As children, many of us learn about the wondrous
process by which a caterpillar morphs into a butterfly. The story usually
begins with a very hungry caterpillar hatching from an egg. The caterpillar, or
what is more scientifically termed a larva, stuffs itself with leaves, growing
plumper and longer through a series of molts in which it sheds its skin. One
day, the caterpillar stops eating, hangs upside down from a twig or leaf and
spins itself a silky cocoon or molts into a shiny chrysalis. Within its
protective casing, the caterpillar radically transforms its body, eventually
emerging as a butterfly or moth.
But what does that radical transformation entail?
How does a caterpillar rearrange itself into a butterfly? What happens inside a
chrysalis or cocoon?
First, the caterpillar digests itself, releasing
enzymes to dissolve all of its tissues. If you were to cut open a cocoon or
chrysalis at just the right time, caterpillar soup would ooze out. But the
contents of the pupa are not entirely an amorphous mess. Certain highly
organized groups of cells known as imaginal discs survive the digestive
process. Before hatching, when a caterpillar is still developing inside its
egg, it grows an imaginal disc for each of the adult body parts it will need as
a mature butterfly or moth—discs for its eyes, for its wings, its legs and so
on. In some species, these imaginal discs remain dormant throughout the
caterpillar's life; in other species, the discs begin to take the shape of
adult body parts even before the caterpillar forms a chrysalis or cocoon. Some
caterpillars walk around with tiny rudimentary wings tucked inside their
bodies, though you would never know it by looking at them.
Once a caterpillar has disintegrated all of its
tissues except for the imaginal discs, those discs use the protein-rich soup
all around them to fuel the rapid cell division required to form the wings,
antennae, legs, eyes, genitals and all the other features of an adult butterfly
or moth. The imaginal disc for a fruit fly's wing, for example, might begin
with only 50 cells and increase to more than 50,000 cells by the end of
metamorphosis. Depending on the species, certain caterpillar muscles and
sections of the nervous system are largely preserved in the adult butterfly.
One study even suggests that moths remember what they learned in later stages
of their lives as caterpillars.
UNIVERSITAS GUNADARMA
www.gunadarma.ac.id
www.studentsite.gunadarma.ac.id
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