Nedsia hurlberti, 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 : 43-47

Nedsia hurlberti n.sp.

Figs 6-8

Etymology. Named for S.H. Hurlbert, noted biostatistician and salt lake limnologist.

Type locality. Western Australia, Barrow Island, Western Australian Museum, Western Australian Museum sample site BES545 .

Material examined. HOLOTYPE ( Western Australian Museum WAM 2-96) female 4.5 mm, unique specimen.

Diagnosis. Pleonite 6: small dorsal spines, displaced laterally. First antenna: ratio of peduncular articles 45:40:15. Second antenna: very short. Upper lip: symmetrical, not excavate. Mandible: palp 2-articulate, article-l not setose, article-2 linear, setae = 2E; plumose interraker setae present between each main raker; no additional serrations beyond rakers. Maxillae: well setose medially. First maxilla: inner plate with 7 plumose medial setae; palps symmetric with 7 thin apical spines. Second maxilla: inner plate wi~h a row of medial setae barely extending onto face aplcally, no other medial setae. Maxilliped: outer plate large, with 2 stout plumose setae distally and a single naked toothspine; paired submarginal medial setae of the outer plate blunt, apically curved; palp articles 2-3 with single lateral setae, article-3 naked basally, moderately setose distally, with rows of short setae adjacent the base of the dactyl, the apex not produced. Coxae: coxae 1-4 lacking posterior spines. First gnathopod: palm slightly oblique, palmar spines apically dentate. Second gnathopod: defining corner with 2 spines. Epimera: without setae, each with some facial spines adjacent ventral and posterior margins. Pleopods: peduncles of pleopods 1-2 without setae, of pleopod 3 with 2 lateral setae; basomedial setae of inner rami bifid, no accessory retinaculae. Telson : cleft 100%.

