What is Larva?
[[File:Zebrarupsen op Jacobskruiskruid Senecio jacobaea (1).jpg|thumb|Caterpillars]] [[File:Echinocardium cordatum (Pennant, 1777) early pluteus width ca.JPEG|thumb|An echinoderm ''pluteus'' larva]] [[File:Haliotis asinina trochophore.jpg|thumb|A ''trochophore'' larva]] Many animals develop in separate stages. A '''larva''' (plural: ''larvae'') develops from the [[egg (biology)|egg]] in those [[animal]]s. It is a separate life stage from the [[adult]] reproductive stage. A larva does not look like the [[adult]] animal, and changes shape (known as [[metamorphosis]]) as it grows up. There may be several larval stages before the adult form. [[Tadpole]]s, [[maggot]]s and [[caterpillar]]s are larvae. [[Ocean|Marine]] organisms with a larval stage often release large numbers of [[ovum|eggs]] and [[sperm]]s into the water column. After [[fertilisation]], the eggs develop into tiny larvae. The larvae develop and grow for some time before metamorphosing into adults. Most marine [[invertebrates]] and many [[fish]] have a [[pelagic]] larval stage or pelagic eggs. These live in the [[plankton]], and may be transported long distances. == Evolutionary theory == Probably the most widely accepted theory explaining the evolution of larval stages is the need for ''dispersal''. [[Sessile]] organisms such as [[barnacle]]s and tunicates, and sea-floor groups like [[mussel]]s and [[crab]]s, need some way to move their young into new territory, since they cannot move long distances as adults. Many species have relatively long pelagic larval stages (how long a larva is in the water column).<ref> Brothers E.B., D.M. Williams, and P.F. Sale. 1983. Length of larval life n twelve families of fishes at “One Tree Lagoon,” Great Barrier Reef, Australia. ''Marine Biol''. '''76''': 319-324.</ref><ref> Scheltema R.S. 1986. On dispersal and planktonic larvae of [[benthos|benthic]] invertebrates: an eclectic overview and summary of problems. ''Bull. Mar. Sci''. '''39''': 290-322.</ref> During this time, larvae feed and grow, and many species move