Nedsia macrosculptilis, 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 : 59-64

Nedsia macrosculptilis n.sp.

Figs 16-18

Etymology. Named for the deep sculpturing of the pleon.

Type locality. Barrow Island, Western Australia, Western Australian Museum sampling site BES786 .

Material examined. HOLOTYPE ( Western Australian Museum WAM 6-96) female 5.5 mm Barrow Island, Western Australia.

Diagnosis. Pleonites 5-6: with 3 pairs of small dorsolateral spines. Head: rostrum absent, lateral cephalic lobes moderately projecting. First antenna: ratio of peduncular articles about 3:3.5:1. Upper lip: symmetrical, apically rounded. Mandible: palp of 2 small articles, truncate, cone like, setae of article 2 = 2E; accessory blades (rakers) = 5 right or 6 left with 3 right and 4 left interraker plumose setae between each main raker. Maxillae: first maxilla inner plate facially pubescent with 8 plumose medial setae, both plates of the second maxilla with distolateral fine pubescence, outer plate with fine pubescence medially. Maxilliped: medial setae of inner plate submarginal to facial, with 1 short, naked, submarginal spine at the base of the first of these, medial margin of face of outer plate scalloped and bearing rugosities; palp third article apex setae not organised to comb rows, apex not produced; dactyl facially setose with 2 medial and 1 terminal accessory spines, the latter as long as the moderate nail. Coxae: coxae 1-4 lacking posterior spines. First gnathopod: palmar spines symmetrically bifid, and without triggers, spines at corner of palm = lateral 4 long and medially a continuous row of 5 bifid and 2 naked spines, palmar edge finely serrated anteriorly. Second gnathopod: enlarged, 2x gnathopod 1, carpus moderate, shorter than propodus; defining corner of palm with 1 enlarged spine. Epimera: posterior margin of epimeron 3 sculptured; epimera with facial and ventral submarginal spines. Coxal gills: 5-6 reduced slightly. Uropods: rami of uropods 1-2 with 2 spine rows; uropod 3 medial setae of outer ramus moderately long; spines of peduncle apical and mid-lateral. Telson : cleft 100%.

