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Larva

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For other uses, see Larva (disambiguation).
Larva of Papilio xuthus, butterfly

A larva (plural larvae /ˈlɑːrviː/) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.

The larva's appearance is generally very different from the adult form (e.g. caterpillars and butterflies). A larva often has 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.[1]

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. In these cases the larval form may differ more than the adult form from the group's common origin.[citation needed]

Selected types of larvae

Animal Name of larva
Porifera (sponges) coeloblastula larvae (= blastula larvae), parenchymula (= parenchymella), amphiblastula
Heterocyemida Wagener's larva
Dicyemida infusoriform larva
Cnidarians planula, actinula
Ctenophora cydippid larvae
Platyhelminthes Götte’s larva, Müller's larva, miracidium, oncomiracidium, coracidium, redia, cercaria
Annelida nectochaeta, polytroch
Nematoda Dauer larva
Sipuncula pelagosphera larva
Ectoprocta cyphonautes, vesiculariform larvae
Nematomorpha nematomorphan larva
Phoronids actinotroch
Cycliophora pandora, chordoid larva
Nemertea pilidium, Iwata larva, Desor larva
Acanthocephala acanthor
Locifera Higgins larva
Brachiopoda lobate larva
Priapula loricate larva
Certain molluscs, annelids, nemerteans and sipunculids trochophore
Certain molluscs veliger
Mollusca: freshwater Bivalvia (mussels) glochidium
Arthropoda: †Trilobita protaspis (unjointed), meraspis (increasing number of joints, but 1 less than the holaspis), holaspis (=adult)[2]
Arthropoda: Xiphosura euproöps larva ("trilobite larva")
Arthropoda: Pycnogonida protonymphon
Crustaceans nauplius, metanauplius, protozoea, antizoea, pseudozoea, zoea, postlarva, cypris, primary larva, mysis
Crustacea: Decapoda zoea
Insecta: Lepidoptera (butterflies and moths) caterpillar
Insecta: Beetles grub
Insecta: Flies, Bees, Wasps maggot
Insecta: Mosquitoes wriggler
Deuterostomes dipleurula (hypothetical larva)
Echinodermata bipinnaria, vitellaria, brachiollaria, pluteus, ophiopluteus, echinopluteus, auricularia
Hemichordata tornaria
Urochordata tadpole (does not feed, technically a "swimming embryo")
Fish (generally) larva
Fish: Petromyzontiformes (lamprey) ammocoete
Fish: Anguilliformes (eels) leptocephalus
Amphibians tadpole, polliwog
Mammal Puggle/Joey

Insect Larva

Within Insects, only Endopterygotes show different types of larvae.[3] Several classifications have been suggested by many entomologists,[4] and following classification is based on Antonio Berlese classification in 1913. There are four main types of endopterygote larvae types:[5]

  • Apodous larvae - no legs at all and are poorly sclerotized. Based on sclerotization, three apodous forms are recognized.
  • 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).

See also

References

  1. ^ Sen, R; Gadagkar, R (2006). "Males of the social wasp Ropalidia marginata can feed larvae, given an opportunity". Animal Behavior. 71: 345–350. doi:10.1016/j.anbehav.2005.04.022.
  2. ^ Moore, R.C. (1959). Arthropoda I - Arthropoda General Features, Proarthropoda, Euarthropoda General Features, Trilobitomorpha. Treatise on Invertebrate Paleontology. Vol. Part O. Boulder, Colorado/Lawrence, Kansas: Geological Society of America/University of Kansas Press. pp. O121, O122, O125. ISBN 0-8137-3015-5.
  3. ^ "Recognizing Insect Larval Types". University of Kentucky. Retrieved 28 April 2016.
  4. ^ "Insect Larval Forms". About.com. Retrieved 28 April 2016.
  5. ^ "Types of Insect Larva". Agri info. Retrieved 28 April 2016.

Bibliography

  • Brusca, R. C. & Brusca, G. J. (2003). Invertebrates (2nd ed.). Sunderland, Mass. : Sinauer Associates.
  • Hall, B. K. & Wake, M. H. (1999, eds.). The Origin and Evolution of Larval Forms. San Diego: Academic Press.
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