Bioacoustics of Allobates tapajos

Variation within type series. SVL of females significantly larger than that of males (T-test: t = 5.98, df = 22, P <0.0001; Table 1 ). Internarial distance in relation to head width significantly shorter in males than in females (mean IN/HW 0.39 ± 0.02 in males, 0.42 ± 0.02 in females; t = 3.81, df = 22, P = 0.001). Remaining morphometric ratios on head not statistically different between sexes. The following ratios are estimated based on all specimens pooled: Head width 0.35 ± 0.01 of SVL (range 0.33–0.37); SL 0.44 ± 0.07 of HL (range 0.31–0.53); HL 0.94 ± 0.05 of HW (range 0.80–1.02); EN 0.25 ± 0.02 of HW (range 0.19–0.28); EN 0.30 ± 0.03 of IO (range 0.24–0.36); tympanic membrane round, 0.43 ± 0.05 of EL (range 0.33–0.53). Character Holotype Males( n = 13) Females ( n = 10) 1-SVL 15.64 15.3 ± 0.4 (14.9–16.1) 16.2 ± 0.3 (15.6–16.5) 2-HL 5.10 5.02 ± 0.35 (4.40–5.60) 5.36 ± 0.24 (4.80–5.70) 3-IO 4.50 4.51 ± 0.19 (4.20–4.90) 4.72 ± 0.18 (4.40–5.00) 4-HW 5.40 5.38 ± 0.21 (5.00–5.80) 5.63 ± 0.09 (5.50–5.80) 5-SL 2.30 2.13 ± 0.29 (1.75–2.50) 2.44 ± 0.26 (2.00–2.75) 6-EN 1.50 1.35 ± 0.10 (1.15–1.50) 1.44 ± 0.16 (1.10–1.60) 7-IN 2.00 2.12 ± 0.06 (2.00–2.25) 2.38 ± 0.08 (2.20–2.50) 8-EL 2.10 2.15 ± 0.08 (2.00–2.25) 2.24 ± 0.09 (2.05–2.35) 9-TYM 0.90 0.92 ± 0.09 (0.75–1.10) 0.94 ± 0.12 (0.75–1.15) 10-FAL 3.20 3.15 ± 0.23 (2.70–3.50) 3.19 ± 0.42 (2.60–3.90) 11-UAL 4.00 4.10 ± 0.26 (3.70–4.50) 4.07 ± 0.24 (3.80–4.50) 12-LL 7.50 7.06 ± 0.35 (6.30–7.50) 7.33 ± 0.22 (7.10–7.70) 13-TL 7.50 7.40 ± 0.29 (6.70–7.90) 7.58 ± 0.22 (7.30–8.00) 14- FL 6.60 6.29 ± 0.23 (5.90–6.70) 6.50 ± 0.21 (6.20–6.80) 15- HAND I 3.00 2.68 ± 0.13 (2.50–3.00) 2.84 ± 0.21 (2.50–3.10) 16-HAND II 2.90 2.60 ± 0.10 (2.40–2.80) 2.67 ± 0.09 (2.50–2.80) 17-HAND III 3.80 3.60 ± 0.12 (3.40–3.80) 3.70 ± 0.09 (3.50–3.80) 18-HAND IV 2.70 2.33 ± 0.19 (2.00–2.70) 2.44 ± 0.16 (2.20–2.80) 19-WFD 0.55 0.53 ± 0.04 (0.50–0.65) 0.56 ± 0.07 (0.45–0.65) 20-DPT 0.40 0.46 ± 0.06 (0.35–0.55) 0.49 ± 0.03 (0.45–0.55) 21-WTT 0.20 0.25 ± 0.02 (0.20–0.30) 0.26 ± 0.03 (0.20–0.30) 22-WPF 0.40 0.35 ± 0.04 (0.30–0.45) 0.34 ± 0.06 (0.25–0.45) 23-WTD 0.60 0.61 ± 0.09 (0.45–0.75) 0.66 ± 0.07 (0.55–0.80) Variation of limb ratios among 24 specimens : length of forearm 0.78 ± 0.06 of upper arm length (range 0.65– 0.87); subarticular tubercles on fingers similar in size and number to those of the holotype in all specimens ( Fig. 3 B). Length of Finger III in relation to SVL is statistically longer in males than in females (mean HANDIII/SVL 0.24 ± 0.01 in males, 0.23 ± 0.001 in females; t = -2.20, df = 22, P = 0.047). Width of the third phalange on Finger III not significantly different between sexes ( t = -0.39, df = 22, P = 0.695); Fingers I, II and IV with nearly the same length. Ratio of leg length 0.96 ± 0.04 (85–100%) of tibia length; foot length 0.85 ± 0.04 (0.79–0.93) of tibia; Ratio of tibia length to SVL in males (mean 0.48 ± 0.02) significantly ( t = -2.07, df = 22, P = 0.05) greater than in females (mean 0.47 ± 0.02); foot length 0.41 ± 0.02 (0.37–0.44) of SVL; basal webbing present between Toes III-IV and a rudimentary webbing present between Toes II-III in all specimens (as Fig. 3 A); disc width on Toe IV 0.64 ± 0.08; metatarsal fold absent; tarsal keel and subarticular tubercles on toes similar as in holotype in all specimens ( Fig. 3 A). Color in life of adults. Color in life of the holotype is shown in Fig. 1 . All specimens have a light brown background on dorsum. Dorsal surface of snout