Evolutionary significance of invertebrate larval stages
Answers
The larva's appearance is generally very different from the adult form (e.g. caterpillars and butterflies) including different unique structures and organs that do not occur in the adult form. Their diet may also be considerably different.
Larvae are frequently adapted to environments separate from adults. For example, some larvae such as tadpoles live almost exclusively in aquatic environments, but can live outside water as adult frogs. By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population.
Animals in the larval stage will consume food to fuel their transition into the adult form. In some species like barnacles, adults are immobile but their larvae are mobile, and use their mobile larval form to distribute themselves.
Some larvae are dependent on adults to feed them. In many eusocial Hymenoptera species, the larvae are fed by female workers. In Ropalidia marginata (a paper wasp) the males are also capable of feeding larvae but they are much less efficient, spending more time and getting less food to the larvae.
The larvae of some species (for example, some newts) can become pubescent and do not develop further into the adult form. This is a type of neoteny.
Eurosta solidaginis Goldenrod Gall Fly larva
It is a misunderstanding that the larval form always reflects the group's evolutionary history. This could be the case, but often the larval stage has evolved secondarily, as in insects.[citation needed] In these cases the larval form may differ more than the adult form from the group's common origin.
Selected types of larvae
More information: Animal, Name of larvae …
Insect larvae
Within Insects, only Endopterygotes show different types of larvae. Several classifications have been suggested by many entomologists, and following classification is based on Antonio Berlese classification in 1913. There are four main types of endopterygote larvae types:
Apodous larvae – no legs at all and are poorly sclerotized. Based on sclerotization, three apodous forms are recognized.
Eucephalous – with well sclerotized head capsule. Found in Nematocera, Buprestidae and Cerambycidae families.
Hemicephalus – with a reduced head capsule, retractable in to the thorax. Found in Tipulidae and Brachycera families.
Acephalus – without head capsule. Found in Cyclorrhapha
Protopod larvae – larva have many different forms and often unlike a normal insect form. They hatch from eggs which contains very little yolk. Ex. first instar larvae of parasitic hymenoptera.
Polypod larvae – also known as eruciform larvae, these larva have abdominal prolegs, in addition to usual thoracic legs. They poorly sclerotized and relatively inactive. They live in close contact with the food. Best example is caterpillars of lepidopterans.
Oligopod larvae – have well developed head capsule and mouthparts are similar to the adult, but without compound eyes. They have six legs. No abdominal prolegs. Two types can be seen:
Campodeiform – well sclerotized, dorso-ventrally flattened body. Usually long legged predators with prognathos mouthparts. (lacewing, trichopterans, mayflies and some coleopterans).
Scarabeiform – poorly sclerotized, flat thorax and abdomen. Usually short legged and inactive burrowing forms. (Scarabaeoidea and other coleopterans).
Answer:
By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population. Animals in the larval stage will consume food to fuel their transition into the adult form.
Explanation:
Evolution, published for the Society for the Study of Evolution, is the premier publication devoted to the study of organic evolution and the integration of the various fields of science concerned with evolution. The journal presents significant and original results that extend our understanding of evolutionary phenomena and processes.
- With the possible exception of inarticulate brachiopods, members of the oligomer (brachiopods, ectoprocts, phoronids, hemichordates, echinoderms) do not reacquire a planktotrophic larval phase once it is lost. The feeding larval stages of inarticulate brachiopods, echinoderms, and ectoprocts evolved in the Ordovician at the latest and probably originated much earlier.
- For functional reasons, larval feeding mechanisms are more readily lost than gained in the oligomer. Loss of obligate larval planktotrophic is accompanied by an extensive loss of larval structures used in feeding.
Hence, By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population. Animals in the larval stage will consume food to fuel their transition into the adult form.
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