Telmatobius culeus

Geographic Range

Telmatobius culeus is a fully-aquatic, freshwater frog species that is endemic to the Lake Titicaca basin, which is located in the Andes mountain range between Peru and Bolivia. Lake Titicaca frogs have been observed in streams found along the eastern coast of Lake Titicaca, extending to Lago Pequeño, but the majority of individuals of are found at the bottom of Lake Titicaca. The species was previously thought to exist around the southern end of the Titicaca basin and the northern end near Lake Arapa and Bahía de Puno, but distribution studies have not found them in these areas. It is possible that the species found in those areas was Telmatobius marmoratur rugosus , which is considered to be a hybrid between Telmatobius culeus and Telmatobius marmoratus . There are two other putative species of Telmatobius : Telmatobius albiventris is restricted to the shallow water area surrounding Lago Grande, while Telmatobius crawfordi is found in small ponds near Lago Saracocha, which is approximately 70 km northwest of Lake Titicaca. However, these species are also considered synonyms of T. culeus .

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Lake Titicaca is at an elevation of 3,812 m and has a maximum depth of 281 m. The temperature is a constant 10°C in deep waters, while surface waters have a fluctuation of ±4°C annually. Therefore, Lake Titicaca is a thermally-stable habitat, and ectothermic residents do not experience major changes in body temperature. The strong wind and wave action of the lake keeps the water saturated with oxygen and the lake water has a partial pressure of oxygen (PO2) value of 100 mm Hg (13.3 kPa). The Titicaca basin is relatively geologically young with an age of 3.0 x 106 years old. In addition, within the last 20,000 years, this basin has experienced dramatic changes in water and salinity levels. In general, Titicaca water frogs are found in deep waters closer to the bottom of the lake, especially adult frogs. However, juveniles are found exclusively in shallower areas of the lake. Four subspecies are present in the same geographic range, but found in slightly different habitats. Telmatobius culeus fluviatilis and T. c. dispar are found in rivers that flow into Lake Titicaca. Telmatobius culeus escomeli and T. c. lacustris are found in small lagoons in the Titicaca basin.

• Habitat Regions
• tropical tropical
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

Physical Description

Lake Titicaca water frogs are easily recognized due to the permanent, loose, fibrous, and glandular skin folds hanging from the sides, dorsum, and hind legs. These folds give the frog a “baggy” appearance. However, dermal folds are important for cutaneous gas exchange because they increase the surface area through which gases can be exchanged. In fact, these folds are so well adapted for cutaneous gas exchange that it is not necessary for the frogs to ventilate their lungs at all. Because these dermal folds essentially act as “gills,” the lungs of the frog are one-third the size of any frog in the family Ranidae , flattened, poorly vascularized, and contain only primary alveoli. Body coloration is highly variable among individuals, but these frogs are always some combination of olive green, dark green, or even black dorsally and either white or pearl-colored ventrally. Their body consists of a large flattened head with a rounded snout and highly vascularized buccal cavity, relatively narrow caudal end, and richly vascularized skin. Lake Titicaca water frogs have long hind legs with webbed digits only on the hind feet. These frogs are relatively large and are the largest fully-aquatic frogs, reaching snout-vent lengths up to 14 cm. Due to their large size and dermal folds, Lake Titicaca water frogs often weigh over 250 g. In comparison to other anurans , they have thinner skin, which makes gas exchange easier. Telmatobius albiventris has less emarginated toe webbing, paler white ventral coloration, and adults of smaller size in comparison to individuals of T. culeus .

Animals that dive to great depths have to overcome problems regarding gas compression and exchange in the body. Titicaca water frogs are well-adapted for existence in water at high elevations where the maximum partial pressure of Oxygen is 100 mm Hg. Their specialized skin functions like a gill that secures enough oxygen to meet metabolic demands, which is the lowest recorded metabolic demand of all anurans . Cutaneous gas exchange is extremely efficient, but if it becomes impossible in a hypoxic environment, pulmonary respiration can maintain the metabolic rate for several hours. Even though they do not rely on pulmonary respiration, air is always found in the lungs of dissected frogs. Though their hematocrit percentage and hemoglobin concentration are within average range, the Lake Titicaca water frog has the smallest erythrocyte volume among all amphibians and the greatest erythrocyte counts among all amphibians aside from tiger salamanders ( Ambystoma tigrinum ). However, these characteristics are subject to environmental influence. During a 10-week acclimation period at 335 m elevation (compared to 3,800 m), the erythrocyte count, hemoglobin concentration, and hematocrit count all steadily declined. Their critical oxygen tension is low compared to other aquatic amphibians, so Titicaca water frogs are highly effective at removing oxygen from the water. The oxygen dissociation curve for whole blood of Lake Titicaca water frogs is sigmoidal. This can be explained by circulatory changes consisting of a separation of oxygen-rich and oxygen-depleted blood through the heart allowing the frog to distribute the blood to areas that will increase gas exchange efficiency. The network of cutaneous arteries and veins is much more elaborate and larger than most other frogs. Their red blood cell (RBC) count is high for anurans, and is only exceeded by males of Hyla hallowelli and Rana tsushimensis during the breeding season. The pH of ventricular blood averages around 7.5, remaining fairly neutral at all times. The “waving” behavioral adaptation allows for increased ventilation across the skin or, in hypoxic conditions, allows for pulmonary gas exchange. No other amphibian is known to possess this combination of adaptations for aquatic life at high altitudes.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

