Lecture 8: Marine Invertebrates to Worms

• Two types of symmetry: radial and bilateral
• Phylum Porifera (Sponges):

  About 5,000 species

  Asymmetrical

  Sessile epifaunal

  Suspension feeders (filter feeding)

  System of water canals with no gut or distinct tissues
• Types of filter/suspension feeding:

  Seiving

  Direct interception

  Inertial impaction

  Gravitational deposition

  Diffusional deposition
• Types of sponge body forms:

  Ascinoid

  Syconoid

  Leuconoid
• Sponge reproduction includes asexual, sexual, and regeneration
• Sponges play an important ecological role by competing for space, being part of the food chain, having symbiotic relationships, and recycling calcium
• Cnidaria include jellyfish, hydroids, corals, and anemones
• Cnidaria make up about 9,000 species, have radial symmetry, have polyp/medusa forms, have no circular system, and have a network of nerve cells
• Stinging cells are referred to as cnidocytes (most contain nematocytes)
• Three classes of cnidaria: hydrozoans, scyphozoans, anthozoans
• Hydrozoans are clonal and sessile
• An example of a hydrozoan is the Japanese Man-of-War
• Hydrozoans have polyp and medusa stages
• Scyphozoans have a dominant medusa stage
• Anthozoans have only a benthic polyp stage
• Scyphozoa are true jellyfish and have complex digestive systems
• Anthozoans are anemones, corals, and sea fans
• Sea anemones have a hydrostatic skeleton:

  Cylinder of soft tissue enclosing a water-filled cavity
• Corals are polyps that secrete a skeleton around their bodies
• Two types of corals: scleractinian corals and octocorals
• Scleractinian corals have a skeleton of calcium carbonate
• Octocorals have feathery tentacles
• Cternopora is made up of comb jellies
• Types of marine worm phylums: Platyhelminthes (flat worms), Nemertea (ribbon worms), Lophophorates
• Platyhelminthes are flattened and have bilateral symmetry, have no circulatory system, have a primitive nervous system
• Nemertea have ribbon-like bodies, are carnivorous, and capture prey via proboscis
• Lophophorates lack a head, contain lophophore, and are filter feeders
• Three types of lophophorates:

  Phoronids (secrete leathery tube around their body)

  Bryozoans (form encrusting colonies)

  Brachiopods (body covered by a shell and contain a pedicle)