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Echinoderms ________________ no distinct head means “prickly skin” !oral vs aboral surface include: starfish, sea cucumbers, basket stars, brittle stars, sea lilies, etc outer surface of body is covered by epidermis has an extremely abundant and diverse fossil record below epidermis is an endoskeleton made of hardened plates (=ossicles) of calcium all marine; found in all oceans at all depths movement & food gathering done predominantly by water vascular system some of the most abundant of all marine invertebrates a series of tubes that open to the sea through a sieve plate (=madreprite) almost all are bottom dwellers mostly drab colors filled with fluid (mainly sea water) but a few are red, orange, purple, blue, etc inside the body the tubes extend into each arm of the 12 major animal groups (phyla) this one is closest to the vertebrates (us) connected to muscular tube feet Unique Echinoderm Characteristics: the tip of the tube feet are flattened, forming suckers 1. most with 5-part radial symmetry suctionlike cups can produce strong force 2. unique water vascular system for feeding and movement the whole system operates hydraulically by muscle contractions & opening and closing valves 3. pedicellariae for protection Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 1 tube feet are used to cling to substrates, move and to feed Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 2 in many echinoderms the body surface bears small jaw-like pedicellariae echinoderms are particle feeders, scavengers or predators ! protect against animals and debris that settle on the animals surface no parasitic species Reproduction & Development most echinoderms have a very simple digestive tract sexes typically separate ! dioecious gas exchange and excretion occur through tiny saclike projections that extend through epidermis usually external fertilization: eggs and sperm are released into the water = dermal branchae produce a free-swimming planktonic larva the same functions are also shared by tube feet in most groups many also have excellent powers of regeneration ! can regenerate from 1/5th of oral disc & a single arm the nervous system consists of nerve fibers that circle the mouth and nerves that branch off into each arm to coordinate movement but may require up to a year some deliberately cast of an arm as a means of asexual reproduction echinoderms have no brain or centralized processing area don’t seem to age ! can liver forever? tube feet are innervated by nervous sysem some examples of echinoderms: ! enables all feet to move in single direction eg. starfish ,seastars & sunstars few specialized sense organs bottom dwellers that inhabit all seas Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 3 Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 4 margins of each groove are guarded by moveable spines common along littoral zone in coastal waters where they may congregate in very large numbers range from ~1/2” (1 cm) to 3’ (1 M) tip of each arm has 1 or more short tactile and a red eye spot in diameter on other side of central disc is a large sieve plate eg. giant Pycnopodia has over 20 arms and is the size of a manhole cover often brightly colored: red, orange, blue, purple, green etc and numerous pedicellariae on central disc and arms keeps skin free of sponges, corals, etc body composed of arms projecting from a central disc also used in feeding and defense most with 5 arms Feeding and Digestion sunstar up to 40 arms a. many starfish are scavengers some have up to 50 arms b. a few are suspension feeders arms not sharply set off from central disc feed on small plankton and organic debris in some arms are very short or absent mucous strands carry food to the mouth eg. Culcita ! a pentagon with no arms the mouth is in the center of bottom (oral) surface c. most are carnivores wide grooves (= ambulacral grooves)project from mouth into each arm feed on molluscs, crustaceans, polychaetes and other echinoderms each groove contains 2-4 rows of tube feet Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 use chemoreceoptors to detect and locate prey 5 some can locate buried prey and dig down to get them Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 6 starfish can regenerate from an arm Sexual Reproduction eg. some swallow prey whole and regurgitate undigested ossicles & spines, etc most are dioecious eg. some attack larger seastars and begin eating the end of an arm and work their way up gonads in small area at base of each arm under the digestive gland eg. many are able to evert their stomachs through the mouth to engulf and eat prey when filled with eggs sor sperm they almost completely fill arm eg. some feed exclusively on bivalves ! some, such as asterias, are notorious predators of oysters egg and sperm are released through pores in the skin wraps itself around its prey 1 female may shed 2.5 M eggs exert steady pull on valves in about a half hour the adductor muscles of bivalve fatigue and relax slightly to create a small gap between the shells sea stars are often the top predators in some benthic communities only need 0.1mm gap to insert stomach and digest oyster though unpalatable to most organisms to some they are the preferred meal: takes 2.5 - 8 hrs to digest a bivalve eg. some fish with strong teeth digestive glands in each arm receive the food from the stomach to complete digestion and absorption Reproduction & Development eg. sea otters eg. brittle stars basket stars the most active members of the phylum Asexual reproduction found in all types of marine benthic habitats many starfish regularly reproduce asexually Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 7 Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 8 tend to be secretive when fish takes an interest in the area under the starfish it quickly wraps its arms around it hide in cracks and crevices on hard substrates eg. sea urchins, sand dollars & sea biscuits some can burrow all are benthic have arms with central disc but: remain close to the substrate long thin arms sharply set off from disc ossicles of arms are arranged into flexible columns connected by muscle strands compact body enclosed within a test (a single shell) of ossicles or plates locked together into a single unit very few tube feet most are more or less hemispherical in shape all visceral organs are confined to central disc no arms, but 5 rows of pores on test through which very long tube feet extend typically 5 arms also with numerous long moveable spines but in basket stars they repeatedly branch to produce tentacle like mass in most urchins, moveable spines cover most of the body movement by snake-like movements of arms have ball & socket joints with tubercles on test can rapidly clamor over rocks and seaweed collagen fibers can make spines stiff and erect for protection brittle stars are carnivores, scavengers, deposit feeders or filter feeders in some urchins spines are hollow and can inject a painful poison some ”ambush” their prey use arms to hold central disc off grand to form a kind of shelter 9 Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 use very long tube feet and prehensile spines to move around most sea urchins are grazers 10 body becomes elongated; long and wormlike or “cucumber shaped” with mouth and anus are on opposite ends scrape algae from substrates with teeth body has a leathery appearance mouth contains a complex chewing mechanism of 5 converging teeth attached to muscle bands ossicles are very small; the tougher skin provides most of the support used to scrape and chew algae from rocks sea cucumbers crawl on bottom side of body eg. Sea Cucumbers relatively sluggish rule the deep ocean benthos lie on bottom or burrow into mud ! make up 90% of biomass on deep ocean floor some live beneath stones or in coral crevices often on sandy or muddy bottoms there are a few deep water pelagic (swimming) forms some crawl on sea floor that have tube feet modified into fins, sails, or medusa-like bells others hide beneath rocks some are burrowers mouth is always surrounded by 10-30 tentacles which are part of the water vascular system sea cucumbers are among the strangest of the echinoderms: tentacles are highly retractile like sea urchins have no arms ! can be completely retracted into mouth tend toward bilateral symmetry: Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 tube feet can also be modified into sensory 11 Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 12 papillae, fins, sails, etc many sea cucumber are capable of evisceration the front or back end ruptures and the internal organs are expelled sea cucumbers are mainly deposit feeders and suspension feeders seems to be a seasonal phenomenon use tentacles to collect food and deliver it to mouth possibly when food is scarce or in order to eliminate wastes stored inside the internaltissue their digestive system is better developed than in most echinoderms the organs are later regenerated may also be a protective mechanism mouth opens into a muscular pharynx a few sea cucumbers posess a large mass of white, pink, or red tubules (= tubules of Cuvier) attached to the base of their respiratory tree then to esophagus and stomach most have a long, looping intestine when irritated or attacked, the anus is directed toward the intruder and the tubules are shot out of the anus leads to anus which opens into cloaca in some the tubules are sticky; in others they release a toxin cloaca = chamber in which digestive system, excretory system & reproductive system all open into small crabs and lobsters may be rendered completely harmless and helpless most have a respiratory tree consisting of two highly branched tubes the sea cucumber later regenerates the tubules for the next attack it’s also attached to the cloaca pumping action of cloaca circulates water a tropical pearlfish makes its home in the respiratory tree of some sea cucumbers leaves at night to search for food Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 13 Ecology & Human Impacts Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 14 don’t transmit any diseases 1. “crown of thorns” starfish destroys Pacific coral reefs although handling poisonous forms can be lethal 5. as food: feed on coral polyps eg. in China and Pacific Islands sea cucumbers are boiled and dried and eaten as a delicacy or used as a food flavoring sometimes attack in “herds” the number of reef attacks is increasing in some areas collecting has severely depleated their populations sometimes results in extensive damage eg. roe (gonads & eggs) are sold, raw or roasted, as a delicacy in Japan and in sushi restaurants very expensive to control outbreaks 2. sea urchins destroy kelp forest >30M pounds of urchins were harvested in 1986 but are preyed on by sea otters 6. echinoderms have been widely used in developmental research 3. predatory starfish can devastate commercial clam or oyster beds “we know more about the embryology of echinoderms than probably any other embryo” eg. a single starfish can eat a dozen clams or oysters in a day sometimes an infestation is treated with quicklime ! destroys dermal branchiae and kills animal ! but also kills many other soft bodied invertebrates; but not the oysters who temporarily close their shells 4. echinoderms never attack humans Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 15 Animals: 1409 Echinoderms; Ziser Lecture Notes 2009 16