What is an animal

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What is an animal?

• Animals are multicellular
• Animal cells are eukaryotic and they lack cell
  walls
• Animals are heterotrophs - cannot produce their
  own food

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Sponges

• Belong to the Phylum Porifera - pore bearers
• Are asymmetric and sessile adults
• Are invertebrates - animals without a backbone

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Sponge Structure

• A sponges body is covered with tiny holes called
  ostia (ostium is the singular)
• Water enters through these ostia carrying vital
  oxygen and nutrients
• Water flows into a spacious cavity called the
  spongocoel where it exits through a large opening
  called the osculum

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Sponge - feeding

• Choanocytes (collar cells) line the spongocoel
• They are oval shaped cells with a single
  flagellum and a collar of finger-like
  projections that act to filter food out of the
  water
• These cells are responsible for the flow of water
  into the ostia and out the osculum - due to the
  beating of their flagella
• Sponges are filter-feeders (also called
  suspension-feeders)

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Sponge - body shape

• There are three main shapes of a sponge
• asconoid - simple body plan, smallest in size
• syconoid - one spongocoel with many invaginations
• leuconoid - many spongocoels and chambers, grow
  largest

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Sponge - reproduction

• Sponges can reproduce sexually or asexually!
  Some hermaphroditic
• Asexual reproduction occurs by budding or
  fragmentation
• Sponges can regenerate - if one part is removed
  then the entire animal can develop from that part

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Sponge Classification

• Sponges are classified by their supporting
  structures called spicules
• There are four classes
• Calcarea small, have spicules of calcium
  carbonate
• Hexactinellida spicules made of silica - also
  called glass sponges
• Demospongia contains larger species, have
  flexible fibers of the protein, spongin and maybe
  some silica spicules
• Sclerospongia also have calcium carbonate
  skeletons

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Why are sponges important to us?

• The large species from Demospongia are harvested
  for commercial use
• They can hold as much as 35 times their weight in
  water!
• Some uses a bath supply, art tool, or metal
  polisher
• Medical research

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Sponge - Ecological role

• Very few animals eat sponges because of the
  spicules (kind of like little needles) - some
  bony fish and molluscs eat them, as well as the
  hawksbill sea turtle. Passive landlord
• Symbiont with cyanobacteria
• Help convert calcium back into soluble form
• Can inhibit growth of other organisms through
  chemicals or through boring into them