Acuticoxa ubatubaensis sp. nov.

Type locality. Brazil, São Paulo State, Ubatuba (23º31.2’ S, 44º51.0’ W); 44 m depth, medium coarse sand.

Type material. Holotype Ƥ dissected on 8 slides (reg. no MZUSP 19626). Collected in March 1989 by T. Corbisier.

Description. FEMALE (Figs 14–17). Total body length 568 μm. Largest width measured at posterior margin of P2-bearing somite (102 μm). Body (Fig. 14 A) cylindrical and elongate, slightly flattened dorsoventrally, without deep constrictions between somites. Urosome slightly narrower than prosome.

Rostrum (Figs 14 A; 15C) well developed, triangular, with acuminate tip; completely defined at base; with pair of dorsal sensillae at about halfway its length; dorsal surface covered by small setules/spinules.

Cephalothorax rectangular, anterior margin with rounded, lobate extensions either side of rostrum; moderately produced ventrally; ornamentation consisting of sensillae and pores as illustrated in figure 14A; posterior margin smooth. Pedigerous somites (Fig. 14 A) densely covered with rows of setules and with sensillae and pores as illustrated; posterior margin finely spinulose. Urosome (Fig. 14 A–C) 5-segmented, comprising P5-bearing somite, genital double-somite, 2 free abdominal somites and anal somite. Urosomites with surface ornamentation consisting of rows of setules, sensillae and minute spinules (Fig. 14 A–C); posterior margin of P5-bearing somite finely spinulose, genital double somite to penultimate somite with incised subulate hyaline frill (Fig. 14 B–C). Genital double-somite (Fig. 14 B–C) completely fused dorsally and ventrally; ventrally with minute spinules anterior to genital field and with transverse setular rows in posterior half (Fig. 14 C–D); large copulatory pore located in midventral depression (Fig. 14 C–D); gonopores fused medially, forming single genital slit covered on both sides by opercula derived from sixth legs. P6 with small protuberance bearing 2 naked setae, innermost longest. Anal somite (Figs 14 B–C; 15A) with moderately developed, rounded, spinulose anal operculum; surface ornamentation consisting of setules and a pair of pores dorsally; anal opening with fringe of fine setules; posterior margin of somite serrate dorsally (Fig. 15 A) and smooth ventrally (Fig. 14 C).

Caudal rami (Fig. 15 A–B) elongate, 3.6 times as long as maximum width; with inner bulge halfway the ramus length and tapering posteriorly. Each ramus with 2 lateral tube-pores near outer margin, surface ornamentation consisting of irregular pattern of striations, and 7 setae: seta I naked, vestigial and closely set to naked seta II; seta III naked and displaced to ventrolateral position; seta IV naked; seta V short and stubby, less than one third the length of the ramus (but setular distal part probably broken off; cf. condition in A. biarticulata); setae IV and V not fused basally; seta VI naked; seta VII incomplete on both sides but triarticulate at base.

Antennule (Fig. 15 D) 4-segmented, arising from subcylindrical pedestal, with segments III–IV oriented posteriorly. Segment I very long, with 1 small naked seta; segment III with aesthetasc fused basally to seta and arising from distinct setophore; segment IV tapering distally. Armature formula: I-[1], II-[7 + 1 pinnate], III- [8 + (1 + ae)], IV-[10 + acrothek]. Acrothek reduced, consisting of fused seta and aesthetasc.

Antenna (Fig. 15 E) 3-segmented, comprising coxa, allobasis and free 1-segmented endopod. Coxa small, with no ornamentation. Basis and proximal endopod segment fused, forming elongate allobasis; with small naked abexopodal seta. Exopod completely absent. Free endopod slightly shorter than allobasis; medial armature consisting of 2 widely separated spines; apical armature consisting of 2 spines and 3 geniculate setae, outermost one of which fused basally to short seta and surrounded at base by few short spinules.

Mandible (Fig. 16 A) with well-developed, elongate gnathobase bearing several multicuspidate teeth and 1 pinnate seta along distal margin. Palp biramous with incorporated exopod and discrete endopod; basis with 2 setae near distal margin (1 naked seta set on a conical protuberance and 1 long pinnate seta); exopod represented by a naked seta arising from proximal half of basis (indicated by asterisk in Fig, 16A); endopod short, about ¼ the length of basis, with about 3 apical setae.

Maxillule (Fig. 16 B–C). Arthrite well developed, with 6 spines/setae around distal margin (Fig. 16 C) and 1 naked seta subapically on both anterior and posterior surface. Coxa with cylindrical endite bearing 2 naked setae. Basis with 2 endites; proximal one with 2 naked setae; distal one with 3 naked setae. Endopod incorporated into basis, represented by 2 naked setae. Exopod absent.

Maxilla (Fig. 16 D–E) with 2 endites on syncoxa. Praecoxal endite absent. Proximal coxal endite with 1 pinnate spine and 1 spine with swollen spinulose tip (Fig. 16 E). Distal coxal endite with 3 naked setae. Allobasis drawn out into strong claw showing pore along outer margin and accompanying naked seta along inner margin. Endopod incorporated into basis and represented by 2 naked setae.

Maxilliped (Fig. 16 F) elongate, arising from short pedestal. Syncoxa and basis unarmed. Endopod drawn out into long and geniculate claw; accompanying armature consisting of 1 naked seta.

P1 (Fig. 17 A) prehensile. Coxa with outer margin forming large unguiform projection. Basis with 1 pore on anterior surface, 1 pinnate seta on outer distal corner and 1 small naked seta along inner margin. Exopod 2- segmented; exp-1 with row of spinules along distal margin and 1 pinnate outer seta; exp-2 with 3 lateral and 2 apical pinnate setae. Pinnules on outer basal seta and exopodal setae long and fine. Endopod 2-segmented, twice longer than exopod; enp-1 at least 4.3 times longer than enp-2, with few spinules along inner margin and cuticular reinforcement near distal margin; enp-2 with few spinules near inner distal corner, 1 claw and 1 long seta with reinforced basal part and setular distal part.

P2–P4 (Fig. 17 B–D) small with reduced segmentation. Coxae with outer margin forming a pointed projection, smooth in P2–P3, fringed with small spinules in P4. Bases with outer corner produced into long setophore bearing pinnate (P2) or naked (P4) seta (lost in P3); with 1 large pore on anterior surface and row of spinules at inner corner (in P3–P4 only). Exopods 1-segmented, with spinules along outer and distal margins (except P4); original segmentation of P2 exopod indicated by transverse row of long spinules; all elements bipinnate and spiniform except for distal outer element on P3–P4 being naked and setiform. Endopods 1- segmented, small; with rows of spinules along inner and outer margins; with 1 naked (P2), plumose (P3) or pinnate (P4) seta apically. Armature formula as follows:

Exopod Endopod

P1 0.023 0.020

P2 0 23 0 10

P3 0 23 0 10

P4 0 23 0 10

P5 (Fig. 17 E) with baseoendopod and exopod fused, forming single plate; not fused to supporting somite; narrow intercoxal plate discernible; anterior surface with 4 secretory pores and densely covered with minute setules; with 8 elements, including 3 pinnate spines, 4 plumose setae and one of unconfirmed shape and size (missing on both sides in holotype; insertion site arrowed in Fig. 17 E).

MALE. Unknown.

Etymology. The new species is named after the Ubatuba municipality where the type locality is situated.