Nedsia urifimbriata, Bradbury & Williams, 1996

Bradbury, J. H. & Williams, W. D., 1996, Freshwater amphipods from Barrow Island, Western Australia, Records of the Australian Museum 48 (1), pp. 33-74 : 51-55

Nedsia urifimbriata n.sp.

Figs 11-13

Etymology. Named for the presence of marginal pubescence on the third uropod.

Type locality. Barrow Island, Western Australia. Western Australian Museum sampling site BES733 .

Material examined. HOLOTYPE ( Western Australian Museum WAM 4-96) male 2.5 mm. ALLOTYPE female 3 mm .

Diagnosis. Mandibular palp: 2-articulate, setae = 2E. Second maxilla: inner plate with submarginal mediodistal row of plumose setae barely extending onto the face apically, without medial setae, without pubescence. Maxilliped: inner plate with a reduced medial row of 1 faciodistal and 1 barely facial (submarginal) ventral seta; outer plate lacking a blunt naked tooth spine contiguous with distal plumose setae, an additional submarginal facial group of 4 setae at MO.3; palp article- 3 with comb rows at the base of the dactyl, the apex weakly produced, dactylar nail moderately long, with a subequal accessory seta. First gnathopod: carpus equal to propodus in male, palmar spines symmetrically bifid. Pereopods: posterior spine sets of article-6 evenly spaced. Pleopods: peduncle 3 with 1 apicolateral seta, basomedial seta of inner rami not bifid; each with 2 retinaculae, no accessory retinaculum. Epimera: posteroventral tooth of epimera 1-3 present, posterior margins without setae, without facial spines. Uropods: uropods 1-2 apicolateral corners of peduncles with 2 and 1 spines, both rami of both uropods with only a single, poorly represented spine row; uropod 3 without subdistal peduncular setae. Telson : cleft 100%, lobes weakly convex laterally and medially; setation subapical, lacking lateral setal spines, single lateral penicillate setules at MO.3-0.5.

Description of holotype (male "x"). Body ( Fig. 11 ) 2.5 mm. Urosome: poorly armed dorsally. Head ( Fig. 11 ): rostrum obsolescent; eyes absent. First antenna ( Fig. 11 ): elongate, longer than antenna-2, broken at article-6 of flagellum-broken length 0.6x body, (length> 2x antenna-2); flagellum longer than peduncle, peduncular article-1 longest and bearing a strong mediodistal spine at MO.85, article-3 shortest, ratio of lengths 90:70:30, setae sparse; flagellum of many articles (broken at article-6), uniform, sparsely setu1ate; ca1ceoli absent, no aesthetascs; accessory flagellum 2-articulate, reaching MO.5 article-1 of primary flagellum, second article tiny. Second antenna ( Fig. 11 ): with weak ventral setation, article-3 without dorsomedial spines; flagellum 5- articulate, lacking ca1ceoli. Upper lip ( Fig. 11 ): (asymmetrical, weakly excavate below). Left mandible ( Fig. 11 ): palp 2-articulate, article-1 shorter than 2 (35:47), article-2 bearing 2 apical E-setae; incisor 5 toothed, lacinia mobilis 5 toothed bearing on the medial face a row of short spines, 4 setose accessory blades and 3 inter-raker plumose setae; molar triturative, with a moderately long distal plumose seta. Right mandible: pa1p absent, incisor 5 toothed and 1acinia mobilis 5 toothed with mediofacial spine row as on left side, 4 setose accessory blades and 2 inter-raker plumose setae; molar triturative, without distal plumose seta. Maxillae ( Fig. 11 ): first maxilla pa1p article-2 bearing thin apical and subapical spines, configuration of the left side being; 4 naked, 1 denticulate, and 1 setate, the right side having one less naked spine, the outer plate of both sides with 7 denticulate spines; inner plate with 4 plumose mediodistal setae and 1 subdistal naked seta; second maxilla outer plate apicolateral margin pubescent, inner plate basomedial margin pubescent; apical spines of both plates mostly setate, but some naked. Maxilliped ( Fig. 11 ): palp article-3 with 3 thin setae on the inner edge, no other facial setae; inner plate with a single midmedial submarginal plumose spine. First gnathopod ( Fig. 12 ): coxal plate bearing 1 or 2 short setae apically and 1 posteroventral spine; article-4 posteriorly bulbous and pubescent; carpus not lobate, propodus trapezoidal, expanding apically, length greater than width, the posterior edge naked; palmar corner rounded, marked by 2 lateral setae and 3 stout, bifid medial spines; palm convex, transverse, lined with fine setules; dactylus reaching slightly beyond the corner of the palm. Second gnathopod ( Fig. 12 ): palm bearing 3 lateral and 6 medial spines, the spine at the palmar corner medial; coxal plate no broader than coxa 1, poorly setose. Pereopods ( Fig. 12 ): coxa 3 bearing 1 anterior seta only, coxa 4 similar but with 1 small posterior seta; pereopods (3)-4 longer than gnathopod 2, pereopod (3) approximately equal to pereopod 4; articles 4-5 of pereopod 4 sparsely setulose posteriorly; posterior margin of article-6 of pereopods (3)-4 armament formula 1-1-1-1-1, i.e. with 1 locking spine; pereopods 5-7 absent; coxae 5-7 bearing few (1) setae on the ventral margin of posterior lobes; dactyls (3-7) simple as in pereopod 4, but without any basal penicillate setule. Gills ( Fig. 12 ): coxal gills of limbs 2-4 flask shaped, none present on coxae 5-6(7); sternal gills absent. Pleopods ( Fig. 13 ): peduncle of pleopod 3 only with an apicolateral seta; two retinaculae on each peduncle, without accessory spines; rami extending subequally, all with 5 articles; setae on basal articles = 3 for all rami, none bifid. Epimera ( Fig. 13 ): epimera 1 and 3 posteriorly quadrate, epimeron 2 more rounded; posterior margins of epimera 1-2 weakly convex, of epimeron 3 linear; smooth, not setulose with no ventrofacial spines, lacking an oblique ridge. Pleon ( Fig. 13 ): pleonites 4 and 5 with distolateral posterior seta, pleonite 6 with distoventral spine. Uropods ( Fig. 13 ): uropod lengths relative to uropod 1 (300)-uropod 2 (165) = 0.55x, uropod 3 (485) = 1.6x; uropod 1 peduncle length 1.3x inner ramus, outer margin without an apicodistal spine, with 2 apicomedial and 2 apicolateral spines, bearing a short row of 2 dorsal and 3 medial spines; rami of subequal length (lateral medial = 116:130), both rami bear a single mid-dorsal spine, medial ramus with 5 terminal spines, the lateral with 4; uropod 2 peduncle 0.7x length of inner ramus, no apicodorsal spines, 1 mid-lateral spine, 1 sub-apicolateral spine, and 2 apicomedial spines; outer ramus shorter than inner (70:95), both with marginal spines; lateral ramus with 1 mid-lateral spine, medial ramus with 2 medial spines; apices of rami with 4 (lateral) and 5 (medial) terminal spines; uropod 3 peduncle length 0.24x outer ramus, shorter than urosomite 3 (47:52), with no subdistal setae, an apicolateral group of 3 spines, single mid-distal spine, single apicomedial spine, and single small mid facial spine; outer ramus lateral margins of both articles and medial margin of distal article, bearing short, marginal pubescent fringe; proximal article with several irregular spine-seta ranks, these submarginal laterally, a pair of mid-facial setae, sparse medial setae, 3 apicolateral and 3 apicomedial setae, terminal article shorter (190:200), similarly armed, distally with a group of 4 long and 2 short setae. Telson ( Fig. 13 ): 1.5x longer than broad, as long as urosomite 3, cleft 100%; apices minutely notched, subapices each with 2 long distal plumose setae, 2 or 3 distal and marginal setae, each lobe bearing a single penicillate setule at MO.3 or 0.5. Small penial processes borne on sternum of thoracic article-7 ( Fig. 13 ).

