genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
frog
A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...
s in the family
Leptodactylidae
The southern frogs form the Leptodactylidae, a name that comes from Greek meaning a bird or other animal having slender toes. They are a diverse Family (biology), family of frogs that most likely diverged from other hyloidea, hyloids during the C ...
. They are known commonly as foam frogs or túngara frogs, though the latter name most commonly refers to ''
Engystomops pustulosus
''Engystomops'' is a genus of frogs in the family Leptodactylidae. They are known commonly as foam frogs or túngara frogs, though the latter name most commonly refers to '' Engystomops pustulosus''. They are native to the Americas from southern ...
''. They are native to the Americas from southern
Mexico
Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
south to the
Amazon Basin
The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Bolivi ...
.
This genus was maintained on its own until 1970, when it was merged into ''
Physalaemus
''Physalaemus'' is a large genus of leptodactylid frogs. These frogs, sometimes known as dwarf frogs or foam frogs, are found in South America. It is very similar to ''Leptodactylus'', a close relative, and indeed the recently rescribed ''Leptod ...
'', a genus of similar frogs. As studies progressed, there was increasing evidence that ''Physalaemus'' was not a
monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
group; it was made up of several groups. One of those groups consisted of several frogs more closely related to each other than to the rest of the ''Physalaemus'', and they were represented by ''P. pustulosus'', now ''Engystomops pustulosus''. This group was split off in 2005 on the basis of characters such as basic
morphology
Morphology, from the Greek and meaning "study of shape", may refer to:
Disciplines
* Morphology (archaeology), study of the shapes or forms of artifacts
* Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
allozyme
Alloenzymes (or also called allozymes) are variant forms of an enzyme which differ structurally but not functionally from other allozymes coded for by different alleles at the same locus. These are opposed to isozymes, which are enzymes that perfo ...
and other
genetic analysis
Genetic analysis is the overall process of studying and researching in fields of science that involve genetics and molecular biology. There are a number of applications that are developed from this research, and these are also considered parts of ...
. The group was given the revalidated name ''Engystomops''. It included two newly described species.
Description
These frogs measure about 1.5 or 1.6 to 3.5 or 3.8 centimeters long.
These frogs live on the forest floor. They breed in temporary pools, sometimes in puddles that form during the rainy season. They are perhaps best known for their foam-nest-building behavior, particularly ''E. pustulosus'', in which the behavior has been well-studied. During mating, the male releases sperm while the female releases eggs and a protein-rich fluid. The male vigorously beats the fluid into a
foam
Foams are materials formed by trapping pockets of gas in a liquid or solid.
A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the reg ...
with his feet. The eggs are suspended in the foam, which acts as a protective matrix. Some of the proteins have
surfactant
Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...
properties, keeping the foam mass stable on the water, while others likely have antimicrobial and antiparasite properties.
Frogs of this genus have been researched in studies of
sexual selection
Sexual selection is a mode of natural selection in which members of one biological sex mate choice, choose mates of the other sex to mating, mate with (intersexual selection), and compete with members of the same sex for access to members of t ...
and communication in animals.
It was previously believed that a female's choice in ''Engystomops'' benefited through indirect exclusion but it is now believed that the extra male activity while nesting influences the fitness of the female directly. Thus creating the operation of sexual selection through direct benefit.
As of early 2018, there are nine species in this genus:
It has been suggested that ''E. pustulosus'' is a
cryptic species complex
In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...