Loboixys palauensis, 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 : 533-536

Loboixys palauensis sp. nov.

( Fig. 355 , 356 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21399 ) , paratypes (4 intact ♀♀, MNHN-IU-2014-21400), anddissectedparatype (♀, figured) from Diplosoma multifidum (Sluiter, 1909) , Palau, Lewin coll., 19 October 1985.

Etymology. The specific name is derived from the type locality Palau Island.

Description of female. Body ( Fig. 355A ) moderately inflated. Body length variable, 1.09 mm in dissected specimen. Prosome bulbous; dorsalcephalic shield bearing small, horn-like process, with slender tip, posterolaterally on each side ( Fig. 355B ). Metasome 1.5 timeslongerthan wide, graduallybroadeningposteriorly, articulated between first and second pedigerous somites. Fifth pedigerous somite completely fused with the fourth. Freeurosome ( Fig. 355C ) 5-segmented: genital and 4 abdominalsomites 38×152, 41×136, 48×130, 32×111, and 56×95 μm, respectively. Caudalramus ( Fig. 355D ) robust, sub-oval, 1.6 timeslongerthan wide (72×45 μm) and slightly longerthan anal somite; armed with 5 short setae (outer lateral, subdistal dorsal, and 3 distal); all setae naked and less than half width of ramus at base; outer lateral seta positioned at 56% of ramus length.

Rostrum ( Fig. 355E ) as long as wide (68×70 μm), tapering, setulose in distal third, with broadly rounded apex. Antennule ( Fig. 355F ) stout, 106 μmlong, 6- segmented; firstandsecondsegments broad; third segment subdivided by trace of articulation posteriorly; armature formula 2, 13, 5, 2, 2, and 8; all setae short and naked. Antenna ( Fig. 355G ) slender, 3-segmented; coxa and basis unarmed; endopod slender, 4.7 times longer than wide (56×12 μm), subequal in length to basis: armed with 5 smallsetae (arranged as 1, 2, and 2) plus small terminal claw, about 0.3 times as long as endopod.

Labrum missing. Mandible ( Fig. 355H ) with coxal gnathobase bearing 5 pointed teeth and 1 smallseta on broadened medial margin: basis with 1 seta on medial margin; exopod with 5 setae, outerseta halflength of outer distal seta: endopod with 1 and 4 setae on first and second segments, respectively. Maxillule ( Fig. 355I ) with 6 setae on arthrite, 1 on basis, 4 onexopodand 3 on endopod; articulation between basis and endopod indistinct; coxal endite and epipodite absent; all setae naked. Maxilla ( Fig. 355J ) 4-segmented; syncoxawith 3, 2, and 2 setaeonfirst to third endites, respectively; basis with 2 unequal setae only; first endopodal segment with 1 thick, spiniform seta; second endopodal segment with 3 unequal setae (1 thick and spiniform). Maxilliped ( Fig. 355K ) as unsegmented lobe armed with 6 setae and ornamented with minute spinules on outer distal surface.

Legs 1–4 ( Fig. 356 A-D) biramous with 2-segmented protopods. Rami of leg 1 incompletely 2-segmented. Legs 2–4 each with 3-segmented exopod and 2-segmented endopod. Inner coxal seta absent in legs 1–4. Outer seta on basis present in leg 1, but absent in legs 2–4. Basis of leg 1 with inner distal seta. First exopodal segments and first endopodal segments of legs 2–4 lacking inner seta. All setae on legs 1–4 short and naked. Armature formula for legs 1–4 as follows:

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

Leg 3	0-0	0-0	1-0; 1-1; 3, 1, 5	0-0; 1, 2, 4
Leg 4	0-0	0-0	1-0; 1-1; 2, 1, 5	0-0; 1, 2, 3

Leg 5 ( Fig. 355C ) bilobed; both lobes tipped with 1 smallseta.

Male. Unknown.

Remarks. In the genus Loboixys the caudal rami exhibit various states of setal loss, with the complete loss of caudal setae in L. ryukyuensis , L. capillosus ( Ho & Kim, 2009) comb. nov., and L. sibogae sp. nov. In contrast, L. palauensis sp. nov. carries 5 caudal setae, the largest number currently known within the genus. This characteristic setation allows the new species to be distinguished from its congeners.

The numbers of setae on the exopods of legs 1–4 of L. palauensis sp. nov. are 9, 12, 12, and 11, respectively. In Loboixys this combination of leg setation is shared only with L. pilosa sp. nov. However, the setation of the endopods of legs 1–4 is different between the two species (see Table 12 ). In addition, the lack of a claw on the basis of the maxilla, the absenceof a setarepresenting the coxal epipodite on the maxillule, and the simple, bilobed state of leg 5 are also diagnostic features of L. palauensis sp. nov., serving to differentiate it from L. pilosa sp. nov.

Figures

FIGURE 355. Loboixys palauensis sp. nov., female. A, habitus, right; B, cephalic horn; C, leg 5 and urosome, ventral; D, left caudal ramus, ventral; E, rostrum; F, antennule; G, antenna; H, mandible; I, maxillule; J, maxilla; K, maxilliped. Scale bars: A, 0.1 mm; B, D–H, J, K, 0.02 mm; C, 0.05 mm; I, 0.01 mm.

FIGURE 356. Loboixys palauensis sp. nov., female. A, leg 1; B, leg 2; C, leg 3; D, leg 4. Scale bars: 0.02 mm.