tadpole

A tadpole is the aquatic larval stage of most frogs and toads (order Anura). Tadpoles hatch from eggs laid in water, often in clusters or strings surrounded by a gelatinous envelope. They are typically elongated with a prominent tail, lack fully developed legs, and breathe mainly through external gills and skin while living in freshwater environments such as ponds, lakes, and marshes.

During development, tadpoles undergo metamorphosis to become juvenile frogs or toads. This process is primarily driven by thyroid hormones and is influenced by temperature, day length, food availability, and population density. Metamorphosis usually begins with the appearance of hind legs, followed by forelimbs, changes to the mouth and jaw apparatus, and the resorption of the tail. The digestive system also changes to accommodate a carnivorous or omnivorous diet typical of adult frogs.

Anatomy and ecology of tadpoles reflect their herbivorous or detritivorous tendencies in many species. They commonly feed on algae, plankton, and plant material, using specialized mouthparts and a simple digestive tract. Tadpoles respire primarily through gills and skin, with some transition to more lung-based respiration as metamorphosis progresses. They are prey for fish, invertebrates, and birds, making pond quality and predation pressures important factors in their survival.

The duration of the tadpole stage varies by species and environmental conditions, ranging from several weeks to several months. Habitat loss, pollution, and invasive species threaten many amphibians by reducing suitable aquatic environments for tadpoles.