© 2006 Thomson-Brooks Cole Chapter 9 Molluscs, Arthropods, Lophophorates, Echinoderms, and Invertebrate Chordates.

© 2006 Thomson-Brooks Cole Key Concepts Molluscs have soft bodies that are usually covered by a shell. Molluscs are important herbivores and carnivores in the marine environment. Arthropods have external skeletons, jointed appendages, and sophisticated sense organs.

© 2006 Thomson-Brooks Cole Key Concepts Crustaceans make up a majority of the zooplanton that are a major link between phytoplankton and higher- order consumers in oceanic food webs. Echinoderms exhibit radial symmetry as adults. Echinoderms have internal skeletons and a unique water vascular system that functions in locomotion, food gathering, and circulation.

© 2006 Thomson-Brooks Cole Molluscs Phylum Mollusca Have soft bodies, usually covered by a calcium carbonate shell One of the largest and most successful groups of animals Wide range of sizes, lifestyles and relationships to humans (i.e., some are food, others cause commercial damage)

© 2006 Thomson-Brooks Cole Molluscan Body 2 major parts: –head-foot—region containing the head with its mouth and sensory organs and the foot, which is the animal’s organ of locomotion –visceral mass—body region containing the other organ systems, including the circulatory, digestive, respiratory, excretory and reproductive systems

Molluscan Body Mantle—protective tissue covering the soft parts, which extends from the visceral mass and hangs down on each side of the body; it forms the shell –mantle cavity—space between the mantle and the body Radula—a ribbon of tissue containing teeth (found in all except bivalves) used for scraping, piercing, tearing or cutting pieces of food

Molluscan Shell Secreted by the mantle Normally comprises 3 layers: –periostracum—outermost layer, composed of the protein conchiolin that protects the shell from dissolution and boring animals –prismatic layer—middle layer, composed of calcium carbonate and protein, which makes up the bulk of the shell –nacreous layer—innermost layer, composed of calcium carbonate in thin sheets, with a different crystal structure

Molluscan Shell Periostracum and prismatic layers form at the mantle’s margin as the animal grows Nacreous layer is secreted continuously –nacreous layer of oysters is known as mother of pearl, which can become layered over irritating particles (such as sand grains) to form pearls

© 2006 Thomson-Brooks Cole Chitons Class Polyplacophora Have flattened bodies most often covered by 8 shell plates Attach tightly to rocks Most scrape algae and other organisms off the rocks with radulae for food –Placipholrella eats small crustaceans and other invertebrates

Scaphopods Tusk shells (class Scaphopoda) Tusk-like shell is open at both ends, with foot protruding from larger end Water enters and exits at smaller end Feed primarily on foraminiferans, which are captured with the foot or tentacles emerging from the head

Gastropods Class Gastropoda May have no shell, or a univalve (one- piece) shell –as the animal grows, whorls of the shell increase in size around a central axis –operculum—covering over the shell’s aperture which allows it to be closed

Gastropods Feeding and nutrition –herbivores – most feed on fine algae; some on large algae like kelps –carnivores – usually locate prey using its chemical trail; have evolved various behaviors for capturing/subduing prey –scavengers and deposit feeders –filter feeders

Gastropods Naked gastropods –nudibranchs—marine gastropods that lack a shell –have cerata—projections from the body that increase the surface area available for gas exchange –some feed on cnidarians and then use their stinging cells as defensive weapons in the tips of cerata –bright colors indicate toxicity to predators

Gastropods Reproduction and development –most have separate sexes –most have internal fertilization –primitive forms shed their eggs directly into the sea –2 types of free-swimming larva trochophore (primitive molluscs) veliger (more characteristic) –some are hermaphroditic e.g. slipper limpets of genus Crepidula

Bivalves Class Bivalvia Have shells divided into 2 jointed halves (valves) Includes: –clams –oysters –mussels –scallops –shipworms

© 2006 Thomson-Brooks Cole Bivalves Bivalve anatomy –no head or radula –laterally compressed bodies –shell halves attached dorsally at a hinge by ligaments umbo—oldest part of the shell, around hinge adductor muscles—large muscles which close the 2 valves –mantle often forms inhalant and exhalant openings to facilitate filter feeding palps form the food into a mass for digestion

