''Atelopus varius'', the Costa Rican variable harlequin toad or clown frog, is a small
Neotropical
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone.
Definition
In bioge ...
true toad from the family
Bufonidae {{Cat main, Toad
This category contains both species commonly called toads, and the true toads from the family Bufonidae {{Cat main, Toad
This category
Category, plural categories, may refer to:
Philosophy and general uses
*Categorization, cat ...
(Crump 1986). Once ranging from
Costa Rica to
Panama
Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Co ...
, ''A. varius'' is now listed as
critically endangered and has been reduced to a single remnant population near Quepos, Costa Rica (rediscovered in 2003) and has only relict populations in western Panama (IUCN). Recent variation in air temperature, precipitation, stream flow patterns, and the subsequent spread of a pathogenic
chytrid fungus ''(
Batrachochytrium dendrobatidis
''Batrachochytrium dendrobatidis'' ( ), also known as ''Bd'' or the amphibian chytrid fungus, is a fungus that causes the disease chytridiomycosis in amphibians.
Since its discovery in 1998 by Lee Berger, the disease devastated amphibian popula ...
)'' linked to
global climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
have been the leading cause of decline for ''A. varius'' (Lips et al. 2003 and Pounds et al. 2006). ''
A. zeteki'' has been considered a
subspecies of ''A. varius'', but is now generally considered a separate species (Savage, 2002).
Geographic range
The historic range of A. varius stretched from the Pacific and Atlantic slopes of the
Cordilleras de Tilaran mountain range in Costa Rica into western Panama. Suitable habitat includes both pre-montane and lower-montane zones as well as some lowland sites along rocky streams in hilly areas (ranging from 6 to 2000m in elevation) (Savage 1972).
Habitat and ecology
''A. varius'' is a
diurnal frog often found on rocks or in crevices along streams in humid lowland and montane forests (Crump and Pounds 1985). It is primarily a
terrestrial
Terrestrial refers to things related to land or the planet Earth.
Terrestrial may also refer to:
* Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...
species, only entering the water during breeding season, relying on spray from streams for moisture (Pounds and Crump 1994).
The Costa Rican variable harlequin frog is slow moving and often remains in the same area for long periods of time. The conspicuous or
aposematic
Aposematism is the advertising by an animal to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defences which make the prey difficult to kill and eat, such as toxicity, venom, foul taste o ...
coloration of ''A. varius'' likely serves as a warning to potential predators of the toxicity of the frog's
integument
In biology, an integument is the tissue surrounding an organism's body or an organ within, such as skin, a husk, shell, germ or rind.
Etymology
The term is derived from ''integumentum'', which is Latin for "a covering". In a transferred, or ...
which contains
tetrodotoxin
Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovere ...
, a potent
neurotoxin (Crump and Pounds 1985). Its main food source is small
arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...
s that are most abundant during the dry season (Crump 1988).
The only known predator of ''A. varius'' is a parasitic
sarcophagid fly ''(Notochaeta bufonivora)'' which deposits its larvae on the surface of the frog's thigh. The larvae then proceed to burrow inside the frog and eat it from within (Pounds and Crump 1987).
Conservation status
In recent decades, ''A. varius'' has become increasingly rare throughout its geographic range. The first incidence of its disappearance was recorded after a census conducted between 1990 and 1992 near
Monteverde
Monteverde is the twelfth canton of the Puntarenas province of Costa Rica. It is located in the Cordillera de Tilarán mountain range. Roughly a four-hour drive from the Central Valley, Monteverde is one of the country's major ecotourism des ...
, Costa Rica revealed zero individuals where its population had previously peaked at 751 adults (Crump and Pounds 1985 and Pounds and Crump 1994). By 1996, ''A. varius'' was believed to be
extinct throughout Costa Rica, however, in a 2019 assessment, two subpopulations were discovered in the country.
In Panama, mass mortality has drastically reduced populations of ''A. varius'' in recent years and it was believed to be locally extinct (Lips 1999), however the species was recorded again in the 2019 assessment.
