If you’ve ever spotted a frog chilling at the bottom of a pond or lake, you may have wondered – are there frogs that live underwater? The answer is yes! Fully aquatic frogs, also called true aquatic frogs, are fascinating amphibians that have evolved amazing adaptations to survive their whole lives submerged in water without ever coming onto land.
These incredible frogs can live and breed entirely underwater thanks to key physiological and behavioral adaptations that allow them to breathe, feed, move, and reproduce in their aquatic environment.
If you want to learn all about these talented amphibians that challenging the notion that frogs must live both on land and in water, read on!
What Makes a Frog Fully Aquatic?
Permanent gills for underwater breathing
Fully aquatic frogs have evolved permanent gill structures that allow them to breathe underwater, unlike other amphibians that lose their gills after metamorphosis. These specialized gills are called internal gills and are covered by a protective flap of skin.
The internal gills extract oxygen from the water as it passes over them, enabling the frogs to stay submerged indefinitely (X. laevis).
Flattened bodies and webbed digits for swimming
Fully aquatic frogs have streamlined, flattened bodies that reduce drag and allow them to swim efficiently underwater. Their hind limbs are also elongated and powerful, with extensively webbed digits that provide propulsion through the water.
These adaptations make them agile swimmers capable of bursts of speed to capture prey or escape predators.
Specialized feeding behaviors and diet
These aquatic frogs have peculiar feeding strategies to survive in their watery habitat. Many have fast, sticky tongues that dart out to capture passing prey. Some also exhibit “gulping” behavior, rapidly sucking water into their mouths to ingest food and oxygen simultaneously.
Their diets generally consist of small aquatic animals like crustaceans, insect larvae, worms, and even fish.
| Frog Species | Diet |
|---|---|
| African clawed frog | Insects, crustaceans, small fish |
| Crab-eating frog | Crabs, shrimp, small vertebrates |
Fully Aquatic Frog Species Around the World
African clawed frogs
The African clawed frog (Xenopus laevis) is one of the most well-known fully aquatic species of frog. Native to sub-Saharan Africa, these frogs spend their entire lives underwater, only surfacing briefly to breathe.
Some key features that make them suited to aquatic life include webbed feet, lateral line sensory organs, and the ability to absorb oxygen through their skin.
African clawed frogs have become popular laboratory animals and are commonly used in pregnancy tests due to their rapid egg production. They have also been introduced widely outside of their native range through the pet trade and have become invasive in some areas, outcompeting native frog species.
Crab-eating frogs of Asia
Crab-eating frogs, also known as rice frogs or rice field frogs (Fejervarya species), are native to Asia where they inhabit slow-moving freshwater sources. As their name suggests, these fully aquatic frogs prey heavily on crabs, often ambushing them from underwater and drowning their victims.
They have several adaptations suited for aquatic life, including durable toe pads for anchoring in muddy substrates and skin flaps across their back that aid in camouflage.
The destruction of rice fields and wetland habitats in Asia has had detrimental effects on crab-eating frog populations. Several species are classified as threatened or endangered due to habitat loss, collection for food, and pollution.
Conservation efforts focused on preserving remaining wetlands are crucial for securing the future of these special frogs.
Pipid frogs of Central and South America
Pipids make up an entire family (Pipidae) of fully aquatic frogs native to Central and South America. Most notably, this family contains the African dwarf frogs and Surinam toads.
These frogs have several extreme adaptations for living underwater including:
- Flattened bodies and wide heads
- Long, muscular hind legs for swimming
- Extensive webbing on feet for paddling
- Skin flaps across the head and back to increase surface area for cutaneous gas exchange
Many pipids are popular in the pet trade; however, some species such as the aquatic African dwarf frog suffer from overcollection in the wild. Public education campaigns on responsible pet ownership help ensure healthy captured populations.
Breeding Behaviors and Life Cycle
Aquatic egg laying and development
Fully aquatic frogs have adapted unique breeding behaviors and life cycles to succeed in their watery environments. Unlike most amphibians that lay eggs in ponds and streams, some aquatic frog species actually give birth to live tadpoles underwater!
