Amphibians (class Amphibia) are ectothermic (cold-blooded) vertebrates that do not maintain their body temperature through internal physiological processes. Next to their blood, the coolest thing about amphibians is metamorphosis: most begin life as an egg laid in water, from which they hatch as aquatic larvae. Throughout the larvae phase they undergo metamorphosis to become land-dwelling, air-breathing adults with lungs. Once on land, amphibians are restricted to moist habitats because of the need to keep their skin damp. They are not found in the seas, unless you count one or two frog species that live in brackish waters in mangrove swamps. With a few exceptions, adult amphibians are predators that feed on virtually anything that moves that they can swallow, such as beetles, caterpillars, earthworms and spiders. Amphibians usually swallow prey whole, but may chew on it lightly first to subdue it. (Little facts like this make me really appreciate being at the top of the food chain.)
With their complex reproductive needs and permeable skins, amphibians are often ecological indicators and in recent decades there has been a dramatic decline in amphibian populations for many species around the globe.
There are three modern orders of amphibians:
Anura (frogs and toads). Their aquatic larvae, tadpoles, have tails and internal gills; both of these features are lost when they morph into tailless adults with lungs. Frog populations have declined significantly: more than one third of species are threatened with extinction and over one hundred and twenty are believed to have become extinct since the 1980s.
Caudata/Urodela (salamanders/newts). Unique among vertebrates, they are capable of regenerating lost limbs and other body parts. Salamanders have shown a significant decline in numbers in the last few decades of the 20th century.
Terribilis frogs are endemic to the rainforests on the Pacific coast of Colombia. They’re tiny and cute, but lethally toxic—in fact they may be the most poisonous of any living animal. Their skin is densely coated in alkaloid poison, which prevents nerves from transmitting impulses, leaving the muscles in an inactive state of contraction and potentially leading to heart failure. For local indigenous cultures, such as the Emberá people in Colombia’s rainforest, these frogs are the main source of poison for the darts they use to hunt their food. The Emberá people carefully expose the frog to the heat of a fire, and it exudes small amounts of poisonous fluid. The tips of arrows and darts are then soaked in the fluid—and the weapons remain deadly for over two years.
These animals are highly social: immune to their own poison, golden poison frogs typically live in groups of six, and interact constantly with each other via calls and gestures. One of the most intelligent anurans, captives can recognize human caregivers after exposure for a few weeks. They are extremely successful tongue hunters, and almost never miss a strike.
Golden poison frogs are curious, bold, and seemingly aware of the fact that they are next to invulnerable, making no attempt to conceal themselves and actually flaunting their beautiful colors to intimidate predators. (They sound like assholes.) They are sexy little critters, too: golden poison frogs demonstrate tactile courtship during reproduction, each partner stroking its mate’s head, back, flanks, and cloacal areas prior to egg deposition. Hawt.
leucistic axolotyl (Ambystoma mexicanum)
melanoid axolotyl (Ambystoma mexicanum)
[PHOTO Stan Shebs]
Unlike their close cousins the Tiger Salamanders, axolotls remain aquatic and do not metamorphosize into land dwellers. This metamorphic failure is apparently caused by a lack of thyroid stimulating hormone which triggers the transformation in other salamanders. Interestingly, if injected with iodine axolotls will indeed metamorphosize, although they will scarcely live five years if they do. (They have been known to metamorphosize in the wild, but this is extremely rare.) Axolotls typically live 10-15 years and reach 6-9 inches in length. A captive specimen in Paris is said to have lived for 25 years.
They used to be found in Lake Chalco in central Mexico, but that lake no longer exists: it was artificially drained to avoid periodic flooding that adversely affected nearby populations of homo sapiens. Now wild axolotls can be found only in Lake Xochimilco near Mexico City, and they are a critically endangered species near extinction due to urbanization and polluted waters. Non-native fish, such as African tilapia and Asian carp, have also recently been introduced to these waters and have been eating the axolotls’ young, as well as its primary source of food. Roasted axolotl is considered a delicacy in Mexico, further shrinking their numbers. : (
There are four different colors of axolotl: wildtype (brown, usually with spots), melanoid (black), leucistic (pale pink with black eyes) and albino (golden, tan or pale pink with pink eyes).
Axolotls can regenerate entire lost limbs and other organs, and some have been found to regenerate lost parts of their brains. One cannot help but wonder if further study into this particular phenomenon might someday lead to a cure for conservatism.
Black Rain Frog (Breviceps fuscus)
Photo: ©2004 Robert C. Drewes (with kind permission).
This species was brought to our attention via an article in The Dodo entitled Meet the World’s Grumpiest Frog, which contains several closeup portraits of the little critter making a bunch of frowny faces. But it turns out that this frog is not particularly grumpy at all, neither in temperament nor, in our opinion, facial cues. Like many animals do when they’re frightened or under attack, the black rain frog will puff itself up in size in an attempt to ward off its enemies, rendering it actually quite adorable:
Photo: Beneke74 via iSpot.
The black rain frog is native to the Southern coasts of Africa, where it hangs out in temperate forests among shrubby vegetation. The species burrows into the forest floor and make tunnels as deep as 6 inches (150 mm) underground. The male stays down there to guard developing offspring—hey, that’s a nice trick you have there, female B.fuscus! (These feminist frogs would obviously make terrible Baptists.) Unlike most frog species, black rain froglets grow to maturity without a water-dwelling phase. And the ladyfrogs have another trick: adhesive amplexus. What the hell is “adhesive amplexus,” you ask? Well, during mating season the female secretes from specialized glands on her back a sticky substance that keeps the male from slipping off of her during intercourse. Until she is damn good and ready, and decides she has had enough. Hahaha. Awesome.
Mostly nocturnal ground dwellers well-adapted to living in underground burrows, black rain frogs fill a unique niche in their environment and thus do not compete extensively with other species in the forest ecosystem. They are threatened by habitat loss, although fortunately, not urgently so.