Adult males 66 to 81 mm SVL. Adult female 77 mm SVL. The smooth dorsal surface has 8 to 12 low transverse ridges. The head is broader than long. From above the snout is blunt and rounded, and in profile is obtuse. The skull is not co-ossified to the skin, but is exostosed. The upper eyelid has a triangular dermal flap. The tympanum is indistinct and measures less than half the diameter of the eye. Finger discs are large, with the disc of finger III equal in size to half the tympanum diameter, and fingers have hardly any webbing. Hindlegs are long. The toes have a moderate amount of webbing. The inner metatarsal tubercle is small and ovoid and the outer metarsal tubercle is lacking. The inner tarsal fold is weakly developed. A triangular calcar is present on the heel. Females have a brood pouch opening on the dorsum, halfway between the sacral hump and vent. Males have no vocal slits but do have a single internal subgular vocal sac that is slightly distensible. On the base of the thumb, in adult males, there is a horny nonspinous brown nuptial pad (Savage 2002).
Ground coloration is dark brown by day and tan at night; this species undergoes metachrosis (color change). Also at night, the light cream to yellow suborbital spot disappears. Unchanging aspects of the coloration include 8-15 narrow, dark brown dorsal transverse lines. Lips are barred. A broad dark brown dorsolateral stripe runs from the tympanum to the groin. The posterior thigh is pale brown. Ventral surfaces are pinkish to pale brown, with the throat being brown. The iris is bronze peripherally, and creamy yellow or olive green medially (Savage 2002).
This frog develops directly into froglets; embryos are thus lacking many morphological features of free-living tadpoles, such as keratinized mouthparts. For a detailed discussion of the morphology of G. cornuta embryos compared to those of several other Gastrotheca species, see Wassersug and Duellman (2004). Gastrotheca embryos have specialized structures called bell gills, which cover 100% of the embryo as it develops within a single chamber in the female's multichambered dorsal brood pouch (del Pino and Escobar 1981).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Colombia, Costa Rica, Ecuador, Panama
From central Costa Rica to central Panama on the Atlantic slope. In Costa Rica, this species is known from three localities in the Limón Province, Costa Rica at 300-700 m above sea level. Also inhabits the Pacific versant from eastern Panama to northwestern Ecuador. Elevation range in Panama is 90 to 1,000 m above sea level. Found in canopy of lowland wet forest and premontane rain forest (Savage 2002), near rivers and creeks (Coloma et al. 2008).
Life History, Abundance, Activity, and Special Behaviors
Gastrotheca cornuta is nocturnal and is a canopy-dweller. The male calls from high trees, with the call sounding like a champagne cork popping (a loud "bop") and consisting of one or two notes at long intervals of eight to twelve minutes. Duration of the note is approximately 80 milliseconds with a dominant frequency of 0.8 kHz (Savage 2002).
This species breeds by direct development and is a member of the "marsupial" frogs, with females carrying the eggs in a pouch on the posterior part of the back (del Pino 1980). The brood pouch (type II of del Pino 1980) has an opening shaped likOne female specimen had seven eggs in her dorsal pouch, and the eggs measured 9.8 mm in diameter (Savage 2002). Another specimen had 9 embryos at 12 mm in diameter (Savage 2002). e an inverted V, with left and right triangular sections separated by a septum. The eggs of this species are the largest known amphibian eggs (del Pino and Escobar 1981) and are unusual for amphibians in that they are multinucleate during oogenesis (del Pino and Humphries 1978). Embryos have large external gills covering about 1/4 of the embryo; two gill stalks and a single fused gill are present on each side of the embryo, for a total of four stalks and two gills (Savage 2002). For the genus Gastrotheca, it is thought that gaseous exchange occurs between the mother's circulation in the pouch and the embryo's umbelliform gills, as the pouch is highly vascularized and each embryo is contained in a separate chamber within the pouch, with gills in close apposition to the chamber walls (del Pino 1980). This has been termed a "gill placenta", which also occurs in some caecilians and some salamanders (Savage 2002).
Trends and Threats
Gastrotheca cornuta has not been seen in Costa Rica since 1996. It has declined significantly in Panama and Ecuador; although it may still be present in both countries, the status is unknown. It was always rare in Colombia. In Costa Rica, Panama, and the lowlands of Ecuador, chytridiomycosis has likely been the main factor responsible for the drastic decline of this species. Extensive loss of habitat is also a factor. This species is no longer present in the type locality of Cachabi, Provincia Esmeralda, Ecuador due to deforestation. In Cauca and Nariño the species is also experiencing a decline in population due to significant habitat fragmentation. Habitat is being lost or degraded due to many causes: deforestation for agricultural development, illegal crops, logging, and human settlement, and pollution resulting from the spraying of illegal crops (Coloma et al. 2008).
Possible reasons for amphibian decline
General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Local pesticides, fertilizers, and pollutants
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).
Coloma, L.A., Ron, S., Jungfer, K-H., Grant, T., Cisneros-Heredia, D., Solís, F., Ibáñez, R., Chaves, G., Savage, J., Jaramillo, C., Fuenmayor, Q., Bolaños, F., Lips, K., Lynch, J.D., and Almendáriz, A. (2008). Gastrotheca cornuta. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. www.iucnredlist.org. Downloaded on 28 July 2009.
Savage, J. M. (2002). The Amphibians and Reptiles of Costa Rica. University of Chicago Press, Chicago and London.
Wassersug, R. J., and Duellman, W. E. (1984). ''Oral structures and their development in egg-brooding hylid frog embryos: evolutionary and ecological implications.'' Journal of Morphology , 182, 1-37.
del Pino, E. (1980). ''Morphology of the pouch and incubatory integument in marsupial frogs (Hylidae).'' Copeia, 1980, 10-17.
del Pino, E. M. and Escobar, B. (1981). ''Embryonic stages of Gastrotheca riobambae (Fowler) during maternal incubation and comparison with development of other marsupial frogs.'' Journal of Morphology, 167, 277-295.
del Pino, E., and Humphries, A. A., Jr. (1978). ''Multiple nuclei during early oogenesis in Flectonotus pygmaeus and other marsupial frogs.'' Biological Bulletin, 154, 198-212.
Written by Lettie Gallup (lettiegallup AT gmail.com), UC Berkeley
First submitted 2009-07-22
Edited by Kellie Whittaker (2009-11-02)
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