Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download 3 slides/page - University of San Diego Home Pages
Document related concepts
Transcript
3/25/11 Invertebrates I • Porifera • Radiata PORIFERA: The sponges • ~9,000 species • Position within Animalia is under debate: • Ancient Animals? • Once considered as subkingdom Parazoa and sister taxon to Eumetazoa. • Recently considered a paraphyletic grade, with one group more closely related to Eumetazoans than others. PORIFERA: The sponges • Position within Animalia is under debate: • Secondarily simplified? • Recent (2008) study of 150 genes found Ctenophora (comb jellies) sister to all remaining animals • Hypothesized that sponges are not primitive, but secondarily simplified – Lost tissues and other Eumetazoan characteristics from their common ancestor 1 3/25/11 PORIFERA: The sponges • Position within Animalia is under debate: • Or monophyletic? • Or even MORE recent: – Philippe et al. 2009, Current Biology • 128 genes • Sponges monophyletic sister taxon to the Metazoa. PORIFERA: The sponges • • • • Regardless, very simple animals. No true tissues or organs Body is a perforated sac surrounding the spongocoel (internal cavity) Two layers a loose aggregate of cells – Epidermis – Choanocytes (collar cells) • Between layers is mesohyl PORIFERA: The sponges • • • Collar cells move large volumes of water through body pores by their beating flagella. They also trap suspended food particles in their microvilli collars. Within mesohyl are Amoebocytes which transport food particles and/or produce Calcium Carbonate (CaCO3) spicules for support. 2 3/25/11 PORIFERA: The sponges • Are very sessile (immobile) filter feeders. • 98% marine, some freshwater PORIFERA: The sponges • Reproduction Hermaphroditic: each individual functions as male & female – Often sequential hermaphrodite • • • • • Sperm and eggs develop from choanocytes & amoebocytes in mesohyl Sperm expelled into spongocoel then out Eggs reside and are fertilized in in mesohyl Zygote Flagellated freeswimming larva disperse settles adult Also, can regenerate, repair, and have asexual reproduction The Eumetazoa • “True multicellular animal” • Generally considered monophyletic, complex, true tissues – Diploblastic & Triploblastic • Most hypotheses consider Radiata (Ctenophora + Cnidaria) as a paraphyletic grade 3 3/25/11 The Eumetazoa • Recent phylogenomic study calls this into question • Eumetazoa no longer a monophyletic group The Eumetazoa • Or… • Metazoa monophyletic AND Coelenterata/ Radiata (diploblasts) monophyletic Ctenophora: Comb Jellies • ~100 species • Transparent, all marine • 1-10 cm, spherical/ovoid, some elongate to 1 m • 8 rows of ciliated comblike plates for locomotion: Ctenophora = “comb bearer” • Long retractible tenticles with colloblasts for food capture • Superficially (?) resemble Cnidaria, relationships under debate 4 3/25/11 Cnidaria: Hydras, jellies, anemones, corals • • • General Diploblastic (what germ layer do they lack?) Radial symmetry Basic body plan: sac with central gastrovascular cavity – One opening for both entrance and exit of food • Two forms: – Polyp: sessile sac with tentacles upward – Medusa: free-swimming, sac and tentacles downward • • Independent as either OR Medusa dispersal stage and settled polyp stage Cnidaria: Hydras, jellies, anemones, corals Feeding • Carnivorous • Tentacles armed with cnidocytes – Specialized cells with nematocysts (stinging capsules) • Response system made of of simple contractile fibers linked to nerves • Gastrovascular cavity a hydrostatic skeleton – Simple nerve net detects, responds to stimuli, changes shape Cnidaria: Diversity Anthozoa Scyphozoa Cubozoa Hydrozoa 5 3/25/11 Cnidaria: Diversity • • • • Hydrozoa: Hydra, Obelia Mostly marine, some freshwater (e.g. Hydra) Polyp & medusa Just polyp Just medusa Cnidaria: Diversity Scyphozoa: Jellies • All marine: medusa prominent stage in life cycle • Many are bioluminescent • Nematocysts in hunting tentacles • Food moved to gastrovascular cavity by unarmed tentacles Cnidaria: Diversity Cubozoa: Box jellies • These are THE nasties! • Known for their toxic venom • Complex eyes embedded in ectoderm of medusa • Main prey item of many sea turtles • All marine 6 3/25/11 Cnidaria: Diversity Anthozoa: Sea