Phylum Porifera, also known as sponges, is a group of simple aquatic animals that lack true tissues and organs. Animals belonging to the Porifera phylum are the smallest multicellular creatures in the animal kingdom. ‘Porifera’ word is taken from Latin which means ‘pore-bearing species’. Around 5000 species are included in the phylum Porifera.

Phylum Porifera

Phylum Porifera includes organisms that lack specialized digestive, nervous, and respiratory systems. These organisms have a radial symmetry, do not possess a coelom, and do not show any segmentation. These organisms either have numerous tiny pores called ostia or larger pores called Oscula which are less in number. The function of these pores is to allow the circulation of water. The members of Phylum Porifera are non-motile and are fixed to a substratum.

Why The Name ‘Porifera’?

Porifera animals have pores which are known as Ostia. They are also called sponges since they are ‘spongy’ in appearance. Since they were green in color, and displayed a symbiotic association with algae, they were classified as plants. However, upon later evaluation, it was seen that they were heterotrophic and multicellular and had a cell membrane present. These characteristics were common with other members of the Animal kingdom. Hence they were classified as invertebrates, under Phylum Porifera in the animal kingdom.

Characteristics of Phylum Porifera

Below are some of the characteristics of Phylum Porifera:

• They are present in both marine and freshwater sources.
• Their bodies are uneven and loosely arranged.
• These are mostly assymetrical
• They are cylindrical and have a cellular level of organization.
• Spicules, which are frequently seen in sponges, are small structural components that are formed of calcium carbonate, silica, or spongin (a protein).
• The sponge is supported and shielded by spicules.
• Porifera reproduces asexually via Fragmentation or budding. Sexual reproduction also occurs sperm and egg formation.
• The cavity present inside the body is known as spongocoel which is open to the surrounding via osculum. A water current flows through it and helps in nutrition, reproduction and respiration.
• They take food via a Holozoic mode of nutrition.
• Animals of the Porifera kingdom exhibit a high rate of regeneration.
• Reproduction involves internal fertilisation. Most of the sponges are hermaphrodites.
• Respiration and excretion occurs via diffusion. These organisms are ammonotelic.

Classification of Phylum Porifera

This phylum is further divided into three classes, depending mostly upon the endoskeleton. Following is detailed brief about its three types:-

Class Calcispongiae or Calcarea

• They all are present in both marine and freshwater.
• Their skeleton comprises calcareous spicules which are formed of calcium carbonate.
• The body is cylindrical and has a vase like structure.
• Body organization of calcera are asconoid, leuconoid and syconoid.
• Examples: Clathrina, Leucosolenia, Scypha

Class Hexactinellida Or Hyalospongiae

• They are present in marine and also in the deep sea.
• They are also known as glass sponges based on their siliceous spicules.
• The canal system is sycon and leucon type
• The body is cylindrical and has radial symmetry.
• Example: Euplectella, Hyalonema

Class Demospongiae 

• Demosponges make up the bulk of sponge species and are the largest and most diversified class of sponges.
• They are present in both