5-WAY SYMMETRY “spiny-skinned” movie ECHINODERMS 5-WAY SYMMETRY “spiny-skinned” movie

ECHINODERM CHARACTERISTICS Radially symmetrical-adults Pentamerous – based on 5-parts Bilaterally symmetrical- planktonic larvae No head No anterior/posterior end; no ventral/dorsal side Refer to the oral and aboral side Complete digestive tract Well-developed coelom

Water-vascular system- waterfilled canals Endoskeleton Water-vascular system- waterfilled canals Tube feet- muscular extensions of canals Extended when filled with water- have muscular sacs called ampullae Used for movement, attachment, and receiving chemical and mechanical stimuli Madeporite- or sieve plate- in sea stars and sea urchins; on the aboral side; where water enters the water vascular system

BIOLOGY OF ECHINODERMS Radial symmetry = sedentary life style Feeding and digestion- sea stars are carnivorous; they extend their stomach out through their mouth and excrete digestive enzymes; the food is then carried into the digestive gland and the stomach moves back into the body; if intestines are present, they are very small Brittle stars- no anus; very simple guts Crinoids- simple guts

Feeding and digestion cont. Sea urchins and sea cucumbers have long coiled guts (sea urchins need this because they are herbivores and the sea cucumbers need this because they need to process sediment) In all echinoderms, nutrients are passed in the coelomic fluid within the coelom Also transports oxygen because they don’t have a circulatory system Sea cucumbers have respiratory trees- which are thin, branched tubes that are connected to the gut and extend out to the anus

REPRODUCTION AND LIFE HISTORY- NERVOUS SYSTEM AND BEHAVIOR- have a nerve net- more complex actions than cnidarians though REPRODUCTION AND LIFE HISTORY- Separate sexes External fertilization Zygote develops into a ciliated larva Some don’t have larva but brood their offspring in specialized pouches Some reproduce asexually by the separation of the central disc or body into two pieces- REGENERATION

TYPES OF ECHINODERMS 7000 KNOWN SPECIES- all marine Bottom dwellers 1. Class Asteroidea= sea stars 5 arms that radiate from central disk Amulacral groove= the radiating channels on the arms Can move in any direction Endoskeleton = interconnected plates of calcium carbonate creating very flexible arms; aboral surface may be covered with spines that are modified into pincer like organs called pedicellariae which helps to keep the surface clean

Class Ophiuroidea= brittle stars; 5 arms are very long and brittle Asteroidea cont. Most are predators of bivalves, snails, barnacles or other attached or slow moving animals Class Ophiuroidea= brittle stars; 5 arms are very long and brittle Most eat detritus and small animals Tube feet don’t have suckers, used for feeding No anus Most species (2000)

Indian Sea Star Anthenea crassa

Sunflower Sea Star Choriaster granulatus , the dough-boy star

Astropectin polyacanthus Arctic Sea Stars eating a Clam

Brittle star (Ophiocoma imbricatus) Orange-banded Brittle Star (Ophiothrix)

Brittle star larvae

CLASS ECHINOIDEA OR SEA URCHINS Endoskeleton forms a round, rigid, shell-like test with movable spines and pedicellariae Body forms a sphere Mouth on bottom; anus on top Graze on seaweeds and seagrasses Have Aristotle’s Lantern- the set of jaws and associated muscles used by sea urchins to bite food 1000 species

Purple Sea Urchin with spines Purple Sea urchin’s test w/o spines

Banded Sea urchin Pencil Sea urchin

Class Echinoidea cont. Heart urchins and sand dollars have flattened bodies and short spines They are deposit feeders using tube feet and mucus to pick up particles

Heart Urchin with and without spines

Internal Sand dollar

Keyhole sand dollar with and without spines

CLASS HOLOTHUROIDEA OR SEA CUCUMBER Worm like No spines and no obvious radial symmetry Look stretched Lies on one side where the 5 rows of tube feet are; oral and aboral surface on the ends Endoskeleton has microscopic spicules Deposit feeders; tube feet around mouth are modified into branced tentacles

Class Holothuroidea cont. Defensive mechanisms Secrete toxic chemicals in filament Might expel the gut or other internal organs; this is called evisceration Prickly red sea cucumber

Orange sea cucumber Warty Sea cucumber

Sea cucumber eviscerating

CLASS CRINOIDEA OR CRINOIDS Suspension feeders Feathery arms 600 species of feather stars and sea lilies Sea lilies are in deep water and attached to bottom Feather stars perch and crawl in both shallow and deep water An upside down brittle star with the amulacral grooves and mouth facing upward

Class Crinodea cont. Can have up to 200 arms Passion flower feather star

Sea lily Feather star

Sea lily reef