ArthropodsEchinoderms

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Arthropods/Echinoderms
By Lauren Clatch, Megan Kubacki, Anna
Christensen, and Adam Corrado
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Arthropods
Arthropods
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Examples

• Eumorpha achemon (left top)
• Crangon septemspinosa (right top)
• Habronattus, schizomid (right bottom)
• Nephila clavipes (left bottom)

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Three Classes

• Crustacea Shrimp and lobsters (Japanese Spider
  Crab Macrocheria kaempferi)
• Ararchnida spiders, scorpions, mites, and ticks
• Insecta grasshoppers, beetles, ants, etc.
  (Blister Beetle Lutta fulvipennis)

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Evolution

• First appeared more than 600 million years ago,
  100 million years before Echinoderms
• All Arthropods evolved from a common ancestor,
  because biologists have noted a pattern of having
  similar structures (true coelom, an exoskeleton,
  and jointed appendages)

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Structural Support

• They have an exoskeleton
• Bones on the outside (in the form of a shell)
• Made of chitin, lipids, and other proteins
• Reduces water loss from their bodies
• Shed exoskeleton, by molting, to grow
• Crustaceans Arachnids cephalothoraxes and
  abdomen

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Nutrition and Digestion

• Carnivores with the exception of daddy longlegs
  and mites
• Feed on smaller arthropods

• External digestion
• System with tubular alimentary canals which
  prevent the mixing of food and waste
• Crustaceans digestive gland
• Arachnids malpighian tubes and coxal glands
• Insecta Malpighian tubes

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Transportation/Circulation

• Move in a variety of ways crawl, walk, climb,
  hop, fly, glide, swim, skate, and dive

• Open circulatory system
• Hermocoel
• Heart
• Sinuses
• pericadial
• Visceral
• Vessels
• Blood
• Crustaceans gills
• Arachnids book lungs, tracheae
• Insects system with tracheae (air is pumped in
  and out of tracheae by wings)

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Gas Exchange/ Respiration

• Gills (top right)
• Aquatic forms
• Book lungs
• In spiders
• Tracheae (windpipe)
• Terrestrial forms

1) Right lung 2) Trachea 3) Left lung 4) Abscess
(Pus Pocket)
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Water Balance and Excretion

• Waxy compound found in outer layer of exoskeleton
  (in arachnids/insects)
• Repels water
• Reduces evaporative water loss

• Class Arachnida, excretion of uric acid
• Myriapods, insects, and some arachnids excrete
  from Malphigian tubules
• solutes and waste products diffuse into tubules
  that drain fluid "urine" into intestine
• rectal glands reabsorb some solutes and recycle,
  conserve fluids
• Crustaceans green glands remove excess water

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Reproduction

• Internal fertilization
• Crustaceans larva is called nauplius
• Arachnids male transfers sperm in special sacs
  in the tips of pedipalps into female genital
  opening and into seminal receptical
• Insects Ovipositor, internal fertilization.
• Develop through Metamorphosis
• usually a courtship ritual (tapping on webs)
• female lays eggs in silk cocoon

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Nervous System

• Dorsal brain
• Ventral nerve cord (s)
• Segmental ganglia and nerves

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Unique Characteristics

• There are a larger number of Arthropod species
  than any other animal (see right). There are 4-6
  million arthropod species.
• Classified by jointed extensions
• painful bites of stings in self-defense, more
  people die of bee and scorpion stings than   by
  snakebite (or shark attacks!)

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Echinoderms
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Examples

• Starfish (Linckia laevigata)
• Sea Cucumber (Pearsonothuria graeffei)
• Sand Dollar (Echinarachnius parma)
• Sea Urchin (Strongylocentrotus purpuratus)
• Total of about 7,000 species of Echinoderms

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Evolution

• Most were sessile when they appeared 500 million
  years ago, 100 million years after Arthropods
• Appeared before most organisms
• During the Cambrian, the super continent,
  Gondwana, was located near the south pole

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Symmetry and Body Cavity

• Symmetry Radial Symmetry, Bilateral on larvae
  (Bilateral has occurred in a few irregular
  examples)
• Many Echinoderms are pentaradial symmetry as well
  (they look like a star)

• Body Cavity
• Coelomates
• Have a spacious coelom (an open, fluid-
• filled body cavity lined with tissue)

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Structural Support

• Structural Support Technically endoskeleton,
  but they act as exoskeleton, have ossicles (any
  small bony or chitinous structure found in
  various skeletal parts of animals)
• Internal organs surrounded by tests in Sand
  Dollars and Sea Urchins
• Pedicellariae help keep off algae and other
  unwanted objects

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Nutrition and Digestion

• Nutrition Heterotrophs, many forms (active,
  omnivorous scavenging, selective predation or mud
  swallowing)
• Digestion- Straddle prey, break food open using
  suction, stomach goes out of body on to prey to
  digest
• Use Tube Feet also
• Cardiac stomach
• can turn inside out through its mouth when they
  feed
• Pyloric stomach-
• stomach that is connected to the digestive glands
• Interesting Facts
• Can survive up to two weeks without any
  food/nutrition
• Can receive nutrition from dissolved organic
  matter that is in the sea
• Have relatively big gut area

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Transportation/Circulation

• Transportation
• Uses the Water Vascular System and tube feet to
  move
• Contraction of muscles surrounding the ampullae
  forces water into the tube feet, causing them to
  extend.
• Contraction of muscles lining tube feet forces
  water back into the ampullae and shortens the
  tube feet

• Circulation Very basic system water-vascular
  systems takes over some functions of the system

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Respiration

• Respiration Basic system water-vascular system
  takes over some functions of the system
• Use skin gills and tube feet for gas exchange

Skin gills
Tube feet
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Water Balance/Excretion

• Water Vascular system (A hydraulic network of
  canals runs throughout the body, usually ending
  in a series of tube feet)
• No excretory systems
• Use skin gills for excretion

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Reproduction

• Asexual- fission (and for regenerating missing
  body parts)
• Sexual- external fertilization of eggs by
  spermatozoa. The fertilized eggs develop into
  planktonic larvae. The larvae typically go
  through two stages, called bipinnaria (sea stars)
  and brachiolaria. They are bilaterally
  symmetrical and have bands of cilia used in
  swimming and feeding. Larvae go through
  metamorphosis until they become adults

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Nervous System

• Simple system no brain or head but do have a
  nerve net and nerve ring
• Nerve cells can detect light and touch
• Starfish have eyespots (cluster of nerve cells)
  at the tips of each ray for light detecting

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Unique Characteristics

• Remarkable powers of regeneration (arms)
• Many have pentaradial symmetry- five extensions
• Deuterostomes- they have an anus
• No circulatory, excretory, or respiratory organ
  systems
• Move by water vascular systems
• Only a few are sessile now