Bivalves Bivalve adaptations to different habitats –soft-bottom burrowers (infauna) siphons—structures formed when the mantle is fused around inhalant and exhalant openings, which project above the surface of sediments siphons facilitate filter feeding while remaining buried in sand

© 2006 Thomson-Brooks Cole Bivalves –attached surface dwellers may lie on one side and cement 1 valve to a hard surface (fusion) byssus—a tough protein secreted by a foot gland, commonly in the form of threads, used to attach to the surface –unattached surface dwellers movement by jet propulsion, used primarily to escape from predators –boring bivalves microscopic teeth on the valves symbiotic bacteria produce wood-digesting enzymes, and live in a special digestive system organ

Bivalves Reproduction in bivalves –majority have separate sexes –fertilization usually occurs in the water –larvae go through trochophore and veliger stages –shipworms and some species of cockle, scallop and oyster are hermaphroditic

© 2006 Thomson-Brooks Cole Cephalopods Class Cephalopoda Named after the foot, which modified into a head-like structure Ring of tentacles projects from the anterior edge of the head, for use in prey capture, defense, reproduction and sometimes locomotion Except for nautiloids, they lack shells or have small internal shells

© 2006 Thomson-Brooks Cole Cephalopods Types of cephalopods –nautiloids produce large, coiled shells composed of chambers separated by septa (partitions) –gas-filled chambers aid with buoyancy –siphuncle—cord of tissue connecting the nautiloid to uninhabited chambers (it inhabits the last chamber) which removes seawater from each chamber as it forms 60-90 tentacles coated with a sticky substance function in sensation or bringing food to the mouth

Cephalopods –nautiloids (continued) move using jet propulsion usually dwell on the bottom during the day and migrate to the surface at night nautiloids eat hermit crabs and scavenge for other food on the bottom food is stored in a crop prior to transport to the stomach for digestion

© 2006 Thomson-Brooks Cole Cephalopods –coleoids (e.g. cuttlefish, squids, octopods) cuttlefish have a bulky body, fins, 10 appendages (8 arms + 2 tentacles), and small internal shells squids have: –large cylindrical bodies with a pair of fins derived from mantle tissue –10 appendages (8 arms + 2 tentacles) arranged in 5 pairs around the head and embellished with cup- shaped suckers surrounded by toothed structures and attached by a short stalk – a pen (a degenerate shell; an internal strip of hard protein) which helps support the mantle

Cephalopods –coleoids (continued) octopods have 8 arms (no tentacles) with suckers without stalks or teeth, and sac-like bodies without fins coleoids cloud the water with a dark fluid called sepia containing melanin (a brown-black pigment) when disturbed swim by jet propulsion by forcing water through a ventrally-located siphon or by fin undulation (in squids) have the most advanced, complex nervous system among invertebrates

© 2006 Thomson-Brooks Cole Cephalopods Color and shape in cephalopods –arm/body movements and color changes are used in communication –chromatophores—special skin cells containing pigment granules which are concentrated or dispersed to change color –cephalopods can produce general body color changes or stripes and other patterns

Cephalopods Feeding and nutrition –carnivores – prey is located with highly developed eyes and captured by tentacles or arms –a pair of powerful, beak-like jaws in the oral cavity is used to bite or tear tissues; octopods use radula to drill holes in shells –diet depends on habitat squids are pelagic: fish, crustaceans, squid cuttlefish find invertebrates on the bottom octopods forage or lie in wait near the entrances to their dens

© 2006 Thomson-Brooks Cole Cephalopods Reproduction in cephalopods –sexes are separate –mating frequently involves some kind of courtship display –male squid have a modified arm used to transfer a spermatophore (sperm package) from his mantle cavity to the female’s, near the opening of the oviduct (tube that carries eggs to the outside of the body)

© 2006 Thomson-Brooks Cole Cephalopods –eggs may be released into the water, laid in shells secreted by modified tentacles, or attached to stones or other objects –females of some octopod species incubate eggs until they hatch –cephalopods usually reproduce once and then die

