Description
Rhinella casconi has a robust body and, from the dorsal view, a distinct head and body. The snout-vent length ranged from 66.3 - 87.9 mm for males and was 85.7 mm for the lone female collected. The head is wider than it is long (width ranging from 24.0 - 30.4 mm and length merely 21.1 - 26.6 mm). The snout is rounded in both dorsal and lateral views. This species has a row of tubercles around the corners of the mouth as well as preorbital, postorbital, supraorbital, parietal, and canthal crests. The canthal ridge is well defined and they possess a pre-ocular ridge. Rhinella casconi have a vocal sac that is externally visible with no pigmentation. All members of this species have a highly visible oval tympanum that is 1.4 - 3.0 mm away from the eye and is 3.3 - 4.4 mm in width and 4.3 - 5.9 mm height. They lack a pretympanic crest, but a supratympanic crest is present. The parotoid is elliptical like it is in all within the R. crucifer group, but in R. casconi the gland hangs over the edges of the body. The anterior distance between the parotoid glands range from 14.2 - 20.0 mm while the posterior distance varies from 21.9 - 30.1 mm. Rhinella casconi has a row of lateral tubercles with the first one fused to the parotoid gland. The dorsal side of this species has a rough texture with many round warts that feature keratinized spines. These warts continue onto the limbs. The forelimbs are long and robust with the forearms being larger than the upper arm. The slender, unwebbed, and mildly fringed fingers have relative lengths of 4 < 2 < 1 < 3. The fingertips expand slightly. The inner metacarpbal tubercle is taller than wide and elliptical while the external metacarpal tubercle is smooth and round. Single round subarticular tubercles are irregularly distributed on the ventral side of the hands and fingers. On fingers 3 and 4 there are divided distal tubercles. Pigmented nuptial pads can be found on the dorsal and lateral sides of fingers 1 and 2. The hindlimbs are robust with the tibia being longer than the thigh. The thigh, tibia, and tarsals range from 29.3 - 35.3 mm, 29.9 - 37.2 mm, and 15.0 - 19.9 mm, respectively. The long toes have relative lengths of 1 < 2 < 5 < 3 < 4 and a webbing formula of I²-2II1-3III2-4IV-2V. There is a protruding, elliptical metatarsal tubercle and an elongated external metatarsal tubercle. Rhinella casconi have an obvious fringe on the ventral surface of the tarsus that extends from the inner metatarsal tubercle and terminates just before tibia-heel articulation (Roberto et al. 2014).

Tadpoles of R. casconi are oval bodied with an oval snout and appear elliptical from the side and compressed from the front. The dorsolaterally positioned eyes are small while the kidney-shaped nostrils are relatively larger and can be seen from both the dorsal and lateral view. The nostrils are located near the snout and have slightly projecting rims. The oral disc is ventral, spanning over a third the width of the body, and has lateral notches. The tooth row formula is 2(2)/3. The lower jaw sheath is V-shaped and the upper jaw sheath is arched. Both have triangular serrations. The marginal papillae have rounded tips and form a simple row while the sub-marginal papillae are clumped. The short spiracle is located on the left side of the last third of the body. Except for the tube opening, the inner wall of the spiracle is fused to the body. The vent is located in the middle of the body and connected to the ventral fin by both walls. The dorsal fin begins at the tail musculature ,increases gradually and ends just after the termination of the rounded tail musculature (Roberto et al. 2014).

Rhinella casconi differs from R. ornate, R. henseli, and R. abei due to its overhanging parotoid glands and the fringe on the ventral surface of the tarsus. Rhinella abei, R. ornata, and R. crucifer vary from R. casconi because the latter has yellow markings on their thighs, flanks, and cloaca. Rhinella abei and R. henseli differ in that their heads are not wider than they are long, like the heads in R. casconi. Rhinella ornate, R. henseli, R. inopina, and R. crucifer all lack well developed vocal sacs, making them different from the R. casconi (Roberto et al. 2014).

Tadpoles have a kidney-shaped nostril which differentiates them from other species (Roberto et al. 2014).

