Pipidae

Pipidae is a family of highly aquatic frogs known as tongueless frogs due to the loss of their tongue and many other aquatic specializations. Members have dorso-ventrally flattened bodies, broad webbed hind feet with paddle-like digits, and smooth skin adapted to life in water. They are obligate aquatic breeders and rely on water for most of their life cycle, with many species exhibiting extensive parental care or distinctive reproductive habits.

Taxonomy and genera within Pipidae include Pipa (South America), Hymenochirus (small African frogs), Xenopus (African clawed frogs), and Silurana (a genus separated from Xenopus in some classifications). The taxonomy of Xenopus and Silurana has been revised over time, with molecular studies prompting periodic reorganization. The family comprises a substantial number of species, many of which are prominent in research or kept as aquarium animals.

Habitat and distribution are tropical and subtropical, with Pipa species native to neotropical wetlands of South America, while Xenopus, Hymenochirus, and Silurana occur across sub-Saharan Africa. Their habitats range from slow-moving rivers and swamps to ponds with vegetation. All members are adapted to an aquatic lifestyle, often with eyes and nostrils positioned to detect prey at the water’s surface.

Reproduction and development patterns vary among genera. Most Pipidae reproduce through external fertilization in water, with eggs laid in aquatic habitats. The Surinam toad (Pipa pipa) is notable for its extreme parental care, as eggs are embedded in skin on the female’s back and the young emerge as froglets. Xenopus species are widely used as model organisms in developmental biology, and Silurana tropicalis is another important research species. Some Pipidae species are kept in aquaria and have established introduced populations outside their native ranges.

Conservation concerns vary by species, but habitat loss and water quality threats affect several Pipidae. The family has a deep evolutionary history, with fossils indicating an ancient lineage dating back to the Cretaceous.