Periproctia acutirostris sp. nov.
(Figs. 129, 130)
Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21259), paratype (intact ♀, MNHN-IU-2014-21260), and dissected paratypes (♀, figured) from Diplosoma multitestis Monniot F. & Monniot C., 1996 (Holotype MNHN-IT-2008-3581 = MNHNA2/DIP.A/109), CRRF OCDN 1813-G, eastern Filed Atoll, 140 km southwest of Port Moresby, Papua New Guinea (10°00.66’S, 145°39.90’E), depth 20 m, 22 October 1993 .
Etymology. The specific name is derived from the Latin words acut (=sharp) and rostrum (=snout) and refers to the acutely pointed apical process on the rostrum.
Descriptionoffemale. Body (Fig. 129A) consisting of stout, unsegmented prosome and narrow urosome. Dorsal shield of cephalosome with slightly produced, angular posterolateral corners (Fig. 129B). Pedigerous somites fused but recognizable by retained dorsal tergites. Fifth pedigerous somite completely fused with fouth. Free urosome (Fig. 129C) 5-segmented: genitalsomite 73×162 μm, much wider than long; copulatory pore present on ventral surface. First to third abdominal somites 75×107, 87×91, and 105×75 μm, respectively. Third abdominal somite distinctly longer than wide. First and second abdominal somites ornamented with multiple rows of minute spinules on posteroventral surface. Anal somite (Fig. 129D) short, with pair of highly sclerotized ventral protuberances ornamented with minute spinules around apex. Caudalramus (Fig. 129D) slightlynarrowing distally, about 1.2 times longer than wide (27×23 μm), armedwith 3 claws and 3 setae, and ornamented with patch of minute spinules near base of proximal seta; 3 claws unequal in length and thickness, 44, 25, and 25 μm long; dorsal and outer lateral setae pinnate, ventral seta naked, all setae longerthan ramus.
Rostrum (Fig. 129E) 85×65 μm, tapering to acute, beak-like apical process. Antennule (Fig. 129F) 136 μm long and 8-segmented; armature formula 6, 10, 8+aesthetasc, 3, 3, 2, 2+aesthetasc, and 7+aesthetasc; about half of setae large and pinnate, smaller setae naked. Antenna (Fig. 129G) withshort, unarmedcoxa; basiswith 1 large seta representing exopod at outerdistal corner; first endopodal segment with 1 naked seta on inner margin; compound distal endopodal segment about 3.3 times longer than wide (65×20 μm), ornamented with several patches of minute spinules; armed with 9 setae plus small terminal claw, less than half length of segment.
Labrum (Fig. 129H) simple with slightly convex posterior margin; ornamented with setules on posteroventral surface. Mandible (Fig. 129I) with 5 teeth on coxal gnathobase and 2 needle-like spinules between distal second and third teeth; basis with 1 seta subdistally onmedial margin; exopod 2-segmented, armed with 3 and 2 setae on first and second segments, respectively, distalmost seta slightly shorter than other 4 setae; endopod 2-segmented and armed with 2 and 5 setae (1 medial, 3 distal, and 1 outer) on first and second segments, respectively. Maxillule (Fig. 129J) with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 on basis, 3 onexopodand 4 on endopod. Maxilla (Fig. 130A) 5- segmented; syncoxa with 4, 1, 2, and 3 setae on first to fourth endites respectively; basiswith 2 setae, shorter distal seta naked; endopod with 1, 1, and 3 setae on first to third segments, respectively; 1 seta on first endite of syncoxa small, needle-like. Maxilliped (Fig. 130B) unsegmented and armed with 10 setae (arranged as 4, 4, and 2); mediodistal corner protruded.
| 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; 0-2; 1, 2, 3 |
| Leg 3 | 0-0 | 1-0 | 1-1; 1-1; 3, 1, 4 | 0-1; 0-2; 1, 2, 3 |
| Leg 4 | 0-0 | 1-0 | 1-1; 1-1; 3, 1, 4 | 0-1; 0-2; 1, 2, 2 |
Legs 1–4 (Fig. 130 C-F) with 3-segmented rami. Inner coxal seta absent in all legs. Inner distal spine on basis of leg 1 extending beyond distal margin of second endopodal segment, 32 μm long. Outersetaonbasis large (longer than exopod) in leg 1 butsmall inlegs 2–4. Exopods slightly longer than endopods in legs 1 and 2, but distinctly longerthan endopods inlegs 3 and 4. In legs 2–4, inner setae on first and second segments and proximal inner setaon third segment pinnate; all other setae on exopods rod-shaped with blunt tip. Outer distal corner of first and second exopodal segments trifurcate in leg 2 but bifurcate in legs 3 and 4. Armature formula for legs 1–4 as follows:
Leg 5 (Fig. 130G) consisting of broad protopod and small, tapering exopodal segment (13×10 μm), each tipped with 1 naked seta.
Male. Unknown.
Remarks. Periproctia acutirostris sp. nov. can be differentiated from all congeners by the possession of 3-segmented endopods in legs 1–4. In all previously described species of Periproctia the endopods of these legs are 2-segmented (Table 3)