Periproctia horrida sp. nov.

(Figs. 147, 148)

Typematerial. Holotype (intact ♀, MNHN-IU2014- 21271), paratypes (25 intact ♀♀, MNHN-IU-2014- 21272), and dissected paratypes (2 ♀♀, figured) from Aplidium rubripunctum (Monniot C. & Monniot F., 1997) (Type MNHN-IT-2008-699 = MNHNA1/APL.B/346), Bahrain (26°12.47’N- 50°58.14’E), CRRFOCDN B18, sea grass bed, depth 5 m, 24 September 1994.

Etymology. The specific name is from the Latin horrid (=prickly), alluding to the denticulate cephalosome of the new species.

Descriptionoffemale. Body (Fig. 147A) consisting of cylindrical prosome and small urosome. Body length 1.27 mm; prosome 1.02 mmlong, and 373 μm in dorsoventral depth. Cephalosome ornamented with longitudinal row of 12 pointed denticles anteriorly along dorsal midline (Fig. 147A, K). First to fourth pedigerous somites fused, retaining 3 weaklyexpressed dorsal tergites corresponding to first to third somites. Fifth pedigerous somite completely fused with fourth. Free urosome (Fig. 147B) 5-segmented: all urosomites wider than long; genital somite 53×185 μm, with small copulatory pore visible on ventral surface. Four abdominal somites 50×125, 51×107, 73×98, and 39×81 μm, respectively: first to third abdominal somites ornamented with rows of minute spinules on ventral surface. Anal somite (Fig. 147C) with pair of strong ventral protuberances, each ornamented with rows of fine spinules around apex. Caudal ramus (Fig. 147C) slightly longer than wide (33×31 μm), positioned dorsolaterally on somite, armed with 2 claws and 4 naked setae; lengths of claws 53 and 27 μm.

Rostrum (Fig. 147D) subcircular, 80×74 μm, wellsclerotized laterally, with small beak-like apical process. Antennule (Fig. 147E) small, 113 μmlong, 8-segmented; armatureformula 6, 10, 7+aesthetasc, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; third segment subdivided by partial suture line; 3 pinnate setae on first and second segments, other setae naked. Antenna (Fig. 147F) stout, 4-segmented; short coxa unarmed; basis as long as wide, armed large pinnate exopodal seta (arrow in Fig. 147F) at outer distal corner; first endopodal segment as long as wide, with naked seta on inner margin; compound second endopodal segment bearing large, conical process on outer margin, ornamented with 3 minute spinules at base of outer process; armedwith 5 setae (including 3 blunt distal setae) plus terminal claw bearing blunt tubercle proximally (arrowhead in Fig. 147F).

Labrum (Fig. 147G) simple, with convex posterior marginand finely setulose posteromedian lobe. Mandible (Fig. 147H) with 5 teeth and 1 proximal seta on coxal gnathobase; basiswith 1 setaonmedial margin; exopod 2-segmented, armedwith 3 and 2 setae on first and second segments, respectively; outer distal seta on second exopodal segment small, less than half as long as other 4 setae; endopod with 2 and 5 setae on first and second segments, respectively. Paragnath (Fig. 147I) as small, simple lobe, bearing setules on medial margin. Maxillule (Fig. 147J) with 7 setaeon arthrite, 1 on coxal endite, 2 on epipodite, 3 on basis, 3 on exopod, and 4 on endopod. Maxilla (Fig. 148A) with 9 setae (3, 1, 2, and 3) on syncoxa, 2 on basis, and 1, 1, and 2 on first to third endopodal segments, respectively. Maxilliped (Fig. 148B) lobate with 8 medial and 1 apical setae.

Legs 1–4 (Fig. 148 C-F) with 3-segmented exopods and 2-segmented endopods. Leg 1 with large outer setaon basis; innerdistal spine on basis longerthan first endopodal segment, 24 μm long. First and second exopodal segments of legs 2–4 with well-developed, dentiform outer distal process. Inner setaon first and second endopodal segments of leg 3 variable in size, from small (Fig. 148E) to large. Leg 4 lacking inner seta on second exopodal segment and first endopodal segment. Armature formula for legs 1–4 as follows:

Leg 5 (Fig. 147B) represented by conical protopod tipped with 1 seta and small, articulating exopodal segment tipped with 1 seta.

Male. Unknown.

Remarks. This new species is readily recognizable by a combination of two unusual features: the presence of a row of denticles along the dorsal midline of the cephalosome, and the large conical process on the second endopodal segment of the antenna. Surface denticles are also present on the cephalosome of P. obtusa sp. nov., but the large process on the second endopodal segment of the antenna is an autapomorphic feature of P. horrida sp. nov. and allows us to differentiate between these two new species.