Allobates grillisimilis

Simões, Pedro Ivo & Sturaro, Marcelo José, 2013, A new diminutive species of Allobates Zimmermann and Zimmermann, 1988 (Anura, Aromobatidae) from the northwestern Rio Madeira — Rio Tapajós interfluve, Amazonas, Brazil, Zootaxa 3609 (3), pp. 251-273 : 254-270

Allobates grillisimilis

Figures 2–10 .

Holotype. INPA-H 30779 (field number APL 12734). Adult male, collected by A. P. Lima after recording of advertisement calls at 07:28 h, on 12th of January 2008, at Ramal Novo Horizonte, about 5 km southwest of the city of Borba, on the right bank of the Madeira River (04°26’03” S, 59°37’25” W), State of Amazonas, Brazil.

Paratopotypes. INPA-H 30780–30808 (original field numbers APL 12735–12740, APL 12746–12750, 12769–12770, APL 12788–12793, APL 12802), 21 males, 8 females, collected by A. P. Lima and P. I. Simões, during two distinct field expeditions, in February 2007 and January 2008. Female INPA-H 30780 (field number APL 12793) is the designated the species allotype.

Paratypes. All from State of Amazonas, Brazil. Nova Olinda do Norte: INPA-H 30809–30823 (field numbers APL 12659–12665, APL 12668, APL 12671–12677), 6 females, 9 males, Ramal do Curupira, Municipality of Nova Olinda do Norte (03°52'28" S, 59°02'46" W), collected in December 2007 by P. I. Simões.

Maués: MPEG 28535, 28536, 28538, 28543, 28545 (field numbers FPR 0 0 5, 0 0 6, 0 0 8, 0 0 9, 237, respectively), all males, Floresta Nacional de Pau-Rosa, Municipality of Maués (03°56’50” S, 58°26’36” W); MPEG 28540, 28541, 28543 (field numbers FPR 109, 116, 126), all males, Floresta Nacional de Pau-Rosa, Igarapé Tabacal, Rio Paraconi, Municipality of Maués (03°55’07” S, 58°24’19” W).

Etymology. The specific epithet refers to the species distinctive advertisement call, which resembles (to the human ear) to the sound produced by crickets. The epithet is formed by the conjunction of the appellative substantive grillus (cricket, genitive grilli) and the adjective similis (similar, alike), meaning similar to a cricket.

Diagnosis. The new species is characterized by: (1) small SVL, adult males 13.9 ± 0.8 mm (range 12.8–15.9 mm), adult females 14.4 ± 0.8 mm (range 12.8–16.0 mm); (2) skin texture of dorsum smooth in most specimens, sometimes granular posteriorly; (3) paired dorsal digital scutes present; (4) median lingual process absent; (5) tympanum inconspicuous, tympanic annulus absent; (6) vocal sac distinct, subgular; (7) maxillary teeth present; (8) distal tubercle absent on Finger IV; (9) tip of finger IV not reaching distal subarticular tubercle of finger III; (10) Finger II about 9% smaller than Finger I; (11) finger discs moderately expanded, middle section of third phalange of Finger III about 35% of finger disc width; (12) lateral fringes absent on fingers; (13) metacarpal ridge absent; (14) Finger III not swollen in males, middle section of the third phalange not measurably wider in males than in females; overall morphology of Finger III similar between males and females; (15) carpal pad absent; (16) thenar tubercle visible, clearly evident on hand profile, but not protuberant; (17) black arm gland absent; (18) tarsal keel present, tubercle-like, strongly curved; (19) disc of Toe IV weakly expanded (20) basal webbing present only between toes III and IV; (21) metatarsal fold absent; (22) fringes absent on toes; (23) external coloration: pattern is cryptic, mostly in shades of brown ( Fig. 2 ); dorsum uniformly tan brown, characterized by evenly distributed reddish-brown dots when seen under stereomicroscope; no distinct larger marks on dorsum; dorsal surfaces of thighs and arms khaki in life, light brown when preserved, with one or more dark brown transverse bars; transverse bars sometimes diffuse; light dorsolateral stripe present or absent; when present, variable in width among individuals; dark brown lateral stripe surrounding the whole body, reaching leg-body insertion; oblique lateral stripe absent; pale ventrolateral stripe present as a diffuse line extending from behind eyes to groin in preserved individuals; small, light-brown irregular blotches or marbling present ventrolaterally from snout to groin; pale paracloacal marks present; (24) throat and abdomen of same color, with no transverse band on chest; (25) dark throat collar absent; (26) throat white to translucent, with a few melanophores only on chin; (27) no sexual dimorphism in ventral coloration, with gular, chest and abdominal regions immaculate in males and females, uniformly white to translucent; (28) iris metallic gold with tiny black flecks and a pupil ring; (29) intestine unpigmented; (30) adult testis unpigmented; (31) mature oocytes pigmented; (32) oral discs of tadpoles emarginate, not umbelliform in shape; (33) papillae on posterior labium of tadpoles pyramidal to very elongate (34) eggs laid on transparent jelly nests, on dead leaves on the forest floor; (35) diurnal habits, males calling during daytime; (36) advertisement calls characterized by trills of 3–15 short notes, repeated between silent intervals.

