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Phylum Porifera (Sponges)
Sponges are interesting because they represent the simplest form of animal, offering insight into the evolution of animals.
- Porifera = "pore bearer"
- Sponges
- ~8,000 species (mostly marine)
- Sessile: attached to one spot and can't move
- Larval stage is motile
- Do not have Hox Genes: genes that determine an organisms body plan
Morphology
- No obvious tissues or organs
- No gut, muscles or nerves
- Cells have specialized function, but are not tissues
- Tissues must be attached by a membrane (sponges do not have)
- Flagellum located in the middle of the sponge
- moves water in and out of the collar
- Collar and flagellum are sticky > traps bacteria
- trapped bacteria are transported to the amoebocytes
- Structural support
- Spicules: tiny hard needles / rods
- Made of calcium carbonate or silica
- Non-living
- Some sponges only have collagen for support (spongin)
- Mesohyl
- Mesohyl = "Middle stuff"
- Acellular layer: between outer skin and choanocyte layer
- Not a tissue
- Suspension Feeding
- Extract small particles from water
- Food particles are engulfed via phagocytosis at the base of the choanocyte
- Amoebocyte: transport food / nutrients from the choanocyte
- Use energy to create spicules or other structures
Exam Tip
Remember that tissues must be attached by a membrane, otherwise they are not considered tissues (like in sponges)
Reproduction
- Hermaphroditic: Male and Female parts at the same time
- Sequential hermaphrodites: Transitions from one sex to the other
- No ovaries or testies
- Amoebocytes make eggs
- Modified choanocytes make sperm
- Mostly internal fertilization
- Adults are sessile
- Ciliated larval stage is motile (dispersal stage)
Ecological Importance of Sponges
- Filter feed: cleans water column
- Symbiotic mutualism with algae and other organisms
- Some are predatory
- Used in pharmacueticals
- Antibiotics
- Cancer drugs
- Bath and Art sponges made from some species
Practice: Sponges
What is the name of the hard rods that provide sponges their structural support?
Practice: Sponges
Which of the following is true about sponges? (select all that apply)
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