Periproctia angusta, 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 : 209

Periproctia angusta sp. nov.

( Figs. 137 , 138 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21264 ) from Hypodistoma deerratum (Sluiter, 1895) CRRF. Coll. , Papua New Guinea.

Etymology. The specific name is derived from the Latin angust meaning “narrow” and refers to the narrow body of the new species.

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

Descriptionoffemale. Body ( Fig. 137A ) narrow, 927 μmlong. Prosome 710 μmlong, cylindrical, slightly dorsoventrally depressed; consistingof cephalosome and fused pedigerous somites, without dorsal tergites. Cephalosome with weakly rounded posterolateral lobes. Fifth pedigerous somite completely fused with fourth. Freeurosome ( Fig. 137B ) 5-segmented: genitalsomite much widerthan long, 99 μm wide; firsttothird abdominal somites 61×73, 67×61, and 58×48, respectively. Second abdominal somite ornamented with row of minute spinules on ventral surface. Anal somite ( Fig. 137C ) short, with pair of large, tubercle-like ventral protuberances covered with dense ornamentation of fine spinules. Caudal ramus ( Fig. 137C ) about 1.2 times longer than wide (17×14 μm); armed with 3 claws and 3 naked setae; lengths of claws 22, 15, and 14 μm; 1 seta (second proximal seta) with blunt tip.

Rostrum absent. Antennule ( Fig. 137D ) 85 μmlong and 8-segmented; armatureformula 5, 10, 7+aesthetasc, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; 3 of 5 setae on first segment pinnate. Antenna ( Fig. 137E ) stout, 4-segmented; coxa, basis, and first endopodal segment subequal in length; basis with large plumose seta representing exopod; first endopodal segment with 1 naked setaon inner margin; compound distal endopodal segment about 2.5 times longer than wide (38×15 μm), ornamented with several patches of minute spinules; armed with 8 setae (including 1 pinnate and 4 bluntly tipped setae) plus terminal claw about half as long as segment.

Labrum ( Fig. 137F ) simple, unornamented, with convex posterior margin. Mandible ( Fig. 137G ) with 5 teeth, 2 spinules between distal second and third teeth, and 1 small proximal setaon coxal gnathobase; basis withsmall medial seta; exopod 2-segmented and armed with 3 setae on first segment and 2 setae on small second segment, outer distal seta on second segment about half as long as other 4 setae; endopod armed with 2 and 6 setae on first and second segments, respectively. Maxillule ( Fig. 137H ) with 7 setae on arthrite, 1 on coxal endite, 2 on epipodite, only 2 on medial margin of basis, 3 on exopod and 4 on endopod. Maxilla ( Fig. 138A ) 5-segmented; syncoxawith 8 setae 8 (3, 1, 2, and 2), 2 on basis, and 1, 1, and 3 on first to third endopodal segments, respectively. Maxilliped ( Fig. 137I ) lobate, armedwith 8 medial and 2 apical setae.

Legs 1–4 ( Fig. 138 B-E) with 3-segmented exopods and 2-segmented endopods. Inner coxal seta absent in all legs. Outer seta on basis large, slightly longer than exopod in leg 1, but much smaller in legs 2–4. Third exopodal segment of leg 1 armed with 3 spines and 3 inner setae. Third exopodal segment of legs 2–4 terminating in acute, spiniform process. Outer and distal setae of exopods of legs 2–4 rod-shaped, bluntly tipped.Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 138F ) small, consistingof broadprotopod and exopod; protopod with digitiform outer extension tipped with weakly pinnate seta; small exopodal segment incompletely articulated at base, tapering, withnaked apical seta.

Male. Unknown.

Remarks. One outstanding setation feature, the possession of only 3 inner setae (armature formula II, I, 3) on the third exopodal segment of leg 1 ( Table 3), serves to characterise the new species. In all other known species of Periproctia , this segment of leg 1 carries 4 inner setae (armature formula II, I, 4). The presence of only 2 medial setae on the basis of the maxillule (rather than the more typical 3 setae) is also an unusual feature, shared only with P. biuncata .

Figures

FIGURE 137. Periproctia angusta sp. nov., female. A, habitus, right; B, urosome, ventral; C, anal somite and caudal ramus, left; D, antennule; F, antenna; G, mandible; H, maxillule; I, maxilliped. Scale bars: A, 0.1 mm; B, 0.05 mm; C, H, I, 0.01 mm; D-G, 0.02 mm.

FIGURE 138. Periproctia angusta sp. nov., female. A, maxilla; B, leg 1; C, leg 2; D, exopod of leg 3; E, leg 4; F, leg 5. Scale bars: 0.02 mm.