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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

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arthropods animals with jointed appendages
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
  • 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
arthropods animals with jointed appendages1
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
chelicerates
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
  • 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
chelicerates1
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
chelicerates2
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
mandibulates
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)
    • 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
mandibulates1
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
Decapods
  • Order decapoda; includes animals with 5 pairs of walking legs:
    • crabs
    • lobsters
    • true shrimp
  • 1st pair of walking legs are chelipeds—pincers used for capturing prey and for defense
  • Wide range in size
  • 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
decapods1
Decapods
  • Specialized behaviors
    • hermit crabs inhabit empty shells
    • decorator crabs camouflage carapaces with bits of sponge, anemones, etc.
    • common blue crabs are agile swimmers
decapods2
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
decapods3
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
decapods4
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
mantis shrimp
Mantis Shrimp
  • Order Stomatopoda
  • Highly specialized predators of fishes, crabs, shrimp and molluscs
  • 2nd pair of thoracic appendages
    • enlarged
    • has a movable finger that can be extended rapidly for prey capture/defense
    • used to spear or smash prey
mantis shrimp1
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
krill
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
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
copepods
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
barnacles
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
  • 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
barnacles1
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
ecological roles of arthropods
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
  • 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
  • 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
ecological roles of arthropods1
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
ecological roles of arthropods2
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
lophophorates
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)
phoronids
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
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
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.
ecological roles of lophophorates
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
echinoderms animals with spiny skins
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
echinoderm structure
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
echinoderm structure1
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
sea stars
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 stars1
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 stars2
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
ophiuroids
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
ophiuroids1
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
ophiuroids2
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
sea urchins and their relatives
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 relatives1
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
sea urchins and their relatives2
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
sea cucumbers
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 cucumbers1
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
crinoids
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
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
tunicates
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
sea squirts
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 squirts1
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
sea squirts2
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
salps and larvaceans
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
cephalochordates
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
cephalochordates1
Cephalochordates
  • Have complex life cycles with benthic adults and planktonic swimming larvae
  • Important as food in parts of Asia
  • Used as chicken feed in parts of Brazil
arrowworms
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