PowerPoint Presentation - Segmented Worms by Y3rA77

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									Phylum Annelida

   Segmented Worms

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What is a segmented worm?
•Body   is divided into segments
that are separated by septa
(septum, sing.)
•Septa are internal walls
between each segment
•Bristles called setae are
attached to septa in most
•Allows great flexibility &
mobility (adaptation for
Annelid Characteristics

•   True coelom (coelomates)
•   More specialized systems
•   Organs are paired in segments
•   Bilateral symmetry
•   About 15,000 species
•   Range in length from less than 1mm to 3-
•   Live in sea, most freshwater habitats &
    damp soil
             Annelid Features
•   Earth’s most advanced worms
•   All are eucoelomate, segmented protostomes
•   Segmentation more correctly known as
    metamerism, meaning that parts like hearts,
    nephridia, and muscle groups repeat in series
    down the animal’s length
•   Most have hairs or setae
•   Head specialized to include differentiated organs
    like tentacles, palps and eyespots
• Thin but effective protein cuticle secreted
  by epidermis, similar to but softer than that
  of arthropods
• hydrostatic skeleton with increased
  efficiency due to segmented body with
  sealed internal chambers
• Often via gills (filamentous organs specialized
  for gas exchange underwater)
• Exchange via moist (mucus) skin
• Digestive waste passes out the anus
• Nitrogenous waste eliminated by nephridia,
  excretory organs that filter fluid in the coelom.
• no specific organs, from nerves only
• Most advanced so far. Large ventral nerve cord
  with fast-conduction neurons. Paired cerebral
  ganglia form a brain near the pharynx.
•   Most reproduce sexually
•   Some use external fertilization and have
    separate sexes
•   Others are hermaphrodites (earthworms &
    leeches) although rarely fertilize themselves
    – Exchange sperm & store is special sacs
    – Clitellum (band of thickened, specialized
      segments) secretes mucus ring were fertilization
      takes place
    – Ring slips off worm’s body & forms protective
      cocoon that hatches young worms
            Feeding Methods
•   Eat decayed plants and leaves via sticky
    mucus covering pharynx
•   Sometimes eat other invertebrates
•   Some filter feed; fan water through tubelike
    burrow which captures food in a mucus bag
•   Pharynx is pushed out the mouth, grabs the
    food, and brings it back in
•   Soaks food with saliva
•   Sit-and-wait predators, hide in burrows from
•   Well-developed nervous system in most
•   Brain & many nerve cords
•   Various adaptations in species:
    – Sensory tentacles
    – Chemical receptors
    – Statocysts to detect gravity
    – Two or more pairs of eyes
•   Two major groups of muscles function
    alternatively as a part of a hydrostatic
•   Longitudinal muscles contract to make worm
    shorter & fatter
•   Circular muscles wrap around each body
    segment & contract to make worm longer &
•   Marine annelids have paddlelike appendages
    called parapodia on each segment for
    swimming & crawling
        The Closed Circulatory
•   Most annelids have closed system where blood is
    contained within a network of blood vessels
•   Blood vessels are the length of the worms’ body
•   Blood in dorsal (top) vessel runs toward head
•   Blood in ventral vessel runs toward tail
•   In each segment, pair of smaller vessels called ring
    vessels connect ventral & dorsal vessels and supply
    internal organs with blood
•   5 pairs of organs that act like hearts on dorsal side
•   Moves blood quicker than an open circulatory system
Open and Closed Circulatory Systems
Phylum Annelida: Classes

•   Oligochaeta (oligo = few; chaeta = bristles)

•   Polychaeta (poly = many; chaeta = bristles)

•   Hirudinea
Class Oligochaeta

   Tubifex worms
   Sludge worms
          Class Oligochaeta
•   ~3000 species, most live in freshwater or in soil
•   Name of class means “few hairs”; many have
    only 2-4 per segment
•   Each seta (made of chitin) has muscles which
    control it
•   Setae are used (in earthworms) along with
    peristaltic muscle contractions to move worm
    through soil
•   most highly organized animals to have
•   Reduced head; no parapodia
      Lumbricus, the earthworm
•   Earthworms do eat soil, but target high concentrations
    of decayed vegetation and other refuse
•   The muscular and chemosensory prostomium aids in
    tunneling and in determining direction of travel
•   Soil is ingested after being moistened by secretions of
    the pharynx, then held in crop before processing in the
    gizzard and intestine.
•   The intestine’s typhlosole helps increase surface area
•   Remember, two nephridia (excretory) per segment…
•   Circulatory system has muscular dorsal vessel and
    aortic arches. The rest of the system is venous
          Earthworm External Anatomy
•Metamerism: serial repetition of body parts
•Setae: Used to grip surface during motion
•Clitellum: produces protective cocoon around eggs
Earthworm Internal Anatomy
        Focus on Earthworms
•   Live in burrows       •   Length - 1mm up to
•   Live in nearly all        3m
    environments          •   Body is made of two
•   Tunnel for a living       tubes, one inside
•   Eat decayed plants        the other
    and animal remains
•   Droppings make soil
  Class Polychaeta

 Sandworms, Bloodworms
Feather worms, Clam worms,
        Tube worms
            Class Polychaeta
•   Largest group of annelids

General Characteristics:
• Well-developed head
• Tube-dwelling & free-living species
• Have numerous setae at ends of parapodia
   – Parapodia – fleshy segmented
     appendages for locomotion & breathing
              Class Polychaeta
•   Most numerous class (in species) of annelids;
    ~10,000 species
•   Bodies covered in many bristles, which are
    modified for feeding, swimming, or defense
•   Complex cephalization in many, with
    reversible pharynx and jaws, also prostomium
    with eyes and tentacles.
•   Group roughly divided into sessile members
    and motile members
•   Most sessile worms filter feeding, while errant
    worms are efficient predators and scavengers.
     Nereis, a polychaete annelid
                   the “clam worm”

•   Marine predatory worm which lives in crevices in
    reefs, and burrows of other animals. Fierce
    predator, grows to 40 cm
•   Most segments contain rudimentary appendages
    with many setae
•   Pharynx is reversible, and includes chitinous
•   Prostomium with palps (food manipulation),
    tentacles (sensory and tactile) and eyespots.
•   Some polychaetes have vertebrate-like eyes
Polychaeta: Neries
Christmas Tree Worm
Class Hirudinea

              Class Hirudinea
•   ~500 species, mostly freshwater and terrestrial
•   Often dorso-ventrally flattened, and have a
    reduced coelom & reduced segmentation
•   Often highly patterned for camouflage
•   Leeches are predatory, temporarily parasitic or
    fully parasitic
•   Most lack setae and have sucker discs instead;
    one on front and back
•   The gut is large and branched for storage of large
    quantities of blood
               Class Hirudinea

•   A clitellum is present - apparently only during
•   True bloodsuckers have cutting plates for cutting
    through tissue of the host organism
•   Most species are free-living carnivores (eat snails &
•   Usually attaches by posterior sucker until suitable
    spot is found for attachment of anterior sucker
Hirudinea: leech
                Class Hirudinea
•   Hirudo medicinalis – medicinal leech
•   Leeches secrete saliva containing a strong anesthetic
    & anticoagulant = painless bite & blood doesn’t clot
•   Leech anticoagulant now synthetically made
•   Leeches are still occasionally used
     – Remove blood from bruised tissues
     – Help relieve swelling in fingers or toes sewn back
       on after accidents to allow small blood vessels
       time to grow back
     – Remove excess blood

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