Sponges

What is a sponge? Is it the soft squishy thing you use to clean things? Is it the poufy lufa you use in the shower? Or is it something much more unique and interesting?

Scientists believe that sponges were the first animals to be alive. The ancestors of today's sponges were alive billions of years ago. Sponges have looked the same for millions of years. They have been helping mankind and nature for as long as they have been on the planet.

Though extremely plant-like in appearance, sponges are actually one of the most primitive animals in the sea. Most of us are familiar with the dried colorless varieties that populate the kitchens and bathrooms of the world. But in the ocean, live sponges can be found in an infinite variety of colors and shapes. Most of them are relatively small, but some varieties can grow to over 6 feet in diameter.

Considered the most primitive of multi-cellular animals, sponges are really loose colonies of cells. Most sponges live in saltwater, with only a few freshwater species. Adult sponges do not move from place to place (they are sessile) Sponges range from slimy encrusting forms to beautiful 3D structures with lacy skeletons made of silicon. They are found from shallow waters down to the depths of the ocean.

Porifera is derived from Greek words meaning Phylum - Porifera Porifera is derived from Greek words meaning "pore bearing" Classes: 4 Orders: 18 Families: 80 Species: 5,000

Fresh water

Characteristics 1- Multi-cellular 2- Body with pores, canals, and chambers. 3- All aquatic; mostly marine. 4- Asymmetrical symmetry. 5- Skeletal structure. Collagen (spongin) Calcium or silicon crystals (spicules) 6- No organs or tissues. 7- Digestion - intercellular

8- Excretion and respiration – diffusion 9- No nervous system or sense organs. 10- Adults sessile and attached to substratum Free swimming larvae 11- Asexual reproduction by budding or gemmules Sexual reproduction – male and females

Body Plan

Sponge structure In between the outside layer of cells and the inside layer of cells is the area of the matrix called mesenchyme, a name which means("middle jelly").

Two types of skeletal material Spicules are needle-like structures composed of minerals either calcium carbonate or silicate. Support and protection.

Spongin is a fibrous protein that provides support and elasticity. ***Commercial sponges are composed of spongin.

Pore types Osculum - a large opening in a sponge through which water flows out of the sponge. Sponges may have more than one oscula.

Ostia/Ostium A series of tiny pores all over the body of a sponge that let water into the sponge.

Cells Sponges have a cellular grade of organization. They do not possess any structures that can be considered organs. For instance, sponges do not have stomachs or kidneys. Instead, sponge cells of various types are responsible for bodily functions, the day-to-day activities that sustain life.

1 - Pinacocytes (Epidermal cells) These cells are the "skin cells" of sponges. They line the exterior of the sponge body wall. They are thin, leathery and tightly packed together.

2 - Porocyte Contract to regulate flow of water through the sponge. These cells surround (ostia) canal openings. Contract to regulate flow of water through the sponge.

3 - Sclerocyte Cells in sponges that produces spongin or spicules.

4 – Choanocytes (collar cells) These distinctive cells line the interior body walls of sponges. These cells have a central flagellum that is surrounded by a collar of microvilli. The flagella beats to create the active pumping of water through the sponge. The collars of the choanocytes are the primary areas that trap the food particles.

5 - Archaeocytes (amebocytes) 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. They digest food caught by the choanocyte collars and transport nutrients to the other cells of the sponge. Archaeocytes develop into gametes.

Digestion Filter feeders A sponge takes in food via the water that flows through the pores. Filter feeders Sponges eat tiny particles, plankton that they filter from the water that flows through them. A few sponges, however, are carnivorous. They engulf and digest small crustaceans or water-dwelling animals.

Choanocytes ingest the food particles and are the primary cells that nutrients are absorbed into the sponge. They store the food in vacules. Archaeocytes ingest food caught by the choanocyte collars. Then digest the food and transport nutrients to the other cells of the sponge.

Circulation, Respiration & Excretion A sponge has water flow in through the pores. The water contains the oxygen the sponge needs. Diffusion A sponge has carbon dioxide and other wastes removed as the water moves in and out through the pores.

Reproduction Sponges reproduce both sexually (with gametes, or egg and sperm) and asexually (without gametes). Some sponges are hermaphrodites. Fertilization occurs external After eggs are fertilized, the larva swims about before it settles to the ocean bottom where it will grow into an adult sponge.

Sponges have strong powers of regeneration, probably due to the interchangeability of their cells, and to their lack of special tissues. Wounded sponges can regenerate cells to replace the wounded part. Some sponges species may be considered "immortal", because if you were to take a sponge, blend it up and put the blended up sponge back in the water it would reaggregate to form a new sponge.

Larva

Sponges also reproduce asexually by the formation of buds or gemmules.

4 - Classes

Demospongiae This class comprises 95% of the world's sponges and include the most colorful and largest species. They range in size from small, encrusting forms to large irregular masses. They have spicules of silica dioxide and spongin. These are the sponges most commonly seen whilst diving or walking along the shore. Unlike the other four classes whose members are all marine, demosponges can also be found in freshwater.

Calcarea Typically pale in color and with a tendency to be small in size. This class of sponges lacks spongin. Their skeletons are composed entirely of calcium carbonate and as a result they are brittle to touch. They are usually found in shallow water.

Hexactinellida These are commonly known as the glass sponges and include the Venus' flower basket. They are often vase- or funnel-shaped. Their distinguishing feature is the network formed by the siliceous spicules. There are about 500 species. They occur mainly in deep, cold waters and are very beautiful.

Sclerospongiae This small class is sometimes included in the Class Demospongiae. It contains species usually found in grottos and tunnels in association with coral reefs. They are unique in having an internal skeleton of siliceous spicules and spongin fibers like those of the Demospongiae together with a massive calcareous basal skeleton.

Threats to Sea Sponges According to the Australian Marine Conservation Society, sea sponges are under threat not only from over-harvesting but also, pollution from sewage discharge and storm water run-off, as well as from dredging activity. Global warming, which has been increasing water temperatures and altering the ocean food chain and sea floor environment accordingly, is also now a factor.