Figure 13.18: A species of toad, showing typical characteristics of leathery and warty skin,
and brown coloration. ( 9 )
Cameroon.
Adult frogs are characterized by long hind legs, a short body, webbed digits, protruding eyes
and no tail. They also have a three-chambered heart, which they share with all tetrapods
except birds and mammals. Most frogs have a semi-aquatic lifestyle, but move easily on land
by jumping or climbing. They typically lay their eggs in puddles, ponds or lakes, and their
larvae, or tadpoles, have gills and develop in water.
The reliance of frogs on an aquatic environment for the egg and tadpole stages gives rise
to a variety of mating behaviors that include the calls used by the males of most species
to attract females to the bodies of water chosen for breeding. Frogs are most noticeable by
these calls, which can occur during the day or night.
Frogs are usually well suited to jumping with long hind legs and elongated ankle bones. They
have a short vertebral column, with no more than ten free vertebrae, followed by a fused
tailbone. Skin hangs loosely on the body because of the lack of loose connective tissue(tissue
that surrounds, supports, or connects organs, other tissues, etc.). Skin texture varies, either
smooth, warty or folded.
Frogs have three eyelid membranes: one is transparent to protect the eyes underwater, and
two vary from translucent to opaque. Frogs have atympanum,involved in hearing, on each
side of the head, and in some species, is covered by skin.
Adult frogs are carnivorous and eat mostly arthropods, annelids and gastropods. Adults
have a ridge of very small cone teeth, called maxillary teeth, around the upper edge of the
jaw and they have what are called vomerine teeth on the roof of the mouth. Since they don’t
have teeth on their lower jaw, frogs usually swallow their food whole, and use the teeth they
do have to hold the prey in place. Toads do not have any teeth, and so they must swallow