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Echinoderms are numerous invertebrates whose adults play an important role in benthic ecosystems, while the larvae are a major component of the plankton. Among the ecological roles of adults are the grazing of sea urchins, the sediment processing of heart urchins, and the suspension and deposit feeding of crinoids and sea cucumbers.
Like all echinoderms, adult sea urchins have ... An unusual feature of sea urchin development is the replacement of the larva's bilateral symmetry by the adult's ...
The name dipleurula, two-sided, was given to stress the fact that the larva of the typically five-rayed, (approximately) radially symmetric adults show a bilateral structure. It was this bilateral structure of the larvae that identified echinoderms as bilaterian animals. The original doliolaria schema shows a benthic, crawling, larva. However ...
The larvae of echinoderms have bilateral symmetry, but during metamorphosis this is replaced with radial symmetry, typically pentameric. [12] Adult echinoderms are characterized by having a water vascular system with external tube feet and a calcareous endoskeleton consisting of ossicles connected by a mesh of collagen fibres. [95]
Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. [5] They live in both shallow water [6] and in depths of over 9,000 metres (30,000 ft). [7] Adult crinoids are characterised by having the mouth located on the upper surface.
A larva (/ ˈ l ɑːr v ə /; pl.: larvae / ˈ l ɑːr v iː /) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects , some arachnids , amphibians , or cnidarians typically have a larval phase of their life cycle .
Echinus is a genus of sea urchins.Sea urchins are echinoderms that are typically spherical or flattened with a covering of spine-like structures. Sea urchins tend to be important members of their ecosystems by grazing on other organisms and stabilizing populations.
In sexual reproduction, they engage in broadcast spawning, which is releasing eggs and sperm in the water where external fertilization occurs. The fertilized egg turns into planktonic larvae that drift before settling on the ocean floor; then, they mature into adult brittle stars. During asexual reproduction, they reproduce through regeneration.