Uroctena setosa Nicholls, 1926

Barnard, J. Laurens & Williams, W. D., 1995, The taxonomy of freshwater Amphipoda (Crustacea) from Australian fresh waters: Part 2, Records of the Australian Museum 47 (2), pp. 161-201 : 181-186

Uroctena setosa Nicholls

Figs 14-17

Uroctena setosa Nicholls, 1926: 107-108 , pI. 12, figs 1- 6, pI. 13, figs 7-9.-? Straskraba, 1964: 128- 130, figs 4-5.­ Williams & Barnard, 1988: 100-103, figs 58, 59.

As previously indicated (Williams & Barnard, 1988: 100), we do not accept Straskraba's (1964) amplified description of this species; his amplification was not based on material from the type locality and he provided no evidence that the material he described did in fact agree with the material described by Nicholls (1926). Our own previous redescription was based on the text and drawings of Nicholls (1926) and we reserved judgement on whether material in the Western Australian Museum (WAM 478-86 [1 slide], 481 -86 [3 slides], all in poor condition) represents type material. We still do. Our description, in the circumstances, was less than complete and contained many indications of where further information was required. We have now been able to procure additional material from the Western Australian Museum from the Nicholls collection. This is in good condition and we judge it to be conspecific with the taxon described by Nicholls (1926) as U setosa . Its description enables us to clarify many points of uncertainty.

Material examined. WAM 93-74 , "From either Kalamunda Mundaring Swan R or Moora Prof Nicholls coIl, n", 11 specimens, including male "c", 7.59 mm (illustrated), female "d", 5.50 mm (illustrated), male "e", 3.91 mm and male "f", 3.37 mm .

Description (male "c"). Body: urosome well armed dorsally; length, 7.59 mm.

Head ( Fig. 14 ): rostrum obsolescent; eyes absent.

First antenna ( Fig. 14 ): length 0.40 of body, 1.1 length of second antenna; peduncular article 1 longest, article 3 shortest, setae sparse; flagellum 1.4 as long as peduncle, poorly setose, primary flagellum with 18 articles, accessory flagellum 4-articulate, reaching to article 5 of main flagellum. Second antenna ( Fig. 14 ); length 0.37 body, almost pediform; peduncle longer than flagellum, article 4 scarcely longer than 5, articles 3, 4 and 5 with dense ventral setation; flagellum 9- articulate, densely setose, lacking calceoli.

Left mandible ( Figs 14 , 17 ): palp article 3 shorter than 2, article 2 with 14 inner marginal setae, article 3 with lA, IB, 3D, 9E setae; incisor 4-toothed, lacinia mobilis 4-toothed, 3 or 4 (badly preserved) setose accessory blades and 3 interrakers; molar ( Fig. 17 ) bearing short plumose seta, 2 large distal (towards incisor) hooked brushy comb setae and 3 proximal (away from incisor) detached flake-pods. Right mandible ( Fig. 14 ): incisor 4-toothed; lacinia mobilis bifid, denticulate, one denticulation moderately extended; accessory blades of 1 (probably aberrant) plumose spine, setae of palp article 3 = lA, lB, 3D, 9E. Left first maxilla: palp article 2 with 6 thin apical and medial spines and 3 subterminal facial setae, outer plate with 11 spines, most denticulate; inner plate with [?] apical setae (maxillae 1- 2 badly eroded or encrusted, unable to analyse fully or illustrate). Right first maxilla: palp article 2 with 5 thick apical spines mostly fused to segment, 1 apicolateral thin spine and 1 subterminal apicolateral facial seta. Second maxilla: outer plate apicolateral face with 1 thick spinule, apicomedial corner of inner plate with 2 weakly submarginal thick setae and no other marginal setae. Maxilliped: palp article 3 with ranks of thin setae on inner edge, apical part with rank of thicker bifid setae, apex poorly produced and not rugose; inner plate with 3 thick spines and plumose setae apically, medial row of 6 plumose setae, and one ventrofacial spine.

