The various functions of amoebocytes in sponges include storage, transport and digestion of food, waste removal, skeletal secretion and bud formation during asexual reproduction. The buds produced can be categorized into five types: large amoebocytes, archaeocytes, calcoblasts, scleroblasts and silicoblasts.
Sponges are the simplest form of animals in terms of anatomical structure. Due to their greenish appearance and sedentary lifestyle, sponges were previously thought of as plants. Currently classified under phylum Porifera, these predominantly marine animals have no levels of organizations where specialized cells group into "true" tissues and tissues group into "true" organs.
A sponge contains four types of differentiated cells that perform all the bodily functions necessary for the survival of the organism. Aside from amoebocytes, these loosely specialized cell types include pinacocytes, porocytes and choanocytes. Pinacocytes provide the outermost layer of the organism; porococytes enable the absorption of water through tiny perforations and choanocytes capture food, pump water and produce sperm. Amoebocytes, which cover the entire organism, are responsible for most of the life processes of the sponge.
The large amoebocytes produced during asexual reproduction use pseudopods for their means of locomotion. They transport nutrients to the other cells of the sponge. The archaeocytes can differentiate and transform into more specialized cells, such as oocytes and pinacocytes. The scleroblasts produce two varieties of skeletal spicules, which can be silicious or spongin. The calcoblasts create spicules composed of calcium carbonate while the silicoblasts produce silicious spicules.