© 2006 Thomson-Brooks Cole Ecological Roles of Molluscs Food for humans and other animals –snail shells are a calcium source for some marine birds –sperm whales consume masses of squid Some snails are intermediate hosts to parasites Shipworms damage wooden pilings and boat hulls, but also prevent wood from accumulating in the marine environment A few bivalves have commensal relationships (attaching to other animals)

© 2006 Thomson-Brooks Cole Arthropods: Animals with Jointed Appendages Phylum Arthropoda = 75% of species Have exoskeleton—a hard, protective exterior skeleton composed of protein and chitin (a tough polysaccharide) –molting—shedding and replacement of exoskeleton to permit animal’s growth Body is divided into segments Usually, each segment has a pair of jointed appendages, for locomotion, mouthparts, sensation, ornamentation

© 2006 Thomson-Brooks Cole Arthropods: Animals with Jointed Appendages Have highly developed nervous systems –sophisticated sense organs –capacity for learning 2 major groups of marine arthropods: –chelicerates – have a pair chelicerae (oral appendages) and lack mouthparts for chewing food –mandibulates – have appendages called mandibles that can be used to chew food

© 2006 Thomson-Brooks Cole Chelicerates 6 pairs of appendages; 1 pair are chelicerae for feeding Horseshoe crabs –3 body regions cephalothorax – largest region with the most obvious appendages abdomen – contains the gills telson – a long spike used for steering and defense –body is covered by a carapace—a hard outer covering

Chelicerates Horseshoe crabs (continued) –locomotion by walking or swimming by flexing the abdomen –mostly nocturnal scavengers –smaller males attach to females to mate, and eggs are laid in a depression on the beach; larvae return to the sea to grow

© 2006 Thomson-Brooks Cole Chelicerates Sea spiders –have small, thin bodies with 4 or more pairs of walking legs –only marine invertebrate known where the male carries the eggs (with an extra pair of appendages) –palps—appendages used in sensation –feed on juices from cnidarians and other soft-bodied invertebrates, using a long sucking proboscis

© 2006 Thomson-Brooks Cole Mandibulates Crustaceans—marine mandibulates Crustacean anatomy –3 main body regions: head thorax abdomen –appendages: 2 pairs of sensory antennae mandibles and maxillae used for feeding walking legs, swimmerets (swimming legs), legs modified for reproduction, chelipeds (legs modified for defense)

Mandibulates –gas exchange small crustaceans exchange gases through their body surface larger crustaceans have gills Molting –Crucial part of the life cycle –Frequency of molting decreases with age –Controlled by specific hormones produced in a gland in the head, and initiated by environmental conditions

Decapods Order decapoda; includes animals with 5 pairs of walking legs: –crabs –lobsters –true shrimp 1 st pair of walking legs are chelipeds— pincers used for capturing prey and for defense Wide range in size

© 2006 Thomson-Brooks Cole Decapods Specialized behaviors –hermit crabs inhabit empty shells –decorator crabs camouflage carapaces with bits of sponge, anemones, etc. –common blue crabs are agile swimmers

Decapods Nutrition and digestion –chelipeds are used for prey capture –appendages are used for scavenging –predation and scavenging are usually combined –some decapods are deposit or filter feeders

© 2006 Thomson-Brooks Cole Decapods Reproduction –sexes usually separate –males have appendages modified for clasping females and delivering sperm spermatophores—sperm packages copulatory pleopods—2 pairs of anterior abdominal appendages that deliver sperm –most brood their eggs in chambers or modified appendages

© 2006 Thomson-Brooks Cole Decapods Reproduction (continued) –larval stages: zoea larval stage—initial stage in crabs, recognized by the very long rostral spine and sometimes lateral spines (thought to reduce predation) nauplius larva—initial stage in shrimp

© 2006 Thomson-Brooks Cole Mantis Shrimp Order Stomatopoda Highly specialized predators of fishes, crabs, shrimp and molluscs 2 nd pair of thoracic appendages –enlarged –has a movable finger that can be extended rapidly for prey capture/defense –used to spear or smash prey