Several theories related to changes in climatic patterns have been put forth to account for the rapid decline of ''A. varius''. A trend toward rising temperatures across the tropics in the late 1980s and early 1990s has been implicated in the declines of multiple
lizard and
amphibian species including several ''Atelopus'' spp. (Pounds et al. 1999). More recently, an observed global
decline in amphibian species richness has been linked to an outbreak of the
pathogenic chytrid fungus
Chytridiomycota are a division of zoosporic organisms in the kingdom Fungi, informally known as chytrids. The name is derived from the Ancient Greek ('), meaning "little pot", describing the structure containing unreleased zoöspores. Chytrid ...
''
Batrachochytrium dendrobatidis
''Batrachochytrium dendrobatidis'' ( ), also known as ''Bd'' or the amphibian chytrid fungus, is a fungus that causes the disease chytridiomycosis in amphibians.
Since its discovery in 1998 by Lee Berger, the disease devastated amphibian popula ...
'' (Pounds et al. 2006). This pathogen can be transmitted between individuals through shed skin cells and is known to infect
keratin
Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up scales, hair, nails, feathers, ho ...
ized body surfaces where it can impair
cutaneous respiration Cutaneous respiration, or cutaneous gas exchange (sometimes called, skin breathing), is a form of respiration in which gas exchange occurs across the skin or outer integument of an organism rather than gills or lungs. Cutaneous respiration may be ...
and
osmoregulation
Osmoregulation is the active regulation of the osmotic pressure of an organism's body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism's water content; that is, it maintains the fluid balance and the concentration o ...
thus resulting in mortality (Pounds et al. 2006). Current attempts to preserve ''A. varius'' include a recently initiated captive breeding program as well as continued efforts to protect vital forest habitat (IUCN). In March 2021, it was announced that the species had been successfully bred in captivity outside of Panama for the first time.
References
*Crump, M.L. 1986. Homing and site fidelity in a Neotropical frog, ''Atelopus varius'' (Bufonidae). ''Copeia'' 1986(4): 1007-1009.
*Crump, M.L. 1988. "Aggression in harlequin frogs: male-male competition and a possible conflict of interest between the sexes." ''Animal Behaviour'' 36(4): 1064-1077.
*Crump, M.L., and J.A. Pounds 1985. "Lethal Parasitism of an Aposematic Anuran (''Atelopus varius'') by ''Notochaeta bufonivora'' (Diptera: Sarcophagidae)." ''Journal of Parasitology'' 71(5), 588-591.
*Lips, K.R. 1999. Mass mortality and population declines of anurans at an upland site in western Panama. ''Conservation Biology'' 13: 117-125.
*Lips, K.R., Green, D.E. and Papendick, R. 2003. Chytridiomycosis in wild frogs from southern Costa Rica. ''Journal of Herpetology'' 37: 215-218.
*Pounds, J.A., Bustamante, M.R., Coloma, L.A., Consuegra, J.A., Fogden, M.P.L., Foster, P.N., La Marca, E., Masters, K.L., Merino-Viteri, A., Puschendorf, R., Ron, S.R., Sánchez-Azofeifa, G.A., Still, C.J. and Young, B.E. 2006. Widespread amphibian extinctions from epidemic disease driven by global warming. ''Nature'' 439: 161-167.
*Pounds, J.A., and Crump, M.L. 1987. "Harlequin Frogs Along a Tropical Montane Stream: Aggregation and the Risk of Predation by Frog-Eating Flies." ''Biotropica'' 19(4): 306-309.
*Pounds, J.A. and Crump, M.L. 1994. Amphibian declines and climate disturbance: The case of the golden toad and the harlequin frog. ''Conservation Biology'' 8: 72-85.
*Pounds, J.A., Fogden, M.P.L., and J.H. Campbell 1999. "Biological response to climate change on a tropical mountain." ''Nature'' 398(6728): 611-615.
*Savage, J.M. 1972. The harlequin frogs, genus ''Atelopus'', of Costa Rica, and western Panama. ''Herpetologica'' 28: 77-94.
*Savage, J.M. 2002. ''The Amphibians and Reptiles of Costa Rica.'' University of Chicago Press, Chicago.
External links
*
IUCN Red List of All Threatened SpeciesThe Rainmaker ProjectAtelopus.com - Fighting to survive
{{Taxonbar, from=Q310885
varius
Amphibians of Costa Rica
Endemic fauna of Costa Rica
Amphibians described in 1856
Taxa named by Eduard von Martens
Taxa named by Hinrich Lichtenstein
Critically endangered fauna of North America