The new species is unambiguously assigned to the genus Allobates by the combination of characters states 4, 10, 20, 23, 25, 30, 32, and 35.

Comparisons with other species. Allobates grillisimilis is only known from forests not subject to long-term seasonal flooding (terra-firme) in the northwestern Madeira-Tapajós interfluve, in a region limited by the Madeira, Aripuanã and Amazon rivers ( Fig. 1 ). Although surveys were undertaken around this region by the authors and other research groups, the species was not found anywhere else, being probably restricted to this relatively central area of Brazilian Amazonia (see details in the “Distribution” section). For this reason, comparisons with other Allobates were limited to species occurring in Brazil, and to three additional species distributed in the Guiana Shield ( Allobates granti , Allobates spumaponens ) and Peruvian Amazon ( Allobates trilineatus ) which are morphologically similar to the new species.

Call structure and acoustic parameters set the new species apart from all species of Allobates with known advertisement calls, being characterized by the emission of short note trills with peak frequency roughly between 6.0–6.5 kHz, split by irregular silent intervals.

Allobates grillisimilis differs from Allobates femoralis (Boulenger 1883) , A. hodli Simões , Lima & Farias 2010, and A. myersi (Pyburn 1981) by the absence of red or yellow flash marks on dorsal surface of thighs, and by the absence of black and white marbling on abdomen.

The new species is readily distinguished from Allobates brunneus (Cope 1887) , A. gasconi (Morales 2000 “2002”), A. crombiei (Morales 2000 “2002”), and A. paleovarzensis Lima, Caldwell, Biavati & Montanarin 2010 by the absence of a distinct dark, diamond-shaped or hourglass pattern on dorsum, or dark brown markings on the head ( Fig. 2 ). Allobates grillisimilis differs from A. olfersioides (Lutz 1981) and A. goianus (Bokermann 1975) in lacking a cross-like pattern on dorsum. Allobates grillisimilis is distinguished from A. nidicola (Caldwell & Lima 2003), A. masniger (Morales 2000 “2002”) and A. vanzolinius (Morales 2000 “2002”) by its smaller size (maximum SVL <16.0 mm, males and females pooled) and unpigmented throat and belly (adult A. nidicola , A. masniger and A. vanzolinius with minimum SVL> 20.0 mm, and dark-gray to black throat and belly). The new species differs from A. fuscellus (Morales 2000 “2002”), A. marchesianus (Melin 1941) , and A. trilineatus (Boulenger 1883) in having unpigmented throat and belly, and males with Finger III not swollen (throat and belly gray, and a swollen Finger III in males of A. fuscellus , A. marchesianus and A. trilineatus ).

Preserved specimens of Allobates grillisimilis are most easily confounded with A. caeruleodactylus (Lima & Caldwell 2001), A. conspicuus (Morales, 2000 “2002”), A. granti (Kok et al. 2006) , A. spumaponens Kok & Ernst 2007 , A. subfolionidificans (Lima, Sanchez & Souza 2007), and A. sumtuosus (Morales 2000 “2002”), and therefore more detailed comparisons between them and the new species is warranted.

