Bioacoustics of Rhinella cerradensis

Description of the holotype : General aspect robust ( Fig. 1 A). Head wider than long; SVL approximately 2.7 × head width; snout mucronate to truncate in dorsal view and obtuse in lateral view ( Figs. 3 A and 3B); almost all cranial crests present and developed, parietal crest absent; pre-tympanic and rostral crests well developed; supranasal crest evident with rugosites, produced by cranial striations; supratympanic crest developed, in contact with the parotoid gland; cranial crests keratinized, especially the supraocular crest; loreal region smooth; nostrils large, with lateral elliptic openings directed upward; interorbital distance and eye diameter equal in length; eye diameter about 1.5 × tympanum diameter; eyelid large, with small keratinous spicules; tympanum visible, well developed, rounded; dorsum of head flat, with small rounded spicules. Parotoid gland evident, elliptical, with keratinous spicules; parotoid length about 2.6 × its width. Tongue longer than wide, smooth, with one single superficial central fold, free in its posterior end, attached to jaw; vomerine teeth absent; choanae elliptical. Fingers thin and developed ( Fig. 3 C); forearm and arm robust; relative finger length II <IV <I <III; fingers without webbing; tips of fingers keratinized and dark in dorsal view; subarticular tubercles at base of all fingers; subarticular tubercles present between phalanges II and III of finger III, subarticular tubercles on phalange III of finger III; outer palmar tubercle large and rounded; inner palmar tubercle rounded at base of finger I. Nuptial pads evident, dorsally visible on fingers I and II. Toes with broad lateral fringes, toe tips keratinized and dark, relative toe lengths I <V <II <III<IV; small subarticular tubercles present on toes, between phalanges II and III on toes III, IV and V. Foot webbing present and well developed; foot webbing formula I 2-2 / 2 II 1- 3 III 2-3/ 2 IV 3/2- 2 V ; outer metatarsal tubercle small oval; inner metatarsal tubercle well developed and elongate, weakly keratinized. Metatarsal fringe present, beginning at tip of toe I, covering 2/3 of metatarsal length (the fringe is interrupted by inner metatarsal tubercle); plantar surface with small, conical callosities. Dorsal skin rough; dorsum covered by rounded and oval glands of different sizes; all glands with black and pointed keratinized spicules; spicule number varies with gland size; glands are smaller and more dense on anterior and posterior limbs. Measurements of holotype (in mm): SVL 109.9; HL 32.8; HH 21.0; HW 40.6; PGL 28.9; PGW 10.8; TD 8.8; ED 13.3; END 4.9; IOC 14.1; IOD 15.0; IND 7.5; FN/DFN 4.1; HAL 26.6; FAR 20.5; UAR 17.3; TIL 47.5; THL 49.8; TL 27.7; and FL 50.2. Morphometric analyses: The PCA suggests the presence of two morphological subgroups in species of R . marina group ( Fig. 4 ). A subgroup of species represented by the white symbols, composed by R . marina , R . icterica , R . schneideri , R . jimi , and R . cerradensis and another represented by the black symbols, consisting of R . arenarum , R . rubescens , R . achavali , and R . veredas . The first two scores account for a total of 94.8% of the variance. The first component accounts for 88.4% of the variance and showed high and positive scores. The second component accounts for 6.4% of the variance and showed positive higher values for tympanum diameter and foot and leg lengths, and negative values for parotoid gland length ( Table 2 ). Examination of factor loadings suggested the formation of two subgroups. The first subgroup (white symbols) is composed of the larger sized species, with developed and marked cranial crests, relatively smaller tympanum, and shorter limb length. The second subgroup (black symbols) is formed by the smaller species with less developed cranial crests and relatively longer parotoid glands ( Fig. 4 ). Variables Score 1 Score 2 Snout-vent length 0.561 0.881 Head height 0.511 0.431 Head length 0.556 0.653 Head width 0.595 0.620 Max. length of parotoid gland 0.706 0.326 Max. width of parotoid gland 0.820 –6.549 Tympanum diameter 0.507 2.897 Hand length 0.597 0.635 Hand, fore arm, and upper arm length 0.592 0.700 Foot length 0.596 1.255 Thigh, tibia, tarsus, and foot length 0.613 1.111 Variance explained 88.39% 6.38% Coloration: Sexual dimorphism is well marked in coloration ( Fig. 2 ). In life, males have a brownish green dorsum (sometimes a dark green dorsum) and a brownish white venter. Females have the same brownish green dorsum and brownish white venter of the male, but show black coloration in many areas of dorsum (sometimes also on hind limbs). In this respect, the females of this species resemble R . icterica females. The coloration of preserved specimens resembles the coloration of males and females in life, but the parotoid glands turn yellowish. Description of the tadpole: Descriptions are based on a tadpole series (CHUNB 49574) collected at Estação Rádio, Centro de Instrução e Adestramento de Brasília , Brasília Municipality, Distrito