Six general questions: How are they classified? What do they look like? How do they support themselves and locomote? How do they feed and digest? How do they maintain homeostasis? How do they reproduce and develop?

Phylum Porifera Parazoan - no true embryonic tissues Cells are totipotent - they change form and function and they are mobile throughout the body. Approximately 9000 species encrusting and upright marine, intertidal, freshwater A group of sponges is a sleeze.

Phylum Porifera Class Calcarea Spicules composed of calcium carbonate. Exclusively marine. Considered the most primitive of sponges. Color usually dull.

Phylum Porifera Class Hexactinellida “Glass sponges” Siliceous, six-rayed spicules of hydrated SiO2. Exclusively marine, found in deep water.

Phylum Porifera Class Demospongiae Siliceous spicules or organic collagen network. Marine and freshwater. Occur at all depths.

What do sponges look like? Aquiferous system Water is pumped through the sponge such that O2 and nutrients are brought in and CO2 and wastes are removed. Sponge walls have pores and chambers so each cell is in close proximity to water.

What do sponges look like? Body structure Layers of cells with specific functions. Contribute to aquiferous system, food uptake, and support. Mesohyl - noncellular mesoglea which contains spicules and many types of ameboid cells.

What do sponges look like? Body structure Pinacoderm - made of pinacocytes. Outer layer perforated with small holes where water enters. Pinacocytes are flattened and overlapping. Epithelial function and are probably phagocytic. Osmoregulation in freshwater sponges.

What do sponges look like? Body structure Pores are called dermal pores if they are composed of more than on cell. Called ostia if they are composed of only one cell. Cells are called porocytes - cylindrical and contractile.

What do sponges look like? Collar of microvilli with flagellum in middle. Collar has mucus to trap food particles. What do sponges look like? Body structure Choanoderm made of choanocytes - inner surface of flagellated cells that create water currents.

What do sponges look like? Body types - Asconoid Small and simple vase shape. Pinacoderm and choanoderm are simple sheets. Porocytes are tube-shaped cells that form ostia on pinacoderm side and open into spongocoel on choanoderm side. Found in all juvenile and some adult calcareous sponges. Water flow: ostia ---> porocyte --->spongocoel ---> osculum

What do sponges look like? Body types - Syconoid Various degrees of infolding to create flagellated chambers containing chanocytes. Mesohyl thickened. Incurrent opening is a dermal pore surrounded by several porocytes. A system of canals leads to the flagellated chambers. The opening into the chamber is the prosopyle. Chambers open to the spongocoel via a wide opening called an apopyle. Found in many calcareous sponges. Water flow: dermal pore ---> incurrent canal --->prosopyle ---> flagellated chamber ---> apopyle ---> spongocoel ---> osculum

What do sponges look like? Body types - Leuconoid Further infolding of pinacoderm and choanoderm to create flagellated chambers that are discreet chambers. Spongocoel is a series of excurrent (or exhalent) canals. Flagellated chambers have large surface area compared to incurrent and excurrent canal systems. Decreases water velocity to maximize gas and nutrient exchange. Typical of most calcareous and all demosponges. Water flow: dermal pore ---> incurrent canal --->prosopyle ---> flagellated chamber ---> apopyle ---> excurrent canal ---> osculum

What do sponges look like? Body types - Hexactinellid sponges No pinacoderm. Dermal membrane with no discreet cell structure and simple holes for pores. Cellular material forms a trabecular network with internal cavities called subdermal lacunae Flagellated chambers are thimble-shaped and supported by the trabecular network. Prosopyles bring water from the lacunae to the chambers. Choanocyte chambers and the trabecular network are syncitial-there are no discrete cells)

How do sponges support themselves? Spongocytes secrete spongin, a supportive collagen. True spongin is found only in demosponges. Collagen Secreted by collencytes, lophocytes, and spongocytes. Lophocytes are motile and have a band of collagen behind them. With collencytes they secrete thin intercellular collagen.

How do sponges support themselves? Spicules Made of CaCO3 or SiO2 Occur in mesohyl. Often used for identification. Produced by sclerocytes. Collect Ca or Si and deposit it. Can work alone or in groups (often two cells per spicule ray).

How do sponges support themselves? Spicules Megascleres and microscleres. Calcareous sponges have only megascleres. Demosponges and hexactinellid sponges have both.

How do sponges feed? Phagocytosis and pinocytosis for intracellular digestion Dermal pores allow 50 mm particles. Motile archeocytes capture small particles (2-5 mm) in lining of inhalent canals. Digestion in food vacuole. Water driven through collar of chaonocytes where other particles trapped. Food partially digested by choanocytes then passed on to archeocytes.

How do sponges reproduce and develop? Gemmules - overwintering bodies of freshwater sponges Asexual reproduction Fragmentation - small bits break off and form a new sponge Budding - new sponges grow attached to an older sponge and eventually form a new sponge.

How do sponges reproduce and develop? Sexual reproduction Most sequential hermaphrodites. Some gonochoristic. Most sponges release egg and sperm into water. Fertilization external. In some sponges, eggs produced by choanocytes or archaeocytes and are kept in the mesohyl. Sperm produced from spermatic cyst. Sperm travel to other sponge, taken up by choanocyte (but not digested) and transferred to egg. Zygote may spend time in maternal sponge.

How do sponges reproduce and develop? Sexual reproduction Larval types: “coeloblastula”, parenchymula, and amphiblastula. Holoblastic cleavage into a coeloblastula Larvae are motile (swim and creep) and lecithotrophic Larvae are released by maternal sponge coeloblastula or larval stages. Demosponges usually incubate embryos to the parenchymula stage.

How do sponges reproduce and develop? Calcareous sponges