Description of holotype (female). Body (Fig. 16) 5.5 mm. Pleon: pleonite 6 with 3 dorsolateral spines and 2 distoventral spines; pleonite 5 with 4 dorsolateral spines. Head: rostrum obsolescent; eyes absent. First antenna (Fig. 16): length about 1.5x body, 2.9x antenna- 2, flagellum longer than peduncle, peduncle article-2 longest, 3 shortest, article-l bearing a strong mediodistal spine; setae moderate, flagellum of many articles (44), and a few aesthetascs; accessory flagellum 2-articulate, 2nd article tiny; article-l of primary flagellum fused, other articles shortest proximally, longest distally. Second antenna (Fig. 16): moderately short, length O.4x body; peduncle longer than flagellum, articles 4-5 equally long, with weak ventral setation, article-3 without dorsomedial spines; flagellum 5-articulate, lacking calceoli. Upper lip (Fig. 16): apical margin convex, slightly extended, spinose and pilose, connection to epistome symmetrical. Left mandible (Fig. 16): left mandible palp missing, incisor 5 toothed, lacinia mobilis 5 toothed and very broad; 6 setose accessory blades; molar with distal plumose seta, triturative, an area of pubescence leading from accessory blades to the base of the molar. Right mandible: palp 2-articulate, reduced, article-l short, naked, second article tapered, setae = 2E; lacinia mobilis with 3 smooth teeth and small denticle medial between 1st and last tooth, 5 setose accessory blades and 3 plumose interraker setae; line of pubescence leading to edge of molar. Lower lip (Fig. 16): bearing prominent inner lobes, outer lobes apically pilose and spinose. First maxilla (Fig. 16): right and left palp article-2 bearing 4 naked thin apical setae, 3 with fine distal setulate rugosities, and 1 plumose thin apical seta; outer plate with 6 denticulate, and 1 naked spines; inner plate ovate and pubescent, with 8 medial plumose setae. Second maxilla: both plates with the outer margin pubescent, as well as the median distal margin of the outer plate; basomedial margin of the inner plate with 5 fine setae grouped 2,3. Maxilliped (Fig. 16): palp article-3 with 2 thin, moderately long setae subdactylar on the inner face, and a longer pair on the outer face; article-3 moderately setose distally leading to the base of the dactyl. First gnathopod (Fig. 17): coxal plate with 5 short setae apically, without posterior ventral spines; article-4 posteriorly bulbous, marginally pubescent, but without a hyaline lobe; carpus not lobate, propodus trapezoidal, slightly expanded apically, longer than wide, posterior margin almost naked with 2 setae only; corner of palm rounded, not clearly defined, with row of 4 lateral setae, medially 2 naked spines and 5 bifid spines; palm convex, dactyl not reaching corner. Second gnathopod (Fig. 17): palm strongly oblique with 5 lateral and 2 medial spines all unevenly bifid with triggers; defining spine near corner medial, dactyl reaching spine, but not corner of palm; coxal plate broader than long, 4 anterior, 1 posterior setae. Pereopods (Fig. 17): coxa 3 with 3 anteroventral setae, similar; coxa 4 with 4 similar setae; pereopods 3-4 longer than gnathopod 2 (287,250:215), pereopod 3 shorter than pereopod 4, articles 4,5 sparsely setose posteriorly; posterior armament formulae of pereopods 3-4; S,S,S,S,S,O and S,S,sS,S,S,S thus with a single locking spine on pereopod 4 only; pereopods 5-7 similar but consecutively elongate, each with 3 locking spines; slight inward expansion of the anterior spines of article-6 of pereopod 7 revealing a slight keel; coxae 5-7 bearing single posteroventral setae on posterior lobes; article-2 of pereopods 5-7 moderately expanded, not lobate, but extended posteriorly, bearing short but moderately stout posterior setae; dactyls of pereopods 3-7 simple with single basal outer penicillate setule, and no accessory setules. Gills: of coxae 2-6 flask shaped, gills 5-6 smaller but not significantly reduced; gill 4 largest, gills 5-6 smallest. Oostegites (Fig. 17): of coxae 2 small, 3-5 thin, strap like, only those of coxa 5 with a few small setae. Pleopods (Fig. 18): retinaculae 2 each, no accessory retinaculae; peduncle of the first pleopod with no setae, of the second with 1 seta, of the third with 4; setae unevenly bifid with triggers; rami extending equally, the inner with 10,10,9 articles, the outer with 11,11, 10 articles. Setae on basal articles of rami = 1-1,1-1,1-0. Epimera (Fig. 18): epimera 1-2 posteroventrally subquadrate, epimeron 3 slightly lobate; posterior margins slightly convex, of epimeron 1 smooth, of epimeron 2 sculptured at the posteroventral corner and posteriorly sinuous, of epimeron 3 finely sculptured posteriorly; epimera with facial and submarginal spines, posterior corners marked with 2-2-1 spines, each lacking an oblique ridge, but with an incomplete row of facial spines. Pleon (Fig. 18): pleonites 1-4 bearing dorsal and dorsolateral posterior setae, and posterior margins sculptured into sharp serrations; pleonites 4-6 with lateral and/or dorsolateral posterior spines-pleonite 4 with 2 lateral, pleonite 5 with 4 dorsolateral, pleonite 6 with 3 dorsolateral as well as 2 blunt ventrolateral spines. Uropods (Fig. 18): uropod 3 strongly extended in entire animal; uropod lengths relative to uropod 1- uropod 2 = 0.6x, uropod 3 = 1.3x; uropod 1 peduncle length subequal to inner, longer ramus (175:165), outer margin with 1 long apicodistal spine besides a row of 6 dorsal spines (the 6th spine subapical), one apicomedial spine and a medial row of 7 spines (the 7th spine subapical); rami of uropod 1 subequal in length, the medial ramus being the longer (155:165); both rami with two rows of marginal spines, and 5 terminal spines, distal margins of the inner ramus finely pubescent; uropod 2 peduncle 0.85x length of inner (longer) ramus, outer margin with 1 apicodorsal and 1 apicoventral spines, dorsolateral row of 5 unevenly spaced spines, medial margin with 2 apicoventral spines and 2 subdistal apicodorsal spines, 1 mid submarginal spine and a single basomarginal spine at MO.3; outer ramus shorter than inner, both with 2 rows of marginal spines in formulae 4,3 and 3,7; distolateral and medial margins of the outer ramus and both margins of the inner ramus finely pubescent; both rami terminating in 4 apical spines; uropod 3 peduncle length 0.24x outer ramus, longer than urosomite 3 (50:40), bearing an apical cluster of 4 dorsolateral spines, 1 mid-lateral spine; all spines marginal; outer ramus proximal article long, 2.3x peduncle, with lateral and medial marginal trigger spines, regularly spaced, an irregular, medial submarginal row of 4 small spines, one displaced toward the mid line, the medial and lateral apices each with a cluster of 4 spines extending partially across the distal margin; article-2 shorter, 0.8x article-I, margins bearing regularly spaced trigger spines, paired distally, the mediodistal and apical margins setate, setae increasing in length distally and with a single apical plumose seta; inner ramus scale like, of 1 article, length 0.1x the length of the proximal article of the outer ramus (16:117), bearing 1 short and 1 medium length apicolateral trigger spines and 1 postero-mid-Iateral, submarginal mediumlength trigger spine. Telson (Fig. 18): length 2.9x width, longer than urosomite 3 (47:40), cleft 100% of its length; subapices with sinuous lateral notch, long, paired, plumose setae arising subapically, a short row of 2 distal medial setae, 3 lateral trigger spines and weak dorsal setation; single small submarginal lateral penicillate setule at MO.6 on either lobe.

