Echinodermata and Invertebrate Chordates Chapter 40

Phylum Echinodermata Characteristics Age of echinoderms is estimated as more than 500 mil years All marine Known as spiny-skinned animals Endoskeleton known as the test is made of calcium plates or ossicles with protruding spines Includes sea stars, brittle stars, sand dollars, sea urchins, & sea cucumbers Undergo metamorphosis from bilateral, free-swimming larva to sessile or sedentary adult Larval stage known as dipleurula or bipinnaria Adults have pentaradial ( 5 part) symmetry Lack segmentation or metamerism Coelomate Breathe through skin gills as adults Capable of extensive regeneration

Characteristics cont… Ventral (lower) surface called the oral surface & where mouth is located Dorsal (upper) surface known as aboral surface & where anus is located Have a nervous system but no head or brain in adults No circulatory, respiratory, or excretory systems Have a network of water-filled canals called the water vascular system to help move & feed Tube feet on the underside of arms help in moving & feeding One-way digestive system consists of mouth with oral spines, gut, & anus Deuterostomes (blastopore becomes the anus) Separate sexes Reproduce sexually & asexually

Phylum Echinodermata Includes 5 classes:           * Crinoidea - sea lilies & feather stars           * Asteriodea - starfish           * Ophiuroidea - basket stars & brittle stars           * Echinoidea - sea urchins & sand dollars           * Holothuroidea - sea cucumbers

Class Crinoidea Characteristics Sessile Sea lilies & feather stars Have a long stalk with branching arms that attach them to rocks & the ocean bottom Can detach & move around Mouth & anus on upper surface May have 5 to 200 arms with sticky tube feet to help capture food (filter feeders) & take in oxygen Common in areas with strong currents & usually nocturnal feeders

Class Crinoidea                                                               SEA LILY                                                               FEATHER STAR

Class Asteroidea Characteristics Usually sedentary along shorelines Starfish or sea stars Come in a variety of colors Prey on bivalve mollusks such as clams & oysters Have 5 arms that can be regenerated Arms project from the central disk Mouth on oral surface (underside)

Class Asteroidea                                       Starfish Feeding on Clam

Class Ophiuroidea Characteristics Largest class of echinoderms Includes basket stars & brittle stars Live on the ocean bottom beneath stones, in crevices, or in holes Have long, narrow arms resembling a tangle of snakes Arms readily break off & regenerate Move quicker than starfish Feed by raking in food with arms or trapping it with its tube feet

Class Ophiuroidea                                                                          BASKET STAR                                                                          BRITTLE STAR

Class Echinoidea Characteristics Includes sea urchins & sand dollars Internal organs enclosed by endoskeleton or test made of fused skeletal plates Body shaped like a sphere (sea urchin) or a flattened disk (sand dollar) Lack arms Bodies covered with movable spines Have a jawlike, crushing structure called Aristotle's lantern to grind food Use tube feet to move

Class Echinoidea Characteristics cont… Sea Urchins:         * Spherical shape         * Live on ocean bottom         * Scrape algae to feed         * Long, barbed spines make venom for protection Sand Dollars:         * Flattened body         * Live in sand along coastlines         * Shallow burrowers         * Have short spines

Class Echinoidea                                                                     SEA URCHIN                                                                SAND DOLLAR

Class Holothuroidea Characteristics Includes sea cucumber Lack arms Shaped like a pickle or cucumber Live on ocean bottoms hiding in caves during the day  Have a soft body with a tough, leathery outer skin Five rows of tube feet run lengthwise on the aboral (top) surface of the body Have a fringe of tentacles (modified tube feet) surrounding the mouth to sweep in food & water Tentacles have sticky ends to collect plankton Show bilateral symmetry Can eject parts of their internal organs (evisceration) to scare predators; regenerate these structures in days

Class Holothuroidea                                                                     SEA CUCUMBER