Males of Allobates caeruleodactylus have sky-blue fingers in life, uniformly dark-gray in preservative (fingers light brown with pale scutes in Allobates grillisimilis ). Color of throat and belly of female A. granti and A. spumaponens are yellowish in life (uniformly white to translucent in Allobates grillisimilis ). Finger I is much longer than Finger II in A. conspicuus , A. sumtuosus and A. spumaponens (Finger I almost the same length of Finger II in Allobates grillisimilis ). Dorsal surface of legs and arms without distinct dark brown transverse bars in A. caeruleodactylus , A. spumaponens and A. sumtuosus (legs and arms with a variable number of transverse bars in Allobates grillisimilis ). Among these species, advertisement calls consist of a single note emitted in a continuous (in A. caeruleodactylus and A. subfolionidificans ) or interrupted series ( A. spumaponens ), or by two notes emitted in a continuous series ( A. granti ). Advertisement call of Allobates grillisimilis consists of a trill of 3–15 short notes (mode = 4–5 notes, depending on sampling locality), emitted between silent intervals. Tadpoles of A. granti , A. spumaponens , and A. subfolionidificans are distinguished from those of Allobates grillisimilis by having short to moderately elongate papillae on posterior labium (moderately to very elongate in Allobates grillisimilis ). Tadpoles of A. sumtuosus also have short, round papillae on posterior labium (Simões & Lima 2012). Tadpoles of A. caeruleodactylus have P-3 tooth row distinctively shorter than P-2 and P-1 rows (tooth rows with same length in Allobates grillisimilis ).

Allobates conspicuus differs from Allobates grillisimilis by the generally larger size of reproductive males and females (minimum SVL of A. conspicuus = 15.4 mm, and maximum SVL of Allobates grillisimilis = 16.0 mm, with 85% of analyzed individuals being smaller than 15.0 mm), and by the presence of lateral fringes on toes (fringes absent in Allobates grillisimilis ). Finger I is also distinctively longer than Finger II in A. conspicuus , as indicated in Fig. 12 of Morales (2000 “2002”) (Finger I and Finger II have almost the same length in Allobates grillisimilis ). The call, color in life, and tadpole of A. conspicuus are unknown. However, it is unlikely that A. conspicuus occurs in locations geographically close to Allobates grillisimilis , as the former has not been recorded within at least 1500 km of the known distribution of the new species.

Description of the holotype. Measurements of the holotype are presented in Table 1. Body robust, head slightly wider than long (HL/HW = 0.91), head length corresponding to 0.31 times the snout-to-vent length ( Fig. 3 A). Eye diameter conspicuously larger than distance from nostril to anterior corner of the eye (EN/EL = 0.66). Nares located posterolaterally to tip of snout, directed anterolaterally, visible in ventral, lateral, and anterior views. Nostrils not visible dorsally. Internarial distance equivalent to 42% of head width. Canthus rostralis convex from tip of snout to nostril, straight from nostril to anterior corner of the eye. Loreal region vertical. Tympanum round, corresponding to approximately 0.4 times the maximum diameter of the eye. Anteroventral margin of tympanum distinct, all other margins indistinct ( Fig. 3 C). Maxillary teeth present. Tongue roughly triangular, slightly longer than wide, anterior tip attached to mouth floor. Median lingual process absent. Choanae round, positioned anterodorsally to eye bulge. A single vocal sac present, corresponding to most of the area of the medial and posterior subgular region. Vocal sac round when expanded. Lateral vocal slits present at level of maxillary articulation when vocal sac is retracted.

Palmar tubercle drop-shaped, tip projecting towards the base of Finger II. Thenar tubercle weakly developed, oval to elliptic, evident in ventral view of hand, but not protuberant. Maximum diameter of thenar tubercle 75% of maximum diameter of palmar tubercle. Subarticular tubercles of Fingers II, II and IV are round to oval, small, never exceeding the width of phalanges. Subarticular tubercle on Finger I oval, 1.1 times larger than thenar tubercle in maximum diameter. Distal subarticular tubercle absent on Finger IV. Supernumerary tubercles absent. Carpal and metacarpal ridges absent. No fringes or webbing on fingers. Length of Finger II approximately 90% the length of Finger I. Tip of Finger IV does not reach distal subarticular tubercle of Finger III when fingers are pressed against each other. Relative lengths of fingers: IV <II <I <III. Finger III not swollen. Disc of Finger IV moderately expanded, width of disc 1.6 times the width of adjacent phalanx. Discs of Fingers I, II, III and IV moderately to weakly expanded, width of discs corresponding to 1.2, 1.3, 1.7 and 1.6 times the width of adjacent phalanx, respectively ( Fig. 4 A).