First gnathopod ( Fig. 15 ): coxal plate with many long setae ventrally; article 4 without posterior hump; carpus well developed, long and not lobate, with at least 3 rastellae; propodus ovatotrapezoidal, slightly longer than wide, posterior edge with 5-6 heavily setose acclivities, some of these setae approaching thickness of spines, posterolateral angle rounded, with 1 medial and 4 lateral spines, no lateral spines elongate, palm slightly oblique, scarcely convex; dactylus not exceeding end of palm. Second gnathopod ( Fig. 15 ): much larger than first gnathopod; article 2 lacking large spines; carpus short, weakly lobate: propodus huge, ovate, posterior margin almost smooth, setose, palm very oblique, palmar corner with 2 medial spines; very long setae fully present on anterior margins of carpus and propodus and on posterior margins of merus and propodus; coxal plate setose.

Pereopods ( Figs 16 , 17): ventral margins of coxae rounded, with numerous long setae, coxa 4 slightly emarginate, with 4 anteroventral but no posterior setae; pereopods 3--4 longer than gnathopod 2, pereopod 3 longer than 4, article 4 moderately setose posteriorly, article 5 less strongly setose posteriorly, posterior margin of article 6 on pereopods 3--4 with spine-seta (total) formulae of 1-2-1-3-2 and 2-3-1-3-2; pereopods 5-7 similar, 6 slightly longest, coxae with spines on ventral margin of posterior lobe, article 2 expanded and weakly lobate posteroventrally on pereopods 5 -6, bearing short to medium posterior setules. Coxal gills sausage-shaped, of medium size, very slightly decreasing in size in following order: 5, 4, 3, 2, 6; seventh segment with pair of strap-shaped penial processes about size of sixth coxal gills.

Sternal processes ( Fig. 14 ): six pairs of fleshy, sausage-shaped sternal gills present on segments 2 -7, attached to front of lateral edge of each of segments 5-7, more closely to mid-transverse line and also more central on other segments.

Epimera ( Fig. 17 ): each epimeron posteroventrally rounded, posterior margins serrate and setose, epimeron 1 with 3 ventral setae, formula of anterofacial spinesetae on epimera 2-3 = 2-2-1-2-1 and 1-2-1-2-1. Pleon ( Fig. 17 ): dorsolateral posterior margin of pleonites 1-

3 sparsely setose, pleonites 4- 5 with several dorsal groups of dense setae, pleonite 6 with few dorsolateral setules on each side; uropod 3 extending beyond uropods 1 and 2 in entire animal, uropod lengths relative to uropod 1: uropod 2 = 0.67, 3 = 0.67. Pleopods: retinacula 2 per pleopod, no accessories; each peduncle well setose; rami of equal extension, articles of outer rami on pleopods 1-3 = l3-ll-9, inner = 11-11-9; setae on basal articles, outer margin of outer ramus to inner margin of inner ramus on pleopods 1- 3 = 3-2-1-2, 3- 2-1-1, 2-1-2-1, no bifid or barbed setae.

First uropod ( Fig. 17 ): peduncle length 1.4 ramI; outer margin with 3 apicodistal spines and 3 setae besides row of 7 dorsal spines, with one apical spine medially and row of 4 widespread medial setae; rami of subequal length, both rami with 2 rows of marginal spines, ramus with 5 apical spines. Second uropod ( Fig. 17 ): peduncle about 1.1 length of inner ramus, with 3 dorsolateral spines and 1 apical, with 6 apical setae, medial margin with hooked and barbed apical spine ( Fig. 15 ) and one medial seta; outer ramus shorter than inner, both with 2 rows of marginal spines, apices with 5 and 4 spines. Third uropod ( Fig. 17 ): peduncle length 0.44 outer ramus, almost as broad as long, shorter than urosomite 3, with 3 lateral long setae besides apicolateral spine and 5 setae; outer ramus proximal article with one lateral spine-setal cluster on body, ventrolateral margin with comb of about 14 short stiff bent setae on flange, distolateral margin with 6 spines and 3 long seta, apicomedial margin with 4 spines, medial margin with 2 spines, distal article large, with 7 apical spines and 4 long setae: inner ramus length 0.36 of outer, with 2 apical spines. Telson ( Fig. 17 ): of ordinary length, shorter than urosomite 3; cleft 80 percent of its length; apices each with 1~2 spines and 7 setae; each lobe with 1~2 dorsal setae, and pair of penicillate setules dorsolaterally at M.50.

