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Sponge - Anatomy

Sponge - Anatomy: Encyclopedia II - Sponge - Anatomy

Sponges comprise only four types of cells: Choanocytes (also known as "collar cells"), which line the spongocoel and function as the sponge's digestive system, are remarkably similar to the protistan choanoflagellates. Porocytes are tubular cells that make up the pores. Flat epidermal cells line the outside of the sponge and form its skin. Amoebocytes live between the choanocytes and the epidermis. They carry out many of the sponge's functions, such as transport of nutrients, secretion of the spicules, ...

Sponge: Encyclopedia II - Sponge - Anatomy

Sponge - Anatomy

Sponges comprise only four types of cells:

Choanocytes (also known as "collar cells"), which line the spongocoel and function as the sponge's digestive system, are remarkably similar to the protistan choanoflagellates.
Porocytes are tubular cells that make up the pores.
Flat epidermal cells line the outside of the sponge and form its skin.
Amoebocytes live between the choanocytes and the epidermis. They carry out many of the sponge's functions, such as transport of nutrients, secretion of the spicules, and production of gametes.

Sponges have only three body types: asconoid, syconoid, and leuconoid. The former two are both vase-like, asconoid being the most primitive with a single chamber, syconoid's are more complex with primary folds in its body wall, while leuconoid are the most advanced taking a lumpy shape much like a rock and have secondary folds. Leuconoid's also have the highest concentration of collar cells (which line the chambers collecting food).

Image:Sponge1.jpg

Although they are animals, sponges may also be considered multi-cellular colonies. A sponge can be placed in a blender and any remaining living cells will reform themselves into another sponge. If multiple sponges are blended together, each species will recombine independently (contrast animal chimera such as the geep).

It is thought that the earliest multicellular life on Earth was a sponge-like creature. The earliest known multicelled animal fossils are sponges from China that are roughly 600,000,000 years old. Sponges have not been as extensively studied as some other phyla and there may be some surprises still to be found. For example, it has recently been shown that some sponges are not sessile and can move to more favorable locations as rapidly as a few centimeters a day. Another sponge, Venus' Flower Basket, has some newly discovered uses involving fiber optics.