Gastrophryne carolinensis

Species of amphibian

Gastrophryne carolinensis, the eastern narrow mouthed toad, is a species of microhylid frog. It is a relatively small, toad like amphibian found in damp, shady habitats. The species is highly fossorial, and feeds primarily on ants. These North American microhylids (Family: Microhylidae) are distinguished from true toads (genus Bufo), and other anurans by their moist, smooth skin, their lack of eardrums or tympana, their distinguishable squat body shape, and the unique fold of skin superior to their eyes. It is found in the United States, from southern Maryland to the Florida Keys, west to Missouri and Texas. While not a true toad, it is so called because it is terrestrial.

Gastrophryne carolinensis belongs to one of the largest anuran families, the microhylids. No subspecies are currently recognized. The eastern narrowmouth toad is one of only three microhylids that currently live in the United States.

The eastern narrow mouthed toad is relatively small, growing to a maximum length of It has an oval shaped body and a narrow head with a pointed snout. On the back of their head, they have a fold of skin that is capable of covering their eyes. They vary in color from brown and grey to green, often with black and white spotting. Usually there will be a dark brown stripe seen on both sides of the body. Gastrophryne carolinensis toads have a typical teardrop shaped body that is characteristic of members of the family Microhylidae. Though its morphology lacks a tympanum (eardrum), the subgular vocal sac is clearly visible. The skin of G. carolinensis is smooth and without ridges or warts. Yet, the skin is extremely tough, which most likely protects them from the ants upon which they feed. Directly behind the eyes, resting on the toad's neck, is a distinctive skin fold evolved for protection from ant bites while feeding. The color of the toad can change depending on its activities and environment. Its legs are generally stubby, short, and heavy, and the tips of the toes are round and tapered. As with the Leptodactylidae, the toes are absent of webbing or toe pads. The sex of the eastern narrow mouthed toad can easily be determined by the characteristic sexual dimorphism. The color of the throat region for males is dark and highly pigmented, while the female's throat is lighter.

Tadpoles transform in about 23–67 days, and unlike other anurans, they filter feed on plankton. They lack beak like mandibles and the specialized labial tooth generally associated with most tadpoles. The newly transformed toads range from 7–12 mm (0.3 0.5 in) in body length. They are found to share the same habitat as adults, and the older stages of the tadpoles are also toxic to many predators. The males reach sexual maturity in a year, while the females reach sexual maturity in at 1–2 years of age. A study in 2013 identified 4,859 individual ants retrieved from stomachs of 146 eastern narrow mouthed toads in Florida scrub. These toads also feed on termites, small beetles, and other various arthropods.

The eastern narrowmouth toad is preyed upon by a variety of organisms. Their first reaction is to burrow out of sight or find a hiding area nearby. However, Gastrophryne carolinensis has been observed using irritating and noxious integumentary secretions as a defense mechanism to discourage predators when caught. In a study on the unpalatability of their skin, eastern narrowmouth toads were refused by predator species significantly more often than the study's control frog species. while as adults, their predator list is reported to include the copperhead (Agkistrodon contortrix) and the common garter snakes (Thamnophis sirtalis). Other known predators include the glossy watersnakes (Liodytes rigida), the eastern cottonmouth (Agkistrodon piscivorus), and the cattle egret (Bubulcus ibis). This particular toad species avoids predators by burrowing, seeking cover, and/or nocturnal activity patterns. Chemically, they are also capable of producing mucus that produces a violent burning sensation and irritates membranes. The toxins secreted from their skin deter predators, but they also plays a role in inhibiting ant attacks when individuals forage near ant mounds. These toads are accomplished burrowers, and are seldom seen on the surface. Though they may be present in large numbers, their existence is hardly suspected.