Nedsia scuiptilis, 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 : 64-67

Nedsia scuiptilis n.sp.

Etymology. Named for the sculpturing of the pleon.

Type locality. Barrow Island, Western Australia. Western Australian Museum sampling site BES787 .

Material examined. HOLOTYPE (Western Australian Museum WAM 7-96) male 4.0 mm.

Diagnosis. Pleonites: without dorsal spines. Head: rostrum obsolescent, lateral cephalic lobes moderately projecting. First antenna: bearing aesthetascs, Second antenna: short. Upper lip: symmetrical, not excavate. Mandibular palp: 2-articulate, articles equal in length, terminal article tapered terminating in 2 E-setae; accessory blades on rakers = 6 left, 4 R, with one interraker plumose seta on the right and one additional seta beyond the left rakers. Maxillae: without medial setae or pubescence except for the lateral margins of the second maxilla; inner plate of the first maxilla ovatoctriangular with six mid-medial to mediodistal plumose setae; palps symmetric; inner plate of the second maxilla with a row of medial setae barely extending onto the face apically with few other medial setae. Coxae: short, broader than long with few posterior spines. Maxilliped: inner plate bearing three distal plumose setae and three blunt naked terminal spines, without plumose medial setae, the outer plate bearing two distal plumose setae contiguous with a blunt naked tooth spine; palp articles 2-3 weakly setate laterally, setae at the dactylar base not organised into comb rows, the palp apex weakly produced, the dactyl with a moderately long nail. First gnathopod: palmar corner marked with one long lateral spine, moderate numbers of setae along palm. Second gnathopod: carpus barely lobate. Pereopods: 3-6 without accessory spinules on dactyls, posterior spine sets on article-6 of pereopod 3 evenly spaced, those on pereopod 4 uneven; dactyl of pereopod 7 with an extra terminal spinule. Gills: present on coxae 2-6. Pleopods: peduncles with 0,2,2 setae, 2 retinaculae and no accessory retinaculae. Epimera: epimeron 3 only with a small posteroventral tooth. Uropods: apicolateral corners of peduncles of uropods 1-2 with 3 and 2 spines respectively, the dorsal margins bearing few spines, the medial margin of uropod 1 with 2 apical spines. Telson : longer than broad, cleft 85%, bearing some medial spines.

