What are the significance of spicules?
Spicules provide structural support for maintaining the vertical body position, minimize the metabolic cost of water exchange, and may even deter predators.
How are spicules used in taxonomy?
Most sponges produce skeletons formed by spicules, structural elements that develop in a wide variety of sizes and tridimensional shapes. The morphologies of spicules are often unique to clade- or even species-level taxa which makes them particularly useful in taxonomic assignments.
Why are spicules important for sponges?
Besides supporting sponge cells, spicules can help larvae stay buoyant while in the plankton or reach the bottom at settlement, enhance reproduction success, or catch prey.
How can the spicules in sponges be classified according to the number of axes?
Classification of Spicules: First, spicules are of two general kinds—megascleres and microscleres. The spicules are further classified according to the number of their axes and rays. Words designating the number of axes end in axons, those referring to the number of rays end in actine or actinal.
What is the difference between spongin and spicules?
Some spicules are formed of the mineralized substances calcium carbonate and silica, while others are made of an organic substance called spongin. Spongin skeletons were and are used as scrubbers in bathtubs, though they are fairly expensive. The ubiquitous bathtub accessory called a lufa is NOT a sponge, but a plant.
What is the function of Ostia in sponges?
Scattered among the pinacoderm are the ostia that allow entry of water into the body of the sponge. These pores have given the sponges their phylum name Porifera—pore-bearers. In some sponges, ostia are formed by porocytes, single tube-shaped cells that act as valves to regulate the flow of water into the spongocoel.
What is the function of archaeocytes in a sponge?
Archaeocytes. Archaeocytes are very important to the functioning of a sponge. These cells are totipotent, which means that they can change into all of the other types of sponge cells. Archaeocytes ingest and digest food caught by the choanocyte collars and transport nutrients to the other cells of the sponge.
What is the job of the amebocyte in a sponge?
Amoebocytes have a variety of functions: delivering nutrients from choanocytes to other cells within the sponge, giving rise to eggs for sexual reproduction (which remain in the mesohyl), delivering phagocytized sperm from choanocytes to eggs, and differentiating into more-specific cell types.
What is the function of archaeocytes?
What is the significance of the epithelial cells in poriferan circulation?
Epithelial cell significance in poriferan circulation. A synonymous term for choanocytes. How sponges exchange gas without a true circulatory system. Where water enters and exits a sponge.
What are the functions of spongin?
Spongin, a modified type of collagen protein, forms the fibrous skeleton of most organisms among the phylum Porifera, the sponges. It is secreted by sponge cells known as spongocytes. Spongin gives a sponge its flexibility.