Zoantharia
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Zoantharia ~Anthozoa.
zoea stage in the larval development of the Malacostraca, which in most cases
appears as the first free stage in the water, after the naupliar development
(two or three stages) in the egg. In some species the zoea is formed during
metamorphosis of the last of a number of free-swimming nauplius stages. The
abdomen of the zoea is already well developed, but the thorax with a few
pairs of appendages is still rudimentary in its hinder part. In crabs the zoea
stage is followed by the first post-larval stage, the megalopa.
zoid free-living eukaryotic cell motile by one or more flagella or cilia. Usually
used for a motile reproductive cell (~Charophyceae and ~Phaeophyta).
zonation marine organisms often occur in belts or depth zones because of gradients in environmental factors. This is easily visible along rocky coasts, with
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Zonation. (After Hedgpeth 1957)