| Pseudis | |
|---|---|
 | |
| Pseudis minuta | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Amphibia |
| Order: | Anura |
| Family: | Hylidae |
| Tribe: | Dendropsophini |
| Genus: | Pseudis Wagler, 1830 |
| Type species | |
| Rana paradoxa | |
| Species | |
See text. | |
Pseudis is a genus of South Americanfrogs (swimming frogs) in the familyHylidae.[1] They are often common and frequently heard, but easily overlooked because of their camouflage and lifestyle, living in lakes, ponds, marshes and similar waters with extensive aquatic vegetation, often sitting at the surface among plants or on floating plants, but rapidly diving if disturbed. Whereas the adults are medium-sized frogs, theirtadpoles are large; in some species the world's longest.[2][3][4]
Pseudis species are distributed throughout tropical and subtropical South America, almost entirely east of theAndes (P. paradoxa is the only species with populations west of the Andes, in Colombia). They are found fromTrinidad to northern Argentina, being absent only in Ecuador and Chile, highland regions, and the southernmost part of South America. All species occur in Brazil, andP. bolbodactyla,P. cardosoi,P. fusca andP. tocantins areendemic to this country.[1][5]
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These frogs have several adaptations to aquatic life, such as protuberant eyes, robust hind limbs, and fully webbed feet.[6] Nevertheless, they belong to the "true" tree frogs, familyHylidae.[1]
Mating and egg-laying inPseudis is typical of frogs. What sets them apart is theirtadpoles that start out as fairly normal, but continue growing until reaching gigantic sizes, sometimes as much as 22–27 cm (9–11 in) in length inP. paradoxa andP. platensis.[3][5][7][8] They are the longest known tadpoles and also large compared to the adult frogs, which are 3.4–7.6 cm (1.3–3.0 in) in snout–to–vent length.[2][5] Less data is available for the tadpoles of most others members of the genus, but they too reach large sizes, although perhaps somewhat less thanP. paradoxa andP. platensis.[9] Their adult frogs also average somewhat smaller with snout–to–vent lengths of 2.4–6.6 cm (0.9–2.6 in).[5][10][11] However, there are two outliers in the genus: The closely relatedP. cardosoi andP. minuta (equalling the proposed genusPodonectes, seePhylogenetic relationships) have more normal tadpoles that are not known to surpass lengths ofc. 9 cm (3.5 in).[9][11][12] This is still large compared to the adults of these two species, meaning that they too "shrink" duringmetamorphosis from tadpole to frog.[9] In most if not all the species, there are noticeable local variations in the final size of the tadpoles, with those in large temporary waters with plenty of food and few aquatic predators growing larger than those in smaller waters with less food or waters with more aquatic predators.[5] In at least the species with very large tadpoles, their final stages have unusually well-developed organs, including nearly ripe reproductive organs. This means that recently metamorphosed frogs rapidly reach maturity and essentially stop growing, whereas most other frogs take more time and growing after metamorphosis before they become mature.[3][5][13]
Pseudis is closely related to a second genus,Lysapsus, that lacks giant tadpoles and in which adults are smaller, up to 2.5 cm (1.0 in).[6][5]
Pseudis tadpoles feed mostly on a wide range of algae, but also take small invertebrates.[14][15] The adult frogs feed mostly on land-based insects and spiders, but also other land-based or aquatic invertebrates, small frogs and—in some species—plant material.[16][17][18][19]
There are seven species in this genus (given thatLysapsus is accepted as a separate genus). Until the late 1990s and early 2000s, most authorities only recognizedP. minuta andP. paradoxa, butP. cardosoi was described in 2010 (having formerly been included as a population ofP. minuta), while the remaining were consideredsubspecies,synonyms or populations ofP. paradoxa.[1] The validity ofP. platensis as a species separate fromP. paradoxa is questionable.[5]
| Binomial name and author | Common name |
|---|---|
| Pseudis bolbodactylaLutz, 1925 | |
| Pseudis cardosoiKwet, 2000 | |
| Pseudis fuscaGarman, 1883 | |
| Pseudis minutaGünther, 1858 | lesser swimming frog |
| Pseudis paradoxa(Linnaeus,1758) | paradoxical frog |
| Pseudis platensisGallardo, 1961 | |
| Pseudis tocantinsCaramaschi & Cruz, 1998 |
Thephylogenetic position of frogs currently included in the genusPseudis in relation to other anurans was for a long time a matter of debate. They have been placed inRanidae,Leptodactylidae,[20]Hylidae,[21] and as their own family Pseudidae[22] This results from their highly derived body plan for a hylid frog due to their mostly aquatic habits. Recent morphological[23] and molecular[24] phylogenetic reconstructions have unambiguously placed them within the subfamily Hylinae withScarthyla as a sister group.
Phylogenetic relationships among species of the group were recently proposed using molecular evidences.[6][25][23] Both publications found identical trees, but proposed differenttaxonomic solutions for the nonmonophyly ofPseudis, either resurrecting the genusPodonectes[6] or placingLysapsus as ajunior synonym ofPseudis.[25] More recent molecular evidence did not findPseudisparaphyletic with respect toLysapsus, so the synonymy is unnecessary.[1]