Physalaemus pustulosus (Cope, 1864)
The túngara frog (Engystomops pustulosus; formerly known as Physalaemus pustulosus) is a species of frog in the Leptodactylidae family. Its local Spanish name is sapito de pustulas ("pustulated toadlet"). It is found in Belize, Colombia, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Trinidad and Tobago, Venezuela, and possibly Guyana. Its natural habitats are subtropical or tropical dry forests, dry savanna, moist savanna, subtropical or tropical dry lowland grassland, subtropical or tropical seasonally wet or flooded lowland grassland, freshwater marshes, intermittent freshwater marshes, pastureland, heavily degraded former forest, ponds, and canals and ditches.
Male túngara frogs are well known for their production of an advertisement call that allows a female to locate and identify them as a potential mate. Males produce a whine, and can also add up to seven short chuck sounds to their mating call. A call consisting of both a whine and a chuck is considered a complex call. The chuck portion of the call is produced by vibrations of a fibrous mass suspended near the frog's larynx. Larger frogs tend to have larger fibrous masses, allowing them to produce more chucks per every whine produced. A male’s whine frequency is used for species recognition by the female.
Sexual selection in túngara frogs is determined by female preference. Females will choose with whom they mate based on the attractiveness of a male’s call. The females are able to recognize the species of the calling male and will preferentially choose to mate with males of the same species. Intraspecific preference of females is based on complexity of call. They generally prefer complex mating calls (whine and chucks) to simple mating calls.  One study found that females will choose a simple call from a member of her own species rather than a complex call from a foreign or different species. Females prefer the mating call of frogs who produce chucks with lower frequencies. One explanation for this preference is that as the frequency of a male’s chuck decreases, their body size increases. A larger body size in males usually correlates with a higher rate of fertilization. If a female finds a specific male to be attractive as a potential mate, she will use his mating call as well as ripples in the water caused by the production of his call to locate her new mate.
Natural selection also plays a role in the varying complexity of a male's advertisement call. Parasites as well as the fringe-lipped bat (Trachops cirrhosis) are able to recognize species of frogs based on their mating calls. These predators, like females, prefer complex calls and will use these calls to locate and prey upon male túngara frogs. It is for this reason that males have been found to alternate between complex and simple calls depending on the situation in which they are.  Males usually produce complex calls only when there are other males nearby also producing mating calls, called a chorus. Males that use calling strategies such as this according to cost and benefits of the complexity of their call are able to maximize the possibility for finding a mate and minimize the possibility of predation.
When mating, the male frog centers himself atop the female to do rhythmic mixing of a foam-producing solvent released by the female to generate a floating foam nest. The foam nests are resistant bio-foams that protect the fertilized eggs from dehydration, sunlight, temperature, and potential pathogens until the tadpoles hatch. The nest degrades when the tadpoles leave after about four days, otherwise the nest can last for up to two weeks.
A protein present in the foam has been used by Carlos Montemagno, David Wendell, and Jacob Todd to create an artificial photosynthetic foam. Unlike chemical detergents the protein does not disrupt cell membranes allowing photosynthetic proteins to be positioned in the foam. This new method for producing biofuel won a 2011 Earth Award.
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- Wendell, D.; Todd, J.; Montemagno, C. (2010). "Artificial photosynthesis in ranaspumin-2 based foam". Nano Letters 10 (9): 3231–3236. Bibcode:2010NanoL..10.3231W. doi:10.1021/nl100550k. PMID 20205454. Free version