Australonura friasica

(Figs 11 – 14)

Redescription. Length: 1.21 (male holotype) – 1.66 mm (female paratype). Habitus like A. limnophila. Colour white in ethanol. Secondary granulation regular, constituted of rounded granules, equal or less than a mac socket in diameter (Figs 11, 12 and 14). No reticulations. Elementary tubercles faint to well differentiated, marked by stronger secondary granules. Most dorsal chaetal groups included in these tubercles, which are slightly more conspicuous than in A. limnophila; tubercles of Th. I, Di and De of Th. II – Abd. III and Di of Abd. IV weakly differentiated, with elementary tubercles hardly recognizable; DL and L of Th. II – Abd. IV and head tubercles well differentiated, with elementary tubercles usually recognizable, but not papillate; tubercles De and DL of Abd. IV and tubercles of Abd. V and VI stronger, with elementary tubercles weakly papillate. Two kinds of ordinary chaetae on tergites: (i) thick mac, straight, subcylindrical, with blunt tips, smooth or for some of them very sparsely serrated (Fig. 13), the dorsal ones slightly sheathed and slightly tapering, the lateral ones not distinctly sheathed and more distinctly tapering; (ii) smooth mes of similar morphology, often bent and more tapering distally. Tergite S-chaetae thin and long, thinner and slightly shorter than closest mac (Fig. 12). Antennae. All antennal chaetae smooth. Ant. I with seven chaetae, Ant. II with eleven chaetae, the dorsal ones thicker and longer than the ventral ones. Ant. III sensorial organ with two thick, bent ms slightly buried in a cuticular fold; guard S thinner than S 1 – S 8 of Ant. IV, with Sgv straight and longer than Sgd (Sgv: Sgd: S 1 = 39: 31 - 34: 28); and one ventral ms. Ant. IV with S 1 - S 8 subequal, 12 long “ mou ” chaetae, one short ordinary chaeta (i), one small subapical organ; apical bulb faint, flat, entire, fused to Ant. IV tip. Ocelli 2 + 2 without pigment, located on the edges of tubercle Oc (Fig. 11). Mandibles thin, bidentate; maxilla heads styliform. Labium long with four basal chaetae (E, F, G, f with F very long), three distal chaetae (A, C, D) with one minute x-papilla, and three lateral chaetae (c, d, e). Labrum elongate, large and rounded apically, with planariahead-like ventral sclerifications; labral formula 0 / 2,4. Dorsal head chaetotaxy and tubercles (Table 2 A and Fig. 11). Eleven tubercles in total: CL, Af, 2 Oc, (Di + Di), 2 De, 2 DL, 2 (L + So). Ten chaetae on tubercle Af, chaeta O absent. Two chaetae present in ocular tubercle, with Ocp absent. Dorso-internal tubercles of the head fused on axis, with four elementary tubercles anterior to the line Di 1 – Di 1 and none posteriorly. Lateral area of head exactly as in A. limnophila, with mac L 1 displaced towards tubercle DL. Postcephalic chaetotaxy and tubercles identical to those of A. limnophila except for Abd. V and ocular chaetae (Table 2 B and Fig. 14). Chaetae Di 1, 2, 3 almost on a line parallel to axis on Th. II – III. Chaetae Di 2 anterior to Di 1 on Abd. I – IV. Chaetal group Di of Abd. IV shifted anteriorly to De. On tubercle Di of Abd. V only Di 1 mac present. Legs (Table 2 B). Ventral mac of the femur moderately differentiated, slightly longer than ventral side of femur. Tita without tenent hairs, without chaeta M and with chaetae B 4 and B 5 moderately elongate. Pretarsal mic relatively long. Unguis without tooth. Microchaetae of furcal vestige either present or undetectable. Male genital plate with 4 + 4 genital and seven circumgenital chaetae; female genital plate with 1 + 1 genital and 14 circumgenital chaetae. Vi: 5 chaetae; Ve: 8 chaetae.

Discussion. Australonura friasica is extremely similar to A. limnophila in its chaetotaxy and tubercle arrangements, the only differences being its slightly more developed tubercles, absence of Ocp on head and only 1 + 1 chaetae Di on Abd. V. The species is only known from Lago Frías area in Argentina, where A. limnophila is also present, but in another sample and site (“ bord du Lago Frías ” versus “ Lago Frías St 2 ”).

Material examined. Holotype male and three paratypes (one female, one preadult female and one juvenile) on slides. The fifth specimen cited in Cassagnau & Oliveira (1990) was not retrieved in the Cassagnau collection. Argentina: Rio Negro Province: “ bord du Lago Frias ”, 06 / 03 / 59, Delamare-Deboutteville leg (ARG-Pat 025). All specimens deposited in MNHN.