light brown, extending posteriorly until eye level. Central region of dorsum with irregular dark brown blotches from eye level to urostyle region. Dorsum light brown laterally from eye level to urostyle region. Width of the light brown area variable among specimens ( Fig. 4 A–D). Dorsal surface of arm orange-brown; upper surfaces of legs light brown with one or two diffuse dark brown bands on tibia and foot; inner surface of thigh and groin dark brown ( Fig.1 A, Fig. 4 A–D). Dorsolateral stripe absent or diffused with the background color of dorsum ( Fig. 1 A, Fig. 4 A, C, D). Throat and chest of calling males golden yellow; abdomen whitish centrally, gradually merging into yellow towards the flanks and ventral surface of legs ( Fig. 1 B, Fig. 4 H). Adult females have a light yellow chin; throat, chest, abdomen, and ventral surface of leg white to translucent, without melanophores ( Fig. 4 G, I). Paracloacal marks cream-colored, forming a half-moon shape; palmar surface of hand light brown; plantar surface of foot dark brown ( Fig. 1 A, Fig. 4 C, H, I). Color photographs and a video of a calling male can be obtained from Project Sapoteca’s website (http://ppbio.inpa.gov.br/en/sapoteca/home). Color of adults in preservative. The color in preservative of the holotype and allotype are shown in Fig. 2 . Considering the type series, background color of dorsum is cream. Dorsal surface of snout cream, extending posteriorly until eye level. Central region of dorsum with irregular dark brown blotches from eye level to urostyle region ( Fig. 4 A). Pale dorsolateral stripe present in all specimens. Ventrolateral stripe absent. Lateral surface below the lateral brown band cream with white spots in some specimens (as in the holotype and allotype, Fig. 2 ). Diffuse, pale cream spots scattered posteriorly on the dark brown lateral band. Tympanum dark brown dorsally (up to about one quarter of its area), same color as the brown lateral band at the supratympanic region. Remaining area of tympanum cream. Dorsal surfaces of hind limb cream with one or two diffuse transversal brown bands on tibia and foot. Paracloacal region and internal surface of thigh brown ( Fig. 2 A–D, Fig. 5 A). Half-moon shaped paracloacal mark cream ( Fig. 5 A). Ventral surfaces of throat, chest, belly, leg and upper arm in males and females pale cream, without melanophores ( Fig. 2 B, Fig. 5 B). Ventral surfaces of forearm and foot brown in all specimens ( Fig. 5 B). Description of tadpoles. Descriptive statistics for 17 morphometric characters were based on 35 tadpoles at developmental stages 25, 33, 35 and 39 ( Table 2 ). The following detailed description is based on a sample of 8 tadpoles from the same lot (INPA-H 34427), collected from a single clutch and reared to stage 35 before preservation. Body ellipsoid, round anteriorly and truncate posteriorly in dorsal view, slightly flattened in lateral view ( Fig. 6 ). Body length 38% and tail length 75% of TL; body wider than deep, BH 45% of BW at the level of spiracle; HWLE at level of eyes 99% of BW at level of spiracle; snout rounded in dorsal and lateral views; END 72 % of ED; eyes dorsal and directed laterally; mean ED 0.8 ± 0.05 mm ; IOD 24% of HWLE at level of eyes. Small naris located dorsolaterally and directed anterolaterally; mean internarial distance 1.08 ± 0.08 mm . Fleshy ring present on the inner margin of nostrils, round and straight, not ornamented. Sinistral spiracle a free tube of 1.12 ± 0.19 mm on average, slightly anterior to mid-body ( Fig. 6 ). Average length of vent tube 1.04 ± 0.16 mm , dextral. Dorsal fin begins at body-tail insertion, its dorsal edge shallow and straight anteriorly (along approximately 20% of its length), deeper and arched posteriorly, reaching its maximum depth about half its length. Dorsal fin slightly deeper than lower fin. Tail tip acuminate. Caudal musculature of tadpoles bifurcated dorsally on body region, reaching up to two thirds of body length from body-tail insertion to past the level of spiracle ( Fig. 6 ). Oral apparatus located anteroventrally, emarginated laterally, transversely elliptical, 1.96 ± 0.21 mm wide in average ( Fig. 7 ). Anterior labium with groups of four or five short and round papillae distributed in a single row on each side of the labium’s lateral margins, and split by a medial gap corresponding to approximately 75% of the apparatus’ width. Posterior labium with a single row of marginal papillae variable in length. Papillae short and round medially (4–5 papillae) and on the outer lateral folds of labium (4–5 papillae on each side). Elongate papillae (4-5 papillae on each side) distributed between the lateral and medial groups of shorter papillae. Elongate papillae reach up to three or four times the length of short papillae ( Fig. 7 ). Upper jaw sheath arch-shaped, longer than lower jaw sheath. Lower jaw sheath V-shaped, deeper than upper jaw sheath. Cutting edge of upper and lower jaw sheaths serrated, serrations extending along the entire length of both sheaths. Labial tooth row formula 2(2)/3(1); tooth row A-1 complete, 1.5 mm long in average; tooth row A-2 interrupted medially, consisting of two widely separated rows at the level of upper jaw sheath, segments 0.50 mm in length, with gap of 0.50 mm , in average ( Fig. 7 A). Posterior tooth rows P-1 and P-2 the same length as row A-1 ( 1.5 mm , in average), both longer than P-3 ( 1.2 mm , in average). Morphology of oral disc is constant throughout all developmental stages examined. Elongate papillae on posterior labium are evident from stage 25 to stage 39 ( Fig. 7 A–D). Color of preserved tadpoles. Background color of dorsum, anteroventral and lateral surfaces of the body of tadpoles pale cream, but all of these surfaces are densely covered with dark brown melanophores. Background color appears as irregular pale blotches or spots, more frequent in lateral view ( Fig. 6 ). Posteroventral surface of body transparent with intestines visible through the skin. Tail musculature cream. Tail fins transparent, with scattered irregular brown melanophores forming irregular blotches ( Fig. 6 ). Comparison of the tadpoles with other species. The tadpoles of Allobates tapajos differ from those of A. granti , A. subfolionidificans , A. brunneus , A. paleovarzensis , A. sumtuosus and A. magnussoni ( Kok et al. 2006 ; Lima et al. 2007 , 2009, 2010, 2014; Simões & Lima 2013) by having a posterior labium partially surrounded by long marginal papillae, variable in length (posterior labium surrounded by short papillae of similar size in tadpoles in the other six species). Tadpoles of A. nidicola and A. masniger are endotrophic and develop entirely in terrestrial nests. Those highly specialized tadpoles lack an oral disc and a spiracle. Character Stage 25 (n=2) Stage 33 (n=13) Stage 35 (n=8) Stage 39 (n=12) 1 -TL 10.58 ± 0.11 (10.50–10.66) 20.03 ± 0.55 (18.46–20.83) 20.15 ± 0.89 (18.46–21.50) 20.46 ± 0.04 (20.41–20.53) 2 - BL 3.25 ± 0.07 (3.20–3.30) 6.96 ± 0.20 (6.60–7.40) 7.03 ± 0.28 (6.70–7.60) 7.80 ± 