Doropygus pinguis Ooishi, 1962

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 : 379-382

Doropygus pinguis Ooishi, 1962

( Figs. 251 , 252 )

Syn.: Doropygus pulex pinguis Ooishi, 1962: 16 , fig. 5, 6. Doropygus pinguis: Seo & Lee, 1997: 550 , figs. 8-10; Kim, 2012: 55, figs. 28, 29.

Material examined. 1 ♀ (dissected, (MNHN-IU-2017- 2165) from Polyandrocarpa zorritensis (Van Name, 1931) , Kochi, Japan, 1993.

Descriptionoffemale. Body ( Fig. 251A ) stout, 2.73 mmlong. Prosome 2.18 μmlong, incompletely 5-segmented. Dorsal cephalic shield well-defined; metasome gradually becoming broader posteriorly. Fourth pedigerous somite swollen and forming brood pouch, about 1.3 times longer than wide in lateral view, with convex dorsal margin and broadly rounded posterior margin. Freeurosome ( Fig. 251B ) 5-segmented: genital somite 136×300 μm; 4 abdominalsomites, 164×264, 155×240, 109×205, and 136×295 μm, respectively. Anal somite wider posteriorly, strongly divergent together with caudal rami, with wide postomedian incision. Caudal ramus ( Fig. 251C ) evenly tapering, about 4.1 times longer than wide (236×58 μm) and about 1.7 times longer than anal somite: armed with 6 small, thin setae; outer proximal and dorsal setae positioned at 34 and 68% of ramus length, respectively.

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

Rostrum ( Fig. 251D ) weak, aslongas wide, nearly semicircular. Antennule ( Fig. 251E ) 320 μmlong, 9- segmented,taperingdistally;armatureformula3,16+spine, 6, 4+aesthetasc, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; 2 larger setae on first segment pinnate, all other setae naked.Antenna ( Fig. 251F ) 4-segmented; coxa unarmed; basis 120×54 μm, with 3 small setae distally, 2 inserted on small knob (representing exopod) at outer distal corner; first endopodal segment unarmed, 74×53 μm; compound distal endopodal segment 4.0 times longer than wide (120×30 μm) and as long as basis; armed with 9 small setae arranged as 1, 1, 2, 2, and 3 (all attenuated at tip) plus terminal claw about half as long as segment.

Labrum ( Fig. 251G ) with large, linguiform posteromedian lobe; posterior marginand lobe all densely setulose. Mandible ( Fig. 251H ) consistingof coxa, basis, exopod and endopod: coxa with 5 teeth and 1 small proximal seta on medial margin of gnathobase: basis with 1 seta mediodistally; exopod armed with 4 equally large setae and 1 small, vestigial seta distally; endopod incompletely articulated from basis, armed with 4 and 8 setae on first and second segments, respectively; first endopodal segment ornamented with minute spinules on ventral surface.Paragnath ( Fig. 251I ) assmalllobe bearing patch of minute spinules apically and setules on medial margin. Maxillule ( Fig. 251J ) with 9 setaeon arthrite, 1 on coxal endite, 2 on epipodite, 3 on medial margin of basis, 4 on exopod and 2 on endopod; setaon coxal endite about twice as long as wide; 4 setae on exopod increasing in length from medial to outer. Maxilla ( Fig. 251K ) 5- segmented, armed with 3, 1, 2, and 3 setae on first to fourth endites of syncoxa, 3 setae on basis, and 1, 1, and 3 setae, respectively, on first to third endopodal segments. Maxilliped ( Fig. 252A ) incompletely 2-segmented and armed with 9 setae on first segment and 2 large setae on short second segment.

Leg 1 ( Fig. 252B ) with 3-segmented rami; exopod distinctly longer than endopod. Outer setaon basis pinnate and evenly attenuated. Inner distal spine on basis 55 μm long, finely spinulose along margins. Legs 2–4 with 3- segmented exopods and 2-segmented endopods ( Fig. 252C, D ); endopod subequal in length to exopod in legs 2 and 3, but slightly shorter in leg 4. Inner coxal seta large in legs 2 and 3, but small in leg 4. Outer seta on basis small and naked in legs 2–4. Outer setae on exopods and all setaeon third exopodal segment naked inlegs 2–4. Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 252E ) comprising protopod with 1 outer seta subdistally and row of minute spinules near base of exopod, plus free exopodal segment about 3.6 times longer than wide (127×35 μm), armed with 2 setae distally (47 and 27 μm long, respectively), ornamented with 3 rows of minute spinules on dorsomedial surface.

Male. Unknown.

Remarks. This species was first described by Ooishi (1962) as a subspecies of Doropygus pulex , but was subsequently raised to species level by Seo & Lee (1997). The form and length of the body, and the armature of the cephalic appendages and legs of our single female specimen show no significant differences from the original description of D. pinguis by Ooishi (1962). There are some differences, such as the relative size of the distalmost small seta on the mandibular exopod and the pinnation of antennular setae, but these are minor.

In the genus Doropygus only three species have the maxillule bearing 4 setae on the exopod and 2 setae on the endopod, combined with the mandibular exopod bearing 4 large setae plus a vestigial seta, as in D. pinguis . Doropygus pinguis is distinguished from these congeners ( D. humilis , D. louisiae Jones, 1979 , and D. parahumilis sp. nov.) by having a typical terminal claw on the antenna (cf. the claw is fringed with a membranous hyaline fringe in both D. humilis and D. parahumilis sp. nov.), by the presence of 8 setae on the second endopodal segment of the mandible (7 setae in D. lousiae according to Jones, 1979), and 9 setae on the first maxilliped segment (8 setae in D. louisiae and D. parahumilis sp. nov.).

Figures

FIGURE 251. Doropygus pinguis Ooishi, 1962, female. A, habitus, right; B, urosome, ventral; C, right caudal ramus, ventral; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, paragnath; J, maxillule; K, maxilla. Scale bars: A, 0.5 mm; B, 0.1 mm; C–K, 0.05 mm.

FIGURE 252. Doropygus pinguis Ooishi, 1962, female.A, maxilliped; B, leg 1; C, leg 2; D, leg 4; E, leg 5. Scale bars: A, D, E, 0.05 mm; B, C, 0.1 mm.