Bioacoustics of Oreobates remotus

Description of the holotype . An adult male, SVL 32.18 mm , with vocal slits and no nuptial pads; head slightly longer than wide, and slightly wider than body; snout moderate in length, subacuminate in dorsal view, slightly protruding in profile; nostril opening laterally, placed on an elevation on the side of snout; eye large, protruding, placed and directed laterally; canthal ridge straight in dorsal view and slightly concave in profile; loreal region slightly concave; no cranial crests; upper eyelid without tubercles; supratympanic fold present, but not well developed; tympanic membrane and annulus distinct, except on supratympanic region; tympanic membrane vertically elliptical, large, diameter about 3/5 of eye diameter; no postrictal tubercles; choanae small, slightly rounded, not concealed, and placed anterolaterally on roof of mouth, separate by a distance of about four times their diameter; dentigerous process of vomers present, elliptical, forming two small barely separated oblique clumps between, and slightly posterior, to choanae; vocal sac simple, subgular, scarcely developed; vocal slit present, slit-like, laterally to tongue, posteriorly on floor of mouth; tongue lanceolate, not notched posteriorly; Eustachian tube opening posteriorly on eye bulge; dorsal surfaces of head, back and limbs smooth; ventral surfaces of limbs, belly, chest and throat smooth; cloacal region slightly shagreen; no cloacal flap present; no scapular-occipital fold nor middorsal and dorsolateral tubercle or fold; discoidal fold slightly visible, no thoracic fold; arm and forearm slender; ulnar tubercles absent; palmar tubercle elliptical, large, prominent; thenar tubercle ovate, large, prominent; supernumerary tubercles present, large, conical with rounded bases; subarticular tubercles large, larger than supernumerary tubercles, conical and projecting, rounded in the base, distal ones are smaller than proximal ones; disks on Fingers III and IV large, broadly expanded, truncated; small, rounded slightly larger than finger width in Fingers I and II; circumferential groove and pad presents in Fingers III and IV; fingers slender and long, not webbed; fingers weakly fringed laterally; relative finger length II<I<IV<III; legs slender and moderately long; toes slender and long (foot length 49% of SVL), not webbed; heel and tarsal tubercles absent, no tarsal fold; inner metatarsal tubercle slightly developed, longer than wide, sub-elliptical; outer metatarsal tubercle rounded, smaller than inner one; a few supernumerary plantar tubercles present, small, weakly distinct; subarticular tubercles conical, projecting, with rounded bases, subarticular tubercles from outer toes smaller than those from inner toes; discs relatively small, slightly expanded, truncated in Toe IV, truncate to rounded in Toes V, III and II, and rounded in Toe I, disk of Toe I as wide as digit width; circumferential grooves and pads present in Toes III, IV and V; toes slightly laterally fringed distally; relative toes length I<II<V<III<IV. Color in life. Interorbital bar dark brown, concave anteriorly, with an irregular posterior medial projection expanded across midline of head, and with irregular lateral borders; canthal stripe dark brown, extending longitudinally from tip of snout to anterior margin of eye, ventrally irregularly edged and dorsally sharply edged along canthal ridge. Supratympanic area blackish, extending along supratympanic fold, dark coloration extends ventrally approximately to the level of mid-tympanum length. Two diagonal labial bars dark brown, slightly faded, irregularly edged and discontinuous, one below eye and one crossing loreal region and connecting to canthal stripe, infralabial region with scattered irregular marks. Dorsal background coloration olive brown, with a large dark brown X-shaped mark over scapulae, connecting with the interorbital bar. Dorsal coloration also includes small scattered black dots. Arm light brown with irregular dark brown transversal marks; forearm light brown with transverse dark brown irregular bars and some flecks. Dorsal surfaces of legs light brown with transverse dark brown bars; hidden surfaces of thighs and shanks slightly translucid producing fleshy brown tonalities. Belly cream centrally, ventrolaterally and anteriorly with faint and fine dark brown flecks extending from dorsolateral coloration. Chest lighter than belly, and throat grey with inconspicuous faint vermiculations posteriorly. Color in preservative. Background color light grey, pattern of dark coloration as described above, but turned in to dark grey, and light ventral coloration whitish. Measurements of the holotype (mm). SVL = 32.18; HL = 11.76; HW = 10.93; EN = 4.14; EE = 5.8; ED = 4.5; TD = 2.54; THL = 16.5; TL = 17.03; FL = 15.94; IND = 2.44. Variation. We found little variation on morphological characters among the specimens, varying mainly in body size. Measurements are presented on Table 1 . The only adult female has a larger SVL than adult males. The dorsum shows some variation in coloration and patterns, varying from yellowish brown background color with scattered dark marks to reddish brown with dorsolateral dark marks aligned marks, forming an irregular longitudinal stripe ( Fig. 3 ). Some individuals also show a slightly visible