INVERTEBRATES

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Chapter 25

• INVERTEBRATES
• COELOMATE PROTOSTOMES

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Coelomate protostomes

• include
• annelids, mollusks, arthropods related phyla
• Have a complete digestive tract with separate
  mouth anus
  
• Organ systems are developed
• circulatory, excretory nervous system

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Coelom

• Advantage
• Independent movement - a hydrostatic skeleton
• Fluid transport materials food, oxygen wastes
  - blood vessel, lung, kidney

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Early protostome embryo. Its four cells are
undergoing cleavages oblique to the original body
axis
Early deuterostome embryo. Its four cells are
undergoing cleavages parallel with and
perpendicular to the original body axis
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How a coelom forms in a protostome embryo
pouch will form mesoderm around coelom
developing gut
coelom
How a coelom forms in a deuterostome embryo
solid mass of mesoderm
developing gut
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• Invertebrate coelomates
• Annelids aquatic (earthworm terrestrial)
• Snails aquatic/terrestrial
• Mollusks (most) marine
• Arthropods
• Insects spiders mainly terrestrial
• Crustacean (crab, lobsters) - marine
• Merostomes (horseshoe crabs)
• Echinoderm marine

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Terrestrial living

• To minimize loss of fluid
• Locate the respiratory surface deep in the
  animal
  
• Lung tracheal tube internal
• Gills external (for aquatic animals)
• have exoskeleton e.g. Arthropods mollusks
• Provides stiffness
• Provides protection against desiccation
• Protects animals from predators
• Serves as a point of attachment for muscles

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• Internal fertilization
• e.g. earthworms, snails, insects,
• reptiles, birds mammals
• Sperm (males) into the females by copulation

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Phylum Mollusca

• The basics
• The best known of the invertebrates
• 50,000 living species
• 35,000 fossil species
• includes clams, oysters, octopuses, snails,
  slugs, squid (giant squid the largest
  invertebrate)
  

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• Four classes
• Polyplacophora chiton
• Gastropoda snails, slugs
• Bivalvia clams, oysters, mussels
• Cephalopoda squid, octapods

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Class Polyplacophora - chitons

• Sluggish marine animals with flattened bodies
• Have a shell with 8 separate, overlapping
  transverse plates
  
• No eyes or tentacles

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Class Gastropoda - snails their relatives

• Habitat marine (gills) terrestrial (lungs)
• Exoskeleton
• Snails shell
• Limpets, abalones shell like flattened caps
• Garden slugs, marine snail no shell
• a well-developed head with tentacles
• a broad flat foot

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Body Plan of a Snail
anus
gill
mantle cavity
excretory organ
heart
digestive gland
shell
stomach
mantle
radula
foot
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Class Bivalvia - Clams, oysters their
relatives

• Characteristics
• Soft body
• Enclosed by two shells hinged dorsally
• Opening ventrally
• Siphons an extension of the mantle
• Incurrent siphon ?Excurrent siphon
• Filter feeder through siphoning

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• A soft body, usually a broad, flat muscular foot,
  ventral location, locomotive device
  
• Fast movement - adductor muscle (edible
  portion of scallops)
  
• A mantle (secreted by the gland) covering the
  visceral mass
  
• The inner pearly layer - CaCO3 called as mother
  of pearl
  
• Radula, a rasp-like structure, a belt of teeth
  within the digestive system

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Open circulatory system
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• Open circulatory system
• slow metabolism
• in bivalves
• Closed circulatory system
• active metabolism
• in squids, octopus

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Class Cephalopoda - Squid, octopus their
relatives

• Active, predatory animals, fast swimming
• No shell in octopus in squids reduced to a pin
• Foot - tentacles (covered with suckers) squid 10
  , Octopods 8
  
• Central mouth in the large head

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• Large, well-developed eye, looks like vertebrate
  eyes, but develop diff.
  
• Mouth with a radula, have two strong, horny
  beaks.
  