Not much is known about the development of Titicaca water frogs. They undergo metamorphosis, like other frogs. Juvenile Titicaca water frogs inhabit shallow waters, closer to the lake perimeter where they hatch. Adults inhabit deeper waters. There is evidence that these frogs continue to grow throughout their lifetimes. Once maturity is reached, development typically occurs at a slower rate.

• Development - Life Cycle
• metamorphosis metamorphosis
• indeterminate growth indeterminate growth

Reproduction

There is little information on mating systems of Lake Titicaca water frogs. They are likely to be polygynandrous. Because Titicaca water frogs are not sexually dimorphic, it is possible that males call for females during mating season. It is common for high-elevation neotropical frogs (especially nocturnal species) to use calling to attract a mate. Because calling is a high intensity behavior, the mating call would only be in use on the shoreline during the summer when the frogs breed. It has been suggested that Titicaca water frogs exhibit dis-assortative mating (random mating of individuals with traits more dissimilar than usual), but there is no direct evidence of this.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Reproductive behavior in Titicaca water frogs is not described in detail in the literature. They reproduce sexually, with egg fertilization occurring externally. The male releases his sperm at the same time the female releases her eggs, but to ensure fertilization, a specific mating posture (amplexus) is used. The specific type of amplexus used by the Lake Titicaca frog is unknown. However, some telmatobiine leptodactylids use a more primitive form of amplexus, which is inguinal. This means that the male holds the female at the waist just in front of her hind legs. This method of amplexus is thought to be less efficient at fertilizing eggs than axillary amplexus, which is utilized by most neobatrachian frogs. Reproduction is thought to take place during the summer in shallow waters near the lake shoreline. Clutch size is estimated to be around 500 eggs per season and the generation time is assumed to be 5 years.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• oviparous oviparous

Because of the large clutch size, it is assumed that there is no parental investment, as many other frog species with similar clutch sizes do not exhibit any form of parental investment.

• Parental Investment
• no parental involvement
• pre-fertilization
  • provisioning
  • protecting
    • female

Lifespan/Longevity

No information exists regarding the lifespan of Titicaca water frogs. In general, frogs live between 4 and 15 years in the wild. No data regarding lifespan of Lake Titicaca water frogs in captivity exists.

Behavior

Titicaca water frogs are solitary and more active at night. Because these frogs do not need to surface regularly to breathe, their most notable behavior occurs when the partial pressure of oxygen decreases to 35 to 89 mm Hg. If they are capable of rising to the surface for air, they point their nostrils into the air and ventilate their small lungs. These frogs remain in this position until the dissolved oxygen increases to its standard amount. However, if they are unable to reach the surface in less oxygenated water, they “stand” on the bottom of the lake bed with all limbs extended to maximize their skin surface area. Once every six seconds, they “bob” by pushing up with their back legs, resulting in them being lifted into the water column. As they sink slowly toward the lake bed, the dermal folds are passively lifted from the force of the water beneath it and the folds “wave” back and forth. The lower the partial pressure of oxygen, the higher frequency with which they attempt to “wave” their dermal folds. This serves to break the boundary layer of water, allowing efficient gas exchange across the skin surface. This behavior is reminiscent of the “rocking” behavior of aquatic hellbenders ( Cryptobranchus alleganiensis ). However, this method only works for a few hours. If the dissolved oxygen content does not increase, the frog will die. Aside from this respiratory behavior, Titicaca water frogs exhibit hiding behaviors whenever a boat comes nearby. Social behaviors in this species are unknown.

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

Home range size of Titicaca water frogs is not reported in the literature.

Communication and Perception

Little is known about communication and perception in Titicaca water frogs. In general, male frogs use calls for mating, whether to call for a female, ward off a male competitor, or perform a release call. Some Telmatobius species have a weak voice or no voice, but nothing is known about the voice of Titicaca water frogs. They sense changes in dissolved oxygen and react accordingly. No literature exists regarding how this species perceives its environment.