Tibia length equivalent to 0.6 times the snout-to-vent length. Tarsal keel present, tubercle-like, strongly curved at its proximal end, flattening and straightening towards metatarsal tubercle. Metatarsal fold absent. A short, weak dermal thickening is observed on the outer edge of the sole, but it does not extend as a continuous ridge from postaxial edge of the base of Toe V to outer metatarsal tubercle. Preaxial edge of tarsus smooth, with no fringe. Basal webbing present only between Toes III and IV. Relative lengths of toes: I <II <V <III <IV. Discs of Toes I, II, III, IV and V moderately expanded, width of discs corresponding to 1.6, 1.7, 1.9, 1.7 and 1.4 times the width of adjacent phalanx, respectively ( Fig. 4 B).

Skin generally smooth on dorsum. Small and unpigmented granules in a small number, barely evident on dorsal surface of urostyle region and shanks. Skin smooth ventrally and laterally ( Fig. 3 A,B,C). Dermal flap above cloaca absent.

Variation in type series. Males from Borba, Nova Olinda do Norte, and Maués differed significantly in snoutto-vent length (ANOVA, F2,36 = 24.71, P <0.01), with specimens from Maués being slightly larger. Therefore, variation in individual morphometric measurements is presented separately according to sampling locality (Table 1).

In localities where males and females were collected (Borba and Nova Olinda do Norte), females had generally longer snout-to-vent length when compared to males (ANOVA, F1,43 = 4.65, P <0.01). Significant differences in body proportions according to sex were found in head measurements relative to body size, HL/SVL and HW/SVL ratios being usually larger in males (HL/SVL ANOVA, F1,43 = 12.69, P = 0.03; HW/SVL ANOVA, F1,43 = 7.42, P <0.01), indicating that males have relatively more robust heads relative to overall body size. Males also have proportionally longer tibiae (TL/SVL ANOVA, F1,43 = 9.18, P <0.01).

Head length 88% of head width in average, considering pooled samples from Borba and Nova Olinda do Norte. Head longer than wide only in males from Maués, which have an average HL/HW ratio of 1.08.

Skin texture of dorsum is smooth to weakly granular posteriorly in 45 individuals. Twelve individuals have slightly protuberant round granules, with dark brown pigmented tips in the posterior region of dorsum.

Color in life. Males and females do not present fixed dimorphism in relation to color or color pattern in life ( Fig. 2 C, D, E, F). Dorsal surface of body is solid tan brown. Lateral surface of body is solid dark brown. Small spots of darker brown, same color as lateral surface of body, can be present posteriorly on dorsum, on top of larger granules. A pale dorsolateral stripe with diffuse inner edge is present in most individuals, but is variable in width and melanophore density, making it more or less conspicuous among individuals. A white, iridescent ventrolateral stripe is present along the lower margin of the dark brown flanks, from tip of snout to the groin, wider and more conspicuous from behind the eye to groin ( Fig 2 A, C, D, E). Ventrolateral stripe is often diffuse or interrupted. Pale iridescent marbling, same color as of ventrolateral stripe, is present below ventrolateral stripe, towards the abdomen, over a light brown or gray background. Throat, gular and pectoral regions and abdomen are uniformly white to translucent ( Fig. 2 B, F). In males, vocal sac is white to translucent when inflated ( Fig. 2 C, E). A few brown melanophores are often present, scattered on chin and anterior margin of vocal sac. Iris metallic gold with tiny black flecks and a pupil ring.

Dorsal surface of upper and forearm predominantly light brown to khaki, white only around arm-body insertion. A few dark brown blotches may be present laterally on upper arm. A variable number of dark brown blotches or incomplete transverse bars are present on dorsal and lateral surfaces of forearm. Upper arm white to translucent, same color as chest in ventral view. Forearm, carpal and metacarpal regions are dark brown in ventral view, with a few light blotches. Fingers uniformly dark brown in ventral view, light brown with dark brown flecks in dorsal view. Paired scutes on finger discs are iridescent white.

The area immediately adjacent to vent is solid dark brown, flanked by a light cream paraclocal mark. Distal edge of paracloacal mark is limited by a solid or interrupted dark brown transverse bar, evident in dorsal view and extending along the inner lateral surface of thigh. Dorsal surface of thigh is light brown to khaki, with a variable number of dark brown transverse bars or irregular blotches (transverse bars absent or interrupted in some individuals). Dorsal surface of shank same color as that of thigh, also with a variable number of dark brown transverse bars or blotches. Ventral surface of thigh and shank generally white to translucent, same color as abdomen, with dark brown marbling along inner and outer edges. Tarsal region is light brown with dark brown flecks in dorsal view, uniformly dark brown in ventral view. Toes with dark brown and light brown patterning. Paired scutes on toe discs are iridescent white.

