Phylum Porifera The “Pore Bearers”

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Why are sponges in the Animalia

Kingdom?

• Multicelluar

• Eukaryotic

• Heterotrophic

• No cell walls

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Simplest multicellular animal

• Have many pores ( ostia), in which water moves through continuously

• ALL aquatic ( 10 000 different species of sponges ), but most in salt water

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Identifying Characteristics

• Acoelomates

– do not possess any true body systems (but they do

have highly specialized cells that perform many

functions)

• Mostly asymmetric

– some exhibit radial symmetry

• Sac body plan

– Possess a central GASTROVASCULAR CAVITY

(GVC)

• Filter Feeders : through pores and special cells

that line the GVC 4

• skeleton made up SPICULES composed

of either calcium, silica or spongin

• Hermaphroditic : can reproduce sexually

(do not self fertilize) or asexually by

regeneration or budding

• Sessile adults(anchored to the ocean floor

as an adult) and free moving larvae

• Found mainly in marine habitats

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Basic Structure of a Sponge

The Gastrovascular Cavity

Has only one opening

Serves two primary functions

1. “Gastro”

digests and absorbs food and nutrients

2. “vascular”

serves as a primitive circulatory system as it moves nutrients around to other parts of the body

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Central Cavity

.

PORE

ARCHAEOCYTE

ARCHAEOCYTE

ARCHAEOCYTE = amoeboid cell

CHOANOCYTE = collar cell

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Structure

• No true tissues, but have specialized cells

• Body of the sponge is composed of three layers

-outer layer: thin and contains many pores (ostia)

-inner layer: contain specialized cells called collar cells.

-Middle layer: Jelly like material containing spicule and amoeboid cells

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Structure Continued

• Adults in fixed in position, except in larva form ( free floating until a suitable position is found )

• The sponge maintains its structure by the spicules, which is a skeletal structure

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• Ameboid cells aid in the production of the spicules

• Sponges are classified according to the chemical make-up of the spicules

-spicules containing calcium carbonate

-spicules containing silica

- spicules containing spongin ( a tough flexible fibre )

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Basic Functions of the Internal Cavity 1. To filter water as it

passes through the

sponge for food and

oxygen (see collar cell

enlargement)

2. To extract particles of

food from passing water

and digest food either in

collar cell food vacuoles

or by roaming

amoeboid cells.

3. To get rid of waste

products through the

osculum 12

Obtaining Nutrients • Through filter feeding ( animals that feed by

filtering water through their bodies )

• Water enters the pores of the cell and is drawn into the central cavity by the flagella of the collar cells

• Food particles in the water are captured by the collar cells and digested

• amebocytes finish the digestion that the collar cells began and then carry the nutrients to other areas of the sponge

• the waste produced and water are carried out of the sponge through a hole in the top of the sponge called the osculum 13

Collar Cells at work bringing in water and

retrieving oxygen and food for the sponge

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Sexual Reproduction • collar cells change into gametes

• the sperm leave through the osculum

• eggs are in the jelly like middle layer

• self fertilization does not occur

• sperm enter the sponge through the pores and will fuse with the egg to form a zygote

• cleavage occurs and the embryo forms a free swimming larva

• the larva passes into the inner layer and leaves the sponge through the osculum

• larva attaches to the ocean floor and develops into an adult sponge

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Asexual reproduction

• occurs by budding

• cells on parent sponge form buds that break off and grow into identical sponges

• in unfavorable conditions asexual reproductive structures are formed called gemmules

• gemmule is a group of cells that are enclosed by a tough outer covering

• when the conditions are again favorable the gemmules develops into new sponges

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Ecological Importance of Sponges 1. provide shelter and

food for other ocean creatures

2. release chemicals that help to break up old shells

3. form symbiotic relationships with bacteria and plant-like protists that produce oxygen through photosynthesis

Sea Crab living inside a

Fluorescent sponge

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Economical Importance of Sponges

• At one time there was

a market for sponges

to be used in the

bathroom and the

kitchen because of

their ability to absorb

water, however

synthetic sponges

have replaced this

industry Sea sponge Skeleton to be used

in the bathroom for washing

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