Phylum Porifera The Sponges

Typical sponges and their structure Figure 12.04

I.Characteristics of Sponges Multicellular – The body of sponges is a loose aggregation of cells Body containing pores, canals and chambers Mostly marine; all aquatic Symmetry is either radial or they have NO symmetry Skeleton of proteins (collagen and/or spongin) with spicules NO true organs or tissues Adults are sessile and attached to substratum

II. Form and Function Sponge Pores A. Incurrent pores are called Ostia B. Excurrent pores are called Oscula.

C. Specialized collar cells known as choanocytes have flagellae that create water flow and aid in the digestion of smaller particles.

Choanocytes in the Mesohyl These choanocytes are located throughout The mesohyl - the matrix in which all sponge cells are embedded.

D. Flat epidermal cells known as pinacocytes aid in surrounding and protecting the body of the sponge.

E. Special amebocytic cells, called archaeocytes, carry out a variety of functions – especially digestion and protein formation and spicule formation.

III.Types of Spicules A. Calcareous spicules are made of CaCO3. They are formed from the mineral elements in the saltwater around them by special archaeocytes.

B. Siliceous spicules are made of SiO2 B. Siliceous spicules are made of SiO2. They are formed from different elements in the water by other archaeocytes.

IV.Types of Proteins Spongin is a protein found in only SOME sponges – not all!

The other form of protein, collagen, is found in ALL sponges, as well as all other animals.

V. Sponge Body Plans The simplest body plan is the Asconoid, where the choanocytes are located in the spongocoel, or hollow, internal, water filled gastrovascular cavity.

A typical Asconoid Sponge

Sponge Body Plans (2) Killing cells The second most complicated sponge body plan is the Syconoid sponge. It’s choanocytes are located in Radial Canals. Sponge Body Plans (2) Killing cells

A Typical Syconoid Sponge

Sponge Body Plans (3) Killer Cells The largest and most complicated sponges by far are the leuconoid sponges. They have their choanocytes in flagellated chambers, which increase water flow and feeding efficiency.

A Typical Yellow Tube Sponge (Demosponge)

A Diver With Barrel Sponge (Demosponge)

VI.Classification A. Class Calcarea – Heavily calcareous sponges containing straight calcareous spicules and collagen B. Class Hexactinellida – radially symmetrical deep water sponges with six-rayed siliceous spicules. These are often beautiful and range from a few centimeters to more than 1.3 meters in length , and contain collagen. C. Class Demospongia – By far the largest group, containing 95% of all living sponges in the world. Spicules are siliceous, but not six rayed. They may or may not contain spongin, but like all sponges , they do have collagen.

Classification (cont.) D. There is a fourth class of sponges, called the Homoscleromorpha that used to be classified as Demosponges. These are all found in dark crevices in the ocean and are seldom found in the open, and are usually fairly colorful.

Calcareous Sponge

Hexactinellid Glass Sponges Two examples of the remains of Euplectella

A Common Demosponge

Class Homoscleromorpha

VII. Sponge Reproduction A. Asexual Reproduction: Carried out by budding (fragmentation) OR by gemmules – internal buds created to allow them to withstand adverse weather conditions; usually over the winter. B. Sexual Reproduction: Carried out by normal sperm and egg process; sperm are usually carried out of the osculum of one sponge and into the ostia of another. All sponges are hermaphrodites – containing both male and female sex organs

Test– Next Class Meeting!