Description of allotype (female "y"). Body 3 mm. First gnathopod ( Fig. 12 ): coxa with 2 anterior setae, article- 2 with 2 long posterior setal spines and 1 distal seta, merus with elongate seta of the pubescent posterior lobe and short setae anterodistally; carpus bearing 12 rather than 9 long spines, propodus and dactyl more spinous than male. Second gnathopod ( Fig. 12 ): more setose and spinous than male; coxa without posterior seta, bearing 3 (rather than 1) anterior setae. Oostegites ( Fig. 12 ): gnathopod 2-pereopod 5 each bearing a simple strap like oostegite with few setae or spines.

Relationship. Nedsia urifimbriata differs from N. douglasi in that the peduncle of the first antenna bears a strong mediodistal spine, the second antenna is slightly longer, the molar is triturative with a moderately long distal plumose seta, the palps of the first maxilla are symmetrical, the maxillipedal palp bears an extra medial seta, the inner plate a single mid-medial, submarginal plumose spine, the first gnathopod bears fewer palmar spines, the dactyl reaches beyond the palmar corner, the palm of the second gnathopod bears more spines, apical setae of the peduncles of the pleopods are present on pleopod 3 only, the first uropod lacks an apicodistal spine, and the rami with single mid-dorsal spines each, the peduncle of the second uropod is relatively short, without apicodorsal spines, and the telson longer than wide, as long as urosomite 3. Nedsia urifimbriata differs from N. straskraba , N. fragilis and N. humphreysi in the presence of marginal pubescence on both pates of the second maxilla, from N. hurlberti in the presence of ventral submarginal spines on the second and third epimera, of organised comb rows of setae at the base of the maxillipedal dactyl, and of more than six flagellar articles on the pleopods, and in the absence of a spine like extension of the first urosome at the base of the first uropod. Nedsia urifimbriata differs from N. macrosculptilis and N. sculptilis in the presence of anterior spines, but absence of setae, on the first coxal plate, the absence of dorsal setae on the telson and of sculpturing of the pleon, and in possessing a long outer plate on the maxilliped.

Distribution. Barrow Island, Western Australia.

Figures

Fig. 11. Nedsia urifimbriata holotype male 2.5 mm. Body, antennae, mouthparts.

Fig. 12. Nedsia urifimbriata holotype male 2.5 mm: all drawings except those indicated as female "y". Legs.

Fig. 13. Nedsia urifimbriata holotype male 2.5 mm. Abdomen, p1eopods, uropods, telson, penis.