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    Invertebrate: Enchinoderm Echinoderm, Any of A Variety of

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    Luisa Marie Casas
    Echinoderms are marine invertebrates characterized by a hard, spiny exterior skeleton. They display radial symmetry with multiple arms radiating from a central disc. Echinoderms lack organs like a heart, brain or eyes. They reproduce through both sexual and asexual means, with larvae that are bilaterally symmetrical settling and developing typical echinoderm features. Some echinoderms exhibit carnivorous, detritus-feeding or plankton-feeding behaviors.

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    Invertebrate: Enchinoderm Echinoderm, Any of A Variety of

    Uploaded by

    Luisa Marie Casas
    29 views2 pages
    Echinoderms are marine invertebrates characterized by a hard, spiny exterior skeleton. They display radial symmetry with multiple arms radiating from a central disc. Echinoderms lack organs like a heart, brain or eyes. They reproduce through both sexual and asexual means, with larvae that are bilaterally symmetrical settling and developing typical echinoderm features. Some echinoderms exhibit carnivorous, detritus-feeding or plankton-feeding behaviors.

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    Echinoderms are marine invertebrates characterized by a hard, spiny exterior skeleton. They display radial symmetry with multiple arms radiating from a central disc. Echinoderms lack organs like a heart, brain or eyes. They reproduce through both sexual and asexual means, with larvae that are bilaterally symmetrical settling and developing typical echinoderm features. Some echinoderms exhibit carnivorous, detritus-feeding or plankton-feeding behaviors.

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    29 views2 pages

    Invertebrate: Enchinoderm Echinoderm, Any of A Variety of

    Uploaded by

    Luisa Marie Casas
    Echinoderms are marine invertebrates characterized by a hard, spiny exterior skeleton. They display radial symmetry with multiple arms radiating from a central disc. Echinoderms lack organs like a heart, brain or eyes. They reproduce through both sexual and asexual means, with larvae that are bilaterally symmetrical settling and developing typical echinoderm features. Some echinoderms exhibit carnivorous, detritus-feeding or plankton-feeding behaviors.

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    © All Rights Reserved
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    Enchinoderm

    Echinoderm, any of a variety of invertebrate marine animals belonging to the phylum


    Echinodermata, characterized by a hard, spiny covering or skin

    Echinoderms are characterized by radial symmetry, several arms (5 or more, mostly grouped 2
    left - 1 middle - 2 right) radiating from a central body (= pentamerous). The body actually
    consists of five equal segments, each containing a duplicate set of various internal organs. They
    have no heart, brain, nor eyes, but some brittle stars seem to have light sensitive parts on their
    arms. Their mouth is situated on the underside and their anus on top (except feather stars, sea
    cucumbers and some urchins). Echinoderms are protected through their spiny skins and spines.
    But they are still preyed upon by shells (like the triton shell), some fish (like the trigger fish),
    crabs and shrimps and by other echinoderms like starfish which are carnivorous. Many
    echinoderms only show themselves at night (= nocturnal), therefore reducing the threat from the
    day time predators.

    They occur in various habitats from the intertidal zone down to the bottom of the deep sea
    trenches and from sand to rubble to coral reefs and in cold and tropical seas.

    Some echinoderms are carnivorous (for example starfish) others are detritus foragers (for
    example some sea cucumbers) or planktonic feeders (for example basket stars).

    Reproduction is carried out by the release of sperm and eggs into the water. Most species
    produce pelagic (= free floating) planktonic larvae which feed on plankton. These larvae are
    bilaterally symmetrical, unlike their parents (illustration of a larvae of a sea star below). When
    they settle to the bottom they change to the typical echinoderm features. Enchinoderms can be
    both sexual and asexual.

    In sexual reproduction, eggs (up to several million) from females and spermatozoa from males
    are shed into the water (spawning), where the eggs are fertilized. Most echinoderms spawn on an
    annual cycle, 

    Asexual reproduction in echinoderms usually involves the division of the body into two or more
    parts (fragmentation) and the regeneration of missing body parts. Fragmentation is a common
    method of reproduction used by some species of asteroids, ophiuroids, and holothurians, and in
    some of these species sexual reproduction is not known to occur. Successful fragmentation and
    regeneration require a body wall that can be torn and an ability to seal resultant wounds.

    Echinoderms can regenerate missing limbs, arms, spines - even intestines (for example sea
    cucumbers). Some brittle stars and sea stars can reproduce asexually by breaking a ray or arm or
    by deliberately splitting the body in half. Each half then becomes a whole new animal.

    Echinoderms serve as hosts to a large variety of symbiotic organisms including shrimps, crabs,


    worms, snails and even fishes.

    https://www.britannica.com/animal/echinoderm

    http://www.starfish.ch/reef/echinoderms.html

    digestive

    In many, the mouth is on the underside and the anus on the top surface of the animal. Sea stars
    can push their stomachs outside of their body and insert it into its prey allowint them to digest
    the food externally. This ability allows sea stars to hunt prey that are much larger than its mouth
    would otherwise allow.

    Nervous

    They have tiny eyespots at the end of each arm which only detect light or dark. Some of their
    tube feet, are also sensitive to chemicals and this allows them to find the source of smells, such
    as food.

    Circulatory

    The network contains a central ring and areas which contain the tube feet which stretch along the
    body or arms. The tube feet poke through holes in the skeleton and can be extended or
    contracted. They do not have a true heart and the blood often lacks any respiratory pigment (pike
    haemoglobin).

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