The porifers , also called spongiaries or sponges , are aquatic animals and invertebrates , which are part of the sub-paradox. This means that poriferous species do not have organs, nerves or muscles, although they do have an inner skeleton made up of spicules.
Of the nine thousand species of porifers that have been recorded throughout the planet , more than 98% He lives in the oceans. Until the middle of century XVIII Porifers were considered plants, until it was detected that they had a system to filter the water and that they performed their digestive process intracellularly.
The cells of these animals are totipotent , which implies that they can acquire different forms according to the different needs of the organism. The water enters the poriferous through the pores that it has on its walls, the animal filters the food through the cells known as coocytes and finally expels the water through the osculus that is in its upper region.
It is important to note that the porifers do not have nervous system No digestive system. Their mobility, on the other hand, is reduced, since they can barely travel up to four millimeters per day.
Due to its toxicity, porifers do not usually serve as food for animal species. As, in addition, they have good resistance to contamination , sponges even manage to dominate certain ocean habitats.
Since ancient times, man uses the body of these porifers for personal hygiene (the bath sponges , although products of plant or synthetic origin are also used). Porifers are also used to fertilize crops.
With respect to anatomy from the porifers, it is possible to distinguish the following parts:
* coanoderm : It is formed by the set of flagellated cells that make up the tapestry inside a sponge and are called coanocitos and they are practically the same as coanoflagellated protozoa, very important for food and producers of the current of Water . Inside a coanoderm, its main cavity is called atrium or spongocele. Its thickness can be the same as a cell, fold back or generate subdivisions to give rise to clusters of separate chambers of co-cells, depending on your organization. asconoid, siconoid or leuconoid, respectively;
* pinacoderm : The outer cells of the sponges are pseudoepithelial, wide and long in appearance and are called pinacocytes. Since they don't have a sheet Basal, do not form a layer known as epithelium. Similar to the epidermis of an eumetazous, the group of pinacocytes forms a pinacoderm (also called ectosome), which goes through a large number of dermal pores, each upholstered by a porocito (a rolled cell). Through these pores the water penetrates and enters the body. In some cases a layer of collagen called cuticle which can replace the pinacoderm, in addition to covering it;
* mesohilo : between the two layers just described there is an area that is organized in a lax way and is called mesohilo. It is possible to find skeletal spicules, support fibers and a large number of ameboid cells that play a fundamental role in the secretion Skeletal, waste and nutrient transport, digestion and gamete production. Its elements are submerged in a colloidal mesoglea;
* skeleton : in the mesohil there are many elastic collagen fibers and calcareous or siliceous spicules, depending on the class, which represent the mineral portion of the skeleton, which provides its rigidity and varies according to proportions mineral and protein, making it harder or more flexible, respectively. Collagen fibers can be of sponge or thin and scattered and they are intertwined with each other and with the spicules.