0.17 (7.50–8.10) 3 -TAL 6.93 ± 0.08 (6.87–7.00) 12.60 ± 0.73 (11.36–13.76) 13.16 ± 0.64 (12.52–14.00) 15.26 ± 0.07 (15.16–15.37) 4 - BW 1.77 ± 0.03 (1.75–1.80) 5.14 ± 0.20 (4.85–5.65) 5.33 ± 0.26 (4.95–5.60) 5.88 ± 0.16 (5.65–6.20) 5 - BH 0.85 ± 0.07 (0.80–0.90) 2.00 ± 0.18 (1.83–2.33) 2.06 ± 0.29 (1.66–2.63) 2.63 ± 0.23 (2.16–2.96) 6 - HWLE 2.00 ± 0.00 (2.00–2.00) 4.96 ± 0.19 (4.50-5.30) 5.18 ± 0.14 (5.00–5.50) 5.87 ± 0.20 (5.50–6.10) 7 - TMW 0.83 ± 0.00 (0.83–0.83) 1.77 ± 0.14 (1.60–2.16) 1.95 ± 0.14 (1.66–2.13) 2.44 ± 0.11 (2.30–2.63) 8 - MTH 1.20 ± 0.14 (1.10–1.30) 3.11 ± 0.26 (2.60–3.56) 3.32 ± 0.21 (3.00–3.63) 3.61 ± 0.20 (3.23–3.90) 9 - TMH 0.91 ± 0.11(0.83–1.00) 1.72 ± 0.09 (1.60–1.93) 1.77 ± 0.15 (1.53–2.03) 2.05 ± 0.10 (1.83–2.16) 10 - IOD 0.61 ± 0.02 (0.60–0.63) 1.20 ± 0.11 (1.00–1.36) 1.22 ± 0.10 (1.06–1.33) 1.37 ± 0.06 (1.33–1.53) 11 - IND 0.46 ± 0.04 (0.43–0.50) 1.06 ± 0.09 (1.00–1.30) 1.07 ± 0.08 (1.00–1.16) 1.19 ± 0.06 (1.06–1.26) 12 - END 0.20 ± 0.04 (0.16–0.23) 0.59 ± 0.06 (0.50–0.66) 0.62 ± 0.06 (0.53–0.73) 0.69 ± 0.04 (0.66–0.80) 13 - NSD 0.33 ± 0.00 (0.33–0.33) 0.60 ± 0.05 (0.50–0.66) 0.59 ± 0.07 (0.50–0.66) 0.72 ± 0.11 (0.50–0.86) 14 - ED 0.46 ± 0.04 (0.43–0.50) 0.77 ± 0.04 (0.66–0.83) 0.80 ± 0.05 (0.70–0.86) 0.97 ± 0.03 (0.90–1.03) 15 - VTL - 1.04 ± 0.19 (0.75–1.40) 1.03 ± 0.16 (0.75–1.25) 1.28 ± 0.19 (0.75–1.50) 16 - STL 0.50 ± 0.00 (0.50–0.50) 1.00 ± 0.14 (0.75–1.25) 1.11 ± 0.18 (0.75–1.30) 1.27 ± 0.14 (1.00–1.65) 17 - ODW 0.47 ± 0.03 (0.45–0.50) 1.86 ± 0.09 (1.75–2.05) 1.95 ± 0.21 (1.75–2.40) 2.05 ± 0.06 (1.95–2.15) Tadpoles of A. tapajos are more similar to those of A. caeruleodactylus , A. marchesianus , and A. grillisimilis (Caldwell et al. 2002a, 2002b; Simões et al. 2013a ) in having fewer and longer papillae on posterior labium. Tadpoles of A. caeruleodactylus and A. marchesianus have distinct transverse dark bars on tail (absent in A. tapajos ) and two short papillae on each side of the lateral margin of anterior labium (four to five in A. tapajos ). The tadpoles of A. tapajos differ from those of A. marchesianus by having labial tooth rows A-2 and P-3 (rows A-2 and P-3 absent in tadpoles of A. marchesianus ). Row A-2 is longer than A- 1 in tadpoles of A. tapajos (row A-2 shorter than A- 1 in A. caeruleodactylus ). The tadpoles of A. tapajos differ from those of A. grillisimilis by having labial tooth row P-3 distinctively shorter than rows P-1 and P-2 (all rows equal to sub-equal in length among tadpoles of A. grillisimilis ); row A-2 is longer than A- 1 in tadpoles of A. tapajos (A-2 and A-1 about the same length in A. grillisimilis ). Call description and call variation. Advertisement calls of Allobates tapajos consist of the continuous emission of short tonal notes, with ascending frequency modulation. Notes predominantly arranged in pairs or couplets ( Fig 8 A, 9), with silent intervals between notes in each pair varying from 0.112 to 0.162 s (0.138 ± 0.015 s in average, n = 135 intervals, measured from calls of nine males). Longer silent intervals split consecutive note pairs. These vary from 0.305 to 0.490 s (0.403 ± 0.058 s in average, n = 135 intervals, measured from calls of nine males). The arrangement in note pairs is not regular along calling bouts. Single notes and note trios emitted irregularly along some call sections ( Fig. 8 C, 9). Note pairs are, however, the prevalent arrangement, corresponding to 311 of 424 (73%) arrangements inspected from call sections of nine males. Single notes emitted between note pairs