They are part of about nine thousand species classified as poriferous. Approximately 98% live in the oceans. At first these animals were considered to be plants. Until in later studies, it was found that they possess a filter for the water. So let’s delve a little deeper into this peculiar species of the invertebrate subphylum.
Meaning and concept of porifera in biology
Also known as sponges, they are small invertebrate aquatic animals. They settle within the subkingdom of the so-called parazoas. So these particular species they do not have organs, muscles or even nerves. Their particularity is that they have an internal skeleton that is made up of spicule structures.
They are called filters, because in their aquifer system, there are pores, chambers and channels. Which produce water currents that are driven by the provocations of the flagellated cells. This type of cell is called a choanocyte. Only a small part of these animals live in fresh water.
It was because of their immobility that they were considered aquatic plants, but later they became known as animals. Its digestion is intracellular. This group is said it is brother to many of the other species. They were the first to form branches of the evolutionary tree. With respect to the common ancestors of other animals.
They are aquatic invertebrates, quite primitive. Well, they lack a brain, organs and nervous system. They are heterotrophs because they cannot produce their own food. Since they feed on other sources that absorb water.
What are the characteristics of poriferous organisms?
One of its main properties, and perhaps the one that causes the most surprise. It is that for the most part they are composed of stem cells. Which are transformed into different cell types, taking into account only the needs of the animal.
It is considered that they have a cellular organization. What it is different from the rest of metazoans, where its structure is tissue dependent. These do not have embryonic layers of truth in their systems.
Its body shape is like a type of “sack” that has a large opening at the top. Which It’s called an osculum that allows the escape of water. These walls have several small-sized pores that contribute to this function.
Regarding the filtration of food, it occurs inside the internal chamber that the animal has. To be carried by means of a specialized and unique class of cells, the choanocytes. This type of cell is very similar to that of protozoa, so there is no doubt that there is a close relationship at the phylogenetic level.
These animals are unable to move, as their bodies are incapable of performing this action. His body symmetry is lacking, Therefore, it is not possible to speak in a very defined way. Some push their growth to the limit with other sponges, which they see as obstacles. Or some burrow into rocks.
Depending on its determined species, it is possible to adapt to different aspects taking into account environmental conditions. Either nature, or the inclination of the substrate. as well as what have space and water currents in which they are found.
The excretion that these animals produce is a basic ammonia. gas exchange it occurs by fairly simple diffusion, which is almost always via the choanoderm.
Porifera do not have a mouth, nor a digestive system, which differentiates them from metazoans. Its digestion is intracellular. So there are certain mechanisms that are of great help for the ingestion of food. They are the only animals that do not have nerve cells, they lack a nervous system.
How do porifera reproduce?
Mostly sponges are fertilized sexually although there are cases where procreation is asexual.
- Asexual reproduction: This is given through the power of the cells it possesses. From some fragments of them. Porifera produce buds, which are small bumps that eventually break off. These in certain cases have stored food. With respect to those that inhabit fresh water, they produce complex gemmules. Small spheres containing protective layers with archaeocytes. Other marine species are producers of simpler gemmules, called sori.
- Sexual reproduction: This fertilization is mostly crossed. Sperm are produced from choanocytes. As long as those of a chamber suffer from spermatogenesis to create a sperm cyst. The ova are given from archaeocytes or choanocytes. These are wrapped in a layer of cells that have food. Both sperm and eggs are expelled abroad through an aquifer system. Fertilization occurs in the water and planktonic larvae emerge from it.
How is the respiration of porifera?
In poriferous organisms, respiration occurs directly. They take the oxygen that is dissolved in the water and the CO2 is expelled from them. This is known as direct diffusion of oxygen. With respect to carbon dioxide and ammonia that are given, they are eliminated by the animal. Through a simple expansion.
They do not have special organs to carry out this gas exchange. Instead, they do it directly by middle of integument or skin. Since, by living in aquatic environments, it makes it easier for them to carry out this process in a bearable way.
The pores that they have on the outside of the organism are what allow them to breathe. Always with the initial absorption of large amounts of water. During this impregnation, the porifera grab the oxygen that is dissolved in the liquid.
They have the ability to totally purify carbon dioxide and ammonia waste, so they work as a very natural filter in their habitat. Of the whole cycle get the oxygen they need in order to live fully.
This system is not only used for breathing, as it cannot be classified for the purpose of a single function. Because its process is through the absorption of water, it enters into three procedures. Those who are digestive, circulatory and respiratory.
What is the excretory and digestive system of porifera?
Porifera do not have a mouth or stomach. They are the only animals that are digested intracellularly. Each of the cells is programmed to digest food independently. Some of the mechanisms it uses are phagocytosis and pinocytosis.
Water enters your system through the small pores it has, called ostioles. This circulates through it thanks to a plan of channels. Regarding the filtering method, the porifera absorbs oxygen. As well as the microorganisms on which it feeds. Then the water is expelled by the osculum.
Are a poriferous organism and sponges the same thing?
Yes, these are synonyms. They are animals where the cells that compose them have great functionality, as well as independence. Well, these achieve change function and form as they see fit for the body. Since it does not have true tissues, its organization scheme is only cellular.
Some examples of porifera can be divided into four classes. Where in three, there is species that are alive. Since one of these became extinct in the middle of the Cambrian period. Between them we have:
- calcareous: They are sponges that have spicules covered with calcium carbonate. These are straight, their body is in the form of a vessel or tubular. They are small in size, as they do not reach very high and their colors are muted. They live in shallower waters.
- Vitreous sponges: they live in much deeper areas compared to the previous class. its stems of spicules are root-shaped. Regarding its body, it could be said that it resembles a funnel. Although we must remember that they have almost no symmetry. Its size can reach one and a half meters.
- demosponge: They are 95% of the species alive today, they are also the largest in volume. Its spicule or spicules are siliceous, these can held together by a sponge or not. They live in any measure of depth and its shape resembles a mushroom.
It is difficult to get used to the fact that these types of species are classified as animals. Given that, lack certain features that in our opinion they must possess to be called accordingly. Although, after reviewing its very specific and functional qualities. We understand that it is extremely important to understand the concept that encompasses these species. Which are so relevant and essential in aquatic environments.