Doropygus flexus Gotto, 1975

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 : 367

Doropygus flexus Gotto, 1975

( Fig. 243 )

Material examined. 1 ♀ (MNHN-IU-2018-1868) and 1 dissected ♀ from Pyura praeputialis (Heller, 1878) , Sydney, Australia, 1846.

Supplementary description of female. Body ( Fig. 243A ) 2.95 mmlong: prosome stout, 2.09 mmlong. Cephalic shield well-defined posteriorly. Metasome graduallybroadeningposteriorly, notsegmentedbutwith 4 pedigerous somites discernible by weak dorsal and lateral constrictions. Fourth pedigerous somite forming brood pouch, slightly longer than wide, with rounded posterior margin in lateral view. Free urosome ( Fig. 243B ) narrow, 5-segmented: genitalsomite 180×380μm; 4 abdominal somites 268×273, 273×252, 205×214, and 127×232 μm, respectively. Anal somite broader posteriorly, with wide posteromedian incision. Caudalramus ( Fig. 243C ) about 4.1 times longerthan wide (253×62 μm), gradually narrowing distally; armedwith 6 smallsetae; 2 proximal setae positioned at 28 and 70% of ramus length; all setae shorter than width of ramus at base.

Rostrum ( Fig. 243D ) slightly longerthan wide, narrowing distally towards rounded distal margin. Antennule ( Fig. 243E ) about 310 μmlong, 8-segmented; firstandsecondsegments expanded; armatureformula 3, 16+spine, 5, 4, 4, 3+aesthetasc, 2, and 9+2 aesthetascs; 2 pinnate setae present on first segment, 4 on second, and 1 each on third to sixth segments. Antenna ( Fig. 243F ) 4-segmented; basis (secondsegment) 102×50 μm, with 2 minute setae on distal region; first endopodal segment 89×50 μm, with 1 smallseta subdistally; secondendopodal segment about 4.5 times longer than wide (136×30 μm) and about 1.3 times longer than basis; armed with 6 setae, including 3 subequal, small, bluntly tipped setae inserted on base of terminal claw; terminal claw short, 53 μm long, about 0.4 times as long as segment.

Labrum as in D. pulex . Mandible ( Fig. 243G ) with 5 teeth, 2 small proximal setae on coxal gnathobase, and 2 small subsidiary denticles each between 2 distal teeth and between proximal second and third teeth: basis with 1 seta mediodistally; exopod 4-segmented with 4 equal setae (1 per segment); endopodwith 4 and 8 setaeon first and second segments, respectively; second and third outer distal setae equal in length, longer than other setae on endopod. Paragnath as lamellate lobe bearing setules on medial margin and shallow, rounded protuberance on outer margin; distal apex smooth, without spinules. Maxillule ( Fig. 243H ) with 9 setaeon arthrite: setaon coxal endite tapering, more than twice as long as wide; epipodite with 1 small and 1 large seta: basis with 3 setae on medial margin; 2 distal setae subequal and longer than proximal: exopod with 4 setae distally, 3 medial setae equal in length, 25 μm long, outermost seta longest, 48 μm long: endopod smaller than exopod with 2 large, subequal setae. Maxilla and maxilliped ( Fig. 243I ) as in D. pulex .

Legs 1–4 as in D. pulex but inner coxal seta of leg 1 larger, extending beyond distal tip of endopod. Leg 5 ( Fig. 243J ) with broad protopod bearing small outer seta and inner distal row of minute spinules: free exopodal segment graduallynarrowing distally, about 2.1 times longerthanwide (103×50 μm); armedwith 2 unequal setae distally (slender outer seta 2.5 times longerthan inner); ornamented with 3 oblique rows of minute spinules on dorsomedial surface.

Male. Not available in present study.

Remarks. The two female specimens of this species examined here were collected from the type host at the type locality. Gotto (1975) differentiated this species from D. pulex by the possession of the 3 blunt distalsetae on the terminal endopodal segment of the antenna and by the evenly circular posterior margin of the brood pouch. As additional differences from D. pulex , the terminal claw of the antenna is short, only about 0.4 times as long as the compound distal endopodal segment (in D. pulex and otherrelatives described above, itis morethan 0.5 times as long), the latter segment is distinctly longer than the basis, the setae on the antennule are longer and many of them are pinnate, and the exopodal segment of leg 5 gradually narrows distally, and is without a distal expansion.

Figures

FIGURE 243. Doropygus flexus Gotto, 1975, female. A, habitus, right; B, urosome, ventral; C, right caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, mandible; H, maxillule; I, maxilliped; J, leg 5. Scale bars: A, 0.5 mm; B, C, 0.1 mm; D–G, I, J, 0.05 mm; H, 0.02 mm.