Chp 10

• Bryozoans


  Also known as moss animals, unsegmented lophophorate coelomates
• Bryozoans


  • Body covered by a chitinous, gelatinous or calcareous exoskeleton
  • Digestive system is U-shaped with mouth surrounded by a crown of hollow ciliated tentacles called lophophore, esophagus, stomach with caecum, and intestine that opens outside the lophophore
  • Lophophore extends by increasing coelomic pressure and withdraws by retractor muscles attached to the body wall
  • Food driven to the mouth through beating of cilia on tentacles
  • Sessile, most are polymorphic and colonial
  • Lack special systems for respiration, circulation and excretion - all these functions take place by diffusion
  • Nervous system includes a ganglion and a nerve ring around the anterior part of the gut, with nerve fibers extending to the lophophore and other organs
• Colony (zooarium)


  Includes feeding individuals (autozooids), and heterozooids such as reproductive individuals (ovicells) and defensive individuals (avicularia), and in some species vibracula
• Reproduction


  1. Asexual reproduction by budding

  2. Sexual reproduction by shedding gametes into the coelom where fertilization occurs

  3. Larva called cyphonautes released in water, settles down and develops a new colony

  4. Freshwater species produce internal buds called statoblasts during unfavorable conditions
• Freshwater species


  • Bugula