stronglytapering, about 1.8 times longer than wide (71×40 μm) and as long as anal somite, densely covered with setules; narrowed distal part pale and with thin cuticle: caudal setae not discernible from setules.

Rostrum ( Fig. 351F ) aslongas wide, denselysetulose, weak, flexible, with rounded distal margin. Antennule ( Fig. 351G ) stronglytapering, incompletely 7-segmented, 160 μm long; setae not discernible from setules. Antenna ( Fig. 351H ) 3-segmented, consistingof coxa, basis, and unsegmented endopod; endopodal segment 2.9 times longer than wide (55×19 μm) and 0.7 times as long as basis: armedwith 6 setae (grouped as 1, 2, and 3) plus small terminal claw, one-third as long as endopod.

Labrum ( Fig. 351I ) with broad convex posterior margin; posterior region soft, flexible, densely setulose. Mandible ( Fig. 351J ) with 5 acute teeth and 1 small setaon coxalgnathobase: basiswith 1 medial seta: exopodwith 5 setae, outersetaeslightlyshorterthan others:endopodwith 1 and 4 setae on first and second segments, respectively; proportional lengths of setae on second segment 3:4:6:5 from inner to outer. Maxillule ( Fig. 351K ) with 7 setae on arthrite, 1 each on epipodite and basis, 4 on exopod and 3 on endopod; coxal endite absent; 3 setae on endopod unequal (medial seta shortest and outer seta longest). Maxilla ( Fig. 352A ) 4-segmented; syncoxawith 4, 2, and 2 setaeon first to third endites, respectively; basis with thick seta plus 1 small seta; endopod 2-segmented with thick seta on first segment and 1 thick and 2 shorter, thin setaeon second. Maxilliped ( Fig. 352B ) as unsegmented lobe bearing 5 or 6 (commonly 6) setae mediodistally and ornamented with fine spinules on distal and outer surfaces.

Leg 1 ( Fig. 352C ) with incompletely 3-segmented rami; inner distal spine on basis 15 μm long, bilaterally serrate; both rami ornamented with slender setules; second exopodal segment lacking outer element. Inner coxal seta absentin legs 1–4. Legs 2–4 with 3-segmented exopods and 2-segmented endopods ( Fig. 352D, E ); secondendopodal segment of legs 2 and 3 with vestige of articulation: first exopodal segment lacking inner seta. Second exopodal segment bearing minute inner seta in legs 2 and 3, but lacking in leg 4. Legs 2 and 3 with same armature formula. Proximal 2 inner setae on endopod of legs 2 and 3 minute. Armature formula for legs 1–4 as follows:

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

Leg 5 ( Fig. 351D ) represented by 2 small lobes positioned posteroventrally on somite; outer lobe tipped withsmall protopodal seta, and inner (exopodal) lobe tipped with 2 small setae.

Male. Unknown.

Remarks. Loboixys sibogae sp. nov. differs from the type species L. ryukyuensis , in the setation of the first exopodal and endopodal segments of leg 1, each of which bears an innerseta (cf. absentin L. ryukyuensis ), the caudal rami are distinct (fused to anal somite in L. ryukyuensis ), the first endopodal segment of leg 4 is unarmed (cf. bears an inner seta in L. ryukyuensis ), and leg 5 is bilobed (leg 5 consists of 1 inner seta and an apparently bipartite outer lobe in L. ryukyuensis ).

The third exopodal segment of leg 4 of L. ryukyuensis is armed with 9 setae (formula 3, 1, 5), such a setation pattern is extremely unusual for a member of the Notodelphyidae .

Figures

FIGURE 351. Loboixys sibogae sp. nov., female. A, habitus, right; B, habitus of young adult, right; C, cephalic horn; D. leg 5 and urosome, ventral; E, right caudal ramus, dorsal; F, rostrum; G, antennule; H, antenna; I, labrum; J, mandible; K, maxillule. Scale bars: A, 0.5 mm; B, 0.2 mm; C, E–K, 0.02 mm; D, 0.1 mm.

FIGURE 352. Loboixys sibogae sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 4. Scale bars: A, C–E, 0.05 mm; B, 0.02 mm.