Phylum Porifera

Phylum Porifera is an exclusive classification of aquatic animals. It belongs to the Animalia kingdom with a sponge-like structure. As it is a multicellular organism, the cells are arranged either randomly symmetrical or asymmetrical. They are simply called with the name of sponges. We can find around 5000 species so far with different shapes and colors. Each species has a distinct feature.

Porifera is a Latin word that means bearing pores. Because if it's a sponge-like structure, it can absorb and hold the water for a long time.

Structure of Porifera

These species have a bundle of little needle-like structures called spicules. And some of the big pores are called ostia which helps to draw into the interior canal called spongocoel. This water is filtered into the radical canal and split out from the organism through exit pores called the osculum. The only purpose of this water is helpful in their reproductive system; for the formation of eggs or for sending sperms.

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Origin and Life Cycle

In the beginning, the sponges are treated as plants due to their immobility. They look like algae in the sea bed. Later observations like preparing its own food, absence of chlorophyll, reproductive system, long life, etc. were confirmed that they belong to the animal kingdom.

They are found in shallow and deep seawater and in the beds of freshwater also. Besides these features, sponges have the classification of four classes.

Classification of Porifera

Based on the spicules which are made up of calcium carbonate, sponges can be classified into three classes. They are as follows:

• Calcarea

These sponges are found in marine forms of living shallow water in small sizes. Calcarea spicules form a skeleton that results in the cylindrical shape of the body for which the animal is symmetrical. Coeloblastula or amphiblastula helps in the development and the body may be organised like the asconoid or conoid type. In this, large cells are known as Choanocytes. Again these Choanocytes are sub-classified into two orders based on the structures. They are Homocoela and Heterocoela.

• Hexactinellida

Large sponges are present in this. As the name itself says that it has six-rayed glossy spicules which can help to grow long from 10 to 30 cms. They are mostly found in deep layers of the sea. They have finger-like canals and possess some inorganic elements. Its shape seems to be like a cup or vase. Euplectella and Hyalonema are some examples.

• Demospongiae 

These sponges may be found from shallow to the depth of the sea in different colors with the presence of pigment granules. Most available species are of this category. The skeleton may or may not be present, and the body will be either in a round shape or flattened shape. Pascarella, Platina, and Geodia are some of examples.

Based on their unique feeding system, also, different classes have been classified, such as carnivorous and many more. Also, we have subclasses in these categories which can be learned in the next grade.

Now, we will see the characteristics of the Porifera in a detailed view.

Characteristics of Porifera

Different characteristics of Porifera are explained below:

• They are sponge-like structures that can be helpful for the circulation of water.

• These are marine aquatic organisms that can be found in shallow and deep freshwaters.

• They grow and seem to be like plants.

• They are available in a cylindrical, round, cup, and vase-like shape based on the presence of pores.

• Pores are arranged in symmetrical as well as asymmetrical which can hold and circulate water for a long time.

• The entire development will be done inside only.

• The reproductive system is done by both the ways called sexual and asexual like budding and fragmentation.

• Sponges can prepare their own food as well as eat other organisms as well.

• Its nutrition is holozoic.

• It is a multicellular organism, but excretory and respiratory systems were absent.

• The diffusion process also takes place in it.

• It can regenerate its power automatically.

Reproduction in Porifera

It plays a vital role in sponges. Because with this system only our scientists transformed this animal kingdom from plant life. It can reproduce in both ways called sexual and asexual. Again in asexual, it undertakes the budding process as well as the fragmentation process. The sexual process is a combination of ova and sperm, just like common to all other species.

Sponge fragments can regenerate into whole new sponges. Budding or fragmentation are two methods of asexual reproduction. Each bud develops into a new person, whether it remains attached to the parent or separates from it. Freshwater sponges, as well as a few marine species, create gemmules, which may tolerate harsh circumstances such as drying or cold and then mature into new individuals. Gemmules are spongy tissue and food aggregates coated in a hard coating of spicules or spongin fibres. There is also sexual reproduction. The majority of sponges are hermaphroditic, meaning that the same individual produces both eggs and sperm, although certain species have different sexes. The larvae are flagellated and can swim freely for a brief period of time. The larvae develop into juvenile sponges after settling and latching to a suitable substrate.