anemones & Corals • All marine • Exist only as polyps • Many corals are colonial & secrete hard external skeleton of calcium carbonate – Reef builders Bilateria • Bilateria STRONGLY supported as monophyletic • Bilateral symmetry • Triploblastic development • All non-Bilateria hox genes homologous with “posterior” hox gene cluster in Bilateria • “Anterior” hox gene cluster is only found in Bilateria Bilateria • Protostomes consist of two major clades (supported in large genomic survey): – LOPHOTROCHOZOA – ECDYSOZOA • Lophotrochozoa contains the most phyla and the highest diversity of body plans 7 3/25/11 Platyhelminthes: Flatworms • ~25,000 species • Protostomes – Triploblastic – Bilateral – Spiral cleavage • BUT lack a coelom – This is a loss of a body cavity – One of 3 bilaterian phyla with no coelom Platyhelminthes: Flatworms • Cephalization present – Unidirectional movement • Complex tissues in mesoderm – Organs, true muscle tissue • Unidirectional gastrovascular cavity (one opening) Platyhelminthes: Flatworms • Dorso-ventrally flattened • All tissues readily exposed to external environment – No need for complex vascular or excretory system – Osmotic balance maintained via protonephridia – Flame bulbs pull fluid through branched openings to outside 8 3/25/11 Platyhelminthes: Flatworms DIVERSITY: 4 classes Turbellarians: Free-living flatworms Trematodes: Blood flukes Cestodans: Tapeworms Monogeneans: Gill flukes Platyhelminthes: Flatworms DIVERSITY Turbellaria • Free-living flatworms • Mostly marine but include common freshwater such as planarians • Carnivores or scavengers (carrion): Active lifestyle Platyhelminthes: Flatworms DIVERSITY Turbellaria • Move by ventral cilia gliding over mucous • Head with eyespots • Lateral flaps for smell • Nervous system more complex than Radiata • Asexual reproduction through constriction • Sexual reproduction: hermaphrodites 9 3/25/11 Platyhelminthes: Flatworms DIVERSITY • • • • • • Trematoda & Monogenea Flukes ALL parasitic Life cycle rotates between sexual and asexual reproduction Usually requires an intermediate host Trematodes: Vertebrate blood/liver Monogeneans: Fish gills Platyhelminthes: Flatworms DIVERSITY • • • • • • Trematoda & Monogenea Blood fluke Schistosoma (causes schistosomiasis) Intermediate snail host infected by free-living larvae Reproduce asexually within snail, produce 2nd larval stage Larvae penetrate skin Migrate to lung via veins, develop more Migrate to liver, complete development: sexual reproduction – Females reside in groove (gynaecophoric channel) of male worm Platyhelminthes: Flatworms DIVERSITY • • • • Cestoda TAPEWORMS! Parasitic flatworms, adults reside in vertebrates Head with suckers and hooks: Scolex Allows tapeworm to adhere to intestinal lining 10 3/25/11 Platyhelminthes: Flatworms DIVERSITY • • • • Cestoda Body made up of segments called proglottids Each is just a sac of sex organs No digestive system (food predigested by host): simply absorbs food across body wall Mature proglottids are full of fertilized eggs and break off from posterior end released in feces contaminate water picked up by pigs, cows, etc. encysts in muscle tissue undercooked meat results in human infections Longest human tapeworm: 11.2m Longest tapeworm: 37m from a whale Lophophorates Ectoprocta (Bryozoans), Brachiopods • Distinguished by lophophore – Circular fold of body wall bearing ciliated tentacles that surround the mouth – Used in filter feeding • • Molecular phylogeny favors protostome affinity, but embryonic development more similar to deuterostomes Pseudocoelomates Lophophorates Brachiopods • “lampshells” • ~330 species, all marine • Resemble Bivalves (clams) but shell halves dorsal/ventral, attached by stalk to substratum • Very important fossils: ~30,000 species Paleozoic, Mesozoic 11 3/25/11 MOLLUSCA • True coelom (body cavity enclosed by mesoderm) • Obvious protostome development • Snails, slugs, oysters, clams, octopus, squid • 50,000 species, 8 classes MOLLUSCA • Most marine, some fresh water, some truly terrestrial • Soft bodies, unsegmented • Protected by hard shell of Calcium carbonate (CaCO3), secondarily lost in some taxa • Larva a trochophore • Body plan: visceral mass, mantle, mantle cavity, muscular foot. Molluscan classes Cephalopoda Scaphopoda