© 2006 Thomson-Brooks Cole Mantis Shrimp Reproduction –some mantis shrimp pair for life and share a burrow –zoea larvae hatch from an egg mass –retain planktonic form for 3 months, then settle and take up adult lifestyle

© 2006 Thomson-Brooks Cole Krill Order Euphausiacea Pelagic, shrimp-like, 3-6 cm long Filter feeders that eat zooplankton Most are bioluminescent –photophore—specialized light organ –swarms—large masses of individuals; bioluminescent is thought to signal swarming behavior Food source for some whales, seals, penguins, and many fishes

Amphipods Order Amphipoda Shrimp-like, with posterior 3 pairs of appendages directed backward Many are burrowers; some construct tubes which they inhabit Most are detritus feeders or scavengers, some are herbivores –gnathopods—special appendages for picking up plant and animal remains Eggs fertilized in female’s brood chamber; young resemble adults upon hatching

© 2006 Thomson-Brooks Cole Copepods Class Copepoda – the largest group of small crustaceans Usually the most abundant member of the zooplankton Mostly suspension feeders; some rely on detritus, some are predators Males fertilize females with spermatophores; eggs are shed into the water column where they hatch

© 2006 Thomson-Brooks Cole Barnacles Class Cirripedia – the only sessile crustaceans Most have calcium carbonate shell Attach directly to a hard surface, or have a stalk for attachment Filter feed using cirripeds—feathery appendages which extend into the water when the shell is open

Barnacles Reproduction –hermaphroditic –cross-fertilized using a long, extensible penis –brooded eggs hatch into nauplius larvae –nauplius larvae develop into cyprid larvae, which have compound eyes and a carapace of 2 shell plates –cyprid larvae attach using adhesive glands in antennae, then metamorphose into adults

© 2006 Thomson-Brooks Cole Ecological Roles of Arthropods Arthropods as food –important food sources for marine animals and humans –copepods form a link between phytoplankton they eat and many animals that use them as a major food source –krill are consumed in large quantities by whales and other organisms

© 2006 Thomson-Brooks Cole Ecological Roles of Arthropods Arthropods as symbionts –cleaning shrimps remove ectoparasites and other materials from reef fish –some copepods are ectoparasites for fish –some copepods are endoparasites or commensals within polychaete worms, echinoderms, tunicates, bivalves or cnidarians –amphipods carry sea butterflies –barnacles are commensal with many hosts

© 2006 Thomson-Brooks Cole Ecological Roles of Arthropods Role of arthropods in recycling and fouling –grass shrimp feed on detrital cellulose material, and so helps break down algae and grasses in tidal marsh ecosystems –barnacles are a serious fouling problem on ship bottoms attached barnacles can reduce ship speed by 30% special paints and other anti-fouling measures

© 2006 Thomson-Brooks Cole Lophophorates Lophophorates are sessile animals that lack a distinct head Possess a lophophore—arrangement of ciliated tentacles that surround the mouth, used for feeding, gas exchange 3 phyla of lophophorates: –Phoronida (phoronids) –Ectoprocta (bryozoans) –Brachiopoda (brachiopods)

© 2006 Thomson-Brooks Cole Phoronids Small, worm-like animals Secrete a tube of leathery protein or chitin that can be attached or buried in bottom sediments Catch plankton and detritus with mucus-coated tentacles Can reproduce sexually or asexually (budding, transverse fission) Have a planktonic larval stage

Bryozoans Small, abundant, colonial animals Most live on rocks, shell, algae, mangroves, etc. in shallow water Colonies are composed of zooids (tiny individuals), each inhabiting a box-like chamber it secretes Most are hermaphroditic brooders Larvae are planktonic; they settle to form new colonies

Brachiopods Most lamp shells are benthic and live in shallow water Have mollusc-like, bivalve shells –valves differ in size and shape, and are dorsal and ventral –a pedicle (fleshy stalk) attaches the shell or is buried Gather detritus/algae with lophophore Generally have separate sexes; larvae are planktonic and settle in 24-30 hrs.

