Living at 12,000 feet – Lake Titicaca “scrotum” frog adapted to the high life

Entirely aquatic and one of the largest frogs on the planet, growing up to the size of a salad plate, the Lake Titicaca water frog also makes one of the stranger fashion statements in the amphibian world. Its excessive skin folds, which look like someone put its skin through a taffy-puller and then sewed the result back on, have earned it the whimsical Latin name of Telmatobius culeus – “aquatic scrotum.”

The scrotum frog’s bizarre outfit is actually the perfect adaptation to the cold waters of its high-altitude home. The bottom-dwelling frog is only found in Lake Titicaca, often called the highest navigable lake in the world, sandwiched between Peru and Bolivia. The frog is entirely aquatic, living in the reed beds of the lake and its rivers. Avoiding the oxygen-depleted air, its ornate skin folds and abundance of capillaries allow it to absorb oxygen directly from the saturated water, making up for its tiny lung size and allowing it to stay permanently below the surface – which protects it from the high levels of ultraviolet radiation found in the area. It also benefits from a high number of small red blood cells, which efficiently deliver oxygen and remove carbon dioxide from its body tissues.

Illustration by P. Roetter, Bulletin of the Museum of Comparative Zoology

Illustration by P. Roetter, Bulletin of the Museum of Comparative Zoology

The oddball frog has fascinated people for centuries. Lake Titicaca frogs were believed to have special powers, particularly in bringing  rain: once carried in a ceramic pot to a hillside, the frogs would call in distress, which supposedly sounded to the gods like a plea for rain. Once the downpour began, the pot would overflow and the sacred animals would escape back to the lake. The frog also captured the imagination of its 1876 European discoverer, S.W. Garman – as witnessed by his choice of a name. Jacques Cousteau, searching Lake Titicaca for Inca treasure in the 1970s, was equally enthralled, reporting “thousands of millions” of the frogs, some almost 20 inches long.

These days, such giants are unlikely to be seen. Aside from global threats to amphibians such as the chytrid fungus and invasive species, in this case a trout that preys on its tadpoles, the Lake Titicaca water frog suffers from over-popularity. It is a favorite menu item at tourist restaurants around the lake, and is also taken to Lima markets – where it’s sold as an aphrodisiac. The frogs are skinned and then blended with water, maca (a local root vegetable) and honey into a juice, thought to be the cure for several ailments, including impotence. It is also collected as a pet or curiosity, while pollution, habitat loss, and overfishing of its main prey, the small fish known locally as ipsi, could also be pushing the critically endangered frog towards extinction.

In response, captive breeding programs have been established for the giant amphibians, both around Lake Titicaca and internationally. One possible plan is to farm the frogs for consumption, taking the pressure off those left in the wild, although this could subject the small population to increased risk of disease from large, densely-kept captive populations. Scientists from both Peru and Bolivia are studying the frog, to assess its ecology and feeding habits as a base for captive breeding.

ARKive video – Lake Titicaca frog

Liberian Tree-Hole Crab (Globonautes macropus)

A freshwater crab that lives in a tree!?

Liberian tree-hole crab (Globonautes macropus)

Liberian tree-hole crab (Globonautes macropus)

What is it?

When we think of freshwater biodiversity we naturally think of places such as rivers, streams, ponds and lakes. But not all freshwater animals live in these habitats. The Liberian tree-hole crab is an amazing species of freshwater crab that lives in the closed canopy rain forests of West Africa. Yep, it’s a freshwater crab that lives in a forest. Living far from permanent freshwater sources such as rivers or lakes, these crabs live in water-filled holes in trees to survive. At night they emerge from their homes in the trees and make their way down to the forest floor to forage for food, mostly small insects. Once they’re finished with their evening meal, they climb back up the tree where they spend their days.

Map of West Africa

Map of West Africa

Range and Habitat

This unique species was first documented in 1898 in Liberia (hence the name), but was not documented until 90 years later in 1988. It is one of only five species that belong to a rare group of freshwater crabs that are endemic to West Africa. Since 1988 sightings have increased but been restricted to small parts of the upper Guinea forest in western Liberia and Guinea and it is also thought their range extends to parts of Sierra Leone’s forest which lie between these two populations. The crab populations are solely restricted to rainforest in areas with rainwater filled natural holes found in suitably sized trees at a height of between 1 to 2 meters above the ground and they are known to exist in just five different locations across these regions. For an interactive map of the tree-hole crab’s range click here.

The Upper Guinea Forest extends from Guinea into Sierra Leone and eastward through Liberia, Côte d’Ivoire and Ghana into western Togo.

The Upper Guinea Forest extends from Guinea into Sierra Leone and eastward through Liberia, Côte d’Ivoire and Ghana into western Togo.

Endangered

As such these tree-climbing crabs are extremely rare and can be hard to spot. The number of tree-hole crabs that still exist is uncertain due to a lack of information, however, it was estimated that before the civil war broke out in Liberia in 1989 there were between 5-10 per km² of closed-canopy rain forest. It is expected that this number has decreased since this time and the species is listed as endangered on the IUCN Red List. Current estimates put the number at fewer than 2500 mature individuals.

It is thought that the population numbers have been declining across its range due largely to habitat loss and deforestation related to years of civil war and political instability in the region. Due to the specific habitat of these cool crustaceans they are very vulnerable to habitat loss. Being a freshwater crab that relies on rainwater captured in tree holes, even the felling of a small number of appropriately hollowed trees in a particular area may threaten local populations. Other threats that these curious critters face include an increase in agriculture, mining and firewood collection, which again contribute to habitat loss. Given these threats, the tree-hole crab’s specialised habitat and small population size, it is of serious concern that this species is not found within a protected area, nor are there any conservation measures in place to protect this unique animal’s existence. Hopefully more research into this incredible creature will raise awareness of its plight and spur on effects to protect it.

Further information:

IUCN Red List of Threatened Species

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