• Self-protection by Rapid color change

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Phylum Annelida

• 3 Classes
• Polychaeta - many bristles
• sandworms, tubewarms
• Oligochaeta - earthworms
• Hirudinea - leeches
• Body plan
• Segmented
• coelomate

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Class Oligochaeta - earthworms

• Terrestrial fresh water
• Few bristles per segments
• Lack a welldeveloped head
• Hermaphroditic
• Body wall
• an outer layer circular muscles
• An inner layer longitudinal muscle

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• Locomotion hydrostatic skeleton
• Complete digestive system
• pharynx ? esophagus ? stomach
• ? intestine ? anus
• Complete coelom
• Metanephridia
• Ganglia (cerebral, ganglia)
• Closed circulatory system

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Class Hirudinea - leeches

• Blood sucking parasites in fresh water
• No setae or appendages
• Muscular suckers.
• Store the blood in pouches in the digestion
  tract, using an anticoagulant
  
• Medicinal leeches

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Phylum Arthropoda

• More than 1,000,000 species
• Characteristics
• Paired, jointed, foot
• Have exoskeleton composed of chitin.
• Segmented body
• Open circulatory system

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Body plan

• Three regions head, thorax, abdomen
• segments
• Nerve system well developed system
• e.g. compound eyes, Organs of hearing antennae.
• Open circulatory system
• dorsal tubular heart ? dorsal artery? sinuses
  (hemocoel)? tissue ? ostia ? heart
  
• Gills for gas exchange, air tube/trachae
• Digestive system similar to that of annelids

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Major groups of Arthropods

• Subphylum Trilobitomorpha fossil trilobites
• Subphylum Chelicerata
• Class Merostomata Horseshoe crabs
• Class Arachnia - scorpions, spiders, mites
  ticks
  
• Subphylum Crustacea
• Class Crustacea lobsters, crabs, shrimps
• Subphylum Uniramia
• Class Insecta insects
• Class Chilopoda centipedes
• Class Diplopoda millipedes

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Class Trilobite

• The primitive arthropods
• Extinct (in Paleozoic seas)
• Flat, segmented body
• Three parts
• Bi-ramous (two-branched) appendages

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Subphylum Chelicerata

• Cephalothorax abdomen
• Appendage (2nd pair) pedipalp
• pedipalps are likely modified
• to hold and chew food
• to sense organs for tasting the food

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Class Merostomata

• Horse shoe crabs - Only living one
• Almost all are extinct
• Horse shoe shaped animal with long spike like
  tail (telson).
  
• telson the posterior end of the abdomen

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Class Arachnida

• Scorpions, spiders, ticks mites
• Approximately 60,000 species known. Old group
  Fossil - Carboniferous period.
  
• Cephalothorax (fused head thorax), abdomen.
• 6 pairs jointed feet
• 1st pair chelicerae to inject poison into the
  prey.
  
• 2nd pair pedipalp to hold chew food or to
  taste the food.
  
• Other 4 pairs for actually walking
• ( 4 pairs of legs)

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• Carnivores (most)
• Prey small arthropods
• Gas exchange by tracheal tubes or book lungs (15
  20 plates with blood vessel)
  
• Silk glands (spiders) secrete elastic protein
• Nervous system ganglia (abdominal)

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• Class Crustacea
• Simply crustaceans - Lobsters, crabs, shrimp
  relateds
  
• Krill (food of many fish) microscopic crustacean.

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Characteristics

• Mandibles, biramous appendages
• Two pairs of antennae (sensory organs)
• Maxillae (two pairs of) appendages manipulate
  food (to mouth)
  
• Walking appendages approximately 5 pairs.
• Swimming appendages.
• Tubular heart
• Gills gas exchange

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Lobster

• Head
• Cephalothorax, covered by carapace, chitin
• Thorax 8 segments
• Antennae (2 sets)
• Mandible
• Maxillipeds (1st 2nd)
• Chelipeds (1 pair)
• Walking legs (4 pairs)
• Swimmerets (4 pairs)
• Uropod - swim backward
• Telson - swim backward.

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Body Plan of a Lobster
one of two eyes
fused segments of cephalothorax
segments of abdomen
antennae (two pairs)
food-handling appendages (three pairs)
tail fin
swimmerets
first leg
five walking legs (five pairs total)
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Class Insecta

• Characteristics
• Articulated (jointed)
• Tracheated tracheal tubes for gas changes
• Hexapod 6 feet (3 pairs), uniramous appendages
• 3 body parts head, thorax abdomen
• Antennae, Complex eyes
• Malpighian tubule excretory
• Separate sex internal copulation.
• Metamorphosis, egg, larva, pupa adult
• Produce pheromones to communicate each other

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Success of the insects

• Body plan modification, adaptation
• Can fly
• Have tough exoskeleton
• Protective colorization

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Body Plan of a Spider
eye
Malpighian tubule
digestive gland
heart
brain
poison gland
book lung
ovary
silk gland
anus
mouth
sperm receptacle
spinners
pedipalp
chelicera
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