Color of the holotype in preservative. Dorsal surface of body is uniformly brown, darker only above the orbits ( Fig 3 A). Lateral surface of body is solid dark brown. A pale dorsolateral stripe is present, characterized by a narrow line (~ 0.3 mm) adjacent to the dark lateral surface of body where the density of melanophores is reduced, gradually increasing towards the center of the dorsum (i. e. the inner edge is diffuse). A narrow bright white ventrolateral stripe is present from tip of snout to groin, wider and more conspicuous from behind the eye to groin. Small patches the same color of ventrolateral line form a marbling pattern on ventrolateral region, towards the abdomen, on darker, light brown background ( Fig. 3 C). Throat, gular region, pectoral region, abdomen and ventral surface of thighs are uniformly white to translucent ( Fig. 3 B). A few melanophores are present only on chin. Tongue is cream-colored.

Arms pale brown in dorsal view, melanophores more concentrated in some areas of the forearm, forming faint blotches or banding patterns. Paler areas are visible on the axilla and metacarpal region, especially on Fingers I and II. Tip of fingers light brown, finger discs with pale scutes. Upper arm pale to translucent in ventral view, continuous with color pattern of chest. Forearm, carpal and metarcarpal regions are tan brown in ventral view, with a few irregular pale blotches. Surface of lateral edge of forearm, carpal and metacarpal regions same color as their ventral surface, extending laterally from elbow to ventral surface of palm and fingers.

The area immediately around vent is solid dark brown, flanked by an unpigmented transverse band, corresponding to the pale paracloacal mark. Distal edge of paracloacal mark is margined by a solid dark brown transverse bar (continuous on right thigh, interrupted on the left), extending along the whole inner lateral surface of thigh. Thigh is brown in dorsal view, with a single solid dark brown transverse bar and a few smaller dark brown blotches appearing on a light brown background. Dorsal surface of shank same color as thigh, with a single dark brown transverse bar. Outer dorsolateral surface of shank with irregular dark brown blotches and patches. Outer dorsal surface of tarsal region is lighter than overall pattern of legs. Inner dorsal surface of tarsal region with dark brown blotches. Toes are generally light brown, with irregularly distributed melanophores. Ventral surface of thigh and shank predominantly white to translucent, same color as abdomen. Dark brown marbling appears along inner and outer edges and around the knee. Ventral surface of tarsal and metatarsal regions is uniformly dark brown. Toes are dark brown in ventral view, with uniformly pale discs.

Color variation in the type series. Allotype same color as holotype except for a pale paracloacal mark flanked distally by a solid dark transverse bar which is interrupted medially ( Fig. 3 D). The allotype also lacks solid dark transverse bars on dorsal surface of thigh and shank. Only a few, weakly marked dark brown blotches are present on dorsal surface of these regions.

The presence of a pale dorsolateral line is highly variable among specimens in the type series ( Fig. 5 ). It is present in eight, absent in 18, and barely distinguished in four specimens from Borba; present in 14 and absent in one individual from Nova Olinda do Norte; and present in four out of seven specimens from Maués.

Dark transverse bars on dorsal surface of thighs are also highly variable in number and width among individuals ( Fig. 5 ). Five of the 52 individuals examined (including the allotype) completely lack transverse bars on dorsal surface of thighs. One, and up to five dark transverse bars may be present on thighs of the remaining individuals. Transverse bars vary from solid, dark brown stripes, to medially interrupted stripes, or diffuse brown blotches. The number and pattern of dark brown transverse bars are also variable on dorsal surfaces of shanks and forearms.

Five males and five females were dissected for close examination of color of internal organs and oocytes. The large intestine is not pigmented. Testes are not pigmented. Mature oocytes are pigmented, with light brown pigments concentrated in a single pole.

Tadpole description. Tadpole measurements were obtained from 91 tadpoles at different developmental stages (Table 2), maintained in lots with the same collection numbers (INPA-H 30828: Stage 25; INPA-H 30827: Stages 26–28; INPA-H 30824, 30825: Stages 35–37; INPA-H 30826: Stages 38–40). One tadpole at stage 27 was used for a detailed description ( Fig. 6 , Fig. 7 A,B). Tadpoles collected from the backs of males and preserved immediately were all at developmental stage 25, with conspicuous and fully developed spiracle and oral disc.