was the second most common arrangement, corresponding to 23% of the arrangements inspected from calls of nine males. Note trios were the rarest arrangement, corresponding to 18 of 424 (4%) arrangements inspected, and being detected only along call sections of five males. Despite the existence of variation in note arrangement, spectral and temporal characteristics of notes are constant along advertisement calls of each individual ( Fig. 8 B, D). Notes 0.042 ± 0.004 s long in average ( n = 250 notes, analyzed from calls of ten males—Table 3). Notes have an average lower frequency of 5093.4 ± 217.9 Hz and an average upper frequency of 6004.0 ± 215.6 Hz. Average peak frequency of notes 5618.9 ± 209.4 Hz. Silent intervals between adjacent notes are more variable, ranging from 0.041 to 0.806 s considering raw individual measurements (0.293 ± 0.037 s , in average), reflecting variations in note arrangement. Notes emitted at a rate of 2.9 ± 1.4 notes per second in average, ranging from 2.73 to 3.23 notes per second among call sections of nine males. INPA-H T (°C) SVL (mm) NDur (s) PeakFreq (Hz) LowFreq (Hz) HigFreq (Hz) SIL (s) RNE (notes/s) 34415 24.4 14.94 0.035 5916.464 5491.456 6204.336 0.324 3.23 34410 24.0 14.87 0.043 5949.200 5425.416 6458.068 0.295 2.96 34405 24.0 14.90 0.047 5818.268 5247.444 6169.904 0.312 2.83 34414 24.0 15.15 0.042 5439.292 5041.064 5938.428 0.349 - Unvouchered 24.0 - 0.042 5467.716 5043.392 5935.060 0.211 2.93 34425 23.8 15.87 0.045 5597.768 4889.208 5989.076 0.278 3.06 34416 23.9 15.01 0.047 5409.132 4950.752 5952.728 0.307 2.93 34402 23.9 15.02 0.036 5379.856 4909.872 5744.884 0.269 3.06 34423 23.9 15.32 0.041 5590.872 5003.416 5800.648 0.282 2.86 34411 25.0 16.08 0.038 5620.996 4932.335 5847.562 0.302 2.73 Mean 24.090 - 0.042 5618.956 5093.435 6004.069 0.293 2.939 s.d. 0.357 - 0.004 209.467 217.924 215.692 0.037 0.147 min. 23.800 - 0.035 5379.856 4889.208 5744.884 0.211 2.730 max. 25.000 - 0.047 5949.200 5491.456 6458.068 0.349 3.230 A single male (INPA-H 34411) was recorded while producing a second type of call before starting to emit regular advertisement calls as described above. From a total recording length of four minutes, this alternative call type was emitted during the first two and a half minutes of recording, after which the focal male shifted to regular advertisement calls. This call type consists of short trills of single notes, split by long and irregular silent intervals, ranging from 10.73 up to 39.16 s ( Fig. 10 ). A total of six complete trills were captured on the recorded section and used for description of call arrangement. Trills formed by 10–14 notes (mode = 13 notes). Duration of trills ranged from 2.46 to 3.37 s (3.04 ± 0.33 s , in average), and the rate of note emission ranged from 3.6 to 4.2 notes per second (4.0 ± 0.3 notes per second, in average). The rate of note emission during trills is measurably faster than that estimated from regular advertisement calls of the same individual (2.73 notes per second), reflecting shorter and less variable silent intervals between notes along trills (0.19 ± 0.02 s in average; silent intervals between notes along regular advertisement calls of the same individual 0.30 ± 0.18 s long, in average; n = 25 intervals, uniformly distributed along each call section). Mean values of note duration and lower, upper and peak frequencies of notes on trills were 0.04 s , 4972.20 Hz, 5883.19 Hz and 5644.28 Hz, respectively. There were no statistically significant differences between