Poriferans
Phylum Porifera
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Phylum Porifera – “pore-bearers”
Sponges
Tiny openings, pores, all over the body
Cambrian Period – 540 m.y.a.; oldest and
simplest animals
Adults are sessile – attached to a single spot
Heterotrophic, multicellular, no cell walls, few
specialized cells
No mouth or gut, no tissues, no organ systems
Evolutionary dead end
Form and Function of Sponges
• Movement of water through sponge provides for
feeding, respiration, circulation, and excretion
• Body plan
– Asymmetrical “water pump” – body forms wall around
central cavity, where water is continuously pumped
– Choanocytes (aka Collar Cells) – create currents with
flagella
– Most have an osculum – large exit hole at top of
sponge
Form and Function of Sponges
(continued)
• Simple skeletons
– Spicules – sponge “bones” made of calcium
carbonate (CaCO3) or silica (SiO2) – these are
in hard sponges
– Archaeocytes – make spicules
– Softer sponges have skeletons made of
spongin – these are used as natural bath
sponges
Sponge Anatomy
Water flow
Osculum
Central cavity
Pores
Choanocyte
Spicule
Pore cell
Pore
Epidermal cell
Archaeocyte
Feeding in Sponges
• Filter feeders – sift microscopic food
particles from water
• Digestion is intracellular
• Food particles engulfed by choanocytes
lining body cavity by endocytosis
• Food may be digested or passed on to
archaeocytes
• Archaeocytes digest food and wander
around to other cells delivering nutrients
Respiration, Circulation, and
Excretion in Sponges
• Rely on movement of water through
bodies to provide simple mechanism for
respiration, circulation, and excretion
• Diffusion is important for sponges
Response in Sponges
• No nervous system, but can produce
toxins
Reproduction in Sponges
• Sexually or asexually
• Sexual – most sponges have eggs and sperm in
one sponge
– Eggs held in body wall
– Sperm released into water
– Eggs and sperm produced at different times within
sponge
– Sperm absorbed by archaeocytes and carried to eggs
Reproduction in Sponges (continued)
• Asexual
– Gemmules – collections of archaeocytes
surrounded by spicules that can survive
freezing and heat
– Conditions favorable, gemmule grows into
new sponge
– Budding – part of sponge breaks off, settles,
grows into new sponge
Ecology of Sponges
• Form sponge “habitats” for worms,
shrimps, snails, and starfish
• Symbionts with bacteria, blue-green
bacteria, or plant-like protists
• Natural bath sponges
• Provide toxins that fight bacteria, viruses,
leukemia, and herpes
Examples of Sponges
Cnidarians
Cnidarians
• Phylum Cnidaria – cnidocytes – stinging cells
• Jellyfish, sea anemone, coral
• Soft-bodied, carnivorous animals with stinging
tentacles arranged around their mouth
• Simplest animals to have body symmetry and
specialized tissues
• Within each cnidocyte is a nematocyst (poisonfilled stinging structure used for food capture
and protection)
Form and Function of Cnidarians
• Only a few cells thick and simple body systems
• Body plan
• Radial symmetry with 2 possible body forms:
– Polyp – sessile and flower-like
– Medusa – motile and bell-shaped
• Three layers of cells
– Gastroderm – inner lining of gastrovascular cavity digestion
– Mesoglea – middle layer – can be a thin or thick layer
– Epidermis – outer layer
Body Forms of Cnidarians
Epidermis
Mesoglea
Gastroderm
Tentacles
Mesoglea
Gastrovascular cavity
Mouth/anus
Mouth/anus
Gastrovascular
cavity
Tentacles
Medusa
Polyp
Feeding in Cnidarians
• Nematocysts – located on tentacles; tiny spring-loaded harpoons
• Food pushed into mouth by tentacles
• Food digested and absorbed by diffusion
Respiration, Circulation, and
Excretion in Cnidarians
• Respiration and wastes eliminated by
diffusion through body wall
• No organized internal transport network or
excretory system
Response in Cnidarians
• No organized central nervous system (CNS)
• Simple nerve nets – loosely organized network
of nerve cells allowing detection of stimuli
• Statocysts – sensory cells for balance
• Ocelli – eyespots detect light
Movement in Cnidarians
• Hydrostatic skeleton – layer of longitudinal
muscles, together with the water in the
gastrovascular cavity, allow movement
• Epidermal cells act as muscles
Reproduction in Cnidarians
• Sexual and asexual
• Asexual – polyps
reproduce by budding
• Sexual – external
fertilization in the
water
Polyp
Larvae
Asexual
Reproduction
Zygote
Medusa
Sexual
Reproduction
Groups of Cnidarians
• Includes hydras and their relatives,
jellyfishes, sea anemones, and corals
Class Hydrozoa – Hydras and
Other Relatives
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Long polyp stage
Short medusa stage
Hydra – fresh-water – no medusa
Portuguese Man-O-War – floating colony
contains specialized polyps; one polyp is
enlarged and full of air to keep the animal
afloat, the other polyps are for feeding and
reproduction
Examples of Hydrozoans
Portuguese
Man-O-War
Colonial
Hydrozoan
Green Hydra
Class Scyphozoa – Jellyfish
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Same life-cycle as hydrozoans
Medusa – long-lived
Lion’s Mane
Reproduce sexually
Some very toxic and even deadly
Examples of Scyphozoans
Class Anthozoa – Sea Anemones
and Corals
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Only polyp life stage
Colonial
Sexual and asexual reproduction
Corals – reef builders and symbionts with
photosynthetic algae
• Skeleton of calcium carbonate (CaCO3)
• Colony grows slowly and lives for
thousands of years
Examples of Anthozoans
Ecology of Corals
• Great Barrier Reef – 2,000km long, 80 km
wide
• Sea anemone and clown fish – mutualism
• Coral – habitat for many animals
– Protect land from wave action
– Building blocks
– Jewelry
– Anti-cancer drugs
– In danger due to human activity