Periproctia robusta, 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 : 236-239

Periproctia robusta sp. nov.

( Figs. 157 , 158 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21279 ) , paratype (intact ♀, MNHN-IU-2014-21280), anddissectedparatype (♀, figured) from Trididemnum discrepans (Sluiter, 1909) (MNHN-IT-2008-8737 = MNHNA 2/ TRI /119), CRRFOCDN 3256-X, Honda Bay, Palawan, the Philippines (09°55.87’N, 118°55.02’E), depth 20 m, 24 November 1997.

Etymology. This new species is named for its robust body.

Descriptionoffemale. Body ( Fig. 157A ) robust, 1.55 mmlong. Prosome unsegmented, 1.40 mm long, occupying 90% ofbodylength; dorsoventraldepth 0.58 mm. Cephalic shield and dorsal tergites of 4 pedigerous somitesdistinct:ventralbodysurfacebetweenlegsstrongly inflated, protrudingventrally( Fig.157A ).Fifthpedigerous somite completely fused with fourth. Free urosome ( Fig. 157B ) robust, steeply tapering: genitalsomite 85×218 μm, bearing copulatory pore on ventral surface. Four abdominalsomites 55×167, 44×135, 45×105, and 55×75 μm, respectively; first and second abdominal somites ornamented with rows of small spinules ventrally. Anal somite with highly sclerotized, blunt ventral protuberance on each side, ornamented with scattered spinules; anal operculum large ( Fig. 157C ). Caudal ramus ( Fig. 157C ) slightly longerthan wide (29×24 μm), armed with 2 stout claws and 4 naked setae; lengths of claws 18 and 10 μm.

Rostrum ( Fig. 157D ) small, rectangular, with stout apical tubercle bearing small irregular papillae. Antennule ( Fig. 157E ) 150 μm long and 8-segmented; suture line between 2 terminal segments indistinct; armatureformula 6, 9, 6+aesthetasc, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; 3 pinnate setaeon first segment and 2 setae on third, all other setae naked. Antenna ( Fig. 157F ) 4- segmented; first 3 segments each nearly as long as wide; coxa unarmed; basis withlarge pinnate (exopodal) seta at outer distal corner; first endopodal segment with 1 naked seta on inner margin; compound distal endopodal segment distinctly narrower than proximal segments, 3.5 times longer than wide (77×22 μm), ornamented with 3 groups of small spinules on inner surface; armed with 8 setae (arranged as 3, 2, and 3) plus small terminal claw, 25% as long as segment, typically capped with mucuslike material.

Labrum ( Fig. 157G ) with linear posteriormargin and large, setulose posteromedian lobe. Mandible ( Fig. 157H ) with narrow coxal gnathobase bearing only 2 teeth; basis with small medial seta; exopod 2-segmented with 3 and 2 setaeon first and second segments, respectively, outer distal seta on second segment about half as long as other 4 setae; endopod with 2 and 5 setaeonfirst and second segments, respectively. Maxillule ( Fig. 157I ) with 5 setae on arthrite, 1 on coxal endite, 2 on epipodite (larger proximal seta swollen proximally), 3 on medial margin of basis, 3 on exopod, and 4 on endopod. Maxilla ( Fig. 158A ) 5-segmented; syncoxawith 3, 1, 2, and 3 setaeon first to fourth endites, respectively; basis with 2 setae; endopod with 1, 1, and 2 setae on first to third segments, respectively. Maxilliped ( Fig. 158B ) with 8 medial and 1 outer distal setae.

Legs 1–4 ( Fig. 158 C-F) with 3-segmented exopods and 2-segmented endopods, with reduced setation. Outer seta on basis elongate in leg 1, short in legs 2–4. Inner distal spine on basis of leg 1 shorter than first endopodal segment. Second endopodal segment of legs 1–4 subdivided by trace of articulation on outer side. Inner setae absent on exopods of legs 2 and 3. Third exopodal segment of leg 1 bearing 3 inner setae. Third exopodal segment of leg 4 with or without 1 minute inner seta (arrowhead in Fig. 158F ). Outer distal process of first and second exopodal segments usually trifurcate. Armature formula for legs 1–4 as follows:

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

Leg 5 ( Fig. 157B ) small, consisting of protopod and free exopod; protopod with 1 pinnate seta on apex of outer process; exopod very small withnaked apical seta.

Male. Unknown.

Remarks. The small terminal claw of the antenna, which is capped with mucus-like material, may be a diagnostic feature of the new species. The new species can also be differentiated from its congeneric species by the extreme reduction of setation elements in the swimming legs. For example, the third exopodal segment of leg 4 is armed only with 4 well developed elements, the smallest number recorded for any species within the genus ( Table 3), although a setal vestige is found in one specimen.

Figures

FIGURE 157. Periproctia robusta sp. nov., female. A, habitus, right; B, urosome, ventral; C, anal somite and caudal ramus, left; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule. Scale bars: A, 0.2 mm; B, G, 0.05 mm; C-F, H, I, 0.02 mm.

FIGURE 158. Periproctia robusta sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, exopod of leg 3; F, leg 4. Scale bars: A, B, 0.02 mm; C-F, 0.05 mm.