Nedsia Barnard & Williams, 1995

Bradbury, J. H. & Williams, W. D., 1996, Freshwater amphipods from Barrow Island, Western Australia, Records of the Australian Museum 48 (1), pp. 33-74 : 34-36

Nedsia Barnard & Williams, 1995

Nedsia Barnard & Williams, 1995: 197.

Type species. Nedsia douglasi & Williams, 1995,by byoriginal designation

Introduction. This genus was erected by Barnard & Williams (1995) for a single species collected from North West Cape in Western Australia; only females were represented in the collection. We now redefine the genus, include description of a male specimen of N. douglasi and describe seven further Nedsia species from Barrow Island, Western Australia.

Modification of the original diagnosis is intended to accommodate: additional dorsal spination of the pleonites, variation in the ratio of lengths of articles of the peduncle of the first antenna and length of the second antenna, variation in the medial setation of the maxillae, asymmetry of the palps of the first maxilla, greater relative length of some coxae with more posterior spines, provision for some variation of length of the inner ramus of the third uropod and division of the telson . Additional diagnostic features include allowance for a symmetrical non-excavate upper lip, presence of three, rather than two, blunt naked spines on the inner plate of the maxilliped, and lack of a contiguous naked tooth spine on the maxillipedal outer plate. Reference to exclusively blunt submarginal setae is deleted, as are variation of the apex of the maxillipedal palp, additional numbers of peduncular setae of the pleopods, equal pleopodal rami, and reduction of the spination of the rami of the first and second uropods.

The species described in this report are congeneric with the hitherto mono-typic genus Nedsia . Examination of these new Nedsia species led to a review of generic characteristics and a redefinition of the genus. All the Barrow Island species of Nedsia display apically dentate palmar spines on the first gnathopod and several also bear posterior hadziid setae on the second gnathopod. Whilst the descriptions ( Barnard & Williams, 1995) of Nedsia and N. douglasi do not make reference to bifid palmar spines, examination of others of the species from North West Cape indicates their presence in all cases. Included in the redefinition is information on sexual differences, since the original description was based only on females; male material is now available.

Diagnosis. Pleonites with few dorsal spines. Head: rostrum weak; lateral cephalic lobes moderately to strongly projecting, very broad; no antennal sinus present; eyes absent. First antenna: elongate, longer than antenna-2; ratio of peduncular articles from 3:2:1 to 2.7:2.6:1; accessory flagellum 2-articulate. Second antenna: short to very short; flagellum much shorter than peduncle; calceoli absent. Mandible: palp reduced, 2-articulate; ratio of mandibular palp articles variable, article-l not setose, terminal article linear or tapered, subtruncate; setae few or nil C- or D-setae, 2 or 3 Esetae. Lower lip: with inner lobes. Maxillae: moderately to well setose medially; inner plate of maxilla 1 ovate with variable number of medial setae, outer plate with denticulate spines, palps symmetric or nearly so, with thin apical spines; inner plate of maxilla 2 with row of medial setae extending onto face apically, other medial setae few or absent. Coxae: 1-7 mostly short, broader than long, with few or no posterior spines; coxa TODO not expanded below; coxa 4 not excavate posteriorly; coxa 5 as long as 4. Gnathopods 1-2 diverse: first gnathopod small, feeble; carpus longer than propodus, not lobate; merus lacking hyaline lobe; palm transverse, spines simple, some bearing trigger hairs and thus asymmetrically bifid, some apically dentate; spines at corner of palm-lateral 2-4 long, medial 2-5 short; setae along palm moderate to sparse and simple; second gnathopod weakly enlarged; carpus short and lobate; propodus of medium enlargement and ovate; palm oblique, irregularly spinose and sparsely setose, defining corner with 1-3 spines. Pereopods 5-7 moderately elongate: pereopod 7 longer than pereopods 5-6; article- 2 moderately expanded, ovato-rectangular, posteroventrally extended but not lobate; dactyls of pereopods 3-7 lacking accessory spinules. Coxae: 2-6 each with flask-shaped gill; coxal gill 6 not reduced; coxae 2-5 each with a thin, poorly setose oostegite. Thoracic segments: lacking sternal gills. Uropod 3: strongly extended, parviramous; peduncle short; outer ramus 2-articulate, huge; inner ramus scale like, reaching to MO.15-0.25 on article-l of outer ramus. Telson : longer than broad; cleft 90-100%; lobes weakly convex laterally, with subapical setation; setal spines, where present, lateral; single lateral penicillate setules at MO.6 to MO.7 on each side.

