Pygodelphys inflata, 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 : 98-101

Pygodelphys inflata sp. nov.

( Figs. 64 , 65 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21234 ), from Perophora sp., CRRFOCDN 8166-L, Palau (07°21.75 Ń, 134°30.31E), depth 1 m, 09 November 2001.

Etymology. The name of the new species alludes to its inflated brood pouch.

Descriptionoffemale. Body ( Fig. 64A ) strongly flexed ventrally. Bodylength 1.19 mm. Cephalosome to third pedigerous somites dorsoventrally depressed. Brood pouch markedly inflated, globular, thin-walled, and longer than anterior part of prosome. Free urosome ( Fig. 64B ) 5- segmented; comprising genital somite, much broader but shorter than abdominal somites, plus 4 freeabdominal somites, gradually narrowing posteriorly; each wider than long. Caudal rami ( Fig. 64B ) divergent, narrowing distally, about 4.6 times as long as wide (132×29 μm) and 2.3 timeslongerthan anal somite, ornamented with setules along inner margin; armed with 6 setae, outer lateral seta naked and positioned at 37% of ramus length; four distal setae pinnate, longest seta as long as ramus, smallest subdistal seta naked.

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

Rostrum ( Fig. 64C ) longerthanwide (80×62 μm), articulated at base, tapering distally towards rounded apex. Antennule ( Fig. 64D ) 9-segmented; armature formula 3, 17, 6, 4+aesthetasc, 4, 3, 2, 2+aesthetasc, and 7+aesthetasc; proximal segments only slightly broader than distal segments; several larger setae on first to fifth segments pinnate. Antenna ( Fig. 64E ) 4-segmented, including short coxa; basis with 2 unequal, pinnate setae at outer distal corner, longer seta 1.5 times length of shorter seta; first endopodal segment with 1 medial seta; compound distal endopodal segment about 3.7 times longer than wide (59×16 μm); armed with 11 setae (grouped as 1, 1, 3, 1, 2, and 3) plus terminal claw, about twice as long as segment.

Labrum ( Fig. 64F ) with patch of setules at each posterolateral corner; posterior margin concave. Mandible ( Fig. 64G ) with 5 teeth and 2 smallsetae on coxal gnathobase and 1 spinule between proximal 2 teeth; basis with 1 seta and tuft of setules on medial margin and setules along outer margin; exopod 3-segmented, with 2, 1, and 2 setae on first to third segments, respectively, 2 distal setae much larger than other 3: endopod with 2 and 8 setae on first and second segments, respectively. Maxillule ( Fig. 64H ) with 8 setae on arthrite, 1 on coxal endite, 2 on epipodite, and 3 (2 small proximal and 1 larger distal) on medial margin of basis; exopod with 4 setae distally; endopod unsegmented with 6 setae (2 medial and 1 on outer subdistal setae smaller than distal 3). Maxilla ( Fig. 65A ) 5-segmentedwith 9 setae (3, 1, 2, and 3 on first to fourth endites, respectively) on syncoxa, 3 on basis, and 1, 1, and 3 on first to third endopodal segments, respectively. Maxilliped ( Fig. 65B ) 2-segmentedwith 9 setae on first segment and 2 setae on second; second segment with partial trace of articulation subdistally and ornamented with long setules on medial margin.

Legs 1–4 with 3-segmented rami. Inner coxal seta large in leg 1, smaller in legs 2 and 3, rudimentary in leg 4 ( Fig. 65 C–E). Outer seta on basis pinnate in leg 1, but smaller and naked in legs 2–4. Inner distal spine on basis of leg 1 elongate, 53 μm long, longerthan first endopodal segment. Outer setaon third endopodal segment of leg 1 with long, stiff setules perpendicular to setal axis; 2 inner subdistal setae on same segment enlarged. Spines on third exopodal segment of legs 2–4, and distal spine on third exopodal segment of leg 1 pectinate along outer margin. Armature formula for legs 1–4 as follows:

Male. Unknown.

Remarks. All described species of Pygodelphys are known to have an allobasis plus a single free compound endopodal segment in the antenna. The retention of a discrete basis plus a 2-segmented endopod is unique to the new species and distinguishes it from all congeneric species. The small body size, the absence of leg 5, and the possession of 2 and 8 setae on the first and second endopodal segments, respectively, of the mandible, are all features that are shared with P. patriciae . However, the latter species has 3 setae on the second segment of the maxilliped (vs. 2 setae in the new species), and has shorter caudal rami which are only about 2.7 times longer than wide, compared to about 4.6 times in the new species. These differences are sufficient to justify the establishment of the new species.

Figures

FIGURE 64. Pygodelphys inflata sp. nov., female. A, habitus, left; B, urosome, dorsal; C, rostrum; D, antennule; E, antenna; F, labrum; G, mandible; H, maxillule. Scale bars: A, 0.1 mm; B, C, 0.05 mm; D–H, 0.02 mm.

FIGURE 65. Pygodelphys inflata sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 4. Scale bars: A, B, 0.02 mm; C–E, 0.05 mm.