Nedsia h:umphreysi, Bradbury, J. H. & Williams, W. D., 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 : 49-51

Nedsia h:umphreysi n.sp.

Figs 9, 10

Etymology. Named for W.F. Humphreys, biologist, instrumental in the collection of Western Australian cave specimens.

Type locality. Barrow Island, Western Australia, Western Australian Museum sampling site BES71O .

Material examined. HOLOTYPE (Western Australian Museum WAM 3-96) male 2 mm.

Diagnosis. Dorsal spines absent from pleonites 4-6. Head: lateral cephalic lobes slightly projecting. Upper lip: symmetrical, slightly excavate below. Mandibular palp: 2-articulate, 2E-setae only; lacking interraker plumose setae Maxillae: without pubescence, sparse to moderately setose medially. First maxilla: palps asymmetric with thin apical plumose or serrate spines. Second maxilla: medial margins sparsely setulate, without pubescence. Maxilliped: apex of third article of palp slightly produced, dactyls with moderate nail and accessory spine of almost equal length. Gnathopods: (diverse, gnathopod 2 dominant); gnathopod 1 palmar spines bifid, spines at corner of palm submarginal = 2 lateral, 3 medial; palmar margin serrate, with submarginal row of fine setae. Pereopods: pereopods 3-4 lacking posterior spine sets on article-6. Coxal gills: gills 5- 6 smaller but not substantially reduced. Sternal gills absent. Epimera: epimera 1-2 with 1, epimeron 3 with 2, posterior spines at the corner, ventrofacial spines absent. Pleopods: peduncles without setae, retinaculae = 2-3-2, accessory retinaculae absent. Uropods: apicolateral corner of peduncles on uropods 1-2 without spines, dorsal margins spineless, medial margins of both with 1 apical spine; rami of uropods 1-2 without spine rows except for inner ramus of uropod 1. Telson : cleft 100%; lobes with a small mid-lateral concavity.

