Other fish in the sea online dating
These are honeycombed structures composed of calcite microcrystals arranged in a lattice.
They vary in form, with some bearing external granules, tubercles and spines, but most are tabular plates that fit neatly together in a tessellated manner and form the main covering of the aboral surface.
Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea.
Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or "basket stars".
Starfish have tube feet operated by a hydraulic system and a mouth at the centre of the oral or lower surface.
They are opportunistic feeders and are mostly predators on benthic invertebrates.
The fossil record for starfish is ancient, dating back to the Ordovician around 450 million years ago, but it is rather sparse, as starfish tend to disintegrate after death.
Water enters the system through the madreporite, a porous, often conspicuous, sieve-like ossicle on the aboral surface.
Several species have specialized feeding behaviours including eversion of their stomachs and suspension feeding.
They have complex life cycles and can reproduce both sexually and asexually.
The body wall consists of a thin cuticle, an epidermis consisting of a single layer of cells, a thick dermis formed of connective tissue and a thin coelomic myoepithelial layer, which provides the longitudinal and circular musculature.
The dermis contains an endoskeleton of calcium carbonate components known as ossicles.