Body depressed dorsoventrally, body width (4.5 mm) larger than body depth (2.3 mm), 6.5 mm in length. Snout is nearly round in dorsal view, flattened anteriorly in dorsal view, and anterodorsally in lateral view, from the level of nostrils to the tip of snout. Nares are small, directed dorsolaterally, 0.7 mm anterior to the eye, and 0.4 mm posterior to tip of snout. Nostrils narrowly spaced, distance between nostrils (1.0 mm) only slightly shorter than distance between orbits (1.1 mm). Eyes dorsal, directed dorsolaterally, 0.6 mm in maximum length, and located 1.2 mm posterior to tip of snout. Spiracle single, sinistral, forming a free short tube opening posterodorsally, about level of body axis in lateral view, 4.1 mm posterior to tip of snout. Vent tube medial, free, 1.0 mm in length, opening dextrally.

Musculature of tail is deeper (1.2 mm) along the first third of tail length and wider at body-tail insertion (1.3 mm). Ventral fin originates at body-tail insertion. Dorsal fin originates slightly anterior (0.3 mm) to body-tail insertion, and reaches maximum height 12.0 mm from tip of snout, approximately at middle tail length. At maximum depth of tail, depth of musculature is 1.0 mm, dorsal fin 1.0 mm and ventral fin 0.5 mm.

Oral disc is positioned anteroventrally, emarginate laterally, transversely elliptical, 1.7 mm in transverse width. Anterior labium 1.7 mm in length, continuous with snout, but delimited by a shallow depression. Round to pyramidal marginal papillae absent dorsally on anterior labium (gap 1.2 mm, 70% of total anterior labium length), but present laterally, on its outer margins. Posterior labium free from body wall, 1.6 mm in length, with a single row of marginal papillae. First five papillae adjacent from lateral emargination are pyramidal to moderately elongate. The following eight papillae are very elongate (up to 0.5 mm long). The most central (posterior) three papillae are moderately elongate.

Labial tooth row formula is 2(2)/3(1). Rows A-1 and A-2 with same length (1.2 mm), A-2 with a large medial gap (0.4 mm). Rows P-1, P-2 and P-3 with same length (1.4 mm), P-1 presenting a very narrow medial gap (<0.1 mm), evidenced by a break between subjacent tooth ridges. Upper jaw sheath flat medially, with lateral flexures, 0.7 mm in length (41 % of oral disc width), <0.1 mm in width. Cutting edge serrate, with serrations not extending to lateral process of the upper jaw. Lower jaw sheath deeper than upper jaw, arch (or V) shaped, 0.6 mm in length, with serrate cutting edge.

Morphology of oral disc is constant throughout all developmental stages examined. Elongate papillae are evident at least from stage 25 to stage 40. The number of marginal papillae on the posterior labium is slightly variable among individuals ( Fig. 7 B,C,D): lateral papillae 4–6, elongate latero-posterior papillae 6–9. Moderately elongate central posterior papillae 3–5.

Color in formaldehyde is grayish brown, body darker than tail ( Fig. 6 ). Body tegument is translucent. Brown melanophores are scattered in blotches on dorsum and lateral surfaces, absent on ventral surface (except for small aggregations approximately the level of the eyes). Intestine coils are visible through skin. Tail musculature is light cream. Tail fins are translucent, with scattered brown melanophores forming irregular blotches.

In life, iridescent, nearly golden pigments are visible on dorsal and lateral surfaces of the body. Shades of red and pink appear on medial region of body, as internal organs and blood vessels are visible through translucent skin ( Fig. 8 ).

Call description and variation. The advertisement call of Allobates grillisimilis consists of groups of very short tonal notes, highly similar in duration, emitted between short silent intervals ( Fig. 9 ). Call parameters measured from calls of the holotype, and from 20 males recorded at the three sampling sites are presented in Table 3.

The number of notes in each call varied from three to 15 among all samples analyzed. At the type locality, the number of notes in each call ranged from four to seven, resulting in average call duration of 0.178 ± 0.035 s. Average peak frequency of calls considering all notes was 6497.6 ± 35.9 Hz at the type locality. Calls were usually longer (0.227 ± 0.053 s in average) and had overall lower peak frequencies (6219.9 ± 153.9 Hz in average) among individuals sampled in Nova Olinda do Norte. Calls were shorter (0.149 ± 0.011 s in average) and had even lower peak frequencies (5964.7 ± 96.3 Hz) among males recorded in Maués.

