Metamorphosis: what is that? Metamorphosis of the Old World swallowtail (Papilio machaon) (Picture by Jens Stolt). Learn more about the different types of metamorphosis, the origin and sense of these transformations through this article. But, have you not ever wondered why they do this transformation? Which are the sense and the origin of the metamorphosis of insects? This process is named metamorphosis, although its essence is far from that of metamorphosis performed by amphibians. The sharp distinction between stages (best seen in insects) is presumably because a longer transition would leave the juvenile less fit, either at its younger or older ways of life.Most of insects undergo some kind of transformation process during their life cycle in order to reach adulthood -also known as imago phase- (e.g. Their development is packaged into stages, and each stage has adaptations to life at its stage. Therefore they must live a different kind of life before they can live as the adults do. The larvae cannot even swim against the current. There is no way they could live like the adults, which are more or less top predators. The female will produce over 100,000 eggs in a single spawning, and the resulting larvae are quite tiny. A mature Atlantic cod can reach two metres long, and weigh over 200 pounds (96 kgm). The need for metamorphosis is clear when the relative size of eggs and adults is understood. These have the capacity to be transported long distances, and so spread the species around to other places. Most marine invertebrates and many fish have a life cycle with pelagic larvae or even pelagic eggs. Then, larvae join the other plankton, eating and growing before metamorphosing into adults. This increases their chance of reproductive success. Many marine species have evolved a system where they release their eggs and sperm into the water at the same time, and fertilisation takes place in the sea over one or two days. Afterwards, newt larvae start a predatory lifestyle, while tadpoles mostly scrape food off surfaces with their horny tooth ridges. Frogs, toads, and newts all hatch from the egg as larvae with external gills. In typical amphibian development, eggs are laid in water and larvae are adapted to an aquatic lifestyle. Sequence illustrating complete metamorphosis in the cabbage white butterfly, Pieris rapaeĪlmost functional common frog with some remains of the gill sac and a not fully developed jaw.Hymenoptera: bees, wasps, ants, sawflies. Many insects have a life cycle of egg-larva-pupa-adult. When the pupa opens, the adult insect comes out. Moth pupae ( plural of pupa) are inside cocoons. The pupa is a special time when the insect is changing into an adult that will look very different from the larva or the pupa. When the larva has grown it changes into a pupa. The larva looks like a worm and eats and eats so that it can grow much bigger. These insects start as eggs, which are very small. Insects that have complete metamorphosis have four life stages. Some insects that have a life cycle of egg-nymph-adult are: Nymphs that live in water are called naiads. These nymphs usually have gills and look very different from the adults they will turn into. Some insect nymphs are aquatic, which means they live in water. Finally, it changes into a mature adult with wings. The nymph grows through stages called instars, shedding its 'skin' ( epicuticle) at each stage ( ecdysis). Most of the time, the nymph looks similar to the adult, but it is smaller, may have different colouration, and does not have wings. When the egg hatches, a larva or nymph comes out. These insects start as eggs, which are usually very small. Insects who go through simple (or incomplete) metamorphosis have three life stages. There are two main types of metamorphosis in insects: simple metamorphosis or hemimetabolism, and complete metamorphosis or holometabolism. Six stages of development, from newly hatched nymph to fully winged adult.
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