Description of holotype (female). Body 4.5 mm. Head (Fig. 6): rostrum obsolescent; eyes absent. First antenna (Fig. 6): length 0.5x body (broken at article- 17), longer than antenna-2, flagellum much longer than peduncle; peduncle article-l longest, 3 shortest, setae sparse; flagellum of many articles (17+), without calceoli or aesthetascs; accessory flagellum of 2 articles, article-2 tiny, extending to MO.7 of article- 1 of the primary flagellum; articles of primary flagellum variable in length. Second antenna (Fig. 6): short, length 0.27x body; peduncle very much longer than flagellum, articles 4-5 equally long, articles 3- 5 with weak ventral setation of 0-2-7 naked setae and 1-2-1 plumose setae, article-3 without dorsomedial spines; flagellum 4-articulate, without ca1ceoli. Upper lip (Fig. 6): without excavation of the apical margin, connection to the epistome symmetrical. Left mandible (Fig. 6): palp article-l shorter than 2 (11:35), setae of article-2 = 2E: incisor 4 toothed; 4 setose accessory blades; lacinia mobilis bearing a row of short facial setae; plumose setae lying between each raker extend to the base of the molar; molar lacking distal plumose seta, without pubescence. Right mandible: incisor 5 toothed; lacinia mobilis 4 toothed and bearing facial setae; accessory blades of 5 plumose spines. Maxillae (Fig. 6): first maxilla palps of both sides bearing 7 thin apical and subapical spines; outer plate with 7 denticulate spines, the inner plate 7 medial setae; second maxilla, medial and apicomedial margin of both plates pubescent as is basomedial margin of inner plate. Maxilliped (Fig. 6): palp article-3 with moderate setae on the inner edge, dactyl bearing a row of midfacial setae and terminal accessory spine slightly longer than the nail. First gnathopod (Fig. 7): coxal plate bearing 4 short setae apically, without posteroventral spines; article-4 posteriorly bulbous and facially pubescent; carpus not lobate; propodus trapezoidal, expanding slightly apically, longer than wide, the posterior edge naked, corner of the palm almost square marked laterally by 2 moderate unarmed spines and 1 long trigger spine, and medially by 4 stout trigger spines, palm convex, dactylus reaching the palmar corner, bearing 3 small spines submarginal to the inner edge. Second gnathopod (Fig. 7): coxal plate broader than coxa 1, poorly setose, with 3 anterior setae; propodus 2x that of gnathopod 1, palm bearing 5 lateral trigger spines, single unarmed distal spine, single medial trigger spine at MO.5 and a single long seta at MO.2 from the palmar corner; the palmar edge is finely serrated, the corner defined by a single long slender trigger spine, 1 long, stout trigger spine and 2 long setae. Pereopods (Fig. 7): coxa 3 slightly larger than coxa 2, coxa 4 more irregular, both with similar setae = 3 anterior, none posterior, coxae 5- 7 with few setae on the ventral margin of posterior lobes (0-0-2); pereopods 3-7 longer than gnathopod 2, progressively elongate; pereopods 3-4 posterior armament formula of article-6 = S-S-S-S and S-2S­ S-S, thus both with a single locking spine; pereopods 5-7 each with 2 locking spines; article-6 of pereopod 7 without posterior keel like expansion; article-2 of pereopods 5-7 expanded, but not posteroventrally lobate, bearing small trigger spines; pereopods 3-7 dactyls simple, naked, with an outer basal penicillate setule and a short subterminal seta. Gills: flask shaped gills on coxae 2-6; gill of coxa 6 not reduced. Oostegites: thin, strap like and poorly setose, present on coxae 2-5. Pleopods ( Fig. 8 ): 2 retinaculae per pleopod, without accessory retinaculae, peduncle 3 only bearing a single apicolateral seta, rami extending subequally, the inner rami bearing 9-9-8 articles, the outer 9-9-6; basal article setae of rami 1-2 = 1-1- 1-1, of which the inner seta is bifid on each. Epimera ( Fig. 8 ): epimera 1-2 posteroventrally curved; epimeron 3 subquadrate, the posteroventral corners with 1-1- 2 setae; posterior margins smooth, barely setulose, ventrofacial spines present as 1-4-6. Pleon ( Fig. 8 ): pleonite 3 with a tiny posterior dorsal seta, pleonite 6 with 2 distolateral and 2 distoventral spines; uropod 3 strongly extended beyond uropods 1-2 in entire animal. Uropod: lengths relative to uropod 1 = uropod 2 0.6x, (uropod 3 1.3x). Urosome ( Fig. 8 ): ventrodistal spine at base of uropod 1 on urosomite 1 absent, although urosomite 1 extended ventrodistally in a spine like projection. Uropods ( Fig. 8 ): uropod 1 peduncle length equal to medial ramus, the outer margin bearing a single apicodistal spine and row of 4 dorsal spines, the medial margin 2 apical spines; rami subequal, both with 2 sparse rows of marginal spines, spines of the apex = 4 and 5; uropod 2 peduncle 0.9x length of outer ramus, bearing, as well as 2 apicolateral spines, single lateral and dorsal subapical spines, 1 dorsolateral spine at MO.7, 1 lateral spine at MO.5 and 1 mid-apical dorsal spine; no apical spines of the medial margin; (outer ramus shorter than inner) (both) with 2 rows of marginal spines of the form 5-1,(1-3), spines of the apex = (4)-5; uropod 3 (lost; similar to others of genus i.e. peduncle much shorter than outer ramus, shorter than urosomite 3, with subdistal seta, an apicolateral cluster of 5 spines, the outer ramus proximal article with several irregular spine/seta ranks, article-2 shorter but similarly armed; inner ramus much shorter than outer (OAx) with a single apical spine). Telson ( Fig. 8 ): 1.3x longer than broad, shorter than urosomite 3 (0.75x); cleft 100% of length; apices barely notched, 2 long penicillate setules and 1 shorter naked seta subapically, dorsal setae at MO.5 and MO.8, single medial seta at MO.6, and a single penicillate setule dorsolateral at MO.6.

Relationship. Nedsia hurlberti varies from N. douglasi in the shorter relative length of the first antenna and the variable length of the articles of the primary flagellum, no excavation or asymmetry of the upper lip, reduced dentition of the left mandibular incisor, inner plate of the first maxilla with an extra seta, the inner plate of the second maxilla apically pubescent, palp and dactyl of maxilliped more spinose, as are the propodus and dactyl of the gnathopods, absence of a posterior keel like extension of the sixth article of the seventh pereopod, the posterior margins of the epimera sinuous and epimeron 2 bearing an additional ventral seta, pleopods bearing an accessory retinaculum, the telson longer and more slender. Nedsia hurlberti differs from N. straskraba , N. fragilis and N. humphreysi in that the margins of both plates of the second maxilla bear pubescence, from N. macrosculptilis and N. sculptilis in that the pleon is not sculpted, nor the epimera bearing facial spines, and from N. urifimbriata in the presence of few ventrofacial spines on the second and third epimera, a spine like extension of the first urosome at the base of the first uropod, less than six articles of the pleopodal rami, and in the absence of organised comb rows of setae at the base of the dactylus of the maxillipedal palp.

Distribution. Barrow Island, Western Australia.

Figures

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