Porifera (Sponges)

Phylum Porifera (Sponges)

• 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

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