Bioacoustics of Elachistocleis cesarii

Miranda-Ribeiro (1920) described two subspecies of Engystoma ovale based on maculate-bellied specimens from the state of São Paulo , Brazil , which were later synonymized by Parker (1934) with Elachistocleis ovalis . Toledo et al. (2010) recently resurrected and redescribed them under the new combination Elachistocleis cesarii . Herein we recognize E . cesarii as a species distributed in south-eastern and central-western Brazil ( Fig. 3 ) and closely related to E . piauiensis and E . magna ( Fig. 1 ). Elachistocleis piauiensis was described and named by Caramaschi & Jim (1983) from Picos, Piauí . We found four lineages distributed in north-eastern Brazil , but we could not confidently assign any to E . piauiensis , because we did not have access to data from the type locality. Specimens assigned to each of these four lineages are morphologically similar to each other and to the original species description of E . piauiensis . The ventral colour pattern varies widely and similarly along the clade composed of E . cesarii , E . magna and the four candidate species E . cf. piauiensis 1–4, with no clear difference between them. The presence/absence of the mid-dorsal line also varies, except for E . cf. piauiensis 3, in which all examined vouchers lack the line. The holotype of E . piauiensis also lacks the line, and this could be evidence to assign the name to this specific clade. However, we cannot rule out that the consistent absence in E . cf. piauiensis 3 is not an effect of our sampling, given the high variability of this character state in several of our delimited species ( Fig. 1 ). Elachistocleis cesarii was distinguished from E . piauiensis by differences in the advertisement call, size of the post-commissural gland and details of the inguinal region colouration ( Toledo et al. , 2010 ) – phenotypic traits that we have not explored for the present contribution. On the other hand, E . magna was distinguished from E . cesarii and E . piauiensis solely by its size (male SVL above 31 mm in E . magna , against SVL below 29 mm in E . cesarii and E . piauiensis ; Toledo, 2010). Among examined specimens, we observed a consistent difference in size between E . magna and E . cf. piauiensis 1–4, but not between E . magna and E . cesarii . Males of E . cesarii can have SVL up to 31 mm , whereas some males of E . magna have SVL below 29 mm . Therefore, a thorough evaluation of phenotypic data allied with a denser molecular sampling is needed to verify if the differential diagnoses among E . cesarii , E . piauiensis and E . magna will hold true with additional data.

Description of the lectotype . Body robust and ovoid. Texture of the dorsal skin and undersurface of the body smooth. Skin on ventrolateral surface of body and area around the cloacal region smooth. Cloacal flap absent; vent opening positioned posterodorsally. Head small and triangular, broader than long. Cranial crests absent. A conspicuous dorsolateral skin fold from the arms to the groin. Another skin fold crossing the chest between axillae. Eyes small, slightly prominent. Snout pointed in dorsal view and protruding in lateral view. Nostrils directed anterolaterally, slightly protuberant. Choanae relatively small and round. A well developed groove in the terminal part of the lower jaw. Internarial distance small. Canthus rostralis distinct, rounded. Loreal region slightly convex. Interorbital space slightly convex. Lips nearly horizontal when belly is touching the ground. Presence of postcommisural glands behind the corner of mouth. Tympanum concealed. Supratympanic fold absent. Upper jaw projects 1.59 mm beyond the lower jaw. Subgular vocal sac not expanded externally. Vocal slits present. Vomerine odontophores absent. Tongue large, oval. Arms and fingers robust and short. Legs extremely robust; almost equal lengths of thigh, tibia, and foot. Finger lengths I<II<IV<III. Toe lengths I<II<V<III<IV. Fingers and toes without webbing, fringes, or ridges. Finger and toe tips rounded, not flattened or expanded in discs; terminal grooves absent. Supernumerary tubercles absent in hands and feet. Large oval inner metatarsal tubercle. Outer metatarsal tubercle absent. Presence of a large oval thenar tubercle and a longitudinally divided palmar tubercle in hand. Nuptial asperities on males' thumb absent. Color in life of individuals apart from the type series ( Figure 3 C, D). – Dorsum and limbs are dark brownish gray with small white dots. The