Post on 14-Jan-2016
Sponges
Sponges
• Phylum Porifera – “pore-bearers” (although now sponges are in multiple phyla)
• Sponges• Tiny openings, pores, all over the body• Cambrian Period – 540 m.y.a.; oldest and
simplest animalsm, probably evolved from colonial protists
• 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
– Amoebocytes (aka archaeocytes) – make spicules
– Softer sponges have skeletons made of spongin – these are used as natural bath sponges
Sponge Anatomy
Water flow
Choanocyte
Spicule
Pore cell
Pore
Epidermal cell
Amoebocyte
Osculum
Central cavity
Pores
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
amoebocytes• Amoebocytes (aka 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– Fertilized eggs forms zygote which develops into
larvae, which are planktonic and motile. Eventually, larvae settle down to bottom and grow into a new sponge.
Sponge Life CycleSperm from a sponge are released into the surrounding water. Water currents carry the sperm to other sponges.
Sperm enter another sponge through pores. The sperm are carried to eggs inside the body wall. Sperm fertilize eggs.
The zygote develops into a free-swimming larva. Water currents carry the larva until it attaches to a surface and grows into a new sponge.
Sperm (N)
Egg (N)
Larva (2N)
Mature sponge (2N)
Swimming larva
New sponge
Haploid (N)
Diploid (2N)
FERTILIZATION
MEIOSIS
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
Summary of Cell Specialization in Sponges
• Choanocytes– Create water currents with flagella– Capture food
• Amoebocytes (aka archaeocytes)– Make spicules– Deliver nutrients to sponge– Assist with reproduction
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 (poison-
filled stinging structure used for food capture and protection)
Form and Function of Cnidarians
• Only a few cells thick and simple body systems, including a gastrovascular cavity with one opening
• 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
Mesoglea
Gastrovascular cavity
Mouth/anus
Tentacles
Tentacles
Mouth/anus
Gastrovascularcavity
Polyp
Medusa
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
Larvae
Medusa
Polyp
Zygote
Asexual Reproduction
Sexual Reproduction
Groups of Cnidarians
• Includes hydras and their relatives, jellyfishes, sea anemones, and corals
Class Hydrozoa – Hydras and Other Relatives
• 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
• 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
• 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