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Sponges
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Sponges have no tissues, no organs, and most lack symmetry.
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You can break a sponge down into individual cells and those cells will reform
a new sponge.
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Sponges are in phylum Porifera.
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Sponges and Cnidarians
Sponges
Body structure
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Sponges are composed of two layers of independent cells with a jellylike
substance in-between.
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Have a mouth-like opening at the top called an osculum.
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Sponges and Cnidarians
Sponges
Feeding and digestion
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Sponges are filter feeders that obtain food by filtering small particles out of
the water.
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Sponges have free-swimming larvae, but are sessile, or attached to stay in
one place, as adults.
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Food particles cling to the cells, and digestion of nutrients takes place within
individual cells.
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Sponges and Cnidarians
Sponges
Support
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Within the jellylike substance between a sponge’s two cell layers are
archaeocytes.
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Archaeocytes are amoeba-like cells that can secrete spicules, the support
structures of sponges
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Also involved in digestion, egg and sperm production, and excretion.
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Sponges and Cnidarians
Sponges
Response to stimuli
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Sponges do not have nervous systems
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Have epithelial-like cells that detect external stimuli, such as touch or
chemical signals
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Respond by closing their pores.
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Sponges and Cnidarians
Sponges
Reproduction
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Some sponges reproduce asexually
• Fragmentation
• Budding
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Sponges and Cnidarians
Sponges
Reproduction
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Most sponges reproduce sexually
• Eggs remain within a sponge.
• Sperm are released into the water.
• After fertilization, the zygote develops into a free-swimming larva.
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Sponges and Cnidarians
Sponges
Sponge ecology
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Sponges are food for some tropical fishes and turtles.
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Also form habitats for a variety of worms, fishes, shrimp, and symbiotic green
algae.
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Sponges are also beneficial to humans
• Spongin fiber sponges are used for household scrubbing purposes
• Potential use in pharmaceutical products
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Sponges and Cnidarians
Cnidarians
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The phylum Cnidaria contains jellyfish and sea anemones
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Contains about 10,000 species, mostly marine
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Sponges and Cnidarians
Cnidarians
Body structure
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One body opening and most have two layers of cells
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Cell layers organized into tissues
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Outer layer provides protection, inner layer digestion
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Exhibit radial symmetry
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Sponges and Cnidarians
Cnidarians
Feeding and digestion
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Tentacles are armed with stinging cells called cnidocytes.
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Cnidocytes contain nematocysts, a capsule that holds a coiled tube
containing poison and barbs.
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Nematocysts work like tiny harpoons in response to being touched or a
chemical stimulus – one of the fastest cellular processes in nature
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Sponges and Cnidarians
Cnidarians
Feeding and digestion
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After capture by nematocysts and
tentacles, prey is brought to the
mouth.
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Inner cell layer surrounds the
gastrovascular cavity, where cells
release digestive enzymes.
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Undigested materials are ejected
through the mouth.
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Sponges and Cnidarians
Cnidarians
Response to stimuli
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Cnidarians have a nerve net that conducts impulses to and from all parts of
the body.
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The impulses cause contractions of muscle-like cells in the two cell layers.
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Sponges and Cnidarians
Cnidarians
Reproduction
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Cnidarians have two body forms: a polyp and a medusa
• Polyps are tube-shaped with a mouth surrounded by tentacles
• Medusas are umbrella-shaped bodies with tentacles hanging down
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Sponges and Cnidarians
Cnidarians
Cnidarian diversity
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Four main classes of cnidarians:
• Hydroids: both polyp and medusa stages; many form colonies
• Jellyfishes: medusa is dominant body form; float near the surface of the
ocean water
• Sea anemones and corals: polyp stage is dominant
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Sponges and Cnidarians
Cnidarians
Cnidarian ecology
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Mutualism is common in cnidarians
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Habitat for fishes
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Beneficial to humans
• Recreational pleasure from visiting coral reefs
• Medical use
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Sponges and Cnidarians