Considering all call samples, frequency modulation is slightly similar among first, central, and last pulses. The first pulse of each call generally present higher frequency modulation (average difference between lower and higher frequencies = 998.9 ± 239.7 Hz) than central, and last pulses (average difference between lower and higher frequencies = 905.1 ± 143.2 Hz, and 891.4 ± 178.0 Hz, respectively).

Reproductive behavior. At the type locality, males were found calling from sites slightly elevated from the forest floor, such as tree roots, logs, lianas, old termite nests or leaves laying on the ground ( Fig. 10 A). Height of calling sites ranged from three to 48 cm (mean 19.6 cm, N =18 observations), the first corresponding to a dead leaf on the ground and the latter to the roots of a palm tree.

Eggs are deposited in terrestrial nests, usually on the inner surface of a curled dead leaf on the forest floor ( Fig. 10 B,C), but also on flat dead leaves. Jelly egg masses contained six to thirteen embryos (mean = 9±2 embryos, N = 13 egg masses observed).

Two courtships were observed by A. P. Lima on January 18 and 19, 2008. Both occurred in the morning, starting approximately at 07:30 to 08:00. Previous to both successful courtships (i. e. those that resulted in oviposition), the two observed females were spotted in the territories of other males, but left some time after being led to potential oviposition sites, and before males attempted amplexus. The following courtship pattern is described based on steps common to the two subsequent courtships, recorded from their outset until oviposition.

The female moved towards a second male who was calling nearby. As the female reached the second male’s sight distance (about 1 m), he changed the calling pattern (alternating advertisement with what is probably a courtship call) and moved inside a small curled dead leaf on the forest floor. The female accompanied, and both stood side by side on the leaf for a few minutes, with the male emitting both types of calls, but no body contact. After this step, the male left the nest formed by the curled leaf and continued calling and moving around his territory, either alone (female remaining inside the nest) or followed by the female. On a second try, the male (while still calling), approached the same nest and was followed inside by the female. In one of the observations, male and female could be clearly observed inside the nest, and the pair gathered in cephalic amplexus for approximately one minute. In the second observation, no tactile interactions could be observed inside the nest. On both observations, males left immediately after pairing, returning to a nearby calling site and emitting advertisement calls. Both females stayed inside the nest for around 20 minutes (first female 07:41–08:01 h; second female: 09:25–09:50 h) laying eggs. First female laid 13 eggs and the second, nine eggs.

Distribution. Allobates grillisimilis was only found in primary terra-firme forests of the northwestern Madeira-Tapajós interfluve, in Brazil ( Fig. 1 ). Its known distribution is limited west and north by the large Madeira and Amazon rivers, respectively. The species is not known to occur in localities south of the municipality of Borba, although an equivalent amount of time was spent in field work by the authors in other sites of adequate habitat around the city of Novo Aripuanã.

From November 2004 to July 2011, the authors conducted field work targeting the study of diurnal frogs in several sampling points a) south of the Aripuanã River, on the right bank of the Madeira River, until the Brazilian border with Bolivia; b) along the left bank of the Madeira River, from the Municipality of Careiro da Várzea to the Brazilian border with Bolivia; c) north of the Amazon River, in the Manaus and Itacoatiara regions, as well as localities in the states of Roraima and Pará; d) in the region of Parque Nacional da Amazônia, on the left bank of Tapajós River, and east of the presumed Allobates grillisimilis distribution. In none of these occasions we were able to detect the new species. Further data were obtained from the Brazilian Program for Biodiversity Research-PPBio online database (http://ppbio.inpa.gov.br). The database is updated frequently with data proceeding from intensive species surveys carried out at standardized sampling grids. The new species has not been recorded at any sampling grid where anuran surveys have been carried out ( Fig. 1 A).

Thus, the available records strongly suggest that the new species has a restricted geographic range, occupying areas on the right bank of the Madeira River, and reaching eastwards, between the Aripuanã River and the Municipality of Maués in central Brazilian Amazonia ( Fig. 1 B).