© 2006 Thomson-Brooks Cole Ecological Roles of Lophophorates As a group, they are filter feeders Food for many invertebrates, especially molluscs and crustaceans Largely responsible for fouling ship bottoms

© 2006 Thomson-Brooks Cole Echinoderms: Animals with Spiny Skins Phylum Echinodermata Larval forms exhibit bilateral symmetry but most adults exhibit a modified form of radial symmetry Mostly benthic, and found at nearly all depths Sea cucumbers and brittle stars are commonly found in deep-sea samples

© 2006 Thomson-Brooks Cole Echinoderm Structure Endoskeleton—internal skeleton that lies just beneath the epidermis –ossicles—plates of calcium carbonate –endoskeleton is composed of ossicles held together by connective tissue Spines and tubercles project outward from the ossicles –pedicellariae—tiny, pincer-like structures around the bases of spines that keep the body surface clean in some echinoderms

© 2006 Thomson-Brooks Cole Echinoderm Structure Water vascular system—unique hydraulic system that functions in locomotion, feeding, gas exchange and excretion –water enters by the madreporite –passes through a system of canals –attached to some canals are tube feet— hollow structures with a sac-like ampulla within the body and a a sucker protruding from the ambulacral groove

© 2006 Thomson-Brooks Cole Sea Stars Class Asteroidea Typically composed of a central disk + 5 arms or rays On underside, ambulacral grooves with tube feet radiate from the mouth along each ray Aboral surface—the side opposite the mouth, which is frequently rough or spiny

Sea Stars Feeding in sea stars –most are carnivores or scavengers of invertebrates and sometimes fish –prey are located by sensing of substances they release into the water –sea stars envelope and open bivalves, evert a portion of the stomach, and insert it into the bivalves to digest them digestive glands located in each ray provide digestive enzymes

Sea Stars Reproduction and regeneration –sea stars can regenerate rays; some can regenerate themselves from a single ray plus part of the central disc –asexual reproduction involves division of the central disk and regeneration of each half into a new individual –most have separate sexes, which shed eggs and sperm into the water for fertilization and hatching into usually planktonic larvae

© 2006 Thomson-Brooks Cole Ophiuroids Class Ophiuroidea –e.g. brittle, basket and serpent stars Benthic with 5 slender, distinct arms, frequently covered with many spines Lack pedicellariae and have closed abulacral grooves Tube feet lack suckers and are used in locomotion and feeding Brittle stars shed arms if disturbed

Ophiuroids Feeding in ophiuroids –carnivores, scavengers, deposit feeders, suspension feeders, or filter feeders –brittle stars usually filter feed by lifting their arms and waving them in the water –deposit feeders use their podia to gather organic particles from the bottom into food balls and pass them to the mouth –basket stars suspension feed by climbing onto corals/rocks and fanning their arms toward the prevailing current

© 2006 Thomson-Brooks Cole Ophiuroids Reproduction and regeneration in ophiuroids –autotomize—to cast off, as of an arm, when disturbed or seized by a predator –asexual reproduction by division into 2 halves and regeneration of individuals –mostly separate sexes –may shed eggs into water or brood them in ovaries or a body cavity –planktonic larvae metamorphose into adults within the water column

© 2006 Thomson-Brooks Cole Sea Urchins and their Relatives Class Echinoidea – echinoids Body enclosed by test—a hard exoskeleton Benthic on solid surfaces (sea urchins) or in sand (heart urchins, sand dollars) Regular (radial) echinoids—sea urchins; spheroid body with long, moveable spines Irregular (bilateral) echinoids—heart urchins and sand dollars; have short spines on their tests

Sea Urchins and their Relatives Echinoid structure –tube feet project from 5 pairs of ambulacral areas –spines project from the test aid in locomotion and protection, and may contain venom –sexes are always separate –regular echinoids have 5 gonads; irregular echinoids, 4 –sperm and eggs shed into the water; fertilized eggs hatch into planktonic larvae