Description of female "d". Up to 5.5 mm long. Antenna ( Fig. 14 ). First antenna as long in relation to body as in male if not longer but second antenna 0.33 length of body. Second antenna ( Fig. 14 ) more slender than in male and scarcely pediform, densely setose but less so than in male, article 4 of peduncle not longer than article 5, flagellum with 9 articles.

Mandibles. Right mandible with 2 rakers, interrakers 2; molarial seta elongate; incisor with 4 teeth; left mandible with 4 rakers, 4 interrakers, molar with 6 leaflobes, seta short, with 2 major hook-comb setae and one rudimentary; left palp setae, lA, lB, 2D, 7E.

Gnathopods andpereopods. First gnathopod ( Fig. 15 ): smaller even than male gnathopod 1, propodus less expanded: 1 medial and 1 lateral spine at defining corner of palm. Second gnathopod ( Fig. 15 ): somewhat larger than gnathopod 1, armament of defining corner of palm similar. Gnathopods 1~2 much more setose than in female of U westralis , with especially long tufts of setae anteriorly on carpus and propodus and posteriorly on merus. Coxae 2-4 with huge oostegite ( Fig. 15 ), that of coxa 5 very small. Coxal gills slightly smaller than in male. Sternal gill number 7, gills slightly larger than in male (relative to surrounding structures), gill 6 as large as in male, then sternal gills 5, 4, 3 and 2 progressively smaller until gill 2 less than half length of article 3 on gnathopod 2. Volume occupied by sternal gills in male filled with 9 hatched juveniles in female.

Illustrations. Maxillae 1 ~2 not illustrated; in poor condition. Lower lip as in other Australian crangonyctoids. Maxillipeds of specimen "c" also in poor shape, illustration thus made of specimen "d".

Remarks. The male differs from the concept of this species proposed by Williams & Barnard (1988) based on the literature in the following ways: the urosome is densely armed dorsally, the posterior margins of the propodi on gnathopod 1 in both sexes have some setae sufficiently thickened to be denoted as spines, the telson is cleft 80 percent (versus 50) and male uropod 3 has a rank of spines laterally beyond the basal comb of setae. The figure of male gnathopod 1 as copied from Nicholls in our figure 58 (Williams & Barnard, 1988) may actually be a female gnathopod 2, although the solabelled female gnathopod 2 is not very different from that one we show herein; if the male gnathopod 1 is indeed as shown by Nicholls, then he probably had a far more mature male than ours.

Relationship. Differing from all other species of Uroctena in the lack of facial spines on article 2 of male gnathopod 2 and the much higher degree of setation on the gnathopods and antennae 1~2 of both sexes. Article 2 of male gnathopod 2 does possess many setae, but no stiff thick spines.

Distribution. Western Australia, reservoir at Katanning.

Figures

Fig. 14. Uroctena setosa Nicholls, male "c" 7.59 mm (all drawings except those indicated); female "d" 5.50 mm.

Fig. 17. Uroctena setosa Nicholls, male "c" 7.59 mm (all drawings except those indicated); female "d" 5.50 mm.

Fig. 15. Uroctena setosa Nicholls, male "c" 7.59 mm (all drawings except those indicated); female "d" 5.50 mm.

Fig. 16. Uroctena setosa Nicholls, male "COO 7.59 mm.