Invertebrates- Phylum Porifera Kingdom Animalia Invertebrates- Phylum Porifera

Sponge Structure Bodies completely lack symmetry (asymmetrical) Masses of specialized cells embedded in gel-like substance of body wall called mesohyl Totipotent- The plasticity of sponge cells and how specialized types can change into others Not organized into tissues nor organs (Parazoa) Body wall covered in tiny pores, ostia, water enters Larger openings, oscula, water exits Sessile- Do not move Attach to surface early in life Can produce toxins as defense

Sponges Pinacoderm- Outer layer of cells of a sponge Pinacocytes- Thin, flat cells on the outer-surface Can be tube-like and contractile (porocytes) Bag-shaped with large internal cavity (Spongocoel) Lined by choanocytes, or collar cells (Choanoderm collectively) Flagellated cells draw in water through pores Amoeboids (Mesenchyme cells)- Irregularly shaped sponge cells Float in mesohyl to supply nutrients and carry away waste for other cells

Structure of a Sponge

Protistan Ancestors Choanocytes closely resemble a protist called a choanoflagellate

Feeding Habits of a Sponge Collar cells function as sieves Trap plankton and other tiny organisms in the small hair-like projections Pulls organisms in and digests them intracellularly (within the cell) Release nutrients and waste into mesohyl Amoebocytes pick up nutrients from mesohyl and supplies to rest of cells

Sponge Skeleton Skeletal support is to prevent sponge from collapsing in on itself Not a fixed skeleton, parts found throughout mesohyl Most sponges composed of spicules Tiny needles composed of silica or calcium carbonate Used for protestion as well Sclerocyte- Cells that produce spicules Microscleres- Smaller spicules Macroscleres- Larger spicules Few composed of spongin (ex: bath sponges) Resilient, flexible protein fibers Some contain both http://player.discoveryeducation.com/index.cfm?guidAssetId=287F0044-982C-4BA6-90E9-BC5863CFB205

Three Types of Sponges Based on skeleton type Class Calcarea- Calcareous sponges Spicules composed of calcium carbonate Class Hexactinellida- Glass sponges- Found in the deepest parts of the ocean Spicules made of silica Hexaxon- Unique six-pointed spicule - Class Demospongiae- Demosponges Also contain spongin (proteinaceous)

Three Body Forms Ascon- Vase-like Porocytes (ostia) lead directly to spongocoel Sycon- sponge wall is folded. incurrent canals -water enters from dermal pores radial canals (lined with choanocytes)- lead to spongocoel Leucon- Branched canal system lacking spongocoel Incurrent canals lead to choanocyte- lined chambers (water slows through these) Multiple oscula from excurrent canals

Reproduction Asexual reproduction: Regeneration- Cut pieces will grow back Budding- Shed fragments constantly to make new individuals Gemmules- Amoebocytes encased in protective coat Develop when living conditions become to harsh to survive Sealed in with food to survive Cells grow into new sponge when conditions

Reproduction Sexual reproduction Most sponges are hermaphrodites (produce both eggs and sperm Do not self fertilize Sperm cells of one sponge enter another through pores Collar cells pass sperm into mesohyl where eggs are located and fertilization occurs Zygotes develop into larvae and leave the sponge Inversion- movement of flagellar cells of developing larvae to the outside Blastula- Hollow larval stage (coeloblastula) Parenchymula- Solid larval stage Macromeres- Large cells that form the outer choanoderm After a brief free-swimming stage they attach to a surface to live as sessile sponges

Sexual Reproduction of Sponges