Sponges have a unique feeding system among animals. Instead of a mouths they have tiny pores (ostia) in their outer walls through which water is drawn. Cells in the sponge walls filter food from the water as the water is pumped through the body and the osculum (“little mouth”).
As water filters through a sponge’s porous exterior, the sponge gains some motion, receives food and oxygen, and dispels waste. Inside the sponge, tiny hairlike structures called flagella create currents to filter bacteria out of the sponge’s cells and trap food within them.
Sponges must pump water through their bodies in order to eat. Because sponges are sessile, meaning they cannot move, they filter water to obtain their food. They are, therefore, known as filter feeders.
Sponges get food by straining the water that comes through their pores. Oxygen is also obtained from the water the sponge lives in. These strange animals have lived on the Earth for a very long time.
Sponges Respire Through Diffusion
Sponges do not have complex digestive, circulatory or respiratory systems to move nutrients and oxygen around their bodies. Rather, each cell is independent and performs its own oxygen, food and waste processes using diffusion.
Most glass sponges live attached to hard surfaces and consume small bacteria and plankton that they filter from the surrounding water.
In 1880, the German zoologist Carl Chun suggested a pair of tiny pores opposite the comb jelly mouth might secrete some substance, but he also confirmed that the animals defecate through their mouths. In 1997, biologists again observed indigestible matter exiting the comb jelly mouth—not the mysterious pores.
The completely butt-less
One animal that does this lives on your face. Face mites, such as Demodex folliculorum, do not have an anus at all. They don’t even poop through their mouths like our ancient ancestors did.
Are there any animals that don’t poop? As a matter of fact yes there are: Tardigrades – These little alien-like critters only excrete when they molt. So any “fecal” matter produced it not really pooped out as we would really describe it.
In sponges, in spite of what looks like a large digestive cavity, all digestion is intracellular. The limit of this type of digestion is that food particles must be smaller than individual sponge cells.
Sponges don’t have tissues and organs. The beating choanocyte cells (specialized cells with flagellae) and the porous structure of a sponge’s body are specialized to pump water throughout the sponge’s body. This brings food to all the cells.
How do sponges get their nutrition? Sponges are filter feeders and retrieve their nutrition from filtering the water that enters their pores and exits their osculum. The food is captured by choanocytes and also amoebocytes who can digest it. Amoebocytes can also digest the food and carry nutrients to other cells.
Digestion in sponges occurs in individual cells. The cells envelop and break down food particles. The tissues, organs and organ systems are absent in sponges. So, they lack digestive systems like other complex animals.
The chambers, scattered throughout the body of the sponge, have pores through which water passes into a complex system of incurrent canals, then into a spongocoel (internal cavity) by way of excurrent canals. Water enters very small pores found among the cells (pinacocytes), which line the outer surface of the sponge.
Phylum Porifera is a group of simple animals that includes the sponges. Porifera have no internal organs, nervous tissue, circulatory system, or digestive systems, making them the most primitive of the multi-cellular animals.
Sponges are a type of aquatic animal whose body is covered in tiny pores called ostia. The ostia allow water, oxygen, and other nutrients to flow into the sponge’s body, and for waste products like ammonia and carbon dioxide to exit their body. The respiratory system of a sponge is based on the process of diffusion.
The sponge is matter and considered as solid because it has a definite volume and shape does not change unless compressed. A sponge can be compressed easily even though it can be considered as solids because they have minute pores in it which are filled with air. Was this answer helpful?
Once the food is trapped, the collar cells digest it (see Figure below). Cells called amebocytes also help digest the food. They distribute the nutrients to the rest of the body as well. Finally, the water flows back out of the body through an opening called the osculum.
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