The female retains the fertilized eggs inside her body until they hatch, then releases the tadpoles directly into the water. This protects the vulnerable developing eggs and embryos from drying out or getting eaten by predators.
Other aquatic frogs lay jelly-like egg masses that attach to underwater plants and rocks. These jelly coats help protect and camouflage the eggs. The eggs then develop entirely underwater, often hatching into tadpoles within a week. How cool is that?
Parental care of eggs and young
Many aquatic frog species exhibit fascinating parental care behaviors to increase their offspring’s chances of survival. Male pipa frogs have pouches on their backs where the female deposits fertilized eggs! The male then carries the eggs until they hatch.
Some poison dart frogs transport newly hatched tadpoles to isolated pools of water held in tree hollows or leaves. They even come back periodically to feed the tadpoles unfertilized eggs! Talk about devoted parenting. Other aquatic frog dads guard the egg clutches from predators until they hatch.
While parental care isn’t universal in aquatic frogs, species that do exhibit it certainly give their young a leg up. Or should I say a leg out, into the water!
Metamorphosis and development
The development and metamorphosis of aquatic frogs is timed perfectly to transition them from water to land. Aquatic tadpoles have gills, fins, and scaleless skin for life underwater. But within weeks to months, they undergo an incredible metamorphosis into the familiar four-legged, air-breathing adult frogs we know and love.
The timing varies between species – some take only 54 days to transform while tropical bullfrogs take up to 2 years! Their bodies transform to lose the gills, fins, and tails while developing lungs, legs, and smooth moist skin. Truly an amazing transition between two very different environments.
Some super freaky aquatic frogs are even neotenic, meaning they become sexually mature while still in their larval tadpole form! So they never transform into terrestrial adults at all! Clearly, aquatic frogs have mastered specialized breeding and development to thrive in their unique underwater homes.
Threats and Conservation Challenges
Habitat loss and degradation
Fully aquatic frogs rely on healthy freshwater ecosystems to survive, but unfortunately over 50% of the world’s wetlands have been lost over the last century. Draining wetlands for agriculture, development, and other human uses has substantially reduced and fragmented the habitat these unique amphibians depend on.
Aquatic frogs are also threatened when people divert water from rivers and streams or extract too much groundwater, resulting in habitat loss from desiccation. Pollution from agricultural and urban runoff can degrade remaining frog habitats by introducing excess nutrients, chemicals, and sediments.
Pollution and toxic contaminants
As largely aquatic species, fully aquatic frogs are especially vulnerable to water pollution. Their permeable skin readily absorbs toxic substances and endocrine disruptors from polluted habitat.
Studies have found deformities and reduced survival rates among frog populations exposed to pesticides, fertilizers, pharmaceuticals, and industrial chemicals. Acid rain also threatens certain aquatic frog species by lowering the pH of their habitat.
| Percentage of studied frog species impacted by deformities or mortality | 60% |
| Minimum pH level tolerated by most aquatic frog species | 4.5 |
Invasive species and disease
Invasive plants, fish, and other introduced species often outcompete native frog populations by altering food webs and habitat. For example, studies show the invasive bullfrog outcompetes and preys on certain aquatic frog species in the western U.S.
Disease also poses a major threat, especially the lethal chytrid fungal infection which has devastated frog populations globally. Climate change may exacerbate disease spread by enabling pathogens to invade new areas.
Protecting remaining habitats from degradation and carefully managing invasive species and disease outbreaks present significant challenges for conserving these unique frogs.
Conclusion
Fully aquatic frogs have fascinated biologists for decades thanks to their incredible morphological, physiological, and behavioral adaptations that allow them to bypass a terrestrial stage and live permanently underwater.
Understanding these aquatic amphibians provides key insights into evolution and sheds light on vertebrate transitions into aquatic life.
While they may look like normal frogs, their specialized adaptations show nature’s ingenuity in equipping certain frog species to inhabit aquatic ecosystems globally. Sadly, many fully aquatic frog species now face grave threats from human activity.
Conservation of their freshwater habitats is crucial for ensuring their survival and maintaining nature’s diversity.