Relationship. Nedsia macrosculptilis varies from N. douglasi in that the pleon is more spinous and setous, the posterior margins of pleosome 1-4 finely sculpted and setate and of 5-6 dorsolaterally spinous, the flagellum of the first antenna extremely long bearing aesthetascs, the second peduncular article is longest, the first article bearing a strong mediodistal spine, and moderately setate, the first article of the primary flagellum is fused and subsequent articles increase in length distally. The second antenna is proportionally longer, the flagellum 5-articulate, the upper lip is slightly convex apically, extended and symmetrical. Left molar bearing long plumose distal seta, is pubescent from the accessory blades to the base of the molar. Right mandibular palp 2-articulate, with a medium length plumose molarial seta, and pubescence. Palp of first maxilla bearing 8 thin apical setae, symmetrical, inner plate with 8 medial plumose setae, second maxilla basomedial margin of inner plate bearing 5 fine setae in 2 groups, maxillipedal palp article-3 with moderate distal setae leading to the base of the dactyl, gnathopod 1 palmar corner rounded, not clearly defined with more setae and spines, The second gnathopod is more spinous in the palm, epimera with facial and submarginal spines and posterior corners with 2-2-1 spines, pleon sculptured to sharp serrations, and bearing setae and dorsolateral spines on pleon 5- 6, peduncle of uropod 1 shorter than in N. douglasi , distal margins of inner ramus finely pubescent, uropod 2 shorter, outer ramus shorter than inner, distolateral and medial margins of outer ramus and all of inner ramus covered in fine pubescence, uropod 3 peduncle longer than urosomite 3, all spines marginal, article-2 0.8x article-I, inner ramus relatively longer than in N. douglasi , telson much longer than wide, subapical notch broader, telson more spinous. Nedsia macrosculptilis differs from N.sculptilis in the absences of spines on the posterolateral margins of the fourth pleonite and of rugosity on the medial face of the maxillipedal outer plate, and in reduced scalloping of the medial margin of that platc. Nedsia macrosculptilis differs from all thc other Nedsia in the presence of deep sculpturing of the pleonie posterior margins and of facial spines on the epimera. The species differs from N. straskraba , N. fragilis and N. humphreysi in bearing marginal pubescence on both plates of the second maxilla.

Distribution. Barrow Island, Western Australia.