Uperoleia micra, Doughty, Paul & Roberts, Dale, 2008

Doughty, Paul & Roberts, Dale, 2008, A new species of Uperoleia (Anura: Myobatrachidae) from the northwest Kimberley, Western Australia, Zootaxa 1939, pp. 10-18 : 12-17

Uperoleia micra sp. nov.

Tiny Toadlet

Figs. 2–4

Holotype. WAM R168043, an adult male collected near Bachsten Creek near the southwest corner of the Prince Regent River Nature Reserve, Western Australia (15º59’29” S; 125º19’54”E) on 22 January 2007 by J. D. Roberts, R. Barrett, P. Doughty and M. Barrett. Call recorded; liver stored at –70ºC at WAM.

Paratypes. WAM R168039-40 and WAM R168042, adult males, location and date as for holotype (15º59’26”S; 125º19’50”E); WAM R168044, adult male, location and date as for holotype; WAM R167989, adult female, collected from the Prince Regent River Nature Reserve (15º40’58”S; 125º34’59”E) on 21 January 2007; WAM R166476, a metamorphosing individual, collected near the Walcott Inlet, Western Australia (16º20’51” S; 124º46’24” E) on 21 January 2008; WAM R164897-8, adult males collected from Katers Island, Western Australia (14º26’56”S; 125º31’22”E) on 14 February 2008.

Diagnosis. Distinguished from congeners by a combination of small body size, presence of maxillary teeth, broadly exposed frontoparietal fontanelle, slightly tubercular skin on dorsum and upper limbs, moderately conspicuous parotoid and inguinal glands and less developed coccygeal glands, toes basally webbed, elongate inner metatarsal tubercle perpendicular to foot, dark brown dorsal surfaces with small darker spots, loreal and lateral zone stippled with bluish-white dots, pale orange-red femoral patches, speckled and slightly granular ventral surface and high-pitched rasp as an advertisement call.

Description. Body small, squat and rotund. Head small with slightly protruding eyes. When viewed laterally, evenly sloping snout with a rounded or truncated tip; when viewed from above, the sides of the snout gradually come to a rounded point. Canthus rostralis rounded; loreal region moderately steep and slightly concave. Sharp medial projection (symphysis of mentomeckelian bones) on lower jaw that matches notch on upper jaw. Nostrils directed upwards; nares with only a slight rim. Anterior corner of eye covered by flap of skin; at dorsal terminus the skin overlaps the skin of the brow above the eye. Posterior edge of brow projects slightly over skin on the side of the head. Tympana covered by skin and parotoid glands. One-three small infralabial glands present below angle of jaw. Tongue oval and elongate. Maxillary teeth present; vomerine teeth absent. Frontoparietal fontanelle broadly exposed. EN slightly larger than IN (EN/IN = 1.15).

Arms and hands slightly built. Arms are of moderate length (ArmL/SUL = 0.44) and the fingers unwebbed. Finger length: 3>4>2>1. Tubercles under fingers moderately developed; one on 1st and 2nd; two on 3rd and 4th. Large outer palmer tubercle on distal portion of wrist. Nuptial pad of males on inner portion of 1st finger (beginning halfway down finger), extending to base of wrist (1/4 along forearm) and slightly encroaching on palmer surface.

Legs short (TL/SVL = 0.36) and of moderate build. Toe length: 4>3>5>2>1. Tubercles under toes moderately developed; one on 1st and 2nd; two on 3rd and 5th; three on 4th. Toes basally webbed. A weakly-developed flange runs along the length of the toes. Inner metatarsal tubercle moderately developed, 1/2– 1/3 the length of the 1st toe; projecting anteriorly (towards toe tips). Outer metatarsal tubercle is moderately developed and larger than inner, usually spatulate (sometimes round) and oriented perpendicular to the foot with the medial edge adrupt and the distal edge gradually sloped.

Skin with scattered low tubercles on dorsum, head and limbs. The ventral surface is slightly granular. Cloacal flap present. Parotoid and inguinal glands moderately developed; coccygeal gland discernible but poorly developed.

