Characteristics of Echinoderms

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2 Characteristics of Echinoderms Adult echinoderms have a body plan with five parts organized symmetrically around a center Does not have an anterior nor posterior end or a brain Most echinoderms are two sided The side where the mouth is located is called the oral surface The other side is called the aboral surface

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4 Characteristics of Echinoderms Five-part radial symmetry (Pentaradial) Internal skeleton - made up of hardened plates of calcium carbonate The madreporite connects to a tube called the ring canal that forms a circle around the animal s digestive system

5 Characteristics of Echinoderms

6 Madreporite

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8 Characteristics of Echinoderms Water vascular system internal network of fluid filled canals connected to external appendages Responsible for feeding, respiration, internal transport, elimination of waste products and movement The water vascular system opens to the outside through a sievelike structure called the madreporite

9 Characteristics of Echinoderms Suction cuplike structures called tube feet Attached to the radial canals Relies on the water vascular system When water is pushed into a tube foot the tube foot expands When water is pulled out, the cup on the end of the tube foot shrinks (creates a vacuum mimicking suction cups)

10 Feeding Carnivores like sea stars use their tube feet to pry open the shells of bivalve mollusks (clams and scallops) Once the shell is opened the sea star flips its stomach out of its mouth and pours out digestive enzymes into the prey s own shell After dining, the sea star repositions the stomach back into its mouth

11 Feeding Herbivores such as sea urchins scrape algae from rocks using their five part jaw Detritus feeders like sea cucumbers move like a bulldozer across the ocean floor taking in a mixture of sand and detritus

12 Feeding

13 Circulation and Respiration Echinoderms need to exchange carbon dioxide for oxygen The thin walled tissue of the tube feet forms the main respiratory surface In other species small outgrowth called skin gills function in gas exchange

14 Circulation and Respiration

15 Circulation and Respiration The process of transporting oxygen, food and wastes are shared by different systems in echinoderms Respiration (gas exchange) and the removal of metabolic waste occur through the skill gills and the tube feet located all over the body, a system to deliver oxygen and carry away carbon dioxide and other wastes is not essential The distribution of nutrients is performed primarily by digestive glands and the fluid within the body cavity

16 Circulation and Respiration Excretion Solid waste is released through the anus in the form of feces Excrete nitrogen containing cellular wastes primarily in the form of ammonia Released where gas exchange occurs (tube feet and the skin gills)

17 Nervous System No head, has a primitive nervous system Have a nerve ring that surrounds the mouth and radial nerves that connect the ring with the body sections Scattered sensory cells that are sensitive to chemicals released by prey

18 Nervous System sea stars have up to 200 light sensitive cells clustered in eyespots at the tip of each arm Tells whether it is dark or light Many echinoderms hide under rocks in crevices by day (comes out during the night to feed when most predators are asleep) Echinoderms are slow moving and are unprotected on one side

19 Locomotion Use tube feet and thin layers of muscle fibers attached to the plate of the endoskeleton to move Mobility is determined by the structure of its endoskeleton Sand dollars have their plates fused together to form a rigid box that encloses the animals internal organs

20 Locomotion These animals usually have movable spines attached to their endoskeleton Combined with their tube feet they can crawl from one place to another In sea cucumbers the loss of the plates makes the body very flexible

21 Video

22 Reproduction Most echinoderms are either male or female Although some can be hermaphrodites The animals such as sea stars release their sperm and eggs into the water The sea star detect the gametes of their own species and respond by releasing their own gametes

23 Reproduction Fertilization occurs in the open water and larvae swim around The larvae which have bilateral symmetry swim to the ocean bottom where they mature and metamorphose into adults that have pentaradial symmetry

24 Regeneration Sea star can regenerate their limbs as long as their central part(core) is not damaged Asexual reproduction called fragmentation Pieces of sea star with their central core intact can regenerate into a completely new organism

25 Sea Stars Also known as starfish Many species have more than five arms sea star creep slowly along the ocean bottom Most are carnivores preying on bivalves they encounter as they move

26 Brittle Stars Live in tropical seas usually on coral reefs Resemble sea stars They have longer, more flexible arms allowing them to move more rapidly across the ocean floor

27 Brittle Stars Has the ability to shed its arms when attacked The detached arm can wiggle resulting in a distraction for predators Are filter and detritus feeders that hide by day and wander around in search of food at night

28 Sea Urchins and Sand dollars Found in almost all marine environments around the world Are grazers that eat large quantities of algae Other species are detritus feeders

29 Sea Urchins and Sand dollars Most sea urchins wedge themselves in crevices in rock during the day and come out only at night Sea urchins have long sharp spines One type have small blue poison sacs covering the tips of each spine

30 Sea Cucumber Most are detritus feeders Found on the sea floors of oceans of great depths

31 How Echinoderms fit into the world Numerous in most marine habitats Sea stars are important carnivores that control the populations of other animals Their numbers can rise and fall suddenly This causes major changes in the number of other forms of marine life Sea Urchins are important in that they control the population of algae

32 How Echinoderms fit into the world Sea urchin eggs and sea cucumber are considered delicacies Echinoderms are easy to study as they produce large numbers of eggs that are fertilized externally and develop in plain water Sea urchin embryos are studied for cell division and development when drugs are applied