Structure & Function of Starfish Body Plan Range in size from 1 centimeter to 1 meter Mouth located on oral surface (underside) Have an endoskeleton made of calcium plates Sharp, protective spines made of calcium plates called ossicles found under the skin on the aboral (top) surface Have pedicellariae or tiny, forcep-like structures surrounding their spines to help clean the body surface

Structure & Function of Starfish Body Plan                                        ABORAL SURFACE

Structure & Function of Starfish Water Vascular System Network of canals creating hydrostatic pressure to help the starfish move Water enters through sieve plate or madreporite on aboral surface into a short, straight stone canal Stone canal connects to a circular canal around the mouth called the ring canal Five radial canals extend down each arm & are connected to the ring canal Radial canals carry water to hundreds of paired tube feet

                                                  WATER VASCULAR SYSTEM

Structure & Function of Starfish Water Vascular System Bulb-like sacs or ampulla on the upper end of each tube foot contract & create suction to help move, attach, or open bivalves Rows of tube feet on oral surface (underside) are found in ambulcaral grooves under each arm

Structure & Function of Starfish Water Vascular System                                                                            TUBE FEET                                     Tube Feet in Ambulcaral Grooves

Feeding & Digestion Tube feet attach to bivalve mollusk shells & create suction to pull valves apart slightly Starfish everts (turns inside out) its stomach through its mouth & inserts it into prey Stomach secretes enzymes to partially digest bivalve then stomach withdrawn & digestion completed inside starfish

Other Body Systems No circulatory, excretory, or respiratory systems Coelomic fluid bathes organs & distributes food & oxygen Gas exchange occurs through skin gills & diffusion into the tube feet No head or brain Have a nerve ring surrounding the mouth that branch into nerve cords down each arm Eyespots on the tips of each arm detect light Tube feet respond to touch

Reproduction Separate sexes Two gonads (ovaries or testes) in each arm produce eggs or sperm Have external fertilization Females produce up to 200,000,000 eggs per season Fertilized eggs hatch into bipinnaria larva which settles to the bottom after 2 years & changes into adult Asexually reproduce by regenerating arms

Characteristics of Chordates All chordates have a notochord, dorsal nerve cord, pharyngeal pouches, & postanal tail at some time in their life Notochord is a firm, flexible rod of tissue located on the dorsal side of the body that becomes part of the endoskeleton in vertebrates Dorsal nerve cord is a hollow tube lying dorsal to the notochord that becomes the brain & spinal cord in vertebrates Pharyngeal pouches are small outpockets of the anterior part of the digestive tract that become gills in aquatic chordates & jaws, inner ear, & tonsils in terrestrial chordates Postanal tail consists of muscle tissue & lies behind the posterior opening of the digestive tract

Characteristics of Chordates

Subphyla of Chordates The Phylum Chordata  includes all of the vertebrates, as well as two groups of marine animals that lack backbones and are called invertebrate chordates The phylum is divided into three subphyla, determined by the development of the notochord Subphylum Cephalochordata contains about 24 species of blade-shaped animals known as lancelates that retain the notochord, dorsal nerve chord, pharyngeal pouches, and postanal tail throughout their life

Subphyla of Chordates cont… Subphylum Urochordata  contains 2,000 species commonly called tunicates because their bodies are covered by a tough covering, or tunic      * Called sea squirts because they shoot out a stream of water when touched      *Sessile, barrel-shaped, filter feeding animals that live on the sea bottom      *Adults have a pouch-like pharynx with slits      *Adults do not have a notochord, dorsal nerve cord, or postanal tail

Subphyla of Chordates cont… Subphylum Vertebrata is the largest subphylum in which the notochord is replaced with vertebrae *  Skeletons consist of bone &/or cartilage * Brain is protected by a cranium * Well developed 4 chambered heart with a closed circulatory system * Includes fish, amphibians, reptiles, birds, & mammals

Chordate Characteristics Feature Vertebrata Cephalo-chordata Uro-chordata Notochord Dorsal Nerve cord Pharyngeal pouch Postanal tail