Echinoderms Chapter 28

Echinoderm characteristics Spiny skin Tube feet Water vascular system Usually body parts are 5x

Sea star wrapped around blue mussel

Water vascular system Filled with fluid Carries out metabolic functions: respiration, circulation, and movement Madreporite: opening that leads to the outside environment, usually forming a ring canal around the mouth Radial canal: extensions in arms from ring canal Tube feet: suckers on ends

Section 28-4 Eyespot Endoskeletal plates Anus Stomach Madreporite Reproductive glands Tube foot Sucker Ring canal Radial canal Digestive glands The Anatomy of a Sea Star Figure 28–23

Feeding Sea urchins: use 5 part jaw to scrape algae from rocks Sea lilies: tube feed and arms to capture floating plankton Sea stars: feed on mollusks’ soft tissues after cracking the shells open

Feeding on blue mussel

Respiration and Circulation Thin wall tissue of tube feet: main respiration surface area Water vascular system: circulation Photo by Biomedia

Excretion and Response Digestive wastes released in feces through anus Nitrogenous waste: ammonia, released through tube feet tissue and skin gills Lack highly developed nervous system Nerve ring around mouth Radial nerves that connect nerve ring to body extensions Scattered sensory receptors

Movement Most use tube feet. Movable spines attached to endoskeleton (sea urchins, sand dollars) Flexible joints (sea stars, brittle stars) Crawl on ocean floor (sea cucumber)

Reproduction External fertilization Both sperm and egg shed into open water Larvae swim around but develop into adults on the ocean floor. Asexual regeneration fragmentation (breaking) of arms

Echinoderm groups Sea urchins and sand dollars Brittle stars Sea cucumbers Sea stars

Sea urchin

Live sand dollar

Dead sand dollar

Brittle star

Blue starfish