The word “metamorphosis” means “transformation”, that is, a set of physical changes that some animals go through during their development.
Insects such as beetles, flies and butterflies, and amphibians , such as the frog, undergo metamorphosis. Some undergo complete metamorphosis and others, incomplete.
Most insects undergo metamorphosis and, depending on the degree, they are classified into three types: hemimetaboles, holometabols and ametaboles.
Types of metamorphosis
Hemimetaboles
From Greek hemi = medium; metabole = change – incomplete metamorphosis , that is, the animal that hatches from the egg differs little from the adult animal. In hemimetabolic insects, as is the case of the grasshopper , a nymph (chick without developed wings) emerges from the egg, which undergoes successive seedlings until it reaches its adult form (with wings).
Holometabols
From the Greek holos = all – complete metamorphosis , it occurs in three stages: larva – pupa – imago or adult; In this type, the insect is very different from the larva, which undergoes successive seedlings.
An example are butterflies and moths: a larva (caterpillar) emerges from the egg, which weaves a cocoon and enters the immobile phase of pupa (also called, in this case, chrysalis); the adult butterfly, sexually mature, emerges from the cocoon.
Larvae often have a different diet than the adult individual, which avoids competition within the species.
Ametabols
From Greek a = without – without metamorphosis ; case of the moth , in which the egg originates the young animal. It only differs from the adult in size and sexual maturity.
Types of development
There are two types of development: direct and indirect . The right occurs in animals that undergo few structural changes from birth to adulthood, such as humans. The indirect, which occurs in animals that have major structural changes from birth to adulthood, also called metamorphosis.
What is metamorphosis?
From the Greek metamorph the sis , which means transformation, metamorphosis is the change in the shape of the body , in the tissues, in the organs, in growth, in the differentiation of animals and in their ways of life. Animals such as insects, amphibians and mollusks , go through larval stages until they reach adulthood.
There are several types of metamorphoses. One of them occurs when there is a change in habitat and habits, such as amphibians and insects.
Habitat change
The dragonfly, for example, in its first stage of development lives only in water, in adulthood it also begins to live in the terrestrial environment, where it begins to fly.
With the frog, as with the dragonfly, in its tadpole phase it lives only in the aquatic environment, but in adulthood, it also lives in the terrestrial environment, already as an amphibian.
Frog Metamorphosis (Image: depositphotos)
Metamorphosis in insects
With insects, the beginning of their lives is called a larva or nymph – the name depends on the post-embryonic development of each type of insect. There is a gradual or incomplete metamorphosis, which is when the being is born with the shape of an adult being, the birth of wings being the visible landmark to notice the transition.
The flight capacity of many species allows them to easily reach distant food sources, in addition to giving them great power of defense and dispersion. The impermeable epidermis, the type of excretion (which saves water) and the egg covered with shell allow its survival in dry environments.
Holometabolism or complete metamorphosis is when the being goes through four well-marked phases of transition: egg, larva or nymph, pupa and adult. There is also hypermetamorphosis, which is when the insect goes through several larval phases to reach the next transition phase, the pupa.
Transition phases
– Larva: the animal feeds a lot and can spend up to months in this phase. The dengue mosquito leaves its larvae submerged in clean and still water, they feed on organic matter existing in the place. The warmer the water temperature, the faster it will develop.
– Pupa: the animal is at rest and without feeding. In the case of the dengue mosquito, this phase is rapid – between two to four days, time for its exoskeleton to harden – it floats under water and soon moves into adulthood.
Butterflies: complete metamorphosis insects
The pupa shape is one of the transition phases of the butterfly (Photo: depositphotos)
Lepidoptera constitute one of the main insect orders with approximately 146,000 species described. Butterflies in the Neotropical region number between 7,100 and 7,900 species, occurring in Brazil between 3,100 and 3,280 species. They are also called holometabolic insects, as they undergo complete metamorphosis during their development.
Once fertilized, the females look for the plant where they will lay their eggs . These hatch after a few days and caterpillars come out of them , which have powerful chewing mouthpieces and voraciously feed on the leaves of the plant where they are found.
As it grows (up to 10 cm), the caterpillar sheds its skin a few times. The period between two seedlings is called instar. The caterpillar stops eating at the last moment, empties its stomach, immobilizes itself and undergoes the last molt . At this stage, it acquires a darker and thicker coating, assuming the characteristic shape of the pupa (or chrysalis).
The pupa (intermediate stage between the larva and the adult) remains immobile, hanging from tree branches, wrapped in leaves, in holes in the ground or in tree trunks. Then, the most significant transformations of these insects begin.
The larvae tissues are digested, new tissues and organs are formed and the caterpillar is slowly transformed into a butterfly. This process is known as complete metamorphosis, and it ends when the pupal lining breaks and an adult (or imago) emerges from it .
The imago already has all the systems of an adult and, in the case of insects, it is already suitable for reproduction. When its wings are stretched and dry, the butterfly will be ready to fly.
Adult butterflies have sucking mouthpieces and feed on the nectar of flowers, decomposing fruits and minerals found in moist soil.
Summary of Content
In this text you learned that:
- Metamorphosis is the set of physical transformations that an animal goes through.
- The species of animals that undergo metamorphosis are insects and amphibians.
- There are three types of insect metamorphosis: complete, incomplete and non-metamorphosis.
- Butterflies are insects with complete metamorphosis.
- Complete metamorphosis has four phases: egg, larva, pupa and adult.
