SPONGES Instructor: Almonther I. Alhamedi The Islamic University of Gaza Department of Biology Web page :

G ENERAL CHARACTERISTICS Non-moving (sessile) animals. No nerves or muscles (no tissue differentiation). Mostly marine, amorphous, no specialized reproductive, digestive, respiratory, sensory, or excretory organs are found in this group. Filter feeders: Collect food particles from water Most sponges are hermaphrodites. Hermaphrodites function as both male and female in sexual reproduction by producing eggs and sperm.

G ENERAL CHARACTERISTICS They are asymmetrical or radially symmetrical. The body is provided with pores, canals, and chambers through which water current flows. The internal cavities are at least partially lined with flagellated cells (choanocytes). Sponges possess high regenerative power. Sponges possess an internal skeleton of spicules and or organic fibers. Skeletons composed of CaCO3 or SiO2 spicules or spongin.

S PONGES ENVIRONMENT less than 2% of all sponge species are found in freshwater, the remaining 98% of the species are marine. Sponges live a single or in colonies on tides. Sponges are attached to the bottom rocks. Sponges live in clear water to avoid the closure of pores.

S PONGES STRUCTURE The sponge body is generally a cavities with main pore called osculum and pored wall. It is a perforated bag. The flagellated cells lining the spongocoel are called choanocytes or collar cells. The collar cells perform the following functions: 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.

S PONGES STRUCTURE Adjacent to the choanocytes layer is a gelatinous, non living layer of material called the mesohyl layer, then amoeboid cells called archaeocytes wander through the mesophyl. Pinacocyte : flattened cell occurring in the dermal epithelium of sponges.

S PONGES STRUCTURE

A RCHAEOCYTES FUNCTIONS : 1. Archaeocytes are responsible for digesting food particles captures by the choanocytes. 2. Some store digested food materials. 3. It may gives rise to both sperm and eggs. 4. They also probably play an active role in non- self recognition reactions in response to contact with other sponges. 5. Archaeocytes play a role in eliminating wastes

T HE SPONGES ARE SUPPORTED BY SPICULES : It may be calcareous (CaCO3) ciliceous spicules (SiO2) fibers composed of a collagenous protein Called spongin.

T HE SPONGES ARE SUPPORTED BY SPICULES : The cells secreting spicules are termed sclerocytes and those producing spicules fibers are termed spongocytes.

P ORIFERAN D IVERSITY  There are 3 basic levels of sponge construction: 1. Asconoid 2. Syconoid 3. Leuconoid  Each form simply reflects an increased degree of evagination of the choanocytes layer away from the spongocoel, increasing the extent of flagellated surface area enclosed by the sponge. Most sponge species are of leuconoid construction.

S PONGE T YPES

Phylum Porifera Class Desmospongiae Class Desmospongiae Class Calcarea Class Calcarea Class Hexactinellida Class Hexactinellida Class Sclerospongia Class Sclerospongia

C LASS C ALCAREA (cal-care-a) (L. calcis, lime) (Calcispongiae). Have spicules made of calcium carbonate Mostly small in size (<15 cm.), and form irregular masses Never contain spongin, restricted to shallow water, and strictly marine. Representatives of all 3 types of construction occur in this class.

C LASS : D EMOSPONGIAE (de-mo-spunjee) (Gr. demos, people, spongos, sponge) 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.

C LASS : H EXAACTINELLIDA (hex-ak-tin-eli-da) (Gr. hex, six, aktis, ray, L. - ellus, dim. suffix) (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. The member of some species live in soft sediment, anchored by tufts of spicules. Usually found in deep water on soft substrates in the tropics 200-1,000m.

S CLEROSPONGIAE Sclerospongiae is no longer considered a class. CaCO3 foundation with SiO2 spicules Found in Pacific and West Indies

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