Periproctia obtusa, 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 : 211-214

Periproctia obtusa sp. nov.

( Figs. 139 , 140 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21265 ) from Trididemnum discrepans (Sluiter, 1909) (MNHN-IT-2008-8737 = MNHN A2/TRI/172), CRRF OPHG 1445-P, Mabul, Malaysia (04°14.05 Ń, 118°53.61 É), depth 8 m, Pilcher coll., 18 July 2004.

Etymology. The specific name is derived from the Latin obtus (=blunt) referring to the stout body of the new species.

Descriptionoffemale. Body ( Fig. 139A ) stout, 954 μm long. Prosome unsegmented, 720 μm long; greatest dorsoventraldepth320μm.Cephalosomewithlongitudinal row of about 25 small denticles along dorsal midline and with blunt, nipple-shaped, sclerotized posterolateral process at each side. Pedigerous somites fused but with 2 weak dorsal tergites present, corresponding to second and third pedigerous somites. Fourth pedigerous somite forming broad, rounded dorsal extension overlapping anterior part of genital somite (stippled area in Fig. 139B ). Fifth pedigerous somite completely fused with fourth. Freeurosome ( Fig. 139B ) 5-segmented: genital somite much wider than long, 51×135 μm, bearing small copulatory pore on ventral surface; 4 abdominal somites 58×104, 57×92, 64×78, and 32×60 μm, respectively. First to third abdominal somites ornamented with transverse rows of minute spinules ventrally.Anal somite with blunt, sclerotized ventral protuberances. Caudal ramus ( Fig. 139C ) narrowing distally, as long as wide (22×22 μm), and armed with 3 strong claws and 3 naked setae; lengths of 3 claws 28, 21, and 20 μm; setae at least as long as ramus.

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

Rostrum ( Fig. 139D ) aslongas wide (40×41 μm), roughly rhomboidal, tapering towards pointed, beaklike apical process; ornamented with 3 pairs of minute sensillae. Antennule ( Fig. 139E ) broad, 117 μmlong, and 8-segmented; armatureformula 2, 14 (or 6, 10), 7+aesthetasc, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; distal segments very short; larger setae on proximal segments pinnate. Antenna ( Fig. 139F ) 4- segmented; coxashortand unarmed; basiswith large, pinnate exopodalsetaat outerdistal corner; firstendopodal segment with 1 naked seta on inner margin; compound distal endopodal segment about 3.1 times longerthan wide (50×16 μm), ornamented with 3 patches of spinules on outer side; armed with 7 setae (including 1 pinnate and 3 bluntly tipped setae) plus small terminal claw, less than half length of segment.

Labrum missing. Mandible ( Fig. 139G ) comprising coxa bearing 5 teeth (2 proximal ones small) and 1 seta on gnathobase, and palp consisting of basis, exopod and endopod; basiswith 1 setaonmedial margin; exopod 2-segmented and armed with 3 and 2 setae on first and second segments, respectively; outer distal seta on second exopodal segment slightly shorter than other 4 exopodal setae; endopod armed with 2 and 5 setae on first and second segments, respectively; second medial seta of second endopodal segment markedly larger than other 4 setaeon segment. Maxillule ( Fig. 139H ) bearing 7 setae on arthrite, 1 on each coxal endite and epipodite, 3 on medial margin of basis, 3 on exopod and 4 on endopod. Maxilla ( Fig. 140A ) 5-segmented, syncoxawith 8 setae (arranged 3, 1, 2, and 2), 2 on basis, and 1, 1, and 3 on first to third endopodal segments, respectively. Maxilliped ( Fig. 140B ) lobate, bearing 8 medial setae and 1 apical seta.

Leg 1 ( Fig. 140C ) with 3-segmented rami. Legs 2–4 ( Fig. 140 D-F) each with 3-segmented exopod and 2- segmented endopod. Innercoxalsetaabsentinlegs 1–4. Outer seta on basis large and pinnate in leg 1, small and naked in legs 2–4. Three distal setae on third endopodal segment of leg 1 enlarged. Inner seta on second exopodal segment of legs 3 and 4 rudimentary ( Fig. 140E, F ). Inner setaon first endopodal segment and proximal inner seta on second endopodal segment of leg 4 also rudimentary ( Fig. 140F ). Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 139B ) represented by small plate bearing 2 distal processes; each process tipped with 1 pinnate seta.

Male. Unknown.

Remarks. Periproctia obtusa sp. nov. can be differentiated from other species in the genus by the combination of three characteristic features: (1) the endopod of leg 1 is 3-segmented; (2) the cephalosome bears a longitudinal row of about 25 minute surface denticles along the dorsal midline; and (3) the coxal epipodite of the maxillule bears only a single seta (it lacks the typically smallsecond seta). The first of these features is shared only with P. acutirostris sp. nov., but the other two features have not been recorded in any Periproctia species.

Figures

FIGURE 139. Periproctia obtusa sp. nov., female.A, habitus, right; B, urosome, ventral; C, caudal ramus; D, rostrum; E, antennule; F, antenna; G, mandible; H, maxillule. Scale bars: A, 0.1 mm; B, 0.05 mm; C-H, 0.02 mm.

FIGURE 140. Periproctia obtusa sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, exopod of leg 3; F, leg 4. Scale bars: 0.02 mm.