Federal on 31 August 2002 , by N.M. Maciel and R.H. Matsushita. Tadpole series measurements are provided in Table 3 . Measurements of the specimen used for description ( Fig. 5 ) (in mm): BL 9.72; IND 1.30; IOD 2.90; MTH 4.30; TAL 12.64; TL 21.76; TMH 1.50; TMW 1.65. The specimen used for description is in stage 40 ( Gosner, 1960 ) ( Fig. 5 ). Body elliptical in lateral ( Fig. 5 A) and dorsal views ( Fig. 5 B). Body 76% of tail length and 45% of total length; body wider than deep; snout rounded in lateral and dorsal views; eyes dorsal, directed laterally; distance between eyes 2.2 × the distance between nostrils; nostril opening kidney shape; spiracle sinistral, near to midbody axis, opening in the body wall, without external tube. Vent tube medial (easily visible in tadpoles in early stages). Tail musculature gradually tapering to rounded tip. Caudal fin fusiform; dorsal fin about same height as ventral fin. Color in preservative uniform, dark brown. Oral disc anteroventral, and emarginated laterally in lower and upper jaw. LTRF 2(2)/3(1); A2 slightly longer than A1, P1 slightly shorter than A1 and longer than P2 and P3. Lower jaw serrate and shallowly V-shaped. The majority of tadpole specimens are in stages 40–42. The tadpoles in stage 42 differed from those in stage 40 mainly by the development of hindlimbs, presence of emerged forelimbs, more rounded snout, and shorter body. The tadpoles described from species of the R . marina group and those of the new species are similar in general shape ( Rosa, 1951 ; Savage, 1960 ; Rosa, 1965 ; Cei, 1980 ; Heyer et al. , 1990 ; Eterovick & Sazima, 1999 ). According to Eterovick & Sazima (1999) the tadpoles of R . rubescens are more similar to those of R . schneideri in body proportions and spiracle position, while the tadpoles of R . arenarum more closely resemble those of R . icterica . The tadpoles of the new species resemble R . rubescens and R . schneideri in body proportions and spiracle position. The tadpole of R . cerradensis can be diagnosed by body proportions, spiracle position, and the absence of an external spiracular tube, with the opening in the body wall ( Fig. 5 A). The absence of an external tube is unique among the tadpoles described of the R . marina group. Osteological features: Skull with the robust general aspect of the species of Rhinella marina group ( sensu Pramuk, 2006 ). The specimens analyzed have extremely well-ossified and exostosed crania that are ornamented with deep striations, pits, and rugosities. The cranium is wider than long, with the greatest width at the level of the quadratojugals, as it is characteristic of other species of the group. All cranial crests present, with the exception of the parietal crest ( Fig. 6 ). The Arabic numbers between quotations marks in the text indicate skull features of the new species (see Fig. 6 ). A detailed description of cranial features follows. Alary process of premaxilla postero-lateraly positioned; premaxilary bones are miss in the figure, frequently split during osteological bufonid preparations; vertical process of maxilla flattened laterally but dilated medially, maxillary crest well developed (5) ( Fig. 6 B and C); nasals in contact medially (1), anterior tips of nasals ventrally projected, ornamentations along edges forming the canthal (3) and supraorbital crests (4) ( Fig. 6 A); vertical arm of nasals robust on top and flattened on bottom; anterior portion of frontoparietal with rectangular shape, posterior portion projected at posterior end of skull, composing apical part of foramen magnum (2); frontoparietal not contacting prootic process (2) ( Fig. 6 A); medial area of frontoparietal large, with a portion that does not compound cranial box; this lateral portion bends in a plane approximately 90° relative to roof of skull, forming supraorbital crests; in this configuration there is no ventral groove for occipital artery. Supraorbital crests ornamented, composing a continuum with canthal crest; squamosal with a great mosaic of planes and processes, formed mainly by dorsal, vertical, and medial planes, medial plane blade-shaped, poorly developed, and projected to maxillary bone, horizontally oriented and poorly developed posteriorly; a large medial projection (otic plate) on top of squamosal; exoccipitals not fused one with another; a well developed prootic process that does not touch frontoparietal; a jagged or “scalloped” suture formed by articulation between pterygoid medial ramus (8) and the parasphenoid alae (7) ( Fig. 6 B and 6C; sensu Pramuk, 2006 ); neopalatine bone bearing a blade-like projection ( Fig. 6 B and 6C); dorsal surface of sphenethmoid covered completely by medial articulation of nasals and frontoparietals (6); nasals not expanded dorsolaterally (as they are in R . granulosa species group), and forming a transverse suture with frontoparietals; jaw articulation lies posterior to level of the fenestra ovalis ; and with a complete temporal arcade ( sensu Pramuk, 2006 ). Variables Mean (±SD) Ranges Body length (BL) 8.93 (±0.63) 8.03–10.02 