the peak frequencies of notes emitted in regular advertisement calls or alternative trills by this male ( t = -0.790, P =0.434, 46.70 d.f. ). Note duration, however, was shorter, on average, when produced in trills ( t = 4.228, P <0.001, 43.18 d.f. ), and notes on trills were emitted at a slightly higher frequency bandwidth than those emitted in regular calls (lower frequency: t = -2.669, P = 0.011, 37.29 d.f. ; upper frequency: t = -2.188, P = 0.034, 44.73 d.f. ). TABLE 4 . Uncorrected pairwise (lower left) and Kimura-2-Parameter (upper right) genetic distances between Allobates tapajos and clades representing cryptically colored Allobates species distributed in the cis-Andean region. Distances were based in a 420 bp fragment of the 16S rDNA mitochondrial gene. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 tapajos 0.09 0.10 0.12 0.11 0.09 0.09 0.07 0.12 0.13 0.10 0.12 0.01 0.09 0.21 0.10 0.08 0.12 0.10 0.10 0.14 algorei 0.08 0.08 0.09 0.10 0.09 0.08 0.10 0.10 0.12 0.09 0.12 0.09 0.12 0.20 0.09 0.08 0.10 0.09 0.08 0.16 Genetic distances and mtDNA relationships. Phylogenetic relationships based on a 420 bp fragment of the 16S rDNA gene indicate that Allobates tapajos is monophyletic in relation to the 20 congeneric taxa analyzed, except in relation to the two samples tentatively identified as Allobates marchesianus taken from a locality near Curuá-Una River on the right bank of the Tapajós River ( Fig. 11 ). Mean uncorrected pairwise and Kimura-2- parameter (K2P) genetic distances between sequences of A. tapajos and A. aff. marchesianus do not exceed 1% (Table 4). Average uncorrected pairwise genetic distances between sequences of the new species and those of other congeneric species occurring in the Amazon region range from 6% ( A. gasconi from Eirunepé, in the middle course of the Juruá River) to 13% (typical Allobates undulatus from Cerro Yutajé, in Amazonian Venezuela ). Average K2P genetic distances ranged from 7% (also between A. tapajos and A. gasconi from Eirunepé) to 14% (between A. tapajos and A. undulatus ). The greatest estimates of average genetic distances are observed between A. tapajos and A. olfersioides , a species distributed in the Brazilian Atlantic Forest (18% uncorrected pairwise, 21% K2P). caeruleodactylus 0.09 0.08 0.10 0.09 0.08 0.10 0.09 0.11 0.12 0.08 0.11 0.10 0.10 0.19 0.09 0.07 0.10 0.10 0.10 0.14 4. conspicuus 0.11 0.08 0.09 0.11 0.10 0.09 0.10 0.11 0.14 0.11 0.13 0.12 0.10 0.19 0.10 0.09 0.02 0.10 0.09 0.15 5. crombiei 0.10 0.09 0.09 0.10 0.10 0.08 0.09 0.11 0.10 0.09 0.10 0.11 0.09 0.17 0.10 0.08 0.12 0.09 0.09 0.12 6. cf. flaviventris 0.09 0.09 0.07 0.09 0.09 0.08 0.07 0.11 0.10 0.06 0.09 0.08 0.09 0.20 0.09 0.09 0.10 0.09 0.08 0.13 7. gasconi (Porto Walter) 0.09 0.07 0.09 0.09 0.08 0.08 0.08 0.10 0.12 0.10 0.11 0.09 0.10 0.19 0.09 0.06 0.10 0.08 0.01 0.15 8. gasconi (Eirunepé) 0.06 0.09 0.08 0.09 0.08 0.07 0.08 0.10 0.11 0.08 0.09 0.06 0.09 0.20 0.08 0.07 0.10 0.09 0.09 0.15 9. granti 0.11 0.09 0.10 0.10 0.10 0.10 0.09 0.09 0.14 0.10 0.15 0.12 0.12 0.18 0.11 0.09 0.12 0.10 0.10 0.15 10. grillisimilis 0.12 0.11 0.11 0.12 0.09 0.09 0.11 0.10 0.12 0.13 0.13 0.12 0.13 0.19 0.13 0.12 0.15 0.12 0.12 0.13 11. magnussoni 0.10 0.09 0.08 0.10 0.08 0.05 0.09 0.08 0.09 0.12 0.09 0.09 0.07 0.19 0.09 0.09 0.11 0.10 0.10 0.13 12. masniger 0.11 0.11 0.10 0.12 0.09 0.09 0.10 0.09 0.13 0.11 0.08 0.11 0.06 0.20 0.13 0.12 0.13 0.12 0.11 0.15 13. aff. marchesianus 0.01 0.08 0.09 0.11 0.10 0.08 0.08 0.06 0.11 0.11 0.09 0.10 0.09 0.21 0.10 