Description of holotype, (male). Body (Fig. 9) 2 mm. Head: rostrum obsolescent; eyes absent. First antenna (Fig. 9): length 0.6x body, 2x antenna-2, flagellum 1.6x peduncle, peduncular article-l longest without mediodistal spines or setae, article-3 shortest, setae sparse, flagellum of 9 articles, sparsely setulate, no aesthetascs or ca1ceoli; accessory flagellum 2-articulate, article-2 tiny, total length 0.6x article-l of the primary flagellum; length of articles of primary flagellum variable, article-7 longest. Second antenna (Fig. 9): length 0.3x body, peduncle longer than (3x) flagellum, articles 4-5 equally long, articles 3-4-5 with sparse ventral setation, article-3 with apicodorsal setae, no dorsomedial spines. Flagellum 4- articulate, no ca1ceoli. Upper lip (Fig. 9): apical margin rounded, symmetrical. Mandibles (Fig. 9): left mandibular palp (2-articulate), article-1 very reduced, bud like, naked; incisor 5 toothed; lacinia mobilis with 4 teeth and 6 setose accessory blades; molar triturative with a short distal plumose seta, lacking other setae or pubescence; right mandible palp 2-articulate, article-1 naked, short, bud-like, article-2 reduced, tapered, 2Esetae only; incisor with 5 teeth; laciniq mobilis with 7 denticles their size increasing distally; accessory blades of 3 plumose spines; a line of setae extending onto the base of the molar. Maxillae (Fig. 9): first maxilla, left palp 2nd article with 5 serrate apical spines, terminally rounded with 3 small to moderate apicomedial setae; right palp article-2 with 4 plumose apical spines, terminally subquadrate, 4 apicomedial setae; outer plate of both sides with 7 terminal spines, some of the left without denticles; left inner plate with 4 apicomedial and apical plumose setae, moderately setose basally; right inner plate with 4 apicomedial and apical plumose setae, moderately setose medially. Second maxilla, inner and outer plates devoid of pubescence. Maxilliped (Fig. 9): palp article-3 with apical pair of slender setae, 1 marginal, 1 submarginal; medial face with 5 slender setae, the basal pair denticulate. Inner plate without ventrofacial spine. First gnathopod ( Fig. 10 ): coxal plate with 1 short seta apically, without posteroventral spines; article-4 posteriorly bulbous, carpus not lobate, propodus trapezoidal, expanding apically, longer than wide, posterior edge almost naked, corner of palm almost square, with 2 lateral and 3 medial spines and several lateral and medial setae set back from the corner; palm convex and serrate; dactylus reaching slightly beyond the corner of the palm. Second gnathopod ( Fig. 10 ): coxal plate equal to coxa 1, with a single ventral spine. Pereopods ( Fig. 10 ): coxa 3 with 1 anterior and 1 posterior ventral setae only; coxa 4 similar; pereopods 3-4-5 longer than gnathopod 1; pereopods consecutively elongate from pereopods 3-7; ratio of lengths = 137:­:140:155:185:220:270; all pereopods sparsely setose, posterior armaments of article-6 of pereopods 3-4 = 1- 0, thus only pereopod 3 with 1 locking spine; pereopods 5-7 significantly longer than pereopods 3-4 with locking spines; 1,2,2; single anterior spines on article 6 of pereopods 6-7, one posterior spine on pereopod 7 only; no keel like expansion of article 6 of pereopod 7; coxae 5 and 7 bearing 1 anterior and 1 posteroventral seta and coxa 6 one anterior seta only; article-2 of pereopods 5-7 weakly expanded posteriorly, each with only 2 setae; dactyls of pereopods 3-7 simple, naked except for outer basal penicillate setule evident on pereopods 4-7 only. Gills: of coxae 2-6 flask shaped, of coxae 5-6, smaller, but not reduced. Pleopods ( Fig. 10 ): retinaculae present on each pair, arranged 2-3-2, accessory retinaculae absent; peduncles without setae; rami extending equally, outer rami of 4-4-3 articles, inner 4-3-5. No setae bifid. Epimera ( Fig. 10 ): each posteroventrally rounded, posterior margins slightly convex, smooth, without setae except for a single seta marking the posterior corner of epimera 1-2 and two on epimeron 3; ventrofacial spines absent; lacking oblique lateral ridge. Pieon ( Fig. 10 ): pleonites with few posterior dorsal or lateral setae; pleonite 1 with 1 dorsal, 2 lateral; pleonite 2 with 1 submarginal and 1 marginal dorsal; pleonite 3 with 2 lateral; pleonites 4 and 5 with 1 lateral; pleonite 6 with 1 mid-lateral and 1 distoventral seta. Uropods ( Fig. 10 ): uropod 1 peduncle length lAx outer ramus, 1.2x inner ramus, apicodistal spines absent, bearing a single medial subapical spine, and basofacial spine at MO.3; inner ramus only with a mid-medial spine; both rami with 4 terminal spines; uropod 2 peduncle subequal to length of inner ramus, 1 apicodorsal spine slightly subdistal; other spines and setae absent; outer ramus shorter than inner (0.8x), both rami without spines, except 3-4 terminal spines. Telson ( Fig. 10 ): longer than broad (1.8x), as long as urosomite 3; cleft 100%; apices pointed, not notched, each with 2 long plumose subapical setae, 2 apical setae, and a single lateral penicillate setule at MO.6.

Relationship. Nedsia humphreysi differs from N. douglasi in the reduced number of articles of variable lengths of the first antenna and relatively longer second antenna, a symmetrical and non-excavate upper lip, greater number of mandibular setose accessory blades and presence of a p1umose mo1aria1 seta and basal mo1arial setae, palps of first maxilla asymmetrical, the inner plate with an extra seta, the second maxilla devoid of pubescence, the inner plate of the maxilliped without a ventrofacial spine, palmar corner of the first gnathopod with fewer armaments, the palm serrate and the dactyl reaching beyond the corner. The coxal plate of the second gnathopod is narrower, posteroventral margins of epimera rounded, epimera lacking ventrofacia1 spines, first uropod lacking apicodista1 spines, second uropod peduncle les spinous, relatively shorter with only a single apicodorsal spine, the telson more slender, the apices pointed, not notched. Nedsia humphreysi is similar to N. straskraba and N. fragilis , but distinct from N. hurlberti , N. urifimbriata , N. macrosculptilis and N. sculptilis , in that marginal pubescence is not present on both plates of the second maxilla. Nedsia humphreysi differs from N. straskraba in that the pleonites bear dorsal spines, and from N. fragilis in that the first epimeron lacks distolateral spines, the peduncle of the first uropod is without a row of facial spines, the palmar corner of the first gnathopod is subquadrate rather than rounded, and the outer plate of the maxilliped is not tapering and is armed with distinct medial cusps.

Distribution. Barrow Island, Western Australia.

Figures

Fig. 10. Nedsia humphreysi holotype male 2 mm. Legs, abdomen, pleopods, uropods, telson.