Gastropoda Bivalvia Polyplacophora (Sigwart, J.D., and Sutton, M.. 2007. Proc. R. Soc. B 274: 2413– 2419; N.G. Wilson et al. 2010. Mol. Phyl. Evol. 54: 187-193) 12 3/25/11 MOLLUSCA: Polyplacophora • Chitons • Marine, oval, shell divided in 8 plates • Intertidal, clinging to rocks with foot • Scrape algae with radula MOLLUSCA: Gastropoda • • • • • • • Snails, slugs 40,000 species, most species-rich class of Mollusca Spiralled shell in most Flat shell in abalones and limpets Slugs, nudibranchs lack shells Often distinct heads, eyes on retractable stalks Radula for grazing, some use it for boring holes, predacious MOLLUSCA: Gastropoda • • • • Embryonic torsion Visceral mass rotates 180°, anus, mantle above head Evolved in concert with a shell with a single opening Gastropods with secondarily lost shell (slugs) have detorted. – Untwisted – Maintain vestige of ancestral twist – One set of gills – Anal papillae and gills functionally related – Gills have secondarily evolved at other structures 13 3/25/11 MOLLUSCA: Bivalvia • • • • Clams, oysters, mussels scallops ~30,000 species Shell divided in half (fundamentally dorsal), hinged mid-dorsally, connected by adductors Mantle cavity has gills for gas exchange, feeding – Gill serves dual function • • • Sedentary: muscular foot for anchor HOWEVER, some can dig very quickly and scallops can swim NO RADULA Mollusca: Scaphopoda • Tooth shells or tusk shells • Open end ‘tooth’ or‘tusk’ shell • Mouth with grinding radula • Tentacles used for grasping substrate and collecting detritus/prey • Tentacles shared with Cephalopods MOLLUSCA: Cephalopoda • Octopus, squid, cuttlefish, chambered nautilus • ~800 species, all marine • Most <75cm; largest 17m, 2 ton squid • Characterized by their speed and rapid movement • PREDATORS with beaklike jaws surrounded by long tentacles • Inside mouth is rasp-like radula 14 3/25/11 MOLLUSCA: Cephalopoda • Shell present in fossil cephalopods (e.g. ammonites) and extant nautilus • Shell internalized in most squids and some octopuses. • Shell lost in most octopuses • Squid movement backward via water jets from mantle cavity modified as muscular cavity MOLLUSCA: Cephalopoda • Only molluscs with closed circulatory system • Well-developed brain, nervous system, sense organs. • Complicated, imageforming eye. Annelida: Segmented worms • ~15,000 species • Marine, freshwater, terrestrial – Some unsegmented phyla (e.g. Echiura and Sipuncula) now included within Annelida • 1mm to 4m (giant Gippsland earthworm)! 15 3/25/11 Annelida: Segmented worms Morphology • Segmented body • Coelom partitioned by septa (singular septum) • Digestive tract, nerves, vessels continuous through septa. Annelida: Segmented worms Morphology • Digestive tract: – – – – – Pharynx Esophagus Crop Gizzard Intestine • Circulatory system: – Blood with hemoglobin – Pumping muscles • Excretory system: – Segmented metanephridia • Nervous system: – Cerebral ganglia – Ventral nerve cord • Respiratory system – Cutaneous respiration Annelida: Segmented worms Movement • Burrowers, some can swim – Creep by longitudinal, circular muscles working against fluidfilled coelom as hydrostatic skeleton – This contracts and elongates segments 16 3/25/11 Annelida: Segmented worms • • • • • Reproduction Hermaphroditic (Hirudinea & Oligochaeta), separate sexes (Polychaeta), cross fertilization Sperm stored in clitellum; cocoon in clitellum houses eggs Trochophore larva in Polychaeta Embryonic worm in terrestrial Hirudinea & Oligochaeta Some asexual reproduction via fission – In some, posterior end breaks off, develops into new individual – In others, penis breaks off, develops into new individual Annelida: Oligochaeta • Typical earth worms and some aquatic forms • Primarily detritivores • Eats through soil or mud, undigested material and mucus egested as casts • Important soil-enhancement animals. Annelida: Hirudinea • Leeches • Primarily freshwater, but also some terrestrial forms • 1-30cm • Many haemophagic (bloodfeeding) – Secrete anticoagulants – Important in medicine • Many predacious 17 3/25/11 Annelida: Polychaeta • Bristle worms (and many other names) • Mostly marine – Drift passively or crawl – Tube (fanworms) burrow, make shell of mucous and sand – Each segment with paired parapodia (extended area of