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Echinoderms “Life with Spiny Skin”. Worms, mollusks, and arthropods all have bilateral symmetry. Worms, mollusks, and arthropods all have bilateral symmetry.

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Presentation on theme: "Echinoderms “Life with Spiny Skin”. Worms, mollusks, and arthropods all have bilateral symmetry. Worms, mollusks, and arthropods all have bilateral symmetry."— Presentation transcript:

1 Echinoderms “Life with Spiny Skin”

2 Worms, mollusks, and arthropods all have bilateral symmetry. Worms, mollusks, and arthropods all have bilateral symmetry. So do echinoderm larvae. So do echinoderm larvae. What kind of symmetry do adult echinoderms have? What kind of symmetry do adult echinoderms have? Radial symmetry Radial symmetry What other animal phyla display radial symmetry? A Radical Radial Change Bipinnaria larvae (sea star)

3 Five Alive Most echinoderms show pentamerous radial symmetry. This means there are usually five arms (or legs) or they are found in multiples of five

4 Spiny Skin – but only the skin! Echinoderm means “spiny skin.” Echinoderm means “spiny skin.” Echinoderms typically have: Echinoderms typically have: well developed digestive tracts well developed digestive tracts well-developed coelom well-developed coelom Internal skeleton called an endoskeleton Internal skeleton called an endoskeleton Spines or bumps are anchored in the endoskeleton but may protrude through the skin. Spines or bumps are anchored in the endoskeleton but may protrude through the skin.

5 What No Top and Bottom? Echinoderms have no head; therefore, there is no anterior or posterior. The echinoderm mouth is usually on the bottom. This is termed the oral side. The echinoderm mouth is usually on the bottom. This is termed the oral side. Rather than use the term dorsal, the side of the echinoderm without a mouth is called the aboral side. Rather than use the term dorsal, the side of the echinoderm without a mouth is called the aboral side. aboral oral

6 Water vascular system A network of water-filled canals that function in movement, feeding, and excretion. A network of water-filled canals that function in movement, feeding, and excretion. Water enters the echinoderm through the madreporite (mother pore) or sieve plate. Water enters the echinoderm through the madreporite (mother pore) or sieve plate. Water is then forced through individual tube feet allowing them to move. Water is then forced through individual tube feet allowing them to move.

7 Water Vascular System

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9 Types of Echinoderms Approximately 7,000 species – all marine Approximately 7,000 species – all marine Located from the poles to the tropics Located from the poles to the tropics Five major classes Five major classes Asteroidea (sea stars) – not starfish –they are definitely not “fish” Asteroidea (sea stars) – not starfish –they are definitely not “fish” Ophiuroidea (brittle stars) Ophiuroidea (brittle stars) Echinoidea (sea urchins and sand dollars) Echinoidea (sea urchins and sand dollars) Holothuroidea (sea cucumbers) – not a vegetable! Holothuroidea (sea cucumbers) – not a vegetable! Crinoidea (feather stars and sea lilies) Crinoidea (feather stars and sea lilies)

10 Asteroidea Endoskeleton rather flexible to allow for movement. Most have five arms radiating from a central disk.

11 Asteroidea Hundreds of tube feet are found in channels called ambulacral grooves radiating from the central disk.

12 Asteroidea Naturally the anus is on the aboral (top) side. Naturally the anus is on the aboral (top) side. Aboral surface covered with pedicellariae – tiny pincer like organs that keep the sea star clean. Aboral surface covered with pedicellariae – tiny pincer like organs that keep the sea star clean.

13 Asteroidea

14 Ophiuroidea Brittle stars Most numerous class of echinoderms. Characterized by thin, very flexible arms. Eat particulate matter on the ocean floor. No anus. Often hidden. Ophiothrix spiculata

15 Ophiuroidea

16 Echinoidea Sea urchins & sand dollars Sea urchins & sand dollars Endoskeleton is a rigid, shell-like “test.” Endoskeleton is a rigid, shell-like “test.” Covered with movable spines – used in locomotion and defense. Covered with movable spines – used in locomotion and defense. Grazers – feed on algae and dead organic matter. Grazers – feed on algae and dead organic matter. oral aboral

17 Echinoidea An intricate mouth and jaw system called the Aristotle’s lantern consists of 50 bones and is controlled by over 60 muscles.

18 Echinoidea Not all “urchins” have prominent spines. Not all “urchins” have prominent spines. Sand dollars have flattened bodies and tiny spines. Sand dollars have flattened bodies and tiny spines. They use a mixture of mucus and physics to capture food. They use a mixture of mucus and physics to capture food.

19 Holothuroidea Sea cucumbers Sea cucumbers Elongated version of the pentamerous body plan. Elongated version of the pentamerous body plan. Lie on side with five rows of tube feet on bottom. Lie on side with five rows of tube feet on bottom. Tough skin supported by calcareous spicules. Tough skin supported by calcareous spicules.

20 Holothuroidea Tube feet near the mouth are modified into tentacles for feeding. Tube feet near the mouth are modified into tentacles for feeding. Some burrow and capture food while others ingest sand and filter out detritus and small organisms. Some burrow and capture food while others ingest sand and filter out detritus and small organisms.

21 Holothuroidea Defense Secrete toxins Discharge sticky toxic filaments Eviscerate – eject a portion of the internal organs to confuse an attacker. Sea cucumber evisceration

22 Crinoidea Feather stars, basket stars, sea lilies Feather stars, basket stars, sea lilies Suspension feeders Suspension feeders Oral surface on top Oral surface on top Can have from 5 to 200 arms! Can have from 5 to 200 arms! Have claw like appendages that hold the aboral surface to the substrate. Have claw like appendages that hold the aboral surface to the substrate.

23 Crinoidea


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