single, subgular vocal sac is darker than the venter. The chest is yellow with gray marks. Belly white or yellow, with gray marks and reticulations, which reach the flanks. Orange femoral stripe present on the posterior surface of the thigh. Orange inguinal spots present. There is a tiny white vertebral line from the snout to the vent. Color in preservative of individuals other than the type series (70% ethanol). – Dorsum and limbs are dark grayish blue. Ventral region is gray with white spots. These spots reach up to the lateral portion of the animals. The throat is darker than chest and belly. The inguinal spots and femoral stripes on the posterior surface of the thigh are white. Vertebral line undistinguished. Variation. Females are larger than males (see Table 1 ). Females present variation in size, with the SVL varying from 19.4 up to 42.7 mm ( Thomé & Brasileiro, 2007 ). The vertebral stripe may be absent. The ventral spots may not reach the flanks and the groin region of some individuals. The throat of males is darker than that of females. E. cesarii E. piauiensis Dominant frequency (kHz) 3.52 ± 0.08 (3.60 – 3.45; n = 8) 4.53 ± 0.06 (4.48 – 4.65; n = 18) Minimum frequency (kHz) 3.13 ± 0.09 (3.01 – 3.23; n = 8) 3.41 ± 0.25 (3.18 – 3.76; n = 18) Maximum frequency (kHz) 4.03 ± 0.11 (3.90 – 4.17; n = 8) 5.00 ± 0.09 (4.86 – 5.10; n = 18) Call duration (s) 1.93 ± 0.46 (1.49 – 2.66; n = 8) 2.24 ± 0.00 (2.01 – 2.51; n = 18) Pulse durantion (ms) 4.23 ± 0.16 (3.82 – 4.60; n = 50) 3,0 0 ± 0.23 (2.89 – 3.55; n = 50) Air temperature 23.1 °C 22 – 27 °C Call descriptions. Advertisement calls of E. cesarii were recorded in Itapé, municipality of Rio Claro, São Paulo state, Brazil , on 29 January 2002 , at air temperature of 23.1 ºC ( Figure 4 ). The call consists of a loud, high pitched, sustained whistle, ranging from 1.49 to 2.66 s of duration, with a mean dominant frequency of 3,515 Hz, with a mean pulse rate of 238.2 per second, and 460.2 pulses per note in average. The frequency ranged from 3.01 to 4.17 kHz. The duration of the pulses did not vary much (mean of 4.23 ± 0.16 ms; n = 50). Further spectral characteristics are presented in Table 2 (see also Figure 4 ). Advertisement calls of E. piauiensis were recorded in the municipalities of Pacatuba on 13 March 2007 (air temperature 22 ºC), Caucaia on 15 May 2005 (air temperature 27 ºC), and Viçosa do Ceará on 24 April 2007 (air temperature 25 ºC), all of them in the state of Ceará, Northeastern Brazil . The call structure of E. piauiensis is very similar to that of E. cesarii and consist of a loud, high pitched, sustained whistle (ranging from 2.45 to 2.51 s of duration). The duration of the pulses did not vary much (3.00 ± 0.23 ms; n = 50). However, the mean dominant frequency is higher in E . piauiensis (4.53 ± 0.06 Hz) compared to the new species and the frequency ranged from 3.18 to 5.10 kHz ( Table 2 ; Figure 4 ). Tadpoles. Tadpoles are unknown; however, 10 tadpoles collected in the municipality of Vitória Brasil , state of São Paulo, Brazil , and briefly described under the name Elachistocleis sp. by Rossa-Feres and Nomura (2006) , could be E. cesarii . Natural history notes . Elachistocleis cesarii calls during the wet and hot season of the year (summer) as a prolonged breeder; however, after heavy rains during the hot nights it may behave like an explosive breeder ( sensu Wells 1977 ). Males call with the legs in the water and the body out of water, holding the emergent vegetation with the forelimbs. The amplexus is axillar. We collected two amplected pairs that laid eggs in plastic bags. One female deposited 736 eggs and the second deposited 1126 eggs. In nature, the eggs are laid in the water surface as a gelatinous mass attached to floating or emergent vegetation ( Figure 3 F). Newly metamorphosed specimens have a mean SVL of 11.83 mm ± 0.38 (11.4 – 12.3; N = 6). The ecology of this species has been studied by Thomé and Brasileiro (2007) and a short communication about the defensive posture was published by Toledo (2004) , in both articles under the name Elachistocleis cf. ovalis . Geographical distribution. Besides the localities of the type series, the species is known in the municipalities of Rio Claro, Campinas, Itirapina, São Paulo, Angatuba, and Ubatuba, all in the state of São Paulo. In the state of Minas Gerais it can be found in the municipalities of Jaboticatubas, Santana do Riacho, Munhoz, and Viçosa. In the state of Goiás it can be found in Pontalina ( Figure 5 ).