Pseudis

Pseudis or the swimming frogs are a genus of frogs that live in South America. They are in the family Hylidae. They are important because they have the largest tadpoles of any frog in the world. The adult frogs are not much bigger than other frogs, but the tadpoles are giant. Human beings hear these frogs more than they see them.  This is because the frogs sing loud but blend into the water and plants so they are hard to see. The frogs live in lakes, ponds, marshes, and other bodies of waters that have many plants in them.  These frogs sit near the top of the water, hiding in the plants or on floating plants. This frog will dive into the water if they see something that looks dangerous to them.

Distribution
Pseudis frogs live in tropical and subtropical South America.  Almost all of them live east of the Andes, on the Atlantic side of South America. P. paradoxa is the only species in Pseudis that has any frogs living west of the Andes. These frogs live from Trinidad to northern Argentina but not in Ecuador or Chile. They live in hills and other highland regions, and they live in the southernmost part of South America. All species in this genus are found in Brazil.

Description

These frogs have several body parts that help them live in the water.  They have eyes that stick up and out, strong hind legs, and fully webbed feet. Scientists say they are still "true" tree frogs, so they are in the family Hylidae.

Breeding and feeding
Frogs in Pseudis find mates and lay eggs the same way most frogs do. However, their tadpoles are different.  The tadpoles start live normal, but they continue growing until they are very, very large, sometimes as large as  in length in P. paradoxa and P. platensis. They are the longest tadpoles in the world.  They are also very large compared to the adult frogs, which are  from nose to rear end. Scientists have not seen enough tadpoles from other species to say for sure, they have seen enough to know they are also very large. Their adult frogs are also somewhat smaller with nose-to-rear-end lengths of . However, P. cardosoi and P. minuta (which could be in the proposed genus Podonectes, see Phylogenetic relationships) have more normal tadpoles that probably do not grow longer than  . This is still large compared to the adults of these two species.  This means that the animal is the largest it will ever be in its life when it is an older tadpole.  It is smaller when it becomes a frog. In most of these frogs, tadpoles from different places can be different sizes. Tadpoles that grow in large, temporary bodies of waters with plenty of food and few animals that want to eat them grow larger than those in smaller bodies of water with less food, or year-round bodies of waters that may have fish or other animals that eat tadpoles in them. The very largest tadpoles usually have well-developed organs, including reproductive organs that are almost ready to be used. This means that the frogs are ready to mate very soon after becoming frogs.  This is different from most genuses of frogs: In most species, the tadpoles become small frogs and then grow larger before they can mate and lay eggs.

Pseudis is closely related to the genus, Lysapsus.  The frogs in Lysapsus do not have giant tadpoles. In Lysapsus, adults frogs grow to .

Pseudis tadpoles eat algae, many different kinds of algae.  They can also eat 
small animals without bones, for example insects. The adult frogs eat land-based insects and spiders, but they also eat other animals without bones and smaller frog.  Some frogs in Pseudis can eat plants.

Species

There are seven species in this genus if we think of Lysapsus as a different genus. Until the late 1990s and early 2000s, most scientists said only P. minuta and P. paradoxa counted as frogs in Pseudis.  Scientists wrote the first paper about P. cardosoi. Before that, scientists thought P. cardosoi was the same frog as P. minuta. All the other species remaining were thought to be subspecies, synonyms or populations of P. paradoxa. Not all scientists agree that P. platensis is not the same frog as P. paradoxa.

Phylogenetic relationships
Scientists argue about how these frogs are related to other frogs and toads.  In the 19th and 20th centuries, scientists could only looking at animals' bodies, the way they acted, and fossils to figure out how they were related to each other.  Then DNA technology became strong enough to help scientists look at the animals' genes.  These frogs were very hard for scientists to put in groups before DNA technology became strong.

Over the years, scientists have said theys hould be in Ranidae, Leptodactylidae, Hylidae, and in their own family, Pseudidae, by themselves. It has been difficult for scientists to say where these frogs belong in taxonomy because their bodies are very different from those of other hylid frogs. The bodies of Pseudis frogs are different from other tree frogs' bodies because Pseudis frogs spend much more time living in water than most tree frogs do.

However, in the early 20th century, scientists did more studies.  Both body-shape-based and molecular (DNA) scientific experiments showed that these frogs are more closely related to tree frogs than to other frogs.  So scientists put them in the subfamily Hylinae with Scarthyla as a sister group.

Since then, two teams of scientists used molecular genetics (DNA) to find how this frog is related to other frogs. Both teams found the same thing, but they had different ideas about how the frogs should be put into groups: One team said scientists should start using the genus Podonectes again and the other team said they should use Lysapsus as a junior synonym of Pseudis. Later, more teams of scientists said Pseudis was not paraphyletic to Lysapsus, so making Lysapsus a junior synonym would not be good.

References

External links

Frogs
Animals of South America