Doropygus parahumilis, 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 : 371

Doropygus parahumilis sp. nov.

( Figs. 245 , 246 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21324 ) from Herdmania pallida (Heller, 1878) (MNHN-IT-2008-4649 = MNHN S2/ HER/44), Djibouti, Case du Général, Monniot coll., 15 October 1996.

Etymology. The name of the new species refers to its similarity to D. humilis .

Descriptionoffemale. Body ( Fig. 245A ) narrow, slightly compressed. Bodylength 3.65 mm: prosome 2.82 mmlong.Dorsalcephalicshieldclearly defined.Metasome unsegmented; 4 pedigerous somites indistinctly defined only by 3 surface constrictions. Fourthpedigerous somite forming elongate oval brood pouch about 1.8 times longer than wide; with rounded posterior margin. Free urosome ( Fig. 245B ) slender, cylindrical, 5-segmented; genital somite 192×277 μm; 4 abdominalsomites 269×277, 254×262, 161×227, and 154×269 μm, respectively. Articulations incomplete between genital and first abdominal somites and between third abdominal and anal somites. Anal somite divergent, broadening distally, with deep and wide posteromedian incision. Caudal rami ( Fig. 245B ) also divergent; each ramus about 5.4 times longer than wide (369×68 μm) and 2.4 timeslongerthan anal somite, graduallynarrowing distally: armedwith 6 small setae; 2 proximal setae located at 29 and 66% of ramus length; all setae short, less than half width of ramus at base.

Rostrum ( Fig. 245C ) 135×133 μm, well-defined from cephalosome, widest at proximal third, with rounded distal margin. Antennule ( Fig. 245D ) 408 μm long, 9- segmented; 2 proximal segments much wider than distal segments; armatureformula 3, 13+spine, 5, 5, 4, 4, 2, 2+aesthetasc, and 7+aesthetasc; 2 pinnate setae on first segment, 4 on second, 2 on each of third and fifth, and 1 on each of fourth and sixth segments. Antenna ( Fig. 245E ) slender; coxashortand unarmed; basis 154×60 μm, with 1 rudimentary setaat outer distal corner; first endopodal segment 115×54 μm, unarmed; compound distal endopodal segment elongate, about 5.8 times longer than wide (192×33 μm); armed with 8 small setae (all attenuated distally) plus slightly curved terminal claw 73 μm long, 0.38 times as long as segment, ornamented with hyaline fringe along concave margin and distal part of convex margin.

Labrum( Fig.245F )withshort,smoothposteromedian lobe; posteriormargin setulose.Mandible ( Fig. 245G ) with 5 teeth and 2 smallproximal setaeon coxal gnathobase: basiswith 1 seta mediodistally; exopod 4-segmented; first to third segments each with 1 large seta; last segment with 1 large and 1 vestigial seta; 4 large setae equal in length; endopod incompletely articulated from basis, armed with 4 and 8 setae on first and second segments, respectively; second and third outer setae on distal margin longest, more than twice length of outermost distal seta. Paragnath ( Fig. 245H ) with well-developed, semicircular outer lobe subdistally, small denticle at apex, and setules along medial margin. Maxillule ( Fig. 245I ) asin D. humilis , but seta on coxal endite broader, twice as long as wide. Maxilla ( Fig. 246A ) 5-segmented; syncoxa armed with 3, 1, 2, and 2 setae on first to fourth endites, respectively; basis with 3 setae, distal seta half length of middle seta; endopod with 1, 1, and 3 setae on first to third segments, respectively. Maxilliped ( Fig. 246B ) unsegmented but with short, transverse suture subdistally on medial side; armedwith 8 medial and 2 apical setae.

Leg 1 ( Fig. 246C ) with 3-segmented rami. Inner coxal seta extending to distal tip of endopod. Outer seta on basis evenly attenuated. Inner distal spine on basis 67 μm long, extending slightly beyond distal border of first endopodal segment. Legs 2–4 with 3-segmented exopods and 2- segmented endopods ( Fig. 246D, E ). Inner coxal seta of legs 2 and 3 extending to middle of second endopodal segment, that of leg 4 shorter, extending to distal border of first endopodal segment. Outer seta on basis of legs 2–4 rudimentary. All setaeon exopods of legs 2–4 naked. Armature formula for legs 1–4 as in D. pulex .

Leg 5 ( Fig. 246F ) consistingof protopod and exopod: protopod with 1 small setaon outer margin and row of minute spinules along distal border; exopod slender, about 4.5 times longer than wide (165×37 μm), armed with 2 unequal setae distally and ornamented with 4 oblique rows of minute spinules on dorsomedial surface; outer seta 154 μm long, slightly shorter than exopodal segment, inner seta 50 μm, about one-third length of outer seta.

Male. Unknown.

Remarks. Doropygus parahumilis sp. nov. is similar to D. humilis in having a membranous hyaline fringe on the antennal claw. It can be differentiated from the latter species by the following character states: (1) the caudal ramus is longer, 369 μm long and 5.4 times longerthan wide (vs. 159 μm long and 3.1 timeslonger than wide in D. humilis ); (2) the distal endopodal segment of the antenna is longer, 192 μm, and about 5.8 times as long as wide (vs. 137 μm long and about 4.3 times as long as wide in D. humilis ); (3) the terminal claw of the antenna is shorter, 0.38 times as long as the distal endopodal segment (vs. 0.55 times as long in D. humilis ); (4) the maxilliped bears 8 medial and 2 apical setae (vs. 9 medial and 2 apical in D. humilis ); and (5) the exopodal segment of leg 5 is longer, 4.5 times longer than wide (vs. 2.8 times longer in D. humilis ). These and other differences are summarised in Table 9 .

Figures

FIGURE 245. Doropygus parahumilis sp. nov., female.A, habitus, right; B, urosome, ventral; C, rostrum; D, antennule; E, antenna; F, labrum; G, mandible; H, paragnath; I, maxillule. Scale bars: A, 0.5 mm; B, 0.1 mm; C–I, 0.05 mm.

FIGURE 246. Doropygus parahumilis sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 4; F, leg 5. Scale bars: A, B, 0.05 mm; C–F, 0.1 mm.