Coral Reef Communities Chapters: 8,9,15

1
Coral Reef CommunitiesChapters 8,9,15
2
What Are Animals?

• Animals
• are multicellular
• distinguishes them from bacteria and most
  protists
• have eukaryotic cells without cell walls
• distinguishes them from bacteria, fungi, algae
  and plants
• cannot produce their own food, so they depend on
  other organisms for nutrients
• can actively move (with the exception of adult
  sponges)

3
Sponges

• Phylum Porifera
• Basic characteristics
• simple
• asymmetric
• sessilepermanently attached to a solid surface
• have many shapes, sizes and colors

4
Sponge Structure and Function

• Body is built around a system of water canals
• ostiatiny holes or pores through which water
  enters the sponges body
• spongocoelspacious cavity in the sponge
• osculumlarge opening through which water exits
  from the spongocoel

5
Sponge Structure and Function

• Lacking tissues, sponges have specialized cells
• collar cells (choanocytes) use their flagella to
  provide force for moving water through the
  sponges body
• archaeocytescells that resemble amoebas, and can
  move through the body
• can assume any of the other cell forms, or
  transport materials

6
Sponge Structure and Function

• Structural materials
• spiculesskeletal elements that give support to a
  sponges body, which are produced by specialized
  cells and composed of calcium carbonate, silica
  or spongin
• spongina protein that forms flexible fibers

7
Sponge Structure and Function

• Sponge size and body form
• size is limited by water circulation
• asconoidsimplest form tubular and always small
• syconoidsponges that exhibit the first stages of
  body-wall folding
• leuconoidsponges with the highest degree of
  folding, which have many chambers lined with
  collar cells

8
Sponge Structure and Function

• Nutrition and digestion
• sponges are suspension feeders they feed on
  material that is suspended in seawater
• sponges are filter feeders they filter their
  food from the water
• sponges are one of the few animals that can
  capture particles 0.1 to 1.0 micrometers in size

9
Sponge Structure and Function

• Reproduction in sponges
• asexual reproduction
• buddinga group of cells on the outer surface of
  the sponge develops and grows into a tiny new
  sponge, which drops off
• fragmentationproduction of a new sponge from
  pieces that are broken off
• sexual reproduction
• eggs usually develop from archaeocytes and sperm
  from modified collar cells
• larval stage is a planktonic amphiblastula

10
Ecological Roles of Sponges

• Competition
• compete for space to attach with corals and
  bryozoans
• Predator-prey relationships
• few species eat sponges
• spicules are like needles
• some produce chemical deterrents
• major food source for hawksbill sea turtle

11
Ecological Roles of Sponges

• Symbiotic relationships
• sponges are mutualistic or commensalistic hosts
  to many organisms
• e.g. mutualistic bacteria
• many organisms live within the canals or
  spongocoel, for protection, water flow
• Sponges and nutrient cycling
• boring sponges recycle calcium as they burrow
  into coral and mollusc shells

12
Cnidarians Animals with Stinging Cells

• Phylum Cnidaria
• Named for their cnidocytesstinging cells
• Cnidocytes are used to capture prey and protect
  the animal

13
Organization of the Cnidarian Body

• Radial symmetrymany planes can be drawn through
  the central axis that will divide the animal into
  equivalent halves
• Often exhibit 2 body plans within their life
  cycles
• polypa benthic form characterized by a
  cylindrical body with an opening at 1 end
• medusaa free-floating stage (jellyfish)

14
Stinging Cells

• Cnidastinging organelle within a cnidocyte,
  which may function in locomotion, prey capture,
  or defense
• nematocystsspearing type, which are discharged
  when the cnidocilla bristle-like
  triggercontacts another object
• Dangerous species
• Portuguese man-of-war (painful stings)
• box jellyfish (can kill within 3-20 minutes)

15
Types of Cnidarians

• Hydrozoans (class Hydrozoa)
• mostly colonial
• colonial forms contain 2 types of polyp
• feeding polypfunctions in food capture
• reproductive polypspecialized for reproduction
• hydrocorals secrete a calcareous skeleton
• some produce floating colonies
• e.g. Portuguese man-of-war

16
Types of Cnidarians

• Scyphozoans
• true jellyfish (class Scyphozoa)
• medusa is predominant life stage
• photoreceptorssense organs that can determine
  whether it is dark or light
• Cubozoa
• box jellyfish (class Cubozoa)
• tropical
• voracious predators, primarily of fish