Figures

FIGURE 1. Geographic distribution of Allobates grillisimilis (A) Inset: relative location of sampling area in northern South America. Red triangles: distribution of Allobates grillisimilis in central Brazilian Amazon. Solid dots: location of permanent grids maintained by the Brazilian Program for Biodiversity Research-PPBio (http: // ppbio. inpa. gov. br), and sites where intensive studies focusing on diurnal frogs have been conducted at least three times, where the new species was not recorded. Open dots: sites sampled for diurnal frogs in one or two consecutive years by the authors, where the new species was not recorded. (B) Detailed view of sites of occurrence of Allobates grillisimilis emphasizing their location in the northwestern Madeira-Tapajós interfluve, State of Amazonas. 1: Nova Olinda do Norte; 2: Type locality in the outskirts of Borba; 3: Rio Paraconi, in Maués; 4: Igarapé Tabacal, a tributary of Rio Paraconi, also in Maués.

FIGURE 2. Color in life of Allobates grillisimilis (A) Dorsolateral and (B) ventral views of holotype (INPA-H 30779), a male collected in Borba, on the right bank of the lower Madeira River, in January 2008. (C) Lateral view of a calling male from type locality (note white vocal sac and multiple dark transverse bars on thighs and shanks). (D) Lateral view of a female photographed at the same locality. (E) Calling male photographed in Nova Olinda do Norte, Amazonas, Brazil. (F) Ventral views of male (left) and female (right) Allobates grillisimilis, from the type locality (note the lack of color dimorphism on ventral surfaces of body). Photos by A. P. Lima (A – D, F) and P. I. Simões (E).

FIGURE 3. Allobates grillisimilis from Borba, Amazonas, Brazil. (A) Dorsal, (B) ventral, and (C) lateral views of Allobates grillisimilis holotype (INPA-H 30779, male). (D) Dorsal, (E) ventral, and (F) lateral views of Allobates sp nov. allotype (INPA- H 30780, female). Both individuals have incisions on ventral surface of thighs, made during removal of muscle tissue samples. Scratches on dorsum of both individuals were caused by manipulation.

FIGURE 4. Allobates grillisimilis from Borba, Amazonas, Brazil (INPA-H 30779, holotype, male) (A) Right hand and (B) Right foot.

FIGURE 5. Variation in color pattern of dorsal surface of body and legs between individuals from the type-series of Allobates grillisimilis. Specimens in upper line from type locality in Borba, Amazonas, Brazil: (A) INPA-H 30784, male; (B) APL 30787, male; (C) INPA-H 30798, male. Specimens in middle line from Nova Olinda do Norte, Amazonas, Brazil: (D) INPA-H 30816, female; (E) INPA-H 30817, male; (F) INPA-H 30823, male. Specimens in lower line from Maués, Amazonas, Brazil, all males: (G) MPEG 28536; (H) MPEG 28545; (I) MPEG 28535.

FIGURE 6. Tadpole of Allobates grillisimilis from Borba, Amazonas, Brazil, collected from an egg clutch in January 2008. From top to bottom: dorsal, ventral, and lateral views of preserved tadpole in developmental stage 27 (INPA-H 30827), used in the detailed description (see text).

FIGURE 7. Oral discs of Allobates grillisimilis tadpoles from Borba, Amazonas, Brazil, collected in January 2008. (A) Oblique and (B) ventral views of oral disc of tadpole at developmental stage 27. (C) Tadpole at stage 38, photographed on dark background, emphasizing distribution and length of papillae. (D) A second tadpole at stage 38, photographed on white background, emphasizing relative length of tooth rows. Scale bars correspond to 0.5 mm.

FIGURE 8. Living tadpoles of Allobates grillisimilis from Borba, Amazonas, Brazil, showing color in life and position of spiracle (indicated by black arrows).

FIGURE 9. Advertisement call of Allobates grillisimilis holotype (INPA-H 30779) recorded in Borba, Amazonas, Brazil, on 12 th of January 2008, at 07: 28 h and 25 ° C. (A) Waveform (upper graph) and sonogram (lower graph) of a 4 s segment of advertisement calls, denoting the arrangement of calls, which consist in groups of very short tonal notes. The number of notes is generally variable between calls in the same calling bout. (B) Detailed view (0.6 s) of a single call, consisting of a group of six short notes.

FIGURE 10. Reproductive behavior of Allobates grillisimilis (A) Female (upper left) attracted by a courting male in Nova Olinda do Norte, Amazonas, Brazil. Courtship did not result in oviposition. (B) Female inside a curled dead leaf, used as an oviposition site. (C) Jelly nest containing 13 eggs deposited by the same female. (D) Allobates grillisimilis male collected while transporting tadpoles. All tadpoles being transported were at developmental stage 25 of Gosner (1960). (B), (C), and (D) from type locality in Borba, Amazonas, Brazil, photographed in January 2008.