In live adult specimens, the general body color is brown. There is a light grey vertebral line and dark brown lateral bands that extend from behind the eyes to the mid-region of the body. The spines on the warts of the dorsum are black. The ventral side is a pale cream color with no visible speckling. There are yellow markings on the posterior surface of the thighs, flanks, and around the cloaca. The irises are gold. In preservative, the body becomes grayish light olive. The vertebral line becomes light grey. Lines on the upper arm and tibia are darker grey. The ventral region is cream olive with pale marks near the cloaca and posterior regions of the thighs. The sides of the animal between the arms and the groin are yellow (Roberto et al. 2014).

Live tadpoles have dark brown bodies that become transparent near the eyes and snout and on the vent and fins. Some individuals have dark, almost black papillae. The tail musculature is dark brown and has an uncolored stripe on the lower part of the ventral tail musculature that does not reach the tip. When preserved, the colors fade slightly (Roberto et al. 2014).

Juveniles typically present a more prominent vertebral line with less granular tubercles on their backs. Females usually have less developed warts and a lighter colored vertebral line (Roberto et al. 2014).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

Rhinella casconi reside only in the forested sections of the Serra de Baturité mountain range at elevations of about 700 meters (Roberto et al. 2014).

Life History, Abundance, Activity, and Special Behaviors
Rhinella casconi are explosive breeders that mate at the start of the area’s first heavy rains. Males utilize various microhabitats at the edges and inside both temporary and permanent ponds for advertisement calls. Each call lasts an average of 2.9 seconds with intervals of around 8.6 seconds. Each call consists of 61 - 67 notes, with each note only lasting around 0.2 seconds. The mean frequency of these calls is 911.6 Hz species. Males have been observed in amplexus with R. jimi and Leptodactylus vastus (Roberto et al. 2014).

Adults disappear before the end of the rainy season and are not seen again until the next rainy season. Juveniles can be found in forests and at forest edges, suggesting that the species is a forest dweller rather than living in open environments (Roberto et al. 2014).

Up to 34 prey items were found in the stomachs of R. casconi specimens and composed mostly of ants (70%) and beetles (11%). Other arthorpods also found in the stomachs included species from the orders Diptera, Orthoptera, Hemiptera, Isoptera, Aranea, and Acari (Roberto et al. 2014).

Trends and Threats
The species authorities of Rhinella casconi recommend the species be listed as "Vulnerable B1 ab (iii, iv)" because of its small range size and fragmented habitat. Like many other species in the Serra de Baturité mountain range, it is threatened by habitat loss due to deforestation for human settlements and banana plantations (Roberto et al. 2014).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Urbanization
Habitat fragmentation

Comments
The species authority is: Roberto IJ, Brito L, Thome MTC (2014). A new species of Rhinella (Anura: Bufonidae) from northeastern Brazil. South American Journal of Herpetology 9:190-199.

Based on mtDNA sequences (386 base pairs of the control region, 401 base pairs of ND1, and 398 base pairs of ND2) and allele frequency-based assignment analysis of the nuclear genes (crystalline, rhodopsin, and alpha polypeptide), R. casconi was identified as a (then unnamed) unique lineage within the greater R. crucifer group (Thome et al. 2012). Roberto et al. (2014) further described the morphology and natural history of the species as well as named it. Rhinella casconi is sister to the clade forming R. crucifer, R. inopina, R. ornate, and R. albei. Rhinella henseli is sister to the clade including R. casconi (Thome et al. 2012).

This species was named after Professor Dr. Paulo Cascon because of his contributions to amphibian research in Ceará (Roberto et al. 2014).

This species has many morphological and ecological similarities with other species in the group including advertisement call, tadpole morphology, diet, and breeding behavior. Calls are similar enough that R. casconi cannot be identified by call alone (Roberto et al. 2014).

References

Roberto, I.J., Brito, L., Thome, M.T.C. (2014). ''A new species of Rhinella (Anura: Bufonidae) from northeastern Brazil.'' South American Journal of Herpetology, 9, 190-199.

Thomé, M.T.C., Zamudio, K.R., Haddad, C.F.B., Alexandrino, J. (2012). ''Delimiting genetic units in neotropical toads under incomplete lineage sorting and hybridization.'' Bio Med Central Evolutionary Biology , 12, 1–13.

Species Account Citation: AmphibiaWeb 2016 Rhinella casconi <https://amphibiaweb.org/species/8294> University of California, Berkeley, CA, USA. Accessed Apr 17, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 17 Apr 2024.

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