17
Types of Cnidarians

• Anthozoans (class Anthozoa)
• sea anemones
• polyps with a vascular cavity divided into
  compartments radiating from the central one
• though sessile, many can change locations
• coral animals
• polyps that secrete a hard or soft skeleton
• form reefs along with types of algae
• soft corals
• polyps that form plant-like colonies

18
Nutrition and Digestion of Cnidarians

• Gastrovascular cavitycentral cavity where
  cnidarians digest their prey
• functions in digestion and transport
• Many hydrozoans and anthozoans are suspension
  feeders
• Jellyfish and box jellyfish eat fish and larger
  invertebrates
• Sea anemones generally feed on invertebrates

19
Reproduction

• Hydrozoans
• generally exhibit asexual polyp stage and sexual
  medusa stage in the life cycle
• reproductive polyps form medusa-like buds which
  grow into adults after release
• adults release gametes into the water, where they
  are fertilized and form larvae
• planula larvaplanktonic larva that grows in the
  water column, then settles

20
Reproduction

• Scyphozoans
• medusae (sexual stage) release gametes into the
  water for fertilization
• planula larvae settle, grow into polyps, and
  reproduce medusa-like buds asexually

21
Reproduction

• Anthozoans
• asexual reproduction
• pedal lacerationleaving parts of the pedal disk
  (base) behind to grow into new animals
• fissionthe anemone splits in two and each half
  grows into a new individual
• budding produces large colonies of identical hard
  corals
• sexual reproduction
• larval stage is a planula larva

22
Ecological Relationships of Cnidarians

• Predator-prey relationships
• cnidarians are predators
• stinging cells discourage predation
• Habitat formation
• coral polyps form complex 3-dimensional
  structures inhabited by thousands of other
  organisms
• coral reefs provide a solid surface for
  attachment, and buffer waves and storms

23
Ecological Relationships of Cnidarians

• Symbiotic relationships
• Portuguese man-of-war and man-of-war fish
• reef-forming corals and zooxanthellae
• sea anemones...
• and clownfish
• and the hermit crab

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Ctenophores

• Phylum Ctenophora
• Planktonic, nearly transparent
• Ctenophore structure
• named for 8 rows of comb plates (ctenes) which
  the animal uses for locomotion
• ctenes are composed of large cilia
• exhibit radial symmetry
• bioluminescent

25
Ctenophores

• Digestion and nutrition
• carnivorous, feeding on other planktonic animals
• may used branched tentacles in a net pattern,
  adhesive cells, jellyfish stingers

26
Coral Animals

• Stony (true) corals deposit massive amounts of
  CaCO3 that compose most of the structure of coral
  reefs
• Hermatypiccoral species that produce reefs,
  found in shallow, tropical waters
• Ahermatypiccorals that do not build reefs, which
  can grow in deeper water from the tropics to
  polar seas
• most do not harbor zooxanthellae

27
Coral Animals

• Coral colonies
• large colonies of small coral polyps, each of
  which secretes a corallite
• a planula larva settles and attaches
• a polyp develops, and reproduces by budding to
  form a growing colony
• polyps gastrovascular cavities remain
  interconnected
• a thin, usually colorful epidermis overlies the
  colony surface

28
Coral Animals

• Sexual reproduction in coral
• mostly broadcast spawnersrelease both sperm and
  eggs into the surrounding seawater
• spawning is usually synchronous among Pacific
  reef species, but nonsynchronous among Caribbean
  species

29
Coral Animals

• Asexual reproduction
• Reproduction by fragmentation
• some branching corals are fragile and tend to
  break during storms
• if they survive the storm, fragments can attach
  and grow into new colonies
• fragmentation is a common form of asexual
  reproduction for branching corals

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Coral Animals

• Coral nutrition
• symbiotic zooxanthellae
• supply 90 of nutritional needs of stony coral
• zooxanthella provide glucose, glycerol and amino
  acids
• coral polyp provides a suitable habitat and
  nutrients, absorbed directly through the animals
  tissues
• zooxanthellae remove CO2 and produce O2
• need of zooxanthellae for sunlight limits depths
  to which stony corals can grow

31
Coral Animals

• Coral nutrition (continued)
• corals as predators
• small animals paralyzed by the nematocysts are
  passed into the digestive cavity

