In the phylum of Porifera, Sea Sponges have extremely interesting qualities. They do not in fact acquire any organ systems, yet they use specialized cells to preform organ functions. Porifera, which means pore bearing, are exactly what sponges are. They are porous organisms that filter out water and many other things through various sizes of holes.
Can be compared to the “Skin Cells“ of the sponge have specialized functions such as maintain the size and the structure of the sponge and expand and contract to alter the size of the sponge. These cells are flattened and are made up of tiny granules. These cells are are found on the outermost layer of the sponge, and have the ability to reproduce.
Choanocytes are lined and packed tightly along the entire internal cavity of a sea sponge. They are also located on the nucleus and the food vacuoles. Attached to the choanocytes are whip-like structures called flagellum.
Circulation is one of the unique functions of choanocytes. Using the flagellum, it circulates water throughout the sponge. Like human lungs, they bring in oxygen and releases carbon dioxide from the sponge. Along with the exchange of oxygen and carbon dioxide, choanocytes assist with capturing food particles. A part of the choanocytes called the collars are the primary areas of the cell that nutrients are absorbed.
The importantance of these cells is that they are totipotent. Because these cells can change into other different kinds of cells, they have a number of different functions. They can assist with reproduction sexually and asexually and can also form gemmules and gametes. These specialized cells also preform ingestion and digestion, which they transport nutrients to other parts of the sponge. They gather the nutrients in the choanocyte collar’s of the sponge.
Sponges do not have a muscular system, which makes mobility scarce. They do however have the ability to contract and let water flow through the sponge. These cells are located in the canal openings of the sponge. The Myocytes are the “muscle” cells that open and close the Porocytes. They work together to keep the sponge functioning.
This is a moving cell withing the sponge that uses its pseudopodia for mobility. These cells also have an array of functions such as waste removal, transportation, digestion, and bud formation during asexual reproduction.
Image Magnification: 10x, Keene State Biology Department
Needle like structures that form the “skeleton” of the sponge
Together, all of these cells work together to function as organ systems. They need all the qualities of all the specialized cells to sustain life. Other organisms have such cells like the amoebocytes which preform similar functions.