© 2006 Thomson-Brooks Cole Sea Urchins and their Relatives Feeding in echinoids –feeding in regular echinoids mostly grazers which scrape algae and other food materials from surfaces Aristotle’s lantern—a chewing structure of 5 teeth –feeding in irregular urchins irregular urchins are selective deposit feeders some sand dollars are suspension feeders

© 2006 Thomson-Brooks Cole Sea Cucumbers Class Holothuroidea Have elongated bodies, and usually lie on 1 side Respiratory trees—a system of tubules located in the body cavity which accomplish gas exchange Sexes are generally separate Eggs may be brooded or incubated; larvae are planktonic

Sea Cucumbers Feeding in sea cucumbers –mainly deposit or suspension feeders –oral tentacles—modified tube feet coated with mucus which are used to trap small food particles Defensive behavior –Cuvierian tubules—sticky tubules released from the anus of some species –eviscerate—to release some internal organs through the anus or mouth

© 2006 Thomson-Brooks Cole Crinoids Class Crinoidea – sea lilies and feather stars Primitive, flower-like echinoderms Most are feather stars, which seldom move and cling to the bottom with grasping cirri Suspension feeders Can regenerate lost arms Separate sexes shed eggs/sperm into the water; larvae have fee-swimming stage, then attach to the bottom and metamorphose into minute adults

Ecological Roles of Echinoderms Spiny skins deter most predators Predators of molluscs, other echinoderms, cnidarians, crustaceans –crown-of-thorns sea star eats coral –sea urchins destroy kelp forests Black sea urchins control algae growth on coral reefs Sea cucumber poison, holothurin, has potential as a medicine

© 2006 Thomson-Brooks Cole Tunicates Subphylum Urochordata Mostly sessile, widely distributed Named for their body covering –tunic—body covering, largely composed of a substance similar to cellulose Types: –sea squirts –salps –larvaceans

© 2006 Thomson-Brooks Cole Sea Squirts Class Ascidiacea Name derived from tendency to expel a stream of water when disturbed Round or cylindrical bodies with 2 tubes projecting from them: –incurrent siphon that brings in water and food –excurrent siphon that eliminates water and wastes

Sea Squirts Lifestyles: solitary, colonial, compound –compound—organisms composed of several individuals (zooids) that share a common tunic Filter feed on plankton in the water passing through their pharynx –some have symbiotic algae or bacteria Can regenerate lost body parts

© 2006 Thomson-Brooks Cole Sea Squirts Asexual reproduction (by budding) occurs in colonial ascidians Most are hermaphrodites that release gametes into the water column for fertilization Tadpole-like larvae are free-swimming for 36 hrs., then settle and metamorphose into the sessile stage

© 2006 Thomson-Brooks Cole Salps and Larvaceans Salps –class Thaliacea –free-swimming tunicates with incurrent and excurrent siphons on opposite ends of their barrel-shaped bodies pump water through to swim Larvaceans –class Larvacea –free-swimming; produce delicate enclosures of mucus used in feeding

© 2006 Thomson-Brooks Cole Cephalochordates Subphylum Cephalochordata- lancelets Fish-like chordates; slender, laterally compressed and eel-like in form and behavior Benthic; burrow in coarse sands Suspension feed by projecting their heads above the sand Separate sexes practice internal fertilization

© 2006 Thomson-Brooks Cole Arrowworms Phylum Chaetognatha Common planktonic animals with a torpedo-shaped body Grasping spines (large curved hooks) hang from the head and flank the vestibule (chamber leading to mouth) Carnivorous; seize other planktonic prey animals with grasping spines and inject tetrodotoxin

© 2006 Thomson-Brooks Cole Chapter 9 Molluscs, Arthropods, Lophophorates, Echinoderms, and Invertebrate Chordates.

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© 2006 Thomson-Brooks Cole Chapter 9 Molluscs, Arthropods, Lophophorates, Echinoderms, and Invertebrate Chordates.

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Presentation on theme: "© 2006 Thomson-Brooks Cole Chapter 9 Molluscs, Arthropods, Lophophorates, Echinoderms, and Invertebrate Chordates."— Presentation transcript:

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