Poriferans

Poriferans

Phylum Porifera

• 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

Choanocyte

Spicule

Pore cell

Pore

Epidermal cell

Archaeocyte

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

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– 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

• 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• 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