When Carl Linnaeus set out to classify animals he struck upon
the term Amphibia to describe creatures that
lived "double lives" in the water as well as on
land. While this classification originally included reptiles,
today there are three recognized groups of amphibians -
tailless (e.g. frogs and toads), salamanders, and caecilians.
These cold blooded animals typically live in moist areas and
use their skin in addition to their lungs for oxygen exchange.
The skin is kept moist with mucus to facilitate breathing.
Amphibians are cold blooded and typically live either in the
ground and ground litter or near water. The prominent
exception is toads which are abundant in some deserts. The
primary reproductive mode for amphibians is by laying eggs
which are cared for in a variety of ways - from being carried
around until maturity in the parent's mouth to simply being
laid in a suitable location and left there. A distinguishing
feature of amphibians is that many species go through
distinctive life stages - starting eggs, hatching as water
breathing juveniles with gills and maturing into adults with
air breathing lungs.
Looking back at the fossil record amphibians preceded
reptiles and large dinosaurs in their development and were
likely among the first creatures to make sound by expelling
air from their lungs. Several groups of amphibians, including
some that were much larger than those found today, no longer
exist. The current amphibians developed relatively recently
and are relatively poorly understood and described due to
their secretive habits. Additionally there are fewer
Amphibians (between 2,500 and 3,000) than any other animal
The most recognizable members of this group are frogs and
toads. Inhabitants of marshy areas are likely familiar with
the mating calls of both toads and frogs. Egg masses are
generally laid in water and small tadpoles emerge which look
quite different from adults and breath water through their
gills instead of the lungs of adults and lack legs. As the
tadpole develops into an adult the tail is gradually
"absorbed" by the body and legs begin to appear.
Adults lack gills and can live terrestrially or, in the case
of frogs, both aquatically and terrestrially.
True frogs (family Ranidae) have a distinctive
appearance that is common throughout this family with
streamlined bodies; moist and smooth skin; long, slender legs;
and webbed toes on their hind legs. Frogs are carnivores
eating most anything that moves (including other frogs) and
can be seized by their powerful mouths or quick tongues.
Toads (family Bufonidae, Hylidae or Pelobatidae) at
first look much like their frog cousins, but their morphology
is quite different with shorter legs and slower movement. Dry,
warty skin is the most obvious distinguishing feature of toads
- with some toads having paratoid glands on their skin that
can excrete toxic fluids. The reproductive cycle of toads and
frogs is identical, except toads generally lay their eggs in
shallow, sometimes ephemeral pools of water and morph into
tiny hopping toads after only a brief developmental period.
Toads are primarily terrestrial once they become adults
returning to water only to breed.
Tree toads (they aren't true
frogs) are a rare type of cold blooded animal in that they
live most of their life away from the ground.
Looking more than a bit like lizards with their short legs,
elongated bodies, and tails, salamanders are easily recognized
by their soft, moist skin. Some salamanders spend their entire
lives away from water, laying their eggs in decaying wood
instead, while mud puppies spend their entire lives in water.
Salamanders are rarely seen because they hide from intense
heat and dry conditions while feeding mostly at night. While
some salamanders "lose" their tails this is most
often in response to a threat and to avoid being eaten. Most
salamanders lay eggs, although a few bear live young.
The size of adult salamanders ranges from a scant 2 inches in
length to as much as 5 feet!
Newts are a distinctive class of salamanders that are often
brightly colored and terrestrial. These animals were once
considered to "rain down" because they often emerge
and travel shortly after or during rain storms. Although newt
legs are short they can move quickly and often do.
Can you pick out the
salamander hiding in this pile of brush? The conspicuous dots
are a common feature of salamanders.
Caecilians - Legless
Amphibians (Order: Apoda)
Resembling snakes these amphibians are most common in humid
tropical environments. These peculiar creatures not only
lack legs, but they also have only a one lung and are often
tailless too! Unfortunately, relatively little is known about
caecilians compared to other groups.
|Making the first step through education!