32
World of Coral Reefs

• Coral reefs are highly productive, but occur in
  nutrient-poor waters
• This is made possible by the symbiotic
  relationship between coral animals and
  zooxanthellae
• These symbionts algae form the basis of the
  community other reef animals depend on these
  organisms

33
Coral Reef Types

• Fringing reefs border islands or continental
  landmasses
• Barrier reefs are similar to fringing reefs but
  separated from the landmass and fringing reef by
  lagoons or deepwater channels
• Atolls, usually elliptical, arise out of deep
  water and have a centrally-located lagoon

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Reef Structure

• Reef front or forereefportion of the reef that
  rises from the lower depths of the ocean to a
  level just at or just below the surface of the
  water, on the seaward side
• drop-offa steep reef-front that forms a vertical
  wall
• spur-and-groove formation or buttress
  zonefinger-like projections of the reef front
  that protrude seaward disperses wave energy and
  helps prevent damage

35
Reef Structure

• Reef crestthe highest point on the reef and the
  part that receives the full impact of wave energy
• where wave impact is very strong, it may consist
  of an algal ridge of encrusting coralline algae,
  lacking other organisms, and penetrated by surge
  channelsgrooves of the buttress zone
• Reef flat or back reefportion behind the reef
  crest

36
Coral Reef Distribution

• Major factors influencing distribution
• temperature corals do best at 23-25o C
• light availability photosynthetic zooxanthellae
  need light
• sediment accumulation can reduce light and clog
  feeding structures
• salinity
• wave action moderate wave action brings in
  oxygenated seawater, removes sediment that could
  smother coral polyps
• duration of air exposure can be deadly

37
Reef Productivity

• Source of nutrients
• land runoff for reefs close to land
• source for atolls unclear
• possible explanations
• nutrients accumulated over time are efficiently
  recycled
• reef bacteria and filter feeders capitalize on
  nutrients from dissolved/particulate organic
  matter
• nutrients brought from other communities

38
Reef Productivity

• Reef photosynthesis
• photosynthetic organisms zooxanthellae, benthic
  algae, turf algae, sand algae, phytoplankton,
  seagrasses

39
Coral Reef Community

• Sponges and cnidarians
• sessile organisms, though anemones can move if
  necessary
• filter feed anemones also paralyze and consume
  small fishes and crustaceans
• Annelids
• sessile filter feeders include featherduster and
  Christmas tree worms
• fireworms are mobile predators
• palolo worms burrow through and weaken coral and
  usually deposit feed

40
Coral Reef Community

• Crustaceans
• shrimps, crabs and lobsters
• vary from parasites to active hunters
• Molluscs
• gastropods eat algae from coral surfaces
• giant clams are filter feeders, but also host
  symbiotic zooxanthellae
• octopus and squid are active predators

41
Coral Reef Community

• Echinoderms
• feather stars, sea urchins, brittle stars, sea
  stars, and sea cucumbers
• filter feed, scavenge, or eat sediment
• Reef fishes
• most prominent and diverse inhabitant
• diverse food sources, including detritus, algae,
  sponges, coral, invertebrates, other fish

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Species Interactions on Coral Reefs

• Competition between corals and other reef
  organisms for space to attach
• Effect of grazing
• grazing of larger, fleshier seaweeds permits
  competitively inferior filamentous forms or
  coralline algae to persist
• herbivory decreases with depth

43
Species Interactions on Coral Reefs

• Effect of predation
• predation of sponges, soft corals and gorgonians
  provides space for competitively inferior reef
  corals
• species that feed on fast-growing coral assist
  slower-growing species to remain
• corallivores seldom destroy reefs
• small invertebrates are almost all well hidden or
  camouflaged, indicating the prevalence of
  predation in the reef

44
Coral Reef Ecology

• Coral provides
• foundation for reef food webs
• shelter for resident organisms
• Reefs form a complex 3-dimensional habitat for
  many beautiful and strange creatures

45
Threats to Coral Reefs

• Effect of physical changes on the health of coral
  reefs
• hurricanes and typhoons topple and remove coral
  formations
• El Niño Southern Oscillation (ENSO)
• changes winds, ocean currents, temperatures,
  rainfall and atmospheric pressure over large
  areas of tropical and subtropical areas
• can cause massive storms