Measurements. Adult males (N = 7): SUL (mean and range in mm)—19.6 (18.0–21.5); HD—3.9 (3.5– 4.4); EN—1.5 (1.3–1.8); IO—3.5 (3.2–3.8); IN—1.3 (1.2–1.4); EyeL—2.2 (2.1–2.4); ArmL—8.5 (8.1–9.0); TibL—7.0 (6.8–7.5); FTL—11.4 (10.3–12.1); EN/IN—1.17 (1.00–1.50); ArmL/SUL—0.44 (0.39–0.46); TL/ SUL—0.36 (0.34–0.38).

Adult female (N = 1): SUL—20.5; HD—4.2; EN—1.4; IO—3.7; IN—1.4; EyeL—2.3; ArmL—9.0; TibL —7.3; FTL—12.0; EN/IN—1.00; ArmL/SUL—0.44; TL/SUL—0.36.

Metamorph (N = 1): SUL—19.0.

Colouration. In life, specimens from the mainland had a dorsum with background shade ranging from a charcoal black to dark brown, with scattered small darker blotches and faint barring on the limbs. There is a zone stippled with pale bluish-white from the tip of the snout, posterior through the loreal region and extending along the sides; also on the undersurfaces of the limbs. There is a subtle wash of orange-red on the dorsum, including more conspicuous blotches on the parotoid glands, the anterior tip of the snout, submandibular glands, vertebral zone of dorsum and upper arms. The fingers and toes are a creamy white. The ventral surface is a dull white peppered with small dark spots; the abdomen lacks the dark spots or white pigment altogether. The margin of chin is only slightly more pigmented than the rest of the chin and ventral surface. Femoral patch a pale orange-red, only moderately contrasting with background colour. The iris is a chestnut brown with a hint of green. Specimens from Katers Island were similar, but differed in having slightly lighter colouration and with inguinal glands with orange-red colouration.

In preservative, the colouration is almost completely black, with the orange-red highlights only faintly visible; the paler loreal and lateral zone is still visible.

Advertisement call. Table 1 summarises the main features of the call. The call is a long high-pitched rasp that has an obvious regular pulse structure and a moderate pulse rate ( Fig. 4 ). The call also shows some evidence of frequency modulation with frequency rising later in the call.

TABLE 1. Call structure characteristics in Uperoleia . A) Uperoleia micra sp. nov. from near Bachsten Creek, Prince Regent River Nature Reserve; B) comparison with other Uperoleia species from the Kimberley region, Western Australia, and U. daviesae from near Darwin, Northern Territory.

A)

Habitat. At Bachsten Creek, U. micra were calling in moist crevices in sandstone rock faces high on a ridge. One male was seen calling at the back of a narrow crevice sitting just above a broad sheet of shallow, flowing water ( Fig. 2 D). Other calling males were collected in crevices and cracks in rock faces with slowly flowing water from seepages among vegetation and litter. Other species calling within a few meters were U. borealis and U. crassa in a flooded grassy area and Limnodynastes lignarius ( Tyler, Martin & Davies, 1979) along a rocky creek. On Katers Island, U. micra was encountered in a low valley near the top of an extensive sandstone plateau. Males were calling from a hard-capped sandstone surface with slow-flowing water forming small pools among Triodia clumps. Other species that were calling at the same sites were U. borealis and L. lignarius . At both sites, males were encountered after heavy early evening showers which may have stimulated calling. The individual collected from near the Walcott Inlet was found on a high flat sandstone rock platform (M. Barrett, pers. comm.).

Distribution. Only known to occur in the high rainfall zone (> 1000 mm /year) of the northwest Kimberley, Western Australia ( Fig. 1 ). On the mainland, from the Prince Regent River Nature Reserve south to Walcott Inlet. Also on Katers Island.

Etymology. Derived from the Greek mikros, alluding to this species’ small size and to the nearby U. minima which is similar in size and external appearance. Used as an adjective.

Comparisons with other species. Uperoleia is a genus characterized by low morphological diversity. Nevertheless, U. micra is distinguished from congeners from a combination of internal and external characters as well as call structure. The small (~ 2 cm) body size rules out U. marmorata (30.1 mm; Tyler et al. 1981a). Within the genus, only U. daviesae Young, Tyler and Kent, 2005 has both the presence of maxillary teeth and a broadly exposed frontoparietal fontanelle like U. micra . This species also shares tubercular skin and basal webbing, but can be distinguished from U. micra by light grey dorsum with faint purple tone, absence of pale loreal and lateral zone and less developed outer metatarsal tubercle. In addition, U. daviesae has only been found in flooded grasslands (versus sandstone boulders and escarpments) and although its call is similar to U. micra , it has fewer pulses and a lower pulse rate (Table 1).