skin) for locomotion, filter feeding, and gill function. Bilateria • Protostomes consist of two major clades (supported in large genomic survey): – LOPHOTROCHOZOA – ECDYSOZOA • Ecdysozoa contains more species than all other groups of multicellular organisms combined! Ecdysozoa • • • • • • Nematoda Arthropoda (and numerous other phyla not covered in Biology 221) Protostomes Proposed as monophyletic based on DNA sequences But originally proposed as early as 1897 (Perrier) because this includes all animals that shed their exoskeleton (ecdysis) 18 3/25/11 Nematoda: Round worms • ~80,000 species described, this is a dramatic underestimate of actual diversity • Possibly the most numerous animals • Pseudocoelomate Nematoda: Round worms • Cylindrical, tapered body; 1mm - 1m • Most aquatic habitats, damp soil; body fluids & tissues (plant & animal parasites) • Alimentary canal • Food transport via fluid in pseudocoel • Longitudinal muscles, thrashing movement Nematoda: Round worms • Reproduction usually sexual • Sexes separate, dimorphic, female larger • Fertilization internal • Female can lay >100,000 eggs/day • Fertilized eggs are a resistant zygote (dormant stage) 19 3/25/11 Nematoda: Round worms • Caenorhabditis elegans • Model organism (like Drosophila) • One of first organisms with complete genome sequenced • Developmental fate of every cell mapped (and mappable!) Nematoda: Round worms • Includes many important parasites of humans and agricultural crops • E.g. root-knot nematode • E.g. Trichinella spiralis – Infects undercooked meat (especially pork) – Encysts in muscle tissue – Juveniles develop in human intestine ARTHROPODA • Nearly 1 million species • The majority are insects • 2/3 of all organisms known are arthropods • The most successful animal phylum 20 3/25/11 ARTHROPODA General Characteristics • Segmentation – – – – Head Thorax Abdomen Tail • Exoskeleton-cuticle – Protein and chitin – Strong armor • Defense • Desiccation resistance – Periodic molting (ecdysis) ARTHROPODA General Characteristics • Jointed appendages – (arthropod = “jointed feet”) – Variously specialized for locomotion, feeding • Well-developed sensory organs – – – – Cephalization pronounced Eyes Olfactory receptors Antennae in many (touch, smell) ARTHROPODA General Characteristics • Open circulatory system – Hemolymph – Heart to sinuses to tissues to heart – Sinuses collectively known as homocoel • Reduced coelom • Gas exchange – Hemocoel becomes body cavity in adults – – – – Diverse mechanisms Gills Book lungs Trachea 21 3/25/11 Arthropoda: Diversity • Four major extant lineages (subphyla) – Chelicerates – Myriapods – Crustaceans – Hexapods Great Devonian Land Grab • One major extinct lineage (subphylum) – Trilobitomorpha Trilobitomorpha: Trilobites • Extinct, ~4,000 fossil species described • Shallow marine environments • Common in Paleozoic, extinct by Permian • Relatively unspecialized body segments Chelicerata • Horseshoe crabs, spiders, scorpions, mites (& a few others) • Anterior appendages modifed as pincers, fangs = chelicerae • No antennae • Cephalothorax (head and thorax fused) • Simple eyes 22 3/25/11 Chelicerata: Eurypterids • “Sea scorpions” • Extinct • Largest known arthropods to have ever lived (2m) • Marine, predaceous • Extinct at Permian extinction Chelicerata: Horseshoe crabs • “living fossils” – Extant forms nearly indistinguishable from Jurassic fossils • Ocean floor, living on soft substrate • come ashore for reproduction Chelicerata: Arachnida Spiders, scorpions, ticks, mites, harvestmen, others 23 3/25/11 Chelicerata: Arachnida • Cephalothorax with six pairs of appendages – Chelicerae – Pedipalps – Four pairs of walking legs • Book lungs for gas exchange • Webs: silky protein from spinnerets; used in feeding, dispersal Arthropoda • Relationships of Chelicerata to other groups under considerable debate. • Remaining groups: Myriapoda, Crustacea, Hexapoda – All without Chelicerae, but with Mandibles – All with antennae – All with compound eyes – Morphology argues for a monophyletic “Mandibulata” – But molecules sometimes suggest Chelicerata + Myriapoda (centipedes, millipedes) Arthropoda • Previously, “Mandibulata” were divided into the Biramia (Crustacea) and Uniramia (Myriapods + Hexapods) • Based on whether appendages are branched (Biramia) or unbranched (Uniramia) – Upper branch acting as gill – Lower branch acting as leg • Probably not a good phylogenetic character: too involved in function. – Some Crustacea are uniramous. Which ones would you guess? 