• Communication Channels
• tactile tactile
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic

Food Habits

Before research was conducted on the diet of Titicaca water frogs, the indigenous people thought that these frogs ate worms, crustaceans, and mollusks. However, stomach analyses showed that amphipods and snails were the most common food item present. Other prey found include tadpoles and fish, including Titicaca orestias ( Orestias cuvieri ). The tongue is relatively short and unforked. Therefore, the tongue is not adapted for capturing terrestrial prey despite its ability to extend. During stomach analyses, no terrestrial species were ever found among stomach contents.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • molluscivore molluscivore

• Animal Foods
• amphibians
• fish
• insects
• mollusks

Predation

Before research, indigenous people reported that birds, specifically herons, fed exclusively on Titicaca water frogs. However, no birds have been found with Titicaca water frogs in their stomachs. Therefore, native predators are unknown. It is suspected that introduced trout feed on larval frogs and that humans harvest adults. The coloration of adult frogs camouflage them from predators. Because the dorsal side is dark green, similar to the lake bed, and the ventral side is light, the animal is camouflaged from predators both above and below. When held or provoked, these frogs secrete large quantities of a sticky, milky substance from the entire body, including dermal folds. The secretion is suspected to have an offensive taste and serve as an anti-predator defense mechanism.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

No literature exists discussing the ecosystem roles of Titicaca water frogs. They are likely to be important predators of amphipods and snails in their aquatic habitat.

Economic Importance for Humans: Positive

There are no known positive effects of Titicaca water frogs on humans.

Economic Importance for Humans: Negative

There are no known negative effects of Titicaca water frogs on humans.

Conservation Status

This species is listed as critically endangered and has undergone population declines estimated to be more than 80% within the last 15 years alone. This population depletion can be explained by over-exploitation, habitat degradation, and invasive species. Telmatobius species are often over-harvested because they are used in Peru and Bolivia for supposed medicinal properties. This means that intense and unsustainable trading of this species is likely occurring, though it is illegal to sell threatened species. In addition, an introduced trout species in Lake Titicaca feeds on these larvae of these water frogs. Titicaca water frogs are also impacted by the water quality in the lake. Human extraction of water from the lake for drinking purposes and pollution from agricultural and domestic runoff has impacted habitat quality for this species. In the future, Chytridiomycosis could pose a threat seeing as it has already infected some species of g. Telmatobius . Though Lake Titicaca is a reserve, other measures have been taken to foster a population increase. A captive-breeding program was the first conservation effort, but it has been unsuccessful to date.

Additional Links

AmphibiaWeb

Encyclopedia of Life

Contributors

Kristen Batko (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Allen, W. 1922. Notes on the Andean Frog, Telmatobius coleus (Garman). Copeia , 108: 52-54.

Altherr, S., A. Goyenechea, D. Schulbert. 2011. "Canapés to Extinction: The International Trade in Frogs' Legs and its Ecological Impact" (On-line). Accessed October 20, 2013 at http://www.defenders.org/sites/default/files/publications/canapes_to_extinction.pdf .

Benavides, E., J. Ortiz, J. Sites Jr.. 2002. Species boundaries among the Telmatobius (Anura: Leptodactylidae) of the Lake Titicaca Basin: allozyme and morphological evidence. Herpetologica , 58: 31-55.

Butler, P., D. Jones. 1982. The Comparative Physiology of Diving in Vertebrates. Pp. 180-326 in Advances in Comparative Physiology and Biochemistry . New York, USA and London, UK: Academic Press.

Duellman, W., L. Trueb. 1986. Biology of Amphibians . Baltimore: The Johns Hopkins University Press.

Feder, M., W. Burgren. 1985. Skin breathing in vertebrates. Scientific American , 253: 126-142.

Hutchison, V., H. Haines, G. Engbretson. 1976. Aquatic life at high altitude: Respiratory adaptations in the Lake Titicaca frog, Telmatobius culeus . Respiration Physiology , 27: 115-129.

Icochea, J., S. Reichle, I. De la Riva, U. Sinsch, J. Kohler. 2004. " Telmatobius culeus " (On-line). The IUCN Red List of Threatened Species. Accessed October 02, 2013 at http://www.iucnredlist.org/details/57334/0 .

Lee, D. 2010. " Telmatobius culeus " (On-line). Amphibiaweb. Accessed October 15, 2013 at http://amphibiaweb.org/cgi/amphib_query?where-genus=Telmatobius&where-species=culeus .

Navas, C. 1997. Thermal extremes at high elevations in the Andes: Physiological ecology of frogs. Journal of Thermal Biology , 22: 467-477.

Ruiz, G., M. Rosenmann, A. Veloso. 1983. Respiratory and hematological adaptations to high altitude in Telmatobius frogs from the Chilean Andes. Comparative Biochemistry and Physiology A , 76: 109-113.