Phylum Porifera: Characteristics, Classification & Examples

Phylum Porifera is a classification of aquatic animals. They are the lowest multicellular animals belonging to the Kingdom Animalia. Phylum Porifera has a structure resembling a sponge and is therefore called sponges. They are attached to the substratum and are not able to move. Poriferans have the ability to absorb and withhold fluids. Porifera are the first pore-bearing multicellular animals. So far, 5000 species of various shapes and colors have been discovered in this phylum.

Each species in Phylum Porifera has unique characteristics. They are capable of sexual and asexual reproduction. Again being asexual, they engage in both the budding and fragmentation processes. In sexual reproduction, the eggs and sperm are fused together. They were initially regarded as plants owing to their green color and their symbiotic relationship with algae. Later on, as their life cycle and feeding system were discovered, they were included in the animal kingdom.

Read More: NCERT Solutions For Class 11 Biology Animal Kingdom

Key Terms: Phylum Porifera, Porifera, Animal Kingdom, Sponges, Poriferans, Sycon, Spongecoel, Reproduction, Calcarea

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Structure of Porifera

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Poriferan species have spicules, which are a collection of tiny needle-like structures. Additionally, some of the large pores are referred to as Ostia, which aid in drawing fluid into the spongocoel internal canal. This water is separated from the organism by exit pores known as the osculum and filtered into the radical canal. This water serves only to support thereproductive system of porifera, either by assisting in egg production or sperm transportation.

Structure of Porifera

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Origin and Life Cycle of Porifera

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Phylum Porifera are initially thought of be plants due to their immobility. They have an aquatic algal appearance. Later findings such as the inability to prepare its own food, lack of chlorophyll, reproductive system, extended lifespan, etc. confirmed that they belong to the animal kingdom.

They can be found in both shallow and deep seas as well as in freshwater lake beds. Apart from these features, sponges have been classified into four classes.

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Classification of Porifera

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Phylum Porifera types can be divided into three groups based on their calcium carbonate spicules. 

Classes of Phylum Porifera

The three classes of Phylum Porifera are as follows:

Calcarea

• These type of Porifera are tiny and live in shallow water in marine forms. 
• The cylindrical body shape of the animal, which is symmetrical, is the result of a skeleton made of Calcarea spicules. 
• The development is aided by coeloblastula or amphiblastula, and the body may be arranged in an asconoid or conoid type fashion. 
• Large cells in this are referred to as choanocytes. 
• Once more, these choanocytes are divided into two orders depending on their structural characteristics. 
• The two sub-orders are Homocoela and Heterocoela.

Class Calcarea

Hexactinellida

• There are sizable sponges or porifera present in this class. 
• It contains six-rayed, shiny spicules that can help it reach lengths of 10 to 30 cm. 
• They are primarily located in the ocean's deepest strata. 
• They have some inorganic components and finger-like channels. 
• Its form resembles that of a cup or vase. 
• Examples include Hyalonema and Euplectella.

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Demospongia

• These porifera come in a variety of hues with pigment granules.
• They can be found from the surface of the ocean to its depths. 
• The majority of species of this phylum are in this group. 
• The body will be either circular or flattened, and the skeleton may or may not be visible. 
• Examples include Geodia, Platina, and Pascarella.

Different classifications, including carnivorous and many others, have been categorized based on each species' distinctive eating strategy. Additionally, there are subclasses within these categories that can be studied in the following way.

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Characteristics of Porifera

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Here are a few important characteristics possessed by the species in Phylum Porifera: 

• The majority of porifera are freshwater species, although there are a few marine species as well.
• The body's shape can be spherical, rounded, vase-like, or sac-like.
• They have two layers- an exterior dermal layer and an inner gastral layer, making them diploblastic animals. 
• Between these two layers is a gelatinous, noncellular mesoglea. This has a large number of unbound amoeboid cells. 
• The Ostia is the body's numerous pores, and the osculum is the top opening.
• The bodily cavity is called a spongecoel.
• Their bodies have a recognizable canal system for the movement of water.
• There is an endoskeleton made up of sponging fibers, siliceous spicules, or calcareous spicules (calcium carbonate) (protein).
• Asexual reproduction in Porifera is demonstrated by fragmentation and blossoming. Several animals exhibit sexual reproduction.

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Porifera Examples

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Some of the common Porifera examples are

Sycon

• These marine sponges can be found in groups or alone, adhering to rocks in shallow water. 
• The body of the sycon is shaped like a cylinder and contains lots of spores. 
• Flagellated cells make up the radial canal. 
• Water enters the body through the Ostia and travels through prosopyles to the radial canals. 
• Both sexual and asexual modes of reproduction are used in these animals.

Hylonema

• These are also referred to as glass rope sponges, and they are found in seawater. 
• The body is oblong or spherical, and the root tufts are twisted. 
• There are tiny amphidiscs in the skeleton.

Examples of Porifera

Cliona

• They can also be found in coral skeletons, mollusk shells, and other calcareous structures. 
• They are known as "boring sponges." 
• They are either pale yellow, green, or purple in color. 
• The leuconoid kind of sponges are distinguished by their canal system, and they can reproduce both asexually and sexually.

Euplectella

• These can be found in deep waters and are also referred to as Venus flower baskets. 
• The body is long and curved, cylindrical, and anchored in the mud at the seafloor. 
• They have a simple synconoid type canal system. 
• Siliceous spicules united at the tips form a three-dimensional network with parietal gaps that make up the skeleton.

Spongilla

• They can be mostly found growing on submerged plants and sticks in ponds, streams, and lakes. 
• The bodily wall is made up of a thin dermis with Ostia, or pores. 
• They have a canal system in the rhagon style. 
• These porifera can reproduce both sexually and asexually.

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Reproduction in Porifera

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Reproduction plays a vital role in sponges as this system only transformed this animal kingdom from plant life. Poriferans can reproduce both sexually and asexually. 

• In asexual reproduction, it undertakes the budding process as well as the fragmentation process. 
• The sexual process involves a combination of ova and sperm, just like common to all other species.
• The majority of sponges are hermaphroditic which means that the same individual produces both eggs and sperm, however, certain species have different sexes. 

Read More: Animal Kingdom Concept Map

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Things to Remember

• Phylum Porifera is considered probably the oldest animal group that lives in an aquatic habitat. 
• They are the simplest multicellular animals that do not have any tissues or organs.
• They are also referred to as Sponges and have many holes or pores called Ostia.
• Phylum Porifera has a water transport system, which achieves the functions of digestion, excretion, and exchange of gases.
• They feed on bacteria and other food particles that are present in the water. 
• Phylum Porifera is classified into three classes namely Calcarea, Hexactinellids, and Desmospongiae.
• Some common examples of Porifera include Sycon, Hylonema, Cliona, Spongilla, and Euplectella.

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Previous Years’ Questions (PYQs)

• Classification of Porifera is based on… (NEET 1991)
• The simplest type of canal system in Porifera is… (AIPMT 1992)
• The commercial bath sponges belong to… (JIPMER 1999)
• Sycon belongs to a group of animals, which are best… (NEET 2003)
• Which group of animals belong to the same phylum… (NEET 2013)
• Canal system in Porifera is not concerned with… (AFMC 2005)
• Which of the following is not related to porifers…
• Symmetry in Cnidaria is…
• When an animal has both the characters of male and… (NEET 1996)
• The taxonomic unit phylum in the classification of animals… (UPSEE 2016)
• Cuttlefish belongs to a phylum… (JIPMER 1995)
• One of the representatives of Phylum Arthropoda is… (JIPMER 2012)