Larva

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Larva of the Papilio xuthus butterfly Papilio xuthus Larva 2011-10-15.jpg
Larva of the Papilio xuthus butterfly

A larva ( /ˈlɑːrvə/ ; plural larvae /ˈlɑːrv/ ) 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.

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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 different environments than 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 organisms like polychaetes and barnacles, adults are immobile but their larvae are mobile, and use their mobile larval form to distribute themselves. [1] [2]

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. [3]

The larvae of some organisms (for example, some newts) can become pubescent and do not develop further into the adult form. This is a type of neoteny. [4]

Eurosta solidaginis Goldenrod Gall Fly larva Eurosta solidaginis larva.jpg
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. [5] [6] In these cases the larval form may differ more than the adult form from the group's common origin. [7]

Selected types of larvae

AnimalName of larvae
Porifera (sponges)coeloblastula (= blastula, amphiblastula), parenchymula (= parenchymella, stereogastrula)
Heterocyemida Wagener's larva
Dicyemida infusoriform larva
Cnidarians planula (= stereogastrula), actinula
Ctenophora cydippid larvae
Platyhelminthes Turbellaria: Müller's larva, Götte’s larva;
Trematoda: miracidium, sporocyst, redia, cercaria;
Monogenea: oncomiracidium;
Cestoda: cysticercus, cysticercoid, oncosphere (or hexacanth), coracidium, plerocercoid
Annelida nectochaete, polytroch
Nematoda Dauer larva, microfilaria
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) [8]
Arthropoda: Xiphosura euproöps larva ("trilobite larva")
Arthropoda: Pycnogonida protonymphon
Crustaceans General: nauplius, metanauplius, protozoea, antizoea, pseudozoea, zoea, postlarva, cypris, primary larva, mysis
Decapoda: zoea
Rhizocephala: kentrogon
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) Ichthyoplankton
Fish: Petromyzontiformes (lamprey) ammocoete
Fish: Anguilliformes (eels) leptocephalus
Amphibians tadpole, polliwog

Insect larvae

The larvae of the Hercules beetle (Dynastes hercules) are among the largest of any species of insect Hercules beetle (larva).jpg
The larvae of the Hercules beetle (Dynastes hercules) are among the largest of any species of insect
Campodeiform larva of Micromus sp. Micromus.aphids.2.jpg
Campodeiform larva of Micromus sp.

Within Insects, only Endopterygotes show complete metamorphosis, including a distinct larval stage. [9] [10] Several classifications have been suggested by many entomologists, [11] [12] and following classification is based on Antonio Berlese classification in 1913. There are four main types of endopterygote larvae types: [13] [14]

  1. Apodous larvae – no legs at all and are poorly sclerotized. Based on sclerotization. All Apocrita are apodous. Three apodous forms are recognized.
  2. Protopod larvae – larva have many different forms and often unlike a normal insect form. They hatch from eggs which contain very little yolk. E.g. first instar larvae of parasitic hymenoptera.
  3. Polypod larvae – also known as eruciform larvae, these larvae have abdominal prolegs, in addition to usual thoracic legs. They are poorly sclerotized and relatively inactive. They live in close contact with their food. Best example is caterpillars of lepidopterans.
  4. 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 prognathous 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

Related Research Articles

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Beetles are insects that form the order Coleoptera, in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 described species, is the largest of all orders, constituting almost 40% of described insects and 25% of all known animal life-forms; new species are discovered frequently, with estimates suggesting that there are between 0.9 and 2.1 million total species. Found in almost every habitat except the sea and the polar regions, they interact with their ecosystems in several ways: beetles often feed on plants and fungi, break down animal and plant debris, and eat other invertebrates. Some species are serious agricultural pests, such as the Colorado potato beetle, while others such as Coccinellidae eat aphids, scale insects, thrips, and other plant-sucking insects that damage crops.

<span class="mw-page-title-main">Hymenoptera</span> Order of insects comprising sawflies, wasps, bees, and ants

Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are parasitic. Females typically have a special ovipositor for inserting eggs into hosts or places that are otherwise inaccessible. This ovipositor is often modified into a stinger. The young develop through holometabolism —that is, they have a wormlike larval stage and an inactive pupal stage before they mature.

