Phylum Porifera

Characteristics of Phylum Porifera Cellular level of organization, without true tissues Adults exhibit radial symmetry or are asymmetrical Possess totipotent cells Possess unique flagellated cells – choanocytes – that create water flow through a water current system Outer and inner cell layers lack a basement membrane Outer and inner cell layers divided by a noncellular layer – the mesohyl – that contains some cells and skeletal material Body support (“skeleton”) provided by spicules composed of calcium carbonate or silicon, a proteinaceous matrix (spongin), or a combination

Amoebocytes Phagocytic – role in digestion Archeocytes – totipotent Sclerocytes – spicule production Spongocytes – spongin Collenocytes – collagen of mesohyl

Choanocytes feeding reproduction

Based on body form and skeleton type Subphylum (sP) Cellularia Classification Based on body form and skeleton type Subphylum (sP) Cellularia Class Calcarea All three body forms Calcareous spicules Class Demospongiae Leuconoid Siliceous spicules, spongin, or both 80 – 90% of described species

Classification Subphylum Symplasma Class Hexactinellida Siliceous spicules (fused) Syncytial tissues

Physiology Dependent on flow of water through the body Brings in food, oxygen, sperm Out – waste materials Stop beating of flagella Not coordinated, local myocytes – Demospongiae osculum

Reproduction Hermaphroditic Some dieocious Eggs – archeocytes or choanocytes Sperm – Choanocytes Sperm released →

Read Chapter on Introduction to Eumetazoa