46
Threats to Coral Reefs

• Coral bleaching
• a phenomenon by which corals expel their
  symbiotic zooxanthellae
• most often associated with warming of the ocean
  water by ENSO or global warming
• if the stress is not too severe, corals may
  regain zooxanthellae and recover
• if the stress is prolonged, corals may fail to
  regain zooxanthellae and die

47
Threats to Coral Reefs

• Coral diseases
• black band diseasea distinct dark band of
  bacteria migrates across the living coral tissue,
  leaving behind a bare white skeleton
• white poxcharacterized by white lesions and
  caused by Serratia marcescens
• other coral diseases
• white band disease
• white plague
• yellow blotch disease

48
Threats to Coral Reefs

• Human impact on coral reefs
• overfishing may occur
• human-sewage bacteria cause white pox
• nutrient-rich runoff (eutrophication) increases
  algal growth, which covers and smothers corals
• e.g. Kaneohe Bay in Hawaii

49
Evolutionary Adaptations of Reef Dwellers

• Protective body covering
• tough, defensive exteriors help animals avoid
  predation, but can limit mobility and growth
• Protective behaviors
• producing a poisonous coating of mucus
• burying the body in sand to hide
• inflating to appear larger
• hiding at night when nocturnal predators are
  active

50
Evolutionary Adaptations of Reef Dwellers

• Role of color in reef organisms
• color for concealment and protection
• countershading
• disruptive coloration
• camouflage (bright colors in reef environment)

51
Evolutionary Adaptations of Reef Dwellers

• Role of color in reef organisms
• other types of camouflage
• body shape
• warning coloration
• other roles of color
• defending territories
• mating rituals

52
Evolutionary Adaptations of Reef Dwellers

• Symbiotic relationships on coral reefs
• cleaning symbioses
• cleaner wrasses, gobies, etc. feed on parasites
  of larger fishes
• cleaning organisms set up a cleaning station
• Other symbiotic relationships
• clownfishes and anemones
• conchfish and the queen conch
• gobies and snapping shrimp
• crustaceans and anemones

53
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)
• Ex Snails, Clams, Squid, Octopus

54
Molluscan Body

• 2 major parts (mostly for snails and
  nudibranchs)
• head-footregion containing the head with its
  mouth and sensory organs and the foot, which is
  the animals organ of locomotion
• visceral massbody region containing the other
  organ systems, including the circulatory,
  digestive, respiratory, excretory and
  reproductive systems

55
Molluscan Body

• Mantleprotective tissue covering the soft parts,
  which extends from the visceral mass and hangs
  down on each side of the body it forms the shell
• Radulaa ribbon of tissue containing teeth (found
  in all except bivalves) used for scraping,
  piercing, tearing or cutting pieces of food

56
Molluscan Shell

• Secreted by the mantle
• Normally comprises 3 layers
• periostracumoutermost layer, composed of the
  protein conchiolin that protects the shell from
  dissolution and boring animals
• prismatic layermiddle layer, composed of calcium
  carbonate and protein, which makes up the bulk of
  the shell
• nacreous layerinnermost layer, composed of
  calcium carbonate in thin sheets, with a
  different crystal structure

57
Molluscan Shell

• Periostracum and prismatic layers form at the
  mantles 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

58
Chitons (class of mollusca)

• 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

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Scaphopods (class of mollusca)

• 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

60
Gastropods (class of mollusca)

• Class Gastropoda (snails and nudibranchs)
• 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
• operculumcovering over the shells aperture
  which allows it to be closed

61
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

62
Gastropods

• Naked gastropods
• nudibranchsmarine gastropods that lack a shell
• have cerataprojections 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

63
Bivalves (class of mollusca)

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

64
Bivalves

• Bivalve anatomy
• no head or radula
• laterally compressed bodies
• shell halves attached dorsally at a hinge by
  ligaments
• umbooldest part of the shell, around hinge
• adductor muscleslarge 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

65
Cephalopods (class of mollusca)

• Class Cephalopoda (nautilus, squid, cuttlefish,
  octopus)
• 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

66
Cephalopods

• Types of cephalopods
• nautiloids
• produce large, coiled shells composed of chambers
  separated by septa (partitions)
• gas-filled chambers aid with buoyancy
• siphunclecord 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