0.08 0.12 0.09 0.09 0.14 14. nidicola 0.09 0.11 0.09 0.09 0.08 0.08 0.09 0.08 0.11 0.11 0.07 0.06 0.08 0.18 0.09 0.09 0.09 0.08 0.10 0.11 15. olfersioides 0.18 0.17 0.17 0.16 0.15 0.18 0.17 0.17 0.16 0.17 0.17 0.17 0.18 0.16 0.20 0.20 0.20 0.21 0.19 0.15 16. ornatus 0.09 0.09 0.08 0.09 0.09 0.08 0.09 0.08 0.10 0.12 0.09 0.12 0.09 0.08 0.18 0.08 0.10 0.10 0.11 0.16 17. paleovarzensis 0.07 0.08 0.07 0.08 0.08 0.08 0.05 0.07 0.08 0.11 0.08 0.11 0.07 0.09 0.17 0.08 0.08 0.05 0.06 0.13 18. subfolionidificans 0.11 0.09 0.09 0.02 0.11 0.09 0.09 0.09 0.11 0.13 0.10 0.12 0.11 0.09 0.17 0.09 0.08 0.10 0.10 0.15 19. sumtuosus 0.09 0.08 0.09 0.09 0.08 0.09 0.07 0.08 0.09 0.11 0.09 0.11 0.09 0.08 0.18 0.09 0.05 0.10 0.08 0.13 20. trilineatus 0.09 0.07 0.09 0.09 0.08 0.08 0.01 0.08 0.09 0.11 0.09 0.10 0.09 0.10 0.16 0.10 0.06 0.09 0.08 0.14 21. undulatus 0.13 0.14 0.13 0.14 0.11 0.12 0.13 0.13 0.13 0.12 0.12 0.13 0.13 0.10 0.13 0.14 0.12 0.13 0.12 0.13 Parque Nacional da Amazônia is the type locality of two additional species of cryptically colored Allobates : A. masniger and A. magnussoni , which are generally syntopic with A. tapajos . Average uncorrected pairwise and K2P genetic distances between typical A. tapajos and A masniger are 11% and 12%, respectively. Mean genetic distance between typical A. tapajos and A. magnussoni is 10%, considering both pairwise and K2P estimates ( Fig. 11 , Table 4).

Diagnosis. A small species of cryptically-colored Allobates . (1) Mean SVL of males 15.5 mm (range 14.9– 16.2 mm ); mean SVL of females 16.3 mm (range 15.5–16.8 mm ); (2) Dorsal surface of snout uniformly light brown, same color extending posteriorly until eye level; dorsum with irregular dark brown blotches scattered from eye level to urostyle region. Dorsum laterally light brown from eye level to urostyle region, width of light brown area variable; background color of dorsal surfaces of legs light brown; diffuse, weakly conspicuous transverse bands of a darker brown shade sometimes present across dorsal surfaces of thigh (on its proximal region), shank (at mid level) and foot (at mid level); posterior surface of thigh and groin dark brown; skin texture of dorsum smooth, with small granules uniformly scattered from the level of the eyes to posterior edge of dorsum; (3) lateral dark brown band with a diffuse lower edge (4) pale dorsolateral stripe present in preserved specimens, inconspicuous in life; (5) oblique lateral stripe absent, pale cream spots scattered on inguinal region of the lateral dark brown band; (6) pale ventrolateral stripe absent; (7) pale paracloacal mark present, half-moon shaped; (8) throat and chest of males cream in preserved specimens, golden yellow in life; abdominal surfaces white centrally, yellow towards the flanks and ventral surface of legs in live males; (9) throat, chest and abdomen uniformly white to translucent in preserved and in live females; chin light yellow in life, cream in preserved female specimens; (10) dark throatcollar absent; (11) iris is metallic gold, without a pupil ring; (12) median lingual process absent; (13) vocal sac distinct, subgular; (14) maxillary teeth present; (15) third phalange of Finger III not swollen in males, morphology of Finger III similar between males and females; (16) distal tubercle absent on Finger IV; (17) tip of Finger IV not reaching the distal subarticular tubercle of Finger III; (18) tip of Finger II reaching the middle of the distal subarticular tubercle of Finger III; (19) basal webbing present