Prepared by : Nada H. Lubbad Phylum Porifera Prepared by : Nada H. Lubbad

Porifera characteristic Sponges are primarily marine, (less than 2% of all sponge species are found in freshwater). They are cellular - level organization: - Cells are specialized (functional). - Cells are not organized into tissue. - Parazoans ( tissue are not true) - No systems for reproduction, digestion, respiration, sensory, excretion. Radially symmetrical or asymmetrical.

Structure of sponges A sponge is a rigid perforated bag. The empty space of this bag is called the spongocoel. It has three layers : - Inner layer : It is lined with flagellated cells called choanocytes or collar cells. Functions of the collar cells : They generate currents that help maintain circulation of seawater within and through the sponge. They capture small food particles. They capture incoming sperm for fertilization.

- Mesohyl layer: a gelatinous, non living layer of material is lining by amoeboid cells called archaeocytes or amoebocytes. Functions of archaeocytes : Responsible for digesting food particles captures by the choanocytes. Some store digested food materials. It may gives rise to both sperm and eggs. Develop into more specialized cell type when necessary. Can specialized to secrete the supporting elements located in the mesohyl layer.

The sponges are supported by spicules: It may be calcareous (CaCO3) or siliceous spicules (SiO2) or fibers composed of a collagenous protein called spongin. The cells secreting spicules are termed sclerocytes and those producing spicules fibers are termed spongocytes. Both of these cells are derived from archaeocytes. Function of spicules & fibers : In species identification. Maintain the shape & prevent predation.

- Outer layer : flattened contractile cells (Pinacocytes). These cells also line the incurrent canals and the spongocoel in some places where choanocytes are lacking. Contraction of Pinacocytes has the functions : Enable sponge to undergo minor shape change. Regulating water flow through the sponge by varying the diameter of incurrent openings. water flow into the spongocoel through narrow openings called the Ostia & exits the spongocoel through larger opening called osculum .

Reproduction in sponges: 1. Asexual : Internal buds. Regeneration: can regenerate from broken pieces. External buds (Gemmules) : Produced in winter as dormant bodies ,coat and supportive cells protects from freezing and desiccation.

2.Sexual: It takes place in in the mesohyl. usually hermaphroditic with male and female gametes , formed by amoebocytes. most hermaphroditic species produce eggs and sperm at different times so they do not self fertilize. sperm is released into environment via osculum and is brought in by another sponge via Ostia. Sperm captured by collar cells, which then lose there collar & transform into specialized amoeba-like cells that carry sperm to the egg. Fertilized egg develops into blastula , which is release into water (in most ) The larvae may settle directly & transform into adult or may be planktonic for a time Larvae are lecithotrophic = use stored yolk

Porifera diversity There are 3 basic levels of sponge construction: 1. Asconoid. 2. Syconoid. 3. Leuconoid. Asconoid : The most primitive and simplistic in structure. They are a perforated tube shaped. Radial symmetry.

Syconoid (scypha) : next level of complexity. typically vase shaped ( tubular ) like the asconoid sponges. Larger than Asconoid. walls are invaginated , thicker & the pores penetrate it are longer forming a system of simple canals. radial symmetry

Leuconoid : The highest level of complexity in sponges. lost radial symmetry and are very irregular in shape and may attain large sizes. invaginated canals are even further invaginated and folded to from small flagellated chambers. Water moves through the canals into these chambers and out via central canal and osculum.

Class Calcarea: Have spicules made of calcium carbonate. Mostly small in size. All species are marine. Representatives of all 3 types of construction occur in this class.

Class Demospongiae Members of the largest class. this class containing 80% of all sponge species. The supporting spicules and fibers may be composed of spongin and silica but never of CaCO3. All freshwater sponges are found in this class. Class Hexactinellida (Hyalospongiae). It contains sponges whose bodies are supported by 6-rayed siliceous spicules. Sponges known as glass sponges are marvels of structural complexity and symmetry.

Class Sclerospongiae Coralline sponge Most of them live in deep water on corals reef Sclerospongiae is no longer considered a class. CaCO3 foundation with SiO2 spicules