Physalaemus nattereri (common name: Cuyaba dwarf frog) is a frog native to central and southeastern Brazil and eastern Bolivia and Paraguay. It inhabits savanna and Cerrado regions, always near permanent or temporary water bodies such as ponds and swamps, where it typically nests. The species is not adapted to areas with human activity. Males have an average length of 4.7 centimeters (1.9 in), while females measure 4.9 centimeters (1.9 in). The dorsal coloration ranges from light brown to dark brown or reddish, featuring a mosaic of darker spots or stripes. The ventral surface is light brown with dark spots. The species is unmistakable in its habitat due to a pair of ocelli on the posterior part of its body. Its testicles and other organs are brightly colored, a rare trait among anurans, caused by a high concentration of melanocytes. Its diet is generalist and opportunistic, primarily consisting of termites and ants. Despite an effective defense strategy and highly potent toxins, it can be preyed upon by various animals, including birds and beetles. Its primary predators are giant water bugs, which often attack during reproduction and metamorphosis. One defense mechanism is deimatic behaviour, where the frog inflates its lungs, lowers its head, and raises its posterior, displaying its ocelli to startle predators, appearing as a larger animal facing them. Additionally, its ocelli contain venomous macro glands that produce a fast-acting toxin with a median lethal dose comparable to that of a jararaca snake. Its reproduction is explosive, meaning all individuals gather synchronously at breeding sites for a few days, typically between October and January. Males form choruses and vocalize after heavy rainfall exceeding 50 millimeters to attract females. Their call consists of simple, multi-pulsed, harmonic notes. During amplexus, which is axillary, the pair moves to the water's edge, where they deposit approximately 3 500 eggs in a foam nest. The nest is created from mucus secreted by the female, whipped into foam by the male's hind legs in a motion akin to whisking egg whites. The tadpoles have a grayish-brown dorsum and a globular body. Their metamorphosis takes 20 to 30 days.
Taxonomy The species was described in 1863 by Austrian researcher Franz Steindachner in a publication of the Austrian Academy of Sciences that same year. It was identified as a new species based on its smooth skin; absence of vomerine teeth, parotoid glands, or hypertrophied forearm tubercles (a protrusion on the front of the forearm); lack of a visible tympanum; and the formation of foam nests for its eggs. At the time, the species was known only from Cuiabá, Mato Grosso. It was originally named Eupemphix nattereri, but the genus Eupemphix was later merged into Physalaemus following studies by Hampton Parker in 1927 and John Lynch in 1970. The species received the epithet nattereri in honor of Johann Natterer. In Brazil, it is commonly known as the four-eyed frog due to the pair of ocelli on its back, resembling an additional pair of eyes.
Distribution and conservation Physalaemus nattereri is found in the Central-West, Southeast, and Northeast regions of Brazil, as well as eastern Paraguay and Bolivia, in areas with altitudes ranging from sea level to 1,500 meters (4,900 ft). It is fossorial and seasonal, highly adapted to the continental semi-arid climate. The species inhabits savanna and low-vegetation areas of the Cerrado, typically near permanent or temporary water bodies such as ponds and swamps, where it nests. It is not adapted to areas degraded by human activity. The International Union for Conservation of Nature (IUCN) classifies it as a least concern species, due to its common occurrence. However, its population is declining and threatened by the expansion of intensive agriculture in its range. Some portions of its distribution area are encompassed by environmental parks, which reduces the risk to the species. Including this species, the genus Physalaemus comprises a total of 47 species.
Description The frog's dorsum varies from light brown to dark brown or reddish, with a mosaic of darker spots and stripes. A distinctive feature is the presence of two large black ocelli over glands in the inguinal region. The inner thigh is white with black, vermiform spots. Its abdomen is light brown with darker spots of the same hue. Males average 4.7 centimeters (1.9 in) in length, while females average 4.9 centimeters (1.9 in). It has a robust trunk, ranging from 29.8 to 50.6 millimeters (1.17 to 1.99 in) in width. Its head is wider than its body. The diameter of the eye equals the distance between the two orbits. It has large inguinal glands but lacks sacral glands. Its snout and canthus are rounded, and the loreal region is concave. The vocal sac is well-developed, and the snout is rounded. The species lacks parotoid glands. A rare characteristic of the species is that males have brightly colored testicles, often with spots of other colors, a trait known in only five other amphibian species, such as Physalaemus cuvieri. This pigmentation also occurs in other organs, including the kidneys, peritoneum, and spleen. It results from a high concentration of melanocytes, possibly due to an interaction between these cells and the vascular system of these tissues. The species can be easily distinguished from other anurans in the same region due to its unique and readily observable traits, such as the pair of ocelli on its dorsum, a feature shared only with Physalaemus deimaticus. However, P. deimaticus is smaller, has a different dorsal mosaic, and is found only in the Serra do Cipó, Minas Gerais.
Dietary habits
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