Description of holotype (male). Body 4 mm. Pleon: pleonite 6 without dorsal spines, bearing two laterodistal and single ventrodistal spines; pleonite 5 with distal dorsolateral spines. Head ( Fig. 19 ): rostrum obsolescent; eyes absent. First antenna ( Fig. 19 ): longer than second (broken at article-ll); flagellum longer than peduncle; peduncular articles 1-2 equal in length, 2.7x article-3, the first article bearing a cluster of ventral subdistal spines and setae, a row of small ventral spines, a dorsal row of three strong spines and a weak distal seta; flagellum moderately setate, bearing aesthetascs on some articles, article-l of the primary flagellum fused, accessory flagellum 2-articulate, second article tiny, extending to MO.8 of the first article of the primary flagellum. Second antenna ( Fig. 19 ): moderately short, 0.3x body length; peduncle longer than flagellum, articles 4-5 subequal with weak setation, article-3 bearing a single dorsomedial spine and 4 ventrodistal spines; flagellum of 5 articles of diminishing dimension, lacking calceoli or aesthetascs. Upper lip ( Fig. 19 ): apically convex, pilose and spinose; symmetrical. Left mandible ( Fig. 19 ): without palp (broken), incisor 5 toothed, lacinia mobilis 5 toothed and elongate, extending to the apex of the incisor; mandible bearing 6 large setose and 1 small naked accessory blades between the incisor and molar, without interraker plumose setae or pubescence; molar triturative, without distal seta. Right mandible ( Fig. 19 ): bearing a short pa1p of two subequa1 articles, the first truncate and naked, the second cone like bearing 2 short apical Esetae; incisor of 5 teeth; lacinia mobi1is shorter than incisor, bifid, bearing anteriorly a median row of short spines, posteriorly a marginal row of setae; mandible bearing 4 accessory blades, the first denticulate, the remainder setose, with a single interraker seta lying between first and second blades, and a row of setae extending posteriorly; molar triturative, without a distal seta. Lower lip ( Fig. 19 ): bearing prominent inner lobes extending to MO.7 of the outer lobes; anterior surfaces of both lobes rugose, inner lobes naked, outer lobes bearing apicomedial spines and setae. First maxilla ( Fig. 19 ): pa1ps of two articles, almost symmetrical, the left side more slender than the right, possibly regenerent, each with 5 apical and 1 subapical slender naked spines; inner plate ovatotriangular, without pubescence except for a small lateral terminal cluster, bearing on the medial margin to the apex 6 p1umose setae; outer plate bearing two naked and five denticulate terminal spines. Second maxilla ( Fig. 19 ): outer dista1 margin of both plates pubescent, facial and medial regions lacking pubescence, outer plate bearing a single distal spine additional to the terminal setae; both plates without other setae. Maxilliped ( Fig. 19 ): palp third article with medial setae confined to the margin of the apex, bearing a single facial spine adjacent the dactylar base; apical setae marginal, not organised to comb rows; dactyl with two accessory spines arising adjacent the base of the nail and as long as the nail; medial margin of the outer plate carved into 4 sinuous indentations, without marginal spines, but associated with each a pair of long submarginal, curved, blunt spines. First gnathopod ( Fig. 20 ): coxal plate bearing 2 apical setae, the fourth article posteriorly bulbous and pubescent, carpus not lobate; propodus trapezoidal and slightly expanded apically, longer than wide, posterior margin naked but for a single submarginal spine and a pair of long apical spines; margin of the palm lined with fine setae anteriorly, posteriorly the palmar corner rounded, marked by a single long lateral bifid spine, the posterior margin of the hand pubescent; adjacent the palmar corner three stout bifid spines and two long terminally bifid spines; dactyl bearing a subterminal accessory spinule extending to the nail-less apex, which reaches to the palmar corner. Second gnathopod ( Fig. 20 ): coxa bearing 2 anterior setae, the palm strongly oblique, bearing 7 lateral and 2 medial stout trigger spines and marginally bordered with short setae, the palmar corner defined by a long lateral trigger spine; dactyl bearing 3 small spines along the inner margin, and extending to a point slightly short of the palmar corner. Pereopods ( Fig. 20 ): coxae 3-4 with 2 anterior setae only, pereopods 3-4 longer than gnathopod 2, pereopod 3 <pereopod 4, both sparsely armed, pereopod 6-7 similar, pereopod 6 <pereopod 7, articles 5 of pereopod 6 and 5-6 of pereopod 7 bearing a slight anterior keel, the anterior spines consequently slightly submarginal; coxae 6-7 bearing single posterior spines, articles 2 of pereopods 6-7 posteriorly expanded but not lobate and bearing stout trigger spines; dactyls of pereopods 3-6 without accessory spinules, pereopod 7 bearing a single subterminal spinule on the dactyl. Gills: flask shaped, present on coxae 2-6, gill 6 not reduced. Sternal gills absent. Pleopods ( Fig. 21 ): each with 2 retinaculae, without accessory retinaculae, peduncles bearing 0,1,1 setae and 0,1,1 spines, all distal, the lateral spine of peduncle 3 bearing a trigger; rami extending subequally, of 7,6,6 inner and 8,8,7 outer articles; setae of basal articles of rami = 3-2,3-2,3-2. Epimera ( Fig. 21 ): first epimera posteroventrally rounded, second posteroventrally quadrate, third slightly extended posteriorly and bearing a small posteroventral tooth, otherwise posterior margins smooth; epimera 1-3 bearing facial and submarginal ventral spines, the posterior corners marked by 2-1-1 spines, epimeron 2 bearing a single anteroventral marginal spine. Pleon ( Fig. 21 ): pleonites 1-4 bearing dorsal and dorsolateral posterior setae, the posterior margins sculptured, with many serrations, less so on pleonite 4; without spines except for pleonite 5 which bears 3 dorsal and dorsolateral spines of moderate length, and pleonite 6 with 2 lateral and 1 ventrolateral posterior spines. Uropods ( Fig. 21 ): first uropod 1.9x length of second, peduncle length greater than rami, outer margin bearing a strong basofacial spine and row of 4 dorsolateral spines, the last subapical, the medial margin bearing 2 anterior and 1 subapical dorsal spines; distal apices of peduncle bearing 1 medial and 1 lateral spines; inner ramus longer than outer, with single marginal spine at MO.6, and terminating in 5 spines, the outer ramus with 2 lateral spines at MO.4 and MO.6, terminating in an apical cluster of 4 spines; second uropod peduncle subequal to outer ramus, outer margin with 3 apical spines, inner margin with 1 mid-marginal and 3 apical spines; outer ramus bearing 1 mid-medial and 2 lateral spines at MO.5 and MO.7, and 4 terminal spines; inner ramus with 1 lateral spine at MO.7, a row of 4 medial spines and 4 terminal spines. Uropod 3 absent. Telson ( Fig. 21 ): length equal to width, as long as urosomite 3; cleft 85% of its length, the subapex notched around an apical spine like extension, the notches bearing long plumose setae; left lobe bearing small lateral spines at MO.6 and MO.8, medial spines at MO.7 and MO.9, and a single penicillate facial setule at MO.5; right lobe bearing small lateral spines at MO.6 and MO.8, facial spines at MO.85, and single lateral penicillate spinule at MO.7.

Relationship. Nedsia sculptilis in the form of the pleonites which are setate and complexly sculptured, and the epimera which are facially and submarginally spinous is similar to N. macrosculptilis and differs from other Nedsia in these ways. N. sculptilis is distinguishable from N. macrosculptilis in that the posterior margins of the fourth pleonite are without spines, and the medial margin of the outer plate of the maxilliped is without facial rugosity and is carved into 4 rather than 5 indentations.

Distribution. Barrow Island, Western Australia.

Figures

Fig. 19. Nedsia sculptilis holotype male 4 mm. Head, antennae, mouthparts.

FIg.20. Nedsla. SCUlptilis ho!otyp emale 4 mm.Legs

Fig. 21. Nedsia sculptilis holotype male 4 mm. Abdomen, pleopods, uropods, telson.