Phylum Phylum EchinodermataEchinodermata

Upper ( ARKARUA )Upper ( ARKARUA )Lower ( left: middle cambrian ctenocyctis carpoid Lower ( left: middle cambrian ctenocyctis carpoid fossil, right: Jurassic sea urchin )fossil, right: Jurassic sea urchin )

What are Echinoderms?What are Echinoderms?

• are a are a phylum of  of marine  animals • they belong to Kingdom Animalia, they belong to Kingdom Animalia,

under Subkingdom Eumetozoa, and under Subkingdom Eumetozoa, and Superphylum DeuterostomiaSuperphylum Deuterostomia

• they are found from intertidal zone to they are found from intertidal zone to abyssal zone of the oceansabyssal zone of the oceans

• largest phylum with no freshwater or largest phylum with no freshwater or terrestrial representativesterrestrial representatives

TaxonomyTaxonomy

  motile  Eleutherozoa

*Asteroidea (*Asteroidea (starfish) ) *Ophiuroidea (*Ophiuroidea (

brittle stars) ) *Echinoidea (*Echinoidea (

sea urchins and  and sand dollars) )

*Holothuroidea (*Holothuroidea (sea cucumbers) )

  sessile  Pelmatazoa

**crinoidscrinoids*extinct paracrinoids*extinct paracrinoids

-> -> two main two main subdivisions of subdivisions of echinodermsechinoderms

the the echinodermsechinoderms(motile (motile eleutherozoa)eleutherozoa)

the the echinodermsechinoderms(sessile (sessile pelmatozoa)pelmatozoa)

Anatomy and Physiology plus Anatomy and Physiology plus Skin and SkeletonSkin and Skeleton• evolved from animals with evolved from animals with bilateral symmetry • the left side of the body grows at the expense of the right the left side of the body grows at the expense of the right

side, which is eventually absorbed. The left side then grows side, which is eventually absorbed. The left side then grows in a in a pentaradially symmetric fashion, in which the body is  symmetric fashion, in which the body is arranged in five parts around a central axis. arranged in five parts around a central axis.

• have a have a mesodermal skeleton composed of calcareous  skeleton composed of calcareous plates or ossicles plates or ossicles

• their epidermis consists of cells responsible for the support their epidermis consists of cells responsible for the support and maintenance of the skeleton, as well as pigment cells, and maintenance of the skeleton, as well as pigment cells, mechanoreceptor cells, which detect motion on the  cells, which detect motion on the animal's surface, and sometimes gland cells which secrete animal's surface, and sometimes gland cells which secrete sticky fluids or even toxins. sticky fluids or even toxins.

• the colours are produced by a variable combination of the colours are produced by a variable combination of coloured pigments, such as the dark melanin, coloured pigments, such as the dark melanin, redcarotinoids, and carotin proteins, which can be blue, redcarotinoids, and carotin proteins, which can be blue, green, or violet. green, or violet.

The Water Vascular SystemThe Water Vascular System

•a network of fluid-filled canals a network of fluid-filled canals that function in gas exchange, that function in gas exchange, feeding, and secondarily in feeding, and secondarily in locomotion. This system is locomotion. This system is derived from both the hydrocoel derived from both the hydrocoel and axocoel. This system may and axocoel. This system may have allowed echinoderms to have allowed echinoderms to function without the gill slits function without the gill slits found in other deuterostomes.found in other deuterostomes.

Evolution Evolution

• first universally accepted echinoderms appear in the Lower first universally accepted echinoderms appear in the Lower Cambrian period (Paul and Smith 1984). Cambrian period (Paul and Smith 1984).

• Based on their bilateral larvae, many zoologists argue that Based on their bilateral larvae, many zoologists argue that echinoderm ancestors were bilateral and that their coelom echinoderm ancestors were bilateral and that their coelom had three pairs of spaces (trimeric).had three pairs of spaces (trimeric).

• Some have proposed that radial symmetry arose in a free-Some have proposed that radial symmetry arose in a free-moving echinoderm ancestor and that sessile groups were moving echinoderm ancestor and that sessile groups were derived several times independently from free-moving derived several times independently from free-moving ancestors. ancestors.

• first echinoderms were sessile, became radial as an first echinoderms were sessile, became radial as an adaptation to that existence, and then gave rise to free-adaptation to that existence, and then gave rise to free-moving groups. moving groups.

Ecological roles of Ecological roles of echinoderms echinoderms • grazing of sea urchins reduces the rate of colonization of bare grazing of sea urchins reduces the rate of colonization of bare

rockrock

• the burrowing of sand dollars and sea cucumbers depleted the the burrowing of sand dollars and sea cucumbers depleted the sea floor of nutrients and encouraged deeper penetration of sea floor of nutrients and encouraged deeper penetration of the sea floor, increasing the depth to which oxygenation occurs the sea floor, increasing the depth to which oxygenation occurs and allowing a more complex ecological tiering to develop.and allowing a more complex ecological tiering to develop.

• Starfish and brittle stars prevent the growth of algal mats on Starfish and brittle stars prevent the growth of algal mats on coral reefs, which would obstruct the filter-feeding constituent coral reefs, which would obstruct the filter-feeding constituent organisms.organisms.

• Some sea urchins can bore into solid rock; this bioerosion can Some sea urchins can bore into solid rock; this bioerosion can destabilise rock faces and release nutrients into the ocean.destabilise rock faces and release nutrients into the ocean.

• many sea cucumbers provide a habitat for parasites, including many sea cucumbers provide a habitat for parasites, including crabs, worms and snailscrabs, worms and snails

Habitat..Habitat..

Benefits to Human…..Benefits to Human…..

•elements of many cuisineselements of many cuisines

•The calcareous tests or shells of The calcareous tests or shells of echinoderms are used as a echinoderms are used as a source of lime by farmers in source of lime by farmers in areas where limestone is areas where limestone is unavailableunavailable

•popular collectiblespopular collectibles

Gracias…Gracias…

Merci……Merci……

Domo Arigatou….Domo Arigatou….

Kamsahamnida….Kamsahamnida….

Thank You…Thank You…

Maraming Salamat….Maraming Salamat….