middorsal fold. Advertisement call. Calls were recorded on 9th January 2009 at 21:16h; air temperature was 21ºC. Sixteen calls from four specimens were analyzed. The advertisement call consist on a series of single short pulsed notes averaging 104 ms in length (range = 89–142 ms) having 2–3 pulses each, however the poor quality of the recordings do not allow an accurate count of pulses. The calls show no harmonic structure, has no amplitude modulation and pulses are amplitude modulated. The average call repetition rate is 31.6 call/min (18–45 call/min). The average dominant frequency is 3150.7 Hz (2866.5–3395.7 Hz) (Fig. 4). FIGURE 4. Advertisement call of Oreobates remotus sp. nov. : (from up to down) Oscillogram of a whole track and; oscillogram of a section comprising one note; Spectrogram of the same note; Amplitude spectrum of the note on the left. The call was recorded about 21:16 h on 9th January 2009 , air temperature was 21ºC. Comparison with other species (data for species other than Oreobates remotus in parenthesis). Oreobates remotus can be distinguished from O . barituensis , O . choristolemma , O . cruralis , O . granulosus , O . lehri , O . madidi , O . pereger , O . quixensis , O . sanctacrucis , O . sanderi , O . saxatilis , O . simmonsi , and O . zongonensis by having dorsal skin smooth and broadly enlarged truncate discs on Fingers III and IV (dorsal skin shagreened to granular and discs on Finger III and IV not enlarged). From O . ibischi by having dorsal skin smooth, broadly enlarged truncated discs on Fingers III and IV, nuptial pads absent and advertisement call notes having 2–3 pulses each (dorsal skin granular, discs on Finger III and IV only slightly enlarged, nuptial pads present and advertisement call notes having 6–8). From O . discoidalis by the absence of toe webbing, larger discs on Fingers III and IV, and advertisement call consisting of a single short pulsed note with 104 ms in length, dominant frequency of about 3150 Hz and 2–3 pulses per note (toes basally webbing, proportionally smaller discs on Fingers III and IV, and call composed of a single longer pulsed note with 582 ms in length, dominant frequency of about 2200 hz and 8–11 pulses per note). Oreobates remotus is more similar to O . heterodactylus , from which it can be distinguished by absence of nuptial pads, subacuminated snout in dorsal view, and shorter advertisement call with dominant frequency of about 3150 Hz, no harmonic structure and 2–3 pulses per note (nuptial pads present, slightly truncated snout in dorsal view and call is a single pulsed note with dominant frequency of about 3950 hz, having 3 to 5 harmonics and 5–9 pulses per note). Additionally O . remotus has, proportionally to body size, a larger hand than any other species of Oreobates . Adult males (n=4) Adult female (n=1) Subadults (n=6) SVL 31.6 ± 1.5 (29.6–33.1) 37.7 25.3 ± 2 (23.4–28.0) HL HW 12 ± 0.7 (11.4–13.0) 11 ± 0.7 (10.2–12.0) 14.0 12.9 9.9 ± 0.8 (9.0–11.0) 9.2 ± 0.8 (8.3–10.1) EN 3.9 ± 0.3 (3.6–4.1.0) 4.6 3.2 ± 0.2 (2.8–3.5) EE 5.8 ± 0.2 (5.6–6.1.0) 7.2 5.4 ± 0.5 (4.9–6.1) ED 4.2 ± 0.2 (3.9–4.5.0) 4.6 3.4 ± 0.2 (3.0–3.7) TD 2.5 ± 0.1 (2.4–2.5) 3.1 2.0 ± 0.3 (1.6–2.8) IND 2.5 ± 0.1 (2.4–2.7) 3.3 2.2 ± 0.2 (1.9–2.5) THL 16.2 ± 0.8 (15.3–17.1) 18.8 13.4 ± 1 (12.4–15.1) TL 16.9 ± 0.6 (16.2–17.7) 19.2 14.1 ± 1.1 (13–15.6) FL 15.5 ± 0.4 (15.1–15.9) 17.6 12.9 ± 1.4 (10.7–14.4) Natural history and distribution. All individuals of Oreobates remotus sp. nov. were found only during the rainy seasons. During our first expedition to Peruaçu valley, only one juvenile was found at a semideciduous forest. However that rainy season was atypical as the precipitation was very low (about 500 mm 3). The second sampled rainy season was a typical one (about 1000 mm 3) and individuals became very abundant. Many juveniles were found in pitfall traps and along the dry forest floor jumping over the leaf-litter. No individual was found in non-forest environments (e.g. savanna and carrasco ). All adults were found in wet limestone outcrops covered with mosses on the roadside within the dry forest ( Fig. 5 ). Males where heard calling at night from the wet walls and crevices of the outcrops, especially during rainy days. The new species is currently known only from the vicinities of the type locality, Peruaçu river valley, and from Pandeiros River, both at northern Minas Gerais state, Brazil ( Figs. 6 and 7 ). Although geographical information for this latter record is imprecise, Pandeiros River is also located at the left margin of São Francisco River, about 70 km SW from Peruaçu region. Both areas lie at the southernmost end of the Atlantic Dry Forest. Phylogenetic relationships. Both individual and combined analyses of mitochondrial genes cytochrome b (cyt b ) and 16S recovered Oreobates remotus sp. nov. deeply embedded within Oreobates and sister to O . heterodactylus ( Fig. 8 ), with 10% of interspecific divergence for 16S and 16–17% for cyt b between them. The clade comprising O . cruralis , O . discoidalis and O . madidi is recovered as sister to that containing O . remotus sp. nov. and O . heterodactylus , while O . quixensis and O . sanderi are recovered in a basal position. The remaining relationships within Strabomantinae were poorly supported, similar to results of Padial et al . (2008b , 2009 ).