Internarial distance (IND) 1.26 (±0.15) 1.00–1.55 Interorbital distance (IOD) 2.78 (±0.20) 2.40–3.00 Maximum tail height (MTH) 3.60 (±0.41) 2.95–4.30 Tail length (TAL) 11.65 (±1.46) 9.66–13.92 Total length (TL) 20.08 (±1.68) 17.76–22.91 Tail muscle height (TMH) 1.51 (±0.15) 1.30–1.75 Tail muscle width (TMW) 1.21 (±0.23) 0.90–1.75 Advertisement call: The recording was made at Centro de Instrução e Adestramento de Brasília , Brasília , Distrito Federal in August 15 2003 , 22:30h. The air temperature was 17.1ºC, with 73% relative humidity. The specimen has SVL= 117.7 mm . The advertisement call graphics are shown in Figure 7 . The calls were variable in duration (1.9– 12.4 s). Mean call rate was 9.8 ± 0.6 notes per second. (19–129 notes per call). Note rate and note interval were based on the means of 10 notes of the calls. The mean note rate was 44.7 ( ± 2.41) ms and the interval among note average 66.5 ( ± 2.17) ms; each note was formed by three pulses ( Fig. 7 B). Dominant and fundamental frequencies were also determined from five notes from various parts of the calls. Mean dominant and fundamental frequencies were 839.0 ( ± 8.9) Hz and 421.0 ( ± 3.3) Hz, respectively. The advertisement call of R . cerradensis resembles that of other species in the R . marina group. Although the calls of the Rhinella marina species group are conservative, they present some differences. The notes per advertisement call of R . cerradensis is more variable than R . schneideri (33–40; Köhler et al. , 1997 ), R . icterica (4–20; Heyer et al. , 1990 ), R . poeppigii (10–45; De La Riva et al. , 1996 ), R . arenarum (61–107; Straneck et al. , 1993 ), R . marina (19–25; Crocroft et al. , 2001 ), and R . rubescens (5–25) (present work). The number of pulses per note of the new species (three) is equal to those of R . schneideri ( Köhler et al. , 1997 ) , and R . arenarum ( Straneck et al. , 1993 ) , while in R . icterica they range from one to three ( Heyer et al. , 1990 ), three to five in R . poeppigii ( De La Riva et al. , 1996 ) , five pulses in R . marina ( Crocroft et al. , 2001 ) , and two pulses in R . rubescens (present work). The advertisement call of R . schneideri has a second power peak of 2100 Hz above the dominant frequency ( Köhler et al. , 1997 ). Rhinella icterica ( Heyer et al. , 1990 ) , R . rubescens ( Haddad et al. , 1988 ) , R . marina ( Crocroft et al. , 2001 ) , R . poeppigii ( De La Riva et al. , 1996 ) , R . arenarum ( Straneck et al. , 1993 ) , and the new species lack the second power peak. However, the spectrogram of R . arenarum provided by Martin (1972) showed a second power peak above the dominant frequency. The re-analyzed call of R . icterica ( Heyer et al. , 1990 ) presented a lower fundamental and dominant frequencies of 324.9 ( ± 4.5) and 646.0 ( ± 0.2) Hz than R . cerradensis 421.0 ( ± 3.3) and 839.0 ( ± 8.9) Hz. Conversely, R . marina ( Crocroft et al. , 2001 ) showed higher fundamental and dominant frequencies of 559.9 and 1119.7 Hz (with no frequency variation among notes) among these three species ( R . icterica , R . cerradensis , and R . marina ). The advertisement call of R . arenarum ( Straneck et al. , 1993 ) presented a dominant frequency of 1348 ( ± 18.3) Hz, similar to R . rubescens , dominant frequency of 1015.6 ( ± 41.1) Hz.

Distribution: Rhinella cerradensis has a large distribution in the Cerrado, occurring in the Brazilian states of Piauí, Bahia, Goiás, Minas Gerais, and Distrito Federal ( Fig. 8 ). Natural history notes: Field observations were made in the states of Distrito Federal, Bahia, and Goiás. We have carried out studies at Centro de Instrução e Adestramento de Brasília (CIAB) since 2001. Rhinella cerradensis was observed in March (end of the rainy season), and August to October of 2002 (from dry season to just before the beginning of the rainy season), when periodical visits were made to the area. Adults were always found in open Cerrado physiognomies (Cerrado and Campo Sujo; see Ribeiro & Walter 2001 for an account of the Cerrado physiognomies). We observed the reproductive activity, recorded the advertisement call, and collected tadpoles. We found a carcass of an adult male of R . cerradensis completely eviscerated with untouched secretory parotoid glands. R . schneideri and R. rubescens were also found breeding in the same permanent pond at Brasília . In Emas National Park we recorded a Conepatus striatus (Mammalia: Mustelidae ) feeding upon an adult R . cerradensis . The new species is sympatric with R . schneideri and R . veredas in western Bahia and Piauí states, and with R . schneideri , and R . rubescens in the states of Distrito Federal and Goiás. Until now few observations on the natural history of the new species exist, and only four advertisement calls have been recorded. The elongate and well developed inner metatarsal tubercle suggests that C . cerradensis might bury itself during the dry Cerrado season as do other Neotropical species (e.g., Eupemphix nattereri , Pleurodema diplolistris , and Odontophrynus cultripes ).