''Calyptocephalella'' is a

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 ...

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

Calyptocephalellidae The Calyptocephalellidae are a family of toads (although not true members of the Bufonidae) found in Chile containing two living genera, ''Calyptocephalella'' and ''Telmatobufo.'' The genus ''Calyptocephalella'' contains one living species, the ...

. It is represented by a single living species, ''Calyptocephalella gayi'', commonly known as the helmeted water toad, Chilean helmeted bull frog or wide-mouth toad. Additionally, there are a few extinct species that only are known from

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

and

Paleogene The Paleogene ( ; British English, also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period, geologic period and system that spans 43 million years from the end of the Cretaceous Period million yea ...

fossil remains from

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and gl ...

in South America and in the

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...

(at times when it was warmer and wetter). The helmeted water toad living today is aquatic to semi-aquatic, and found in deep ponds and reservoirs in central Chile and possibly adjacent west-central Argentina.AmphibiaWeb:
Calyptocephalella gayi.
' Retrieved 21 March 2015. This very large toad typically weighs up to , but sometimes considerably more. It's the world's second largest frog after the

goliath frog The goliath frog (''Conraua goliath''), otherwise known commonly as the giant slippery frog and the goliath bullfrog, is a species of frog in the family Conrauidae. The goliath frog is the largest living frog. Specimens can grow up to in lengt ...

. It is threatened by capture for human consumption,

habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

, pollution,

introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...

and the disease

chytridiomycosis Chytridiomycosis ( ) is an infectious disease in amphibians, caused by the chytrid fungi ''Batrachochytrium dendrobatidis'' and ''Batrachochytrium salamandrivorans''. Chytridiomycosis has been linked to dramatic population declines or extincti ...

. It is often kept in

herpetoculture Herpetoculture is the keeping of live reptiles and amphibians in captivity (animal), captivity, whether as a hobby or as a commercial biological reproduction, breeding operation. "Herps" is an informal term for both reptiles and amphibians, shorten ...

; mostly locally where farmed for food, but also in other countries as a pet.

Characteristics

The helmeted water toad is a robust species with a broad head and large mouth. It is very large, and can reach a snout–to–

vent Vent or vents may refer to: Science and technology Biology *Vent, the cloaca region of an animal *Vent DNA polymerase, a thermostable DNA polymerase Geology *Hydrothermal vent, a fissure in a planet's surface from which geothermally heated water ...

length of up to in males and in females. The typical maximum weight is , but exceptionally large individuals can reach . Such giants are essentially unheard of today, although there are recent records of several individuals weighing . It is the largest

anuran A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' ...

(frogs and toads) of the Americas, surpassing other large species like the Blomberg's,

cane Cane or caning may refer to: *Walking stick or walking cane, a device used primarily to aid walking *Assistive cane, a walking stick used as a mobility aid for better balance *White cane, a mobility or safety device used by many people who are b ...

Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid drainage basin, watershed that encompasses parts of ...

, cururu and

smooth-sided toad The smooth-sided toad or spotted toad (''Rhaebo guttatus''), formerly known as ''Bufo guttatus'', is a species of toad in the family Bufonidae. It is found in the Amazonian Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela, as well as the ...

s, and the American bull-,

Lake Junin Lake Junin (; Spanish ''Lago Junín'', named after the nearby town of Junin) or Chinchaycocha (possibly from Quechua ''chincha, chinchay'' north, northern, ''chinchay'' ocelot, ''qucha'' lake, lagoon, "northern lake" or "ocelot lake") is the larg ...

mountain chicken ''Leptodactylus fallax'', commonly known as the mountain chicken or giant ditch frog, is a critically endangered species of frog that is native to the Caribbean islands of Dominica and Montserrat. The population declined by at least 80% from 19 ...

and

Titicaca water frog ''Telmatobius culeus'', commonly known as the Titicaca water frog, is a medium-large to very large and endangered species of frog in the family Telmatobiidae. It is entirely aquatic and only found in the Lake Titicaca basin, including rivers th ...

s. The maximum snout–to–vent is similar to that of the world's largest frog, the African

(''Conraua goliath''), which however can weigh more. Helmeted water toads are colored yellow, brown and green, with light green in mature specimens, while the oldest are gray, or have gray patches on a dark background. The

olive The olive, botanical name ''Olea europaea'', meaning 'European olive' in Latin, is a species of small tree or shrub in the family Oleaceae, found traditionally in the Mediterranean Basin. When in shrub form, it is known as ''Olea europaea'' ...

