Crustacean larva

Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form.

This is especially true of crustaceans which live as benthic adults (on the sea bed), more-so than where the larvae are planktonic, and thereby easily caught.

The names of these genera have become generalised to cover specific larval stages across wide groups of crustaceans, such as zoea and nauplius.

Antonie van Leeuwenhoek was the first person to observe the difference between larval crustaceans and the adults when he watched the eggs of Cyclops hatching in 1699.

[1] The genus name Nauplius was published posthumously by Otto Friedrich Müller in 1785 for animals now known to be the larvae of copepods.

The nauplius stage (plural: nauplii) is characterised by consisting of only three head segments, which are covered by a single carapace.

[5] The genus Zoea was initially described by Louis Augustin Guillaume Bosc in 1802 for an animal now known to be the larva of a crab.

[5] The post-larva or Megalopae, also found exclusively in the Malacostraca,[5] is characterised by the use of abdominal appendages (pleopods) for propulsion.

This characteristic, which is shared with malacostracan groups such as the Decapoda and Euphausiacea (krill) has been used to suggest a link between Remipedia and Malacostraca.

[9] Young isopod crustaceans hatch directly into a manca stage, which is similar in appearance to the adult.

[13] The larvae show abbreviated development, and hatch with a full complement of adult appendages with the exceptions of the uropods and the first pair of pleopods.

In the South American freshwater genus Aegla, the young hatch from the eggs in the adult form.

[1] Squat lobsters pass through four, or occasionally five, larval states, which have a long rostrum, and a spine on either side of the carapace; the first post-larva closely resembles the adult.

[1] Porcelain crabs have two or three larval stages, in which the rostrum and the posterior spine on the carapace are "enormously long".

Crab prezoea larvae have been found fossilised in the stomach contents of the Early Cretaceous bony fish Tharrhias.

[1] Chalimus (plural chalimi) is a stage of development of a copepod parasite of fish, such as the salmon louse (Lepeophtheirus salmonis).

They were first described by Christian Andreas Victor Hensen in 1887, and named "y-nauplia" by Hans Jacob Hansen, assuming them to be the larvae of barnacles.