Page 40 - Amphibian

Very short
tail Metamorphosis Twisting
embryo

Metamorphosis means “change of body form and
NOW A FROGLET appearance.” Amphibians are the only four-limbed,
At 12 weeks, the tail has
been reduced to a bud or land, vertebrates (animals with a backbone) to
and will soon disappear.
The froglets will leave go through a metamorphosis – that is, a change
the water shortly or may from the larval, or tadpole, state into an adult.
have already left. Every
generation re-enacts the This change is easier to see in frogs and toads
water-to-land transition than in other amphibians (pp. 40–41). Frog and
that occurred in the first
amphibians (pp. 8–9). toad larvae look completely different from their
parents. The most notable difference is that a LIFE BEGINS
tadpole has an all-in-one head and body, a long tail, and no legs. 2The first signs of life occur when the
central yolk divides in two, then four, and
Also, a tadpole must live in water to survive. The change from newly then eight – until it looks like a berry
hatched tadpole to fully formed froglet takes about 12 to 16 weeks, inside a jelly coating. The developing
embryo, or tadpole, grows longer and
but this time span is greatly affected by water temperature and food begins twitching. The eggs hatch about
supply. Tadpoles found in colder regions or at high altitudes may six days after fertilization.
overwinter in the tadpole state and not turn into a frog until the
following spring. Not all frogs and toads have a free-living
tadpole. For some, development takes place within an egg Female
European
or inside the body of a parent (pp. 36–37). common
Frog

A pair of
Frog’s egg European
common
frogs in
amplexus

Male
European
common frog

A TIGHT SQUEEZE
1The male frog clasps
the female underneath
him in a tight mating
embrace, called
“amplexus.” The male’s
arms grasp the female
behind her front legs, as
shown here; in other
species, the male may
grasp her in front of the
hind legs or around her
head. Amplexus can last
for several days. In this
position, the male
fertilizes the eggs as they
are laid. They may be laid
singly or in clumps or
strings of over 20,000
(pp. 36–37).