<span class="mw-page-title-main">Metamorphosis</span> Profound change in body structure during the postembryonic development of an organism

Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some insects, fish, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, which is often accompanied by a change of nutrition source or behavior. Animals can be divided into species that undergo complete metamorphosis ("holometaboly"), incomplete metamorphosis ("hemimetaboly"), or no metamorphosis ("ametaboly").

<span class="mw-page-title-main">Echinoderm</span> Exclusively marine phylum of animals with generally 5-point radial symmetry

An echinoderm is any member of the phylum Echinodermata. The adults are recognisable by their radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine phylum. The first definitive echinoderms appeared near the start of the Cambrian.

<span class="mw-page-title-main">Lepidoptera</span> Order of insects including moths and butterflies

Lepidoptera is an order of insects that includes butterflies and moths. About 180,000 species of the Lepidoptera are described, in 126 families and 46 superfamilies, 10 percent of the total described species of living organisms. It is one of the most widespread and widely recognizable insect orders in the world. The Lepidoptera show many variations of the basic body structure that have evolved to gain advantages in lifestyle and distribution. Recent estimates suggest the order may have more species than earlier thought, and is among the four most speciose orders, along with the Hymenoptera, Diptera, and Coleoptera.

<span class="mw-page-title-main">Pupa</span> Life stage of some insects undergoing transformation

A pupa is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages thereof being egg, larva, pupa, and imago. The processes of entering and completing the pupal stage are controlled by the insect's hormones, especially juvenile hormone, prothoracicotropic hormone, and ecdysone. The act of becoming a pupa is called pupation, and the act of emerging from the pupal case is called eclosion or emergence.

<span class="mw-page-title-main">Sawfly</span> Suborder of insects

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<span class="mw-page-title-main">Caddisfly</span> Order of caddisflies

The caddisflies, or order Trichoptera, are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the basis of the adult mouthparts. Integripalpian larvae construct a portable casing to protect themselves as they move around looking for food, while Annulipalpian larvae make themselves a fixed retreat in which they remain, waiting for food to come to them. The affinities of the small third suborder Spicipalpia are unclear, and molecular analysis suggests it may not be monophyletic. Also called sedge-flies or rail-flies, the adults are small moth-like insects with two pairs of hairy membranous wings. They are closely related to the Lepidoptera which have scales on their wings; the two orders together form the superorder Amphiesmenoptera.

<span class="mw-page-title-main">Veliger</span> Larval stage of some snails

A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells.

Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago. Holometabolism is a synapomorphic trait of all insects in the superorder Endopterygota. Immature stages of holometabolous insects are very different from the mature stage. In some species the holometabolous life cycle prevents larvae from competing with adults because they inhabit different ecological niches. The morphology and behavior of each stage are adapted for different activities. For example, larval traits maximize feeding, growth, and development, while adult traits enable dispersal, mating, and egg laying. Some species of holometabolous insects protect and feed their offspring. Other insect developmental strategies include ametabolism and hemimetabolism.

<span class="mw-page-title-main">Ceratopogonidae</span> Family of flies commonly known as no see ums, or biting midges

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<span class="mw-page-title-main">Stratiomyidae</span> Family of flies

The soldier flies are a family of flies. The family contains over 2,700 species in over 380 extant genera worldwide. Adults are found near larval habitats, which are found in a wide array of locations, mostly in wetlands, damp places in soil, sod, under bark, in animal excrement, and in decaying organic matter. The Stratiomyinae are a different subgroup that tends to have an affinity to aquatic environments. They are diverse in size and shape, though they commonly are partly or wholly metallic green, or somewhat wasplike mimics, marked with black and yellow or green and sometimes metallic. They are often rather inactive flies which typically rest with their wings placed one above the other over the abdomen.

The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa, trochanter, femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus, patella.

<span class="mw-page-title-main">Arthropod exoskeleton</span>

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<span class="mw-page-title-main">Crustacean larva</span> Crustacean larval and immature stages between hatching and adult form

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