Phylum Porifera: Sponges

Biology 11

Name means “pore bearers”- body has many pores in it

Sessile

Multicellular

Mostly marine (only 100/9000 are freshwater)

Characteristics

Asymmetrical body shape

Made of 2 cells layers◦ Ectoderm◦ Endoderm

No specialized tissue or organ systems◦ Individual cells sense and react to environmental

changes

Structure

Do have specialized cells that fulfill the sponge’s life functions

◦Epidermal cells◦Pore cells◦Collar cells◦Amoebocytes

Specialized Cells

Epidermal cells form outer covering

Water is drawn in through pore cells into a central cavity

The collar cells have flagella that beat to create a current to make sure water is being drawn in through pore cells

Water flows out of sponges through a larger opening called the osculum

Make spicules◦Needle-like structures that provide

structural support◦Made of silica or calcium carbonate◦Some made of spongin protein (softer

skeleton) Carry nutrients to other cells Aid in reproduction

Amoebocytes

Contain a flagellum to move water in

Brings oxygen and food particles into body of sponge

Collar Cell

Water acts as the circulatory, respiratory, reproductive, and excretory systems

Brings in food, oxygen, carries away waste, gametes, larvae

Oxygen is brought in and carbon dioxide and other metabolic wastes are given off

Movement of Water

Feeding and Digestion◦ No mouth or digestive tract

◦ Are filter feeders- sift food particles from the water Driven by water flow Filtered by collar cells

Excretion◦ Driven by water flow

Life Functions

Respiration◦Oxygen diffused from surrounding water

into cells◦Carbon dioxide diffused from cells to

surrounding water

Movement◦Adults sessile: Remain attached, don’t move

◦Larvae are mobile

Sexual

Most are hermaphrodites (produce both egg and sperm)

Reproduction

Sperm released out of osculum and swim to another sponge (with the help of currents)◦Enter another sponge’s pore cell◦Picked up by collar cells◦Carried to an egg by amoebocytes◦Fertilization occurs◦Zygote develops into a flagellated larvae

which is mobile (can be dispersed)

Increase change of fertilization

They do not fertilize their own eggs with their own sperm

Why do sessile animals tend to be hermaphroditic?

Can also reproduce asexually by:◦Fragmentation: part of sponge breaks off◦Budding: mitotic growth and break off◦Gemmules: collection of cells that are

enclosed by hard outer covering contain spicules Form when conditions are unfavourable

Provides habitat for many other animals◦ Like snails, shrimp, sea stars, bacteria…

Is a food source for other animals

Provides a symbiotic relationships with bacteria (bacteria provide food and oxygen to sponge and remove wastes)

Ecological Importance

Used as bath sponges

Produce chemicals (to discourage other animals from eating them) that are being used in research for cancer, viruses, and antibiotics