24 3/25/11 Myriapoda Millipedes & Centipedes • Terrestrial • Diplopoda: Millipedes – Wormlike, 2 pair walking legs/segment (actually one segment is derived from two fused segments) – Detritus feeders • Chilopoda: Centipedes – 1 pair walking leg/segment – Venom claws as first appendage Hexapoda Insects and close relatives • >1,000,000 described species (more than half are beetles…) • Everywhere in terrestrial environments • Rare in marine environments • First fossils in Devonian (mid-Paleozoic): Oldest 400 mya • First winged insects in Carboniferous 320 mya Hexapoda Insects and close relatives • Why so diverse??? • Hypotheses: – Intimate associations with plants (mutualisms & parasitisms) – Flight – Compartmentalized body plans – Partitioning of the life cycle 25 3/25/11 Insect Flight • Wings not true appendages, extensions of exoskeleton • No appendages given over to flight (compare to other winged animals) Insect Flight • Two forms of flight: – Direct – Indirect • Direct flight – Ancestral form, found in Paleoptera: Dragonflies & Mayflies – Muscles directly attached to wings – Very fine control – One nerve impulse = one muscle contraction = one wing beat Insect Evolution Wings & Flight Pterygota Ancestral Direct Flight Paleoptera 26 3/25/11 Insect Flight • Indirect flight – Flight muscles attached to interior of thorax (NOT directly to wings) – Downstroke is accomplished solely through the elastic recoil of the thorax • Reduces number of muscle contractions per wingstroke by half – Single nerve impulse required to initiate muscle contraction, single impulse to cease. • Reduces number of nerve impulses to muscle contractions immensely. • Results in much more rapid wing beats (up to 1,000 times per second in some gnats) • Derived form found in Neoptera Insect Evolution Wings & Flight Pterygota Derived Indirect Flight Neoptera Compartmentalized Body Plan Insect Segments • • Three main segments Head – – – – • Segments fused One pair antennae Compound eyes Numerous pairs of appendages modified for feeding Thorax – Three pairs walking legs – Two pairs wings • Abdomen – Most of the digestive, respiratory, excretory and reproductive internal structures – Only appendages used in mating 27 3/25/11 Compartmentalized Body Plan Insect Segments • • Internal: Several complex organs Nervous system – Pronounced cephalization – Paired ventral nerve cords – Segmented ganglia (minibrain in each segment) • Excretory system – Malpighian tubules – Remove waste from hemolymph • Cardiovascular – Open circulatory system with heart – Spiracles open to tracheal tubes, breathe through body – Spiracles muscularized to inhale and exhale Partitioning of Life Cycle • Most insects sexual, internal fertilization • Many insects mate only once • Juvenile stage unwinged, can be dramatically different from adult stage – E.g. many orders with aquatic larvae, terrestrial adults – Allows occupation of multiple niches by a single individual Partitioning of Life Cycle • Evolutionary Trend: More distinction between life cycles • Incomplete metamorphosis (Hemimetabolous) – Ancestral state – Juvenile form closely resembles adult, but without wings – Grows by successive molts – Ultimate stage is winged adult 28 3/25/11 Partitioning of Life Cycle • Evolutionary Trend: More distinction between life cycles • Complete metamorphosis (Holometabolous) – Derived state – Juveniles are larvae: maggots, grubs, caterpillars, etc. – Larval stage grows by successive molts – Enter an inactive stage: pupa, chrysalis – Entire body digested, reformed as adult, winged insect Incomplete Metamorphosis Insect Evolution Incomplete Metamorphosis Insect Evolution Complete Metamorphosis 29 3/25/11 Crustacea Chelicerata • But the Crustacea are the dominant arthropod group in the oceans. • Indeed, insects are probably crustaceans that colonized land. • Crustacea paraphyletic • Biramous appendage probably lost as a consequence of move to terrestrial environment. Myriapoda Crustacea • Plesiomorphically biramous. • Dominant marine arthropods: ~52,000 