Rhinella icterica (Spix, 1824)

Body Shape

Rhinella icterica are relatively large, stout-bodied toads.

Size

Males have a snout–vent length of 100–166 mm (3.9–6.5 in), while females have a snout–vent length of 135–190 mm (5.3–7.5 in).

Gland and Crest Features

This species has prominent parotoid glands and strong cephalic crests.

Dorsal Coloration

The dorsum is yellowish in females and juveniles, with a light midline stripe and a consistent pattern of black blotches; males are often bright greenish yellow, with only a few black blotches.

Ventral Coloration

The belly is white and marbled with brown.

Skin Texture

Blunt, thorny warts are scattered across the skin, and this trait is especially noticeable in males.

Prey Species

Rhinella icterica is the most common toad species in southeastern Brazil, and preys on the yellow scorpion Tityus serrulatus.

Scorpion Consumption Tolerance

It has been observed eating scorpions without experiencing any adverse effects.

Toxic Secretion Neuromuscular Effect

This tolerance may be connected to Rhinella icterica toxic secretion (RITS), which acts as an irreversible, concentration-independent neuromuscular blockade.

RITS Interaction with Acetylcholinesterase

Acetylcholinesterase enzyme inhibits the activity of RITS.

RITS Cardiac Pump Inhibition

RITS also acts as an inhibitor of the cardiac Na+, K+-ATPase pump.

RITS Bioactive Effects Summary

Researchers have concluded that this toad's toxic secretion inhibits calcium pumps in the heart (which causes twitching), AChE, and the Na+, K+-ATPase pump.

Predator Defense Overview

This toad species has a documented defense mechanism against predators.

Amphibian Cutaneous Gland Functions

Cutaneous glands scattered across the bodies of amphibians support respiration, water balance, and chemical defense.

Cutaneous Gland Types

There are two types of these glands: mucous glands and poisonous glands.

Parotoid Macrogland Location

The poisonous granular glands that support defense form glandular structures called parotoid macroglands, located one on each side of the body in the dorsal region behind the eyes.

Threat Response Posture

When threatened, the toad inflates its lungs and points one of the glands toward the attacker, positioning the gland to respond to pressure.

Poison Release Trigger

When the region is pressed, poison is released quickly.

Poison Delivery to Predators

If a predator bites the toad, poison is ejected directly into the predator's oral mucosa, poisoning the predator.

Geographic Range

Rhinella icterica is found in the Atlantic Forest, covering southeastern and southern Brazil, eastern Paraguay, and the Misiones and Corrientes provinces of Argentina.

Breeding Season Aggregation

During the breeding season, this species gathers in large groups primarily in streams or ponds.

Larval Diet

It feeds on detritus and submerged plants.

Habitat Range

This common toad occurs across a wide range of habitats, from forests to open habitats such as Cerrado savanna, and it also lives in disturbed habitats.

Breeding Period and Sites

Breeding occurs from August to January in both permanent and temporary ponds and streams.

Conservation Status

It is an adaptable species present in many protected areas, and is not considered threatened.

Historical Distribution in Brazil

Historically, these toads were restricted to forested, less urbanized areas of Brazil.

Breeding Habitat Threats

More recently, deforestation and new road construction have reduced toads' access to the water required for breeding.

Population Decline Impacts

As a result, Rhinella icterica populations have gradually declined, which has led to an increase in the number of scorpions in affected areas.