-brown to dusky tadpoles also grow unusually large, typically exceeding lengths of and reaching up to .

Behavior

Reproduction and aggressive behavior

The helmeted water toad breeds in the South Hemisphere spring (September–October) when males call. The female lays between 1,000 and 16,000 eggs in shallow, well-vegetated water. Although many eggs never hatch, captive studies have shown that a single spawning may result in more than 1,000 tadpoles. Typical larval (tadpole) life lasts five months to a year, but up to two years. After hatching, larval survival depends on the presence of vegetation as the existence of movements in the body of water maintain good oxygenation, but the presence of seasonal ponds with some degree of drainage is essential for hatching, as these sites contain fewer predators to the larvae. Then, the transport of larvae from ponds, to larger bodies of water during the rains, or transport of these among several bodies of water facilitates the survival and allows a good development of populations. The larvae prefer cooler areas of the body of water and protective aquatic vegetation, unlike toad larvae that occupy the same sites and have a higher degree of pigmentation that protects them from the solar rays. While the species is almost entirely aquatic, especially young helmeted water toads that are recently metamorphosed from the tadpole stage often can be seen on land. In captivity, they can breed when 2 years old and a female was able to breed until 24 years old. The helmeted water toad is quite aggressive and it has an aggressive call specifically directed at other individuals of the same species. During encounters with conspecifics they inflate their body, open their large mouth and may jump forward towards an opponent. The same behavior can be directed at potential predators, including humans, although they may choose to escape silently by diving into the water.

Feeding

Their food in the tadpole stage is vegetation and

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

. Adults feed on virtually any animal they can overpower and swallow, including fish, invertebrates, small birds, small mammals and other frogs.

Cannibalism Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...

also occurs.

Conservation status

The helmeted water toad is a

vulnerable species A vulnerable species is a species which has been Conservation status, categorized by the International Union for Conservation of Nature as being threatened species, threatened with extinction unless the circumstances that are threatened species, ...

according to

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

due to capture for human consumption (to a lesser degree also to supply the pet trade),

, pollution, introduced species (especially

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salmoni ...

and

African clawed frog The African clawed frog (''Xenopus laevis'', also known as the xenopus, African clawed toad, African claw-toed frog or the ''platanna'') is a species of African aquatic frog of the family Pipidae. Its name is derived from the three short claws ...

) and the disease

(caused by ''

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 popul ...

''). The species is kept in frog farms that supply the food market, but helmeted waters toads take three years to reach a marketable size; they have been unable to produce enough to meet the demand and the farms have not been lucrative. Despite being illegal in Chile, wild caught individuals are still frequently sold for food in the country and control is insufficient. International trade require a permit, as the species is listed on

CITES Appendix III CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...

. On average, helmeted water toads experience water temperatures of about in the winter and in the summer. While their tolerance is broader, they already have an increased mortality rate at and are entirely unable to cope with temperatures of or warmer. It is projected that a significant percentage of the population will disappear before the year 2100 due to

global warming 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 ...

. In some places where water levels have been greatly reduced due to a combination of climate change (drought) and extraction for agriculture, mass deaths of helmeted water toads have already been recorded. It is also threatened by the introduction of the African clawed frog (known in Chile as the African toad), a species that has affected, as in other parts of the world, local amphibians when carrying the

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. Chytrids ...

''Batrachochytrium dendrobatidis'', which passes through the skin of amphibians not adapted to it. Their cells react to the

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

, causing hardening and, therefore,

hyperkeratosis Hyperkeratosis is thickening of the stratum corneum (the outermost layer of the epidermis, or skin), often associated with the presence of an abnormal quantity of keratin,Kumar, Vinay; Fausto, Nelso; Abbas, Abul (2004) ''Robbins & Cotran Patholo ...

and death by asphyxiation. The fungus has been classified as a major factor in the decline in amphibian populations worldwide, but in Chile has been reported recently, in 2009. Other causes cited are competition that occurs between African clawed frog and helmeted water toad, introduced for sale in the market for frog legs.

References