species. Crustacea • General morphology: • Two paired antennae • Modified appendages (e.g. lobster has 19 pairs) – 3 or more pairs as mouthparts – Walking legs on thorax and abdlomen – Lost appendages can regenerate 30 3/25/11 Crustacean Diversity • DECAPODS • Most commonly encountered – lobsters, crabs (land, marine), shrimp, crayfish (fresh) – Antarctic krill – exoskeleton hardened with CaCO3 Crustacean Diversity • BRANCHIOPODS • Fairy shrimp, brine shrimp, water fleas, sea-monkeys • Primarily fresh-water • Fertilized eggs can go dormant, survive extreme conditions Crustacean Diversity • BRANCHIOPODS • Fairy shrimp, brine shrimp, water fleas, sea-monkeys • Primarily fresh-water • Fertilized eggs can go dormant, survive extreme conditions 31 3/25/11 Crustacean Diversity • ISOPODS • Most widespread group of Crustacea • From deep sea vents to truly terrestrial • Diverse habitats from herbivorous to parasitic • Pill bugs, roly-poly, sea lice Crustacean Diversity • COPEPODS • Marine and freshwater • Numerous – Millions can be present in m3 of seawater • Important as fresh and marine plankton • Include krill, major component of plankton and major prey item of baleen whales • Some parasitic forms Crustacean Diversity • • • • CIRRIPEDIA Barnacles Sessile crustaceans Carapace hardened by CaCO3 • Limbs modified as filter feeding appendages • How do they mate? 32 3/25/11 Summary • Protostomes are characterized by specific early embryonic features • Include two main lineages – Lophotrochozoa – Ecdysozoa • Lophotrochozoa most diverse in phyla (fundamentally different body plans) • Ecdysozoa most diverse in species Deuterostomia • Deuterostomes are sister-group to Protostomes within Bilateria 33 3/25/11 Deuterostomia • Deuterostomes are sister-group to Protostomes within Bilateria • Deuterostomes also characterized by details of early embryonic development Deuterostomia • Includes two major lineages • Echinodermata • Chordata – Cephalochordata – Urochordata – Vertebrata Echinodermata • Sea stars, urchins and relatives • ~7000 species, six classes • All marine • “Spiny skin” – Calcareous shell, often w/ bumps, spines – Covered with thin epidermis 34 3/25/11 Echinodermata • SECONDARY RADIAL SYMMETRY – Bilateral larvae – Left side grows at expense of right side (eventually absorbed) – Five radiating spokes from central axis • • Slow-moving, sessile or sedentary Separate sexes, external fertilization Echinodermata • Water vascular system • Operates hydraulic canals, branching and ramifying into tube feet – Locomotion – Feeding – Gas exchange Echinoderm Diversity • 1: Asteroidea - sea stars • Five or more arms radiate from central disc • Tube feet on undersurface of arms, act like suction disc for slow walking • Also for feeding, grasping clams, mollusks; inverts digestive tract inside animal and secretes digestive enzymes: predators • Some with powers of regeneration 35 3/25/11 Echinoderm Diversity • 2: Ophiuroidea- brittle stars and basket stars (sister-taxon to Asteroidea) • Distinct central disc; thin flexible arms • Tube feet lack suckers; move by thrashing arms • Feeding modes vary: scavenging, predaceous (brittle stars), suspension feeders (basket stars) Echinoderm Diversity • 3: Echinoidea - sea urchins, sand dollars • No arms, spherical (urchins); or flat, disc-shaped (sand dollars) • Five rows of tube feet for locomotion • Long external spines controlled by muscles, also for movement • Complex mouth for eating seaweed Sea Urchins & Sea Otters • Sea urchins are voracious herbivores of kelp • Sea otters eat lots of sea urchins. • Sea otters hunted to ~38 individuals, kelp forests crashed. • Sea otters protected, now >3,000, kelp beds recovering • Effect visible from space. 36 3/25/11 Echinoderm Diversity • 4: Crinoidea - sea lilies, feather stars • Ancient group, to Cambrian • Attaches to substratum by stalk • Others crawl by long flexible arms, also used in filter feeding, mouth upward Echinoderm Diversity • 5: Holothuroidea - sea cucumbers • Lack spines, exoskeleton reduced • Elongate, “cucumber” shape, but... • Five rows of tube feet as in other echinoderms; • Some oral tube feed modified as tentacles. Echinoderm Diversity • Concentricycloidea - sea daisies • First discovered in 1986 • Live on sunken deep-sea wood (>1000m) 37