67
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

68
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

69
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

70
Cephalopods

• Color and shape in cephalopods
• arm/body movements and color changes are used in
  communication
• chromatophoresspecial 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

71
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

72
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 females, near the opening of the
  oviduct (tube that carries eggs to the outside of
  the body)

73
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)

74
Arthropods Animals with Jointed Appendages

• Phylum Arthropoda 75 of species
• Ex crabs, lobsters, shrimp, crawfish
• Have exoskeletona hard, protective exterior
  skeleton composed of protein and chitin (a tough
  polysaccharide)
• moltingshedding and replacement of exoskeleton
  to permit animals growth
• Body is divided into segments
• Usually, each segment has a pair of jointed
  appendages, for locomotion, mouthparts,
  sensation, ornamentation

75
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

76
Chelicerates (group of arthropods)

• 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 carapacea hard outer
  covering

77
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

78
Mandibulates (group of arthropod)

• Crustaceansmarine 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)

79
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

80
Decapods (group of mandibulate)

• Order decapoda includes animals with 5 pairs of
  walking legs
• crabs
• lobsters
• true shrimp
• 1st pair of walking legs are chelipedspincers
  used for capturing prey and for defense
• Wide range in size

81
Decapods

• Specialized behaviors
• hermit crabs inhabit empty shells
• decorator crabs camouflage carapaces with bits of
  sponge, anemones, etc.
• common blue crabs are agile swimmers

82
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

83
Decapods

• Reproduction
• sexes usually separate
• males have appendages modified for clasping
  females and delivering sperm
• spermatophoressperm packages
• copulatory pleopods2 pairs of anterior abdominal
  appendages that deliver sperm
• most brood their eggs in chambers or modified
  appendages

84
Cirripedia (class of arthropods)

• 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 cirripedsfeathery appendages
  which extend into the water when the shell is open

85
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

86
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

87
Ecological Roles of Arthropods

• Arthropods as symbionts
• cleaning shrimps remove ectoparasites and other
  materials from reef fish
• Some are ecotoparasites and endoparasites
• barnacles are commensal with many hosts

88
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

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Echinoderms Animals with Spiny Skins

• Phylum Echinodermata (sea stars, sea urchins, sea
  cucumbers, brittle stars)
• 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

90
Echinoderm Structure

• Endoskeletoninternal skeleton that lies just
  beneath the epidermis
• Spines and tubercles project outward from the
  ossicles
• pedicellariaetiny, pincer-like structures around
  the bases of spines that keep the body surface
  clean in some echinoderms

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Echinoderm Structure

• Water vascular systemunique 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 feethollow
  structures with a sac-like ampulla within the
  body and a a sucker protruding from the
  ambulacral groove

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Asteroidea (class of echinoderm)

• 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 surfacethe side opposite the mouth, which
  is frequently rough or spiny

93
Asteroidea

• 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

94
Asteroidea

• 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

95
Ophiuroidea (class of echinoderm)

• 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

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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

97
Ophiuroids

• Reproduction and regeneration in ophiuroids
• autotomizeto 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

98
Echinoidea (class of echinoderm)

• Class Echinoidea sea urchins and sand dollars
• Body enclosed by testa hard exoskeleton
• Benthic on solid surfaces (sea urchins) or in
  sand (heart urchins, sand dollars)
• Regular (radial) echinoidssea urchins spheroid
  body with long, moveable spines
• Irregular (bilateral) echinoidsheart urchins and
  sand dollars have short spines on their tests

99
Echinoidea

• Feeding in echinoids
• feeding in regular echinoids
• mostly grazers which scrape algae and other food
  materials from surfaces
• Aristotles lanterna chewing structure of 5
  teeth
• feeding in irregular urchins
• irregular urchins are selective deposit feeders
• some sand dollars are suspension feeders

100
Holothuroidea (class of echinoderm)

• Class Holothuroidea- Sea Cucumbers
• Have elongated bodies, and usually lie on 1 side
• Respiratory treesa 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

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Holothuroidea

• Feeding in sea cucumbers
• mainly deposit or suspension feeders
• oral tentaclesmodified tube feet coated with
  mucus which are used to trap small food particles
• Defensive behavior
• Cuvierian tubulessticky tubules released from
  the anus of some species
• eviscerateto release some internal organs
  through the anus or mouth

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Crinoidea (class of echinoderm)

• 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

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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