In nature, some animals when they reach certain stages of their life cycle go through a process called metamorphosis by which they change their physiognomy, physiology and behavior. This process is carried out by many animals of the groups of insects and amphibians.
What is metamorphosis – summary
Metamorphosis is a hormonally regulated process consisting of a series of morphological and structural changes that an organism undergoes after its birth, together with physiological, biochemical and behavioral alterations. There are different types of metamorphosis depending on whether it is complete or incomplete.
Complete metamorphosis or holometabolism is typical of insects (especially winged ones). The phases of complete metamorphosis are four: egg, larva, pupa and adult or imago. Changes that occur between the larval and adult stages require such an amount of energy that they cannot happen all at once. Within the complete metamorphosis, there are types such as hypermetamorphosis, which takes place in certain types of beetles and flies and is characterized by different larval stages.
Incomplete metamorphosis or hemimetabolism is composed of three stages or phases : egg, nymph and adult, the egg state being the only one that presents anatomical and physiological differences. On the other hand, the nymph forms are very similar in the different cases of incomplete metamorphosis. About 10% of insects show hemimetabolism.
The metamorphosis of insects encompasses a series of changes that take place throughout their life cycles at different stages. The development is not the same in all insects, but they differ according to the pattern of structural changes they go through in 3 groups : ametabolos, hemimetabolos and holometabolos.
- Amethabolic insects , which are usually more primitive (such as collembola and silverfish), undergo a slight or “not true” metamorphosis, whereby, from their hatching from an egg, the young forms they grow and undergo periodic molts, gradually increasing in size until they reach the typical dimensions of the adult form and, with it, sexual maturity, but always maintaining a similar appearance.
- Hemimetabolic insects (such as grasshoppers, dragonflies, cockroaches or termites), somewhat more evolutionarily advanced than the previous ones, undergo a gradual or incomplete metamorphosis with its 3 characteristic vital phases (egg, nymph and adult). The nymph or immature insect is the phase that undergoes growth and resembles the adult in appearance, behaviors, and eating habits, but differs from it in size, body proportions, and color pattern. In these cases, development is gradual and takes place through a series of periodic exoskeleton molts. In the case of winged hemimetabolic insects, it is the appearance of functional wings that marks the transition from nymph to adult.
- Holometabolic insects, on the other hand, they undergo a complete metamorphosis, in which each vital stage presents a totally different form from the one that precedes it and the one after it. In this way, the larvae of holometabolic insects differ from adult forms in the absence of wings, as well as in morphology, the habitats they occupy and their food sources. The larvae undergo growth based on numerous and periodic molts, which culminate in a last one that marks the passage to the pupal stage. Although this phase is characterized by a state of apparent inactivity, numerous changes take place in it in which the insect loses larval tissues and organs and develops those of the adult form (including wings), which represents the last stage of the life cycle of the insect. insect. Complete metamorphosis is the most common among insects,butterflies , beetles, moths, ants, flies, bees, or wasps.
It is thought that the metamorphosis in insects occurred with the gradual separation experienced by adults and larvae, as they acquired different life forms and reached a point of life when their characters became genetically independent. In cases where these differences were extreme, an intermediate pupal stage developed to serve as a bridge between the larval stage and that of the imago, the adult insect.
Amphibians go through a process of metamorphosis in their life cycle. In their larval stage, prior to metamorphosis, amphibians live in water and breathe through gills . As they develop, they undergo the process of metamorphosis through which they reach their adult form and go on to live in terrestrial environments, returning to the water only during the spawning season. Thus, most amphibians change from an aquatic larval phase that breathes through gills to an adult terrestrial form that uses lungs in its respiration (or, in other cases, has skin respiration, that is, it performs gas exchange through the skin).
Examples of animals that have metamorphosis
Once we have explained what metamorphosis is, we present some examples, such as the metamorphosis of the toad, the metamorphosis of the frog or the metamorphosis of the butterfly, among others. Here are some examples of metamorphosed animal species :
- Golden Toad
- Red-eyed tree frog
- Red fire ant
- European bee
- Cardboard wasp
- European rhinoceros beetle
- Mariposa monarca
- Rainbow grasshopper