Kingdom Animalia

Invertebrates- Phylum Porifera

Sponge StructureBodies 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 othersNot organized into tissues nor organs (Parazoa)

Body wall covered in tiny pores, ostia, water entersLarger openings, oscula, water exitsSessile- 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 itselfNot a fixed skeleton, parts found throughout mesohylMost 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

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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 • Spicules made of silica• Also contain spongin (proteinaceous)

Three Body FormsAscon- Vase-like Porocytes (ostia) lead directly to spongocoelSycon- 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