Phylum Echinodermata “spiny” “skin”

http://www.youtube.com/watch?v=8JOxiT5_zpc&feature=related http://www.youtube.com/watch?v=2UYoruRNBwo

Major Classes of Echinoderms ECHINOIDEA: Includes the sea urchins and sand dollars ASTEROIDEA: includes the sea stars

OPHIUROIDEA: includes the brittle stars (below: a fossilized brittle star) HOLOTHUROIDEA: includes the sea cucumbers

CRINOIDEA: includes the sea lilies and feather stars

Unifying Characteristics Coelomate and radially symmetrical Body is usually 5 rayed (pentaradial) Have a calcareous skeleton Composed of calcium carbonate Possess a water vascular system used for gas exchange, feeding and locomotion

Unifying Characteristics Complete digestive system Open/reduced circulatory system (no heart) with a central ring and vessels Simple radial nervous system (no brain)

Unifying Characteristics Reproductive system consists of gonads which take up a significant amount of space in the body cavity Sexual reproduction with fertilization outside body (most) Have ciliated, free-swimming larvae Abundant on most sea coasts especially on rocky shores

Echinoderm Larvae

Defense systems of Echinoderms Spines are observed on many echinoderms and can be soft or hard and sharp. Their presence deters predators Pedicellariae are pincer-like structures that protrude from the body surface between the spines They keep the body surface clear of encrusting organisms Echinoderms also camouflage with their natural color into their environment

Ecological Roles of Echinoderms Starfish and brittle stars prevent the growth of algal mats on coral reefs Part of the food chain, larvae produce food for other creatures The death of echinoderms often is followed by an increase in seaweed growth and destruction of reefs

Ecological Roles Sea urchin grazing reduces the rate of colonization of bare rock Burrowing of sand dollars and sea cucumbers depletes the sea floor of nutrients and encourages deeper penetration which increases levels of oxygen and ecological tiering Sea urchins bore into rocks releasing nutrients Sea cucumbers provide habitats for parasites Echinoderms feed on dead and decaying organisms

Cool Echinoderm Facts Sea stars are capable of regeneration of body parts as long as part of the central disk remains The gonads of Sea urchins and cucumbers are considered a delicacy in SE Asia Sea cucumbers will eviscerate (shoot out parts of their internal organs) when they sense extreme danger (the organs then re-grow) Sea urchins can replace spines that are damaged or lost