Phylum Echinodermata The spiny skinned animals 1 Echinoderm

Phylum Echinodermata “The spiny skinned animals” 1

Echinoderm Facts • Hard, spiny, bumpy endoskeleton made of calcium carbonate covered w/a thin epidermis. • As adults, echinoderms have radial symmetry with branching arms called rays. • As larva, echinoderms have bilateral symmetry. • Echinoderms have no head or brain, but they do have a central nerve ring that surrounds the mouth. • Water vascular system (WVS) is a hydraulic system that operates under water pressure used for movement. 2

Echinoderm facts • The water vascular system’s opening is called a madreporite. It opens into a ring canal. The ring canal then goes out to the arms in radial canals. The radial canals then feed water to the tube feet. • Each arm contains two rows of tube feet 3

Echinoderm facts • Tube feet are used in movement, gas exchange and excretion; nitrogen waste excreted as ammonia exits the anus. • At the top of each tube foot is the ampulla which acts like a bulb on a medicine dropper. • Echinoderms are considered to carnivores, herbivores and detritus feeders. • Simple nervous system for most echinoderms – Starfish have up to 200 light sensitive cells clustered in eyespots of each arm. No actual eyes. • Pedicellariae are pincher-like appendages used for protection and for cleaning the surface of the body. • For balance & hearing, statocysts or tiny stones pass over hairs to tell the starfish up from down and sense motion or sound by vibrations in the water. 4

Echinoderm Reproduction • Echinoderms can reproduce sexually or asexually. • Reproduction – echinoderms are either male or female. Sperm and eggs produced in the testes or ovaries is released into the water to become fertilized. This is sexual reproduction. • Reproduction – ask a Fisherman and he will tell you that tearing starfish into chunks is a great way to increase their population. Each chunk will undergo regeneration (asexual reproduction) and form new starfish. So, ripping them up is not a great way to reduce predation on shellfish, which bring in a pretty -penny. 5

Echinoderms • The spiny skinned animals include these Classes: 1. Class Asteroidea - starfish (sea stars) 2. Class Crinoidea - the crinoids or “feather stars” 3. Class Ophiuroidea - brittle stars, basket star 4. Class Echinodermata - sea urchin, sand dollar 5. Class Holothuroidea - sea cucumbers 6. Class Concentricycloidea – sea daises 6

Class Asteroidea • Includes ¼ of the echinoderms • Sea stars or starfish • Sea stars typically have 5 arms but can have up to 40. • The mouth is located on the oral or bottom side. • The anus is located on the aboral or top side. 7

Starfish arm • Each arm or ray contains a digestive glands, a radial canal and gonads. • Each arm also contains two rows of tube feet. • Arm will regenerate if torn off = Asexual Reproduction. • Starfish are carnivores that eat clams, mussels, and other bivalves. 8

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Sea stars Pedicellariae Endoskeleton Ray Madreporite Radial canal Radial nerve Tube feet Eyespots Anus Ring canal Ampullae Nerve ring Stomach Mouth Reproductive organ Digestive gland Endoskeletal plates 10

Class Crinoidea • Sea lilies & feather stars • Filter feeders • some are sessile • some are motile • Their bodies are often found in limestone deposits 11

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Class Ophiuroidea • Brittle stars & Basket Stars • These are perhaps the fastest of the echinoderms. Do not use tube feet for movement. • Most of them are filter feeders or detritus eaters • Flexible arms, and may be offered as food to get away from predators 14

Basket Star 15

Brittle Star 16

Class Echinoidea • Sea Urchins & sand dollars • Lack arms or rays • eat algae or are detritus eaters • usually have spines • Gonads prized for sushi • Endoskeleton called a test. 17

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Class Holothuroidea • Sea cucumbers • Detritus eaters – the vacuum cleaners of the sea • do not have skeletal parts • will eviscerate if they are scared, meaning offer up internal organs as food to distract predator 20

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Class Concentricycloidea • Sea daises • Discovered off the coast of New Zealand. • Flattened disc bodies less that 1 cm in diameter. • Three known species to date. 22

Phylum Chordata • Three subphyla –Phylum Urochordata - tunicates –Phylum Cephalochordata lancelets –Phylum Vertebrata - vertebrates 23

Invertebrate Chordates • This group belongs to the Phylum Chordata because they contain a stiff but flexible rod called a notochord. • Characteristics – dorsal nerve chord - hollow tube – pharyngeal pouches - out pockets in pharynx – postanal tail - used for propulsion 24

Subphylum Cephalochordata • Lancelets-retain all characteristics throughout its life. • Like to burrow in shallow water sand. • Usually about 5 cm long. • Filter feeders http: //bioweb. uwlax. edu/zoolab/Table_of_Contents/Lab-9 a/Lancelets/Lab_9 a-03 a. jpg 25

Subphylum Urochordata • Tunicates - AKA “Sea squirts” because their bodies are covered with a tough covering like tunic. • Filter feeds as adults w/incurrent siphons • External fertilization - hermaphrodites that release sperm through excurrent siphons. 26

http: //www. ucmp. berkeley. edu/chordata/urochordata. gif 27