Phylum Annelida

1
Phylum Annelida

• By Esther Lien
• Harlan Cox
• Siva Gandu

5th period
2
Phylum

• General Characteristics
• Annelids are all bilaterally symmetrical animals.
  They range in size from much less than 1 mm in
  length to more than 3 m
• Their bodies are divided into segments that may
  or may not be visible externally
• Their body is composed of a series of ring-like
  segments that are specialized.
• In most annelids there are usually two fluid
  systems, the coelom and the circulatory system,
  and both (if present) are involved in the
  excretion of waste products.
• Classes
• CLASS Polychaeta- Bristle worms
• CLASS Clitellata- Leeches
• CLASS Pogonophora- Beard Worm
• CLASS Echiura- Spoon Worm
• CLASS Oligochaeta- Earthworms

3
Body Plan

• Triploblastic
• is a condition of the blastula in which there are
  three primary germ layers the ectoderm,
  mesoderm, and endoderm
• Most remarkable advance is segmentation or
  metamerism
• They have Elongate body which is usually round.
  For polychaetes and clitellidae, the head has
  prostomium and peristomium which have sensory
  organs and feeding organs.
• Trunk segmentation appears in external annuli,
  and it is internally separated by coelomic
  compartments which are also separated by septae.
• Some are homonomous, with body segments mostly
  similar, others are heterononmous, with
  specialized segments

4
Feeding

• For polychaetes and oligochaetes
• Raptorial
• Prey captured with Head Appendages and then
  swallowed as a whole
• Deposit
• They ingest the substrate and then they derive
  the nutrients from it
• Suspension
• They use tentacles or mucus webs to filter
  nutrients from fluid environment
• Clitellata
• Have a straight gut
• It has specialized organs and accessory organs,
  but the digestion is extracellular
• Echiura
• They have a coiled gut
• The mouth is by the anus and the gut is long and
  coiled
• Pogonophora
• Have no known digestive system

5
Respiration

• They have no true respiratory organs.
• Respiratory gas exchange through skin, gills,
  parapodia.
• They secrete moisture from the dorsal pore
• The skin has many tiny blood vessels to gather
  oxygen across the moist film covering it. 
• Since they breathe with their whole body surface,
  they will suffocate if their skin becomes dry.

6
Circulation

• Their blood is red because it has hemoglobin
• Most annelids have closed and well-develop
  circulation
• In certain smaller forms, the circulation is
  reduced or absent. They have Coelomic canals that
  serve as their blood channels.
• The enlarged and heavily muscular vessels at the
  anterior end serve as the hearts that pump the
  blood.
• Their blood is carried from dorsal to ventral
  vessel in the head.
• Earthworms have five pulsating blood vessels that
  help pump blood from the main dorsal vessel to
  the main ventral vessel.

7
Excretion

• Each segment has a pair of nephridia which are
  long coiled ciliated tubes to excrete their
  metabolic wastes.
• Blood and coelomic fluid enter these tubes where
  nutrients, water and salts are removed.
• Their waste products are transported out of the
  body through the coelom by specialized excretory
  tubes.

8
Response

• The nerve cord has two sorts of fibers normal
  and giant nerves
• The nerve cord runs down the whole body .
• The giant nerves are only important during rapid
  escape maneuvers.
• Polychaeta
• Bodies organized into regions according to the
  function and structures.
• They have a well-developed head with specialized
  sense organs
• Oligochaeta
• They have no eyes, but they have many
  photoreceptors, chemoreceptors, and
  mechanoreceptors that are concentrated near the
  ends of their body.
• They have fewer setae than polychaetes and no
  parapodia or head region.

9
Movement

• Polychaetes
• Parapodia, paired, fleshy, paddlelike flaps, used
  for swimming, burrowing, or slow crawling.
• Fast crawling is performed by undulating the
  body.
• Oligochaeta
• Chaetae tiny hairs that provide anchoring
  points for burrowing
• They deform either the whole body, or segments of
  the body by contracting the circular and
  longitudinal muscles alternately
• Hirudinea
• Swim with snake-like motions
• Use suckers to anchor themselves to objects
• Non-aqueous leeches crawl by extending and
  contracting their body

10
Reproduction

• Polychaetes
• Involves separate sexes and external
  fertilization, usually in water away from both
  parents
• Lack permanent gonads, the gamete producing sex
  organs
• Gametes are produced from the germ cells in the
  lining of the coelom or in the septa
• Oligochaeta
• Hermaphrodites each worm has both eggs and
  sperm
• When reproducing sperm goes in both directions to
  and from each worm
• Fertilized eggs are put in a cocoon that forms
  over the parent body and then falls off
• Hirudinea
• Internal fertilization within the females body.
• A sperm sac passes over the eggs which are
  deposited inside

http//image.tuorvista.com/content/diversity-livin
g-world/earthworm-structure.jpeg
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Works Cited

• "Annelida." Bumblebee.org. Web. 17 Apr. 2010.
  lthttp//www.bumblebee.org/invertebrates/ANNELIDA.
  htmgt.
• Mehaffey, Leathem. "Outline for Annelids." Vassar
  College. 2001. Web. 17 Apr. 2010.
  lthttp//faculty.vassar.edu/mehaffey/academic/anim
  alstructure/outlines/an nelida.htmlgt.
• Ramel, Gordon. "The Annelids (Phylum Annelida)."
  The Earth Life Web. Web. 15 Apr. 2010.
  lthttp//www.earthlife.net/inverts/annelida.htmlgt.
  
• Raven, Peter H., and Peter H. Raven. Biology. 6th
  ed. New York McGraw-Hill, Higher Education,
  2002. 906-09. Print.
• Rouse, Greg W. "Characteristics of
  Annelida." Tree of Life Web Project. 2002. Web.
  16 Apr. 2010. lthttp//tolweb.org/articles/?articl
  e_id57gt.