Spongilla is a powder of colonial fresh water sponge which composed of siliceous needles connected by organic matter called SPONGIN, a material related to siik in its chemical composition. Spongilla powder also consists of calcium phosphate and carbonic calcium oxide and a number of organic substances.
|Scientific name||Various species, to quote some: Ephydatia muelleri, Ephydatia fluviatilis, Spongilla lacustris|
|Familly||Spongillidae (only familly that lives in freshwater)|
|Origin||All the world|
|Size||several millimeters, the specimen shown is 5 mm "long"|
|Breathing||gas exchanges performed at cell level, no gills or lungs|
|Temperature|| Around 20°C|
Nowadays there exist about 120 freshwater sponge species, all belong to the spongillidae familly. They develop as an irregular mass attached to supports like stones, plants or wood.
This is a Metazoaria without predefined symetry and without any organs, it is also void of nervous or sensorial cells. A sponge can be seen as a vase that is fixed to a support, letting water pass through its numerous pores. Water also passes by the central cavity and exits by another opening. The pores have a function in the feeding process, indeed the water is inhaled and filtered by the numerous pores that cover the sponge body, this also gives an explanation to it belonging to the Porifera phylum.
The body walls are constituted of three layers, the continuous external layer, an internal layer composed of digestive cells (choanocytes) and between these two a layer of jelly. The latter is more or less fluid and is filled with amiboid like and constitutive cells.
Whereas totally immobile and without any muscular tissues, sponges have the capacity to contract. This is not to be considered as movement though, as contractions are the result of an internal need for constituting cells to reorganize.
Freshwater sponges vary in colour according to the zoochlorela (microscopic algae) they are associated (symbiosis).
They have two ways to reproduce, one being totally asexuated and being represented by the division and regeneration of cells and the other - sexuated - which occurs through the formation of gemmules, mainly when the sponge is dying.
A gemmule (or spongilla) is the assembly of amiboid type cells that are filled with proteic and lipidic enclaves around which a membrane with one opening has formed. This membrane is surrounded by spicules (composed of calcium carbonate or of hidrated silicium). The gemmule eclodes when conditions are favourable (temperature above 16°C), by then the cells leave the gemmule by the opening and form an inert mass.
Should one describe the gemmule simply, lets say that it is a group of identical cells surrounded by nutrients).
After they are released, the cells start transforming, develop their nucleus and diferentiate to reach several cell categories. Finally, a tiny sponge is constituted.
In terms of sexuated reproduction, sponges are hermafrodite with reproduction cells rather than reproduction organs. These cells go through several mitoses (indirect division) and become ovocytes. The latter associate to cells filled with proteins and lipids before they are ready for the reproduction process.
Suffice to say that to complete the process the "feeding cells" are consumed by phagocytosis - a behaviour vary similar to protozoaria - the newly formed choanocyte in turn has associated to a spermatozoid who has lost then lost its flagellum to form the spermiocyst.
Freshwater sponges can in many aspects be seen as the association or as a colony of independent protozoaria, but the main difference from such view is that there exist the abovementioned layers of cohesive cells that constitute its body.
The abovementioned choanocytes also pertain to its feeding mode as they absorb and feed on the colloidal particles that have entered the sponge. They ingest these particles by fagocytosis and evacuate needless materials towards the layer that constitutes the outter layer of the body, i.e. the layer of amiboid cells.