Kingdom: Animalia Phylum: Porifera

Phylum Porifera Characteristics (Sponges) 1. Asymmetrical 2. Evolved from the Kingdom Protozoa to be one of the first organisms characterized as a true animal. 3. Mostly marine, but a few live in freshwater. 4. As adults, they are immobile, but the larvae are free- swimming, ciliated creatures. 5. Have a central cavity or a series of branching chambers through which water circulates during filter feeding. 6. No circulatory, digestive, or nervous system. No organs or well-defined tissues. 7. Vary in size from less than a centimeter to a mass that would fill your arms.

3 Types of Sea Sponges 1. Glass Sponges (Class Hexactinellida) – have a fragile skeleton made of silica spicules. 2. Demosponges (Class Demosponiae) – often brightly colored and can grow to be the largest of the three sponge types. This type of sponge accounts for about 90% of all know sponges, including the rare predatory sponges. 3. Calcareous Sponges – have a fragile skeleton made of calcium carbonate spicules. This type of sponge is often the smallest of the three.

Cell Types Like us, sponges exhibit a “division of labor”, meaning that they have different cells specialized for doing different things. The only difference is that we have hundreds of different cell types, while sponges have only three. Pinacocytes – thin, flat cells that line the outer surface of a sponge; regulate water circulation and serve as pathways for water moving through the body wall. Mesenchyme cells – amoeboid cells that form a jellylike layer just below the pinacocyte layer; specialized for secreting skeletal spicules, and transporting and storing food. Choanocytes (collar cells) – flagellated, tentacle-lined cells that form the inner layer of a sponge; create water currents through the sponge, filter microscopic food particles from the water, and are specialized for reproduction.

Morphology of a Simple Sponge

Skeletons Sponges are supported by a skeleton that consists of microscopic needle-like spikes called spicules. The spicules are secreted and deposited by the mesenchyme cells and are made of calcium carbonate (the same materials that sea shells are made of) or silica (the same material sand is made of).

Feeding Most sponges are filter feeders, meaning that they eat whatever bits of food they can “filter” out of the water as it passes through their body (just like a swimming pool filter). Water enters through the pinacocytes, is filtered through the collar cells (choanocytes), and flows out the hole at the top called the osculum. Due to this filtering ability, sponges play an important role in reducing turbidity (muckiness) of coastal waters. Their “food” consists mainly of bacteria, algae, and protists. Once the food is trapped by the collar cells, it is transported to a food vacuole ( a mesenchyme cell) for digestion. Removal of wastes is controlled solely by diffusion.

Exceptions to the Rule Some demosponges are sedentary predators and can snatch things like shrimp, small fish, and other crustaceans. http://scitechdaily.com/carnivorous-deep-sea- sponge-discovered-off-coast-of-california/

Reproduction Most sponges are monoecious, meaning that they can produce both eggs AND sperm, though usually not at the same time. When the time is right, sponges can turn their choanocytes into sperm or eggs. The newly formed “sperm” exits through the osculum and enters another sponge through its pinacocyte. The sperm is then filtered just like food and gets trapped in a second sponge’s newly formed “egg”. The zygote then breaks free of the mother sponge and enters a “free-swimming” ciliated, larval stage. After 2 to 3 days, it finds a good spot on the bottom to settle down, and begins to develop into the adult sponge form. ALSO, sponges can regenerate!! Portions of a sponge that are cut or broken from one individual regenerate new individuals.