Additional description. Upper lip: symmetrical or asymmetrical; sometimes weakly excavate below. Mandibles: accessory blades (rakers) very few (3-4) on right side, with or without interraker plumose setae between each main raker; both mandibles with few or no additional serrations beyond rakers. Maxillae: both plates of second maxilla with apical setae of medium length; inner plates of maxillae 1-2 and medial and lateral margins of maxilla 2 poorly covered with pubescence. Maxilliped: inner plate very long with distal row of several plumose setae and 3 blunt naked spines, and short medial row of plumose setae; outer plate large, with few distal plumose setae, continuous with a blunt naked tooth spine in some; medial margin carved into sinuosities, spineless; submarginal face with pairs of setae; palp articles 2-3 weakly setose laterally, article- 2 moderately setose medially, article-3 with setae or comb rows of setae near the base of the dactyl, apex weakly or not produced, dactyl unguiform, with short to moderate length nail. Gnathopods: dactyls lacking inner tooth spine, lacking nail; first gnathopod without rastellate seta of article-4. Pereopods: 3-4 of proportions similar to pereopods 5-7; posterior spine sets on article- 6 of pereopods 3-4 unevenly spaced. Pleopods: similar; peduncles with 1-3 setae each; rami extending subequally to equally, basomedial setae of inner rami of some bifid; retinaculae 2 or 3, no more than one accessory retinaculum present. Epimera: posteroventral tooth of epimera 1-3 usually absent; posterior margins smooth, and/or sinuous and sparsely setulose; some bearing facial spines near ventral margin. Uropods: apicolateral corner of peduncles on uropods 1-2 with 1 and 2 spines (thus with no more than 1 ventrally displaced spine on uropod 2); dorsal margins with or without spines; medial margin of uropod 1 with 1 or 2 apical spines; rami of uropod 1 extending subequally; outer ramus of uropod 2 shortened; uropod 1 with basofacial spine; most rami of uropods 1-2 with two spine rows, albeit reduced; medial setae of outer ramus of uropod 3 sparse, usually with subdistal peduncular setae or spines. Urosome: ventrodistal spine on urosomite 1 at base of uropod 1 absent.

Composition. Nedsia now contains eight species. All the species recorded here are thought to be marine invaders or "strandings".

Key to Species of Nedsia

1. Second maxilla with sparse marginal basomedial pubescence on inner plate (e.g., Fig. 3) or no pubescence on either plate ................................................. 2

--SecondSecondmaxilla withmoderateto dense marginalpubescence TODO TODO TODO TODO TODO TODO TODO TODO TODO

2. straskraba

3. Epimeron 1 without distolateral spines, peduncle of uropod 1 with a lateral row of short facial spines besides the basofacial and distal spines, the palmar corner of gnathopod 1 rounded, the outer plate of the maxilliped tapering apically and with weakmedialcusps ........................................................................................................ N.fragilis

--Epimeron 1 with distolateral spines, peduncle of uropod 1 without facial spines besides basofacial and distal spines, palmar corner of gnathopod 1 subquadrate, outer plate of maxilliped not tapering, but rounded apically and with strong medialcusps ............................................................................................................ N.humphreysi

4. Posterior margins of pIeon sculpted, epimera with facial spines as well as ventral submarginal spines (e.g., Fig. 18)...........................................................7

--Posterior margins of pleon smooth, epimera without facial spines other than ventral submarginal spines (e.g., Fig. 8 )..................................................5

5. Epimera 2-3 with few ventral submarginal spines, urosomite 1 with a spine-like extension at the base of the first uropod, rami of pleopods with more than six articles, maxillipedal palp article-3 without organised comb rows of setae at base ofdactyl....................................................................................................................... N.hurlberti

6. Coxa1 with one ormore more anterior spines,without anterior TODO TODO setae, telsonwithout withoutdorsal setae,length ofthe maxillipedal TODO TODO TODO TODO TODO TODO TODO urifimbriata

--Coxa1 without anterior spine(s),with anteriorsetae setae, telson TODO TODO TODO withdorsal dorsalsetae, lengthof themaxillipedal outer outerplatenot TODO TODO TODO TODO TODO TODO TODO TODO douglasi

7. Posterolateral marginsof pleonite4with spines,medial margin TODO TODO of outer plateof maxilliped rugose, with5 indentations TODO ......................... N. macrosculptilis

--Posterolateralmargins ofpleonite 4 withoutspines, medial TODO TODO marginof outer plateof maxilliped TODO notrugose,with 4 TODO TODO TODO TODO sculptilis

Figures

Fig. 8. Nedsia hurlberti holotype female 4.5 mm. Abdomen, pleopods, uropods, telson.