between Toes III and IV, rudimentary basal webbing present between Toes II and III; (20) fringes absent on toes; (21) testes not pigmented, extending one-half the length of kidney; (22) mature oocytes pigmented; (23) eggs laid on opaque jelly nests, on dead leaves on the forest floor; (24) caudal musculature of tadpoles bifurcated dorsally on body region; (25) anterior labium of tadpoles with short round papillae only on lateral margins, 4–5 on each side; posterior labium with a single row of marginal papillae variable in length, short and round medially and on the outer lateral folds, elongate between these regions; (26) diurnal habits, males calling in daytime; (27) advertisement calls characterized by the continuous emission of note pairs; notes with ascending frequency modulation with peak frequencies between 5.3–5.9 kHz, split by approximately regular silent intervals of 0.30 to 0.49 s; additional call arrangements (random emission of single notes and note trios, and emission of short trills) produced less frequently. The new species is unambiguously assigned to genus Allobates by the combination of the above characters 10, 12, 19, 21, 26. Comparisons with other species. Because the new species is distributed in the Tapajós River basin (see “Distribution and natural history” below), comparisons with other Allobates species are limited to all species occurring in Brazil , and to two additional species distributed in the Guiana Shield ( Allobates granti and A. amissibilis— Appendix II).

Distribution and natural history. At present, Allobates tapajos is known from the Tapajós River basin, in terra-firme rainforests on both banks of the river´s middle and lower course. Known occurrences include the type locality in Parque Nacional of Amazônia, a federal conservation unit and forest reserve located on the western bank of the Tapajós , about its middle course, in the south of Pará State, Brazil ( Fig. 12 ). Within the park, the species inhabits forested areas along the margins of clearwater streams. The species is also distributed across the Tapajós River, in forests located near the city of Santarém, near Curuá-Una River, about Tapajós River’s lower course. Preliminary observations of the latter populations (from which “ aff. marchesianus ” in Fig. 11 proceed) indicate that they markedly differ from typical A. marchesianus (which have uniformly brown dorsum, solid lateral dark brown band with a continuous lower edge and dark grey vocal sac pigmentation, among other distinctive characters —Caldwell et al. 2002), rendering earlier identifications equivocal and supporting their assignment to the new species. At the type locality, A. tapajos is most active early in the morning and late in the afternoon. Most calling males are found from 0 530 to 0 930 h, and again from 1630 h until dusk. Two jelly nests were found on the leaf litter, inside folded and rolled leaves. One clutch had 27 eggs and the second 23 tadpoles at developmental stage 25. The jelly protecting both clutches was opaque ( Fig. 13 A and 13B). A single calling male was observed entering a folded leaf on the leaf litter and being followed by a conspecific female. It was not possible to observe courtship movements inside the leaf. However, a recently laid clutch was found after the couple left the nest. When we played a recorded advertisement call back to 10 male individuals engaged in calling activity, they all advanced towards the speakers. Thus, it appears that males of this species are territorial.