The most similar Kimberley species in external appearance to U. micra is U. minima which occurs at Mitchell Plateau and may prove to be sympatric with U. micra (see Fig. 1 ). Both species have small body size, dark mottled coloration, pale speckled venter and tubercular skin. They can be distinguished, however, by the following external traits. In U. minima , the dorsal tubercles are denser and often form short scapular folds in some specimens; in U. micra the tubercles are less dense and lower. In U. micra , the outer metatarsal tubercle is elongate and orientated perpendicular to the foot ( Fig. 3 D); in U. minima this tubercle is round ( Fig. 3 E). In U. micra , males have few markings on the chin; in U. minima there is a conspicuous dark pigmentation bordering the edge of the jaw. Internally, U. micra has maxillary teeth and a broadly exposed frontoparietal fontanelle, whereas U. minima lacks teeth and has well-developed frontal bones.

Calls of U. micra can be readily distinguished from other Kimberley species. Uperoleia aspera , U. lithomoda , U. minima and U. trachyderma have a much shorter call duration and lower pulse numbers (Table 1b); the calls sound like ‘clicks’ to the ear. Uperoleia borealis , U. crassa and U. mjobergii have much longer call durations and higher pulse rates (Table 1b); the calls sound like a short rasp or grate. The call of U. talpa has a similar pulse rate to U. micra but much lower frequency and higher pulse number. The calls of all eight Kimberley species are clearly discrete in two or more characters. The variation in temperature between sets of recording was 3.9ºC, but temperature is unlikely to have affected any metric used to differentiate calls over that small a range. For example, pulse rate in U. laevigata Keferstein, 1867 of eastern Australia is strongly temperature dependent, but the regression coefficient is only 5.56 which would generate a maximum increment in pulse rate of 21.7 between the high and low temperatures compared here (data reported as U. rugosa Andersson, 1916 by Robertson 1986; Davies & Littlejohn 1986). The only other Uperoleia species known from the Kimberley is U. marmorata , but no call data are available.

Remarks. The discovery of another species of Uperoleia brings the total number of species in the genus to 26. This is the second-largest genus of Australian frog after Litoria . Continued exploration of remote areas of the Kimberley and revision of Uperoleia using morphology, genetics and call data may reveal further species.

The new species has only been found at four locations in the high rainfall zone of the northwest Kimberley. This area is rich with terrestrial vertebrate species, including frogs, lizards, snakes and mammals ( Storr & Smith 1975; Smith & Johnstone 1991). Biological surveys continue to discover new species of vertebrates with regularity, including other new species of frogs ( Doughty & Anstis 2007; Doughty et al. in press). Invertebrate and plant species are being discovered at even higher rates (e.g. McKenzie et al. 1991; Barrett 2006; Harvey & Edward 2007). These findings indicate that the true biodiversity of the region is underestimated. With recent interest in increasing mining, agriculture and tourism in the region, it is essential that large areas are set aside in managed reserves to ensure protection of both described species and additional new species awaiting discovery and description.

Figures

FIGURE 1. Distribution of Uperoleia micra sp. nov. and U. minima in the northwest Kimberley, Western Australia.

FIGURE 2. Uperoleia micra sp. nov.: A) WAM R 164988 from Katers Island, Western Australia; B) WAM R 168042; C) WAM R 168044 from near Bachsten Creek, Western Australia; D) collection location of calling males (WAM R 168039 – 40) near Bachsten Creek; males were calling from the low crevice within which had flowing water, and U. borealis and U. crassa were calling from the flooded grassy areas in the foreground (height of boulders ~ 2.5 m).

FIGURE 3. Holotype (WAM R 168043) of Uperoleia micra sp. nov.: A) dorsal, B) lateral and C) ventral views of head; D) plantar surface of left foot; E) plantar surface of left foot of U. minima (WAM R 167878).

FIGURE 4. Oscillogram (a), sound spectrograms (b) and spectrum display (c) for a call of U. micra sp. nov. (WAM R 168042). The bar in (a) and (b) represents 20 ms. In (b) we manipulated contrast, brightness and spectrum window display to maximise the loudest frequency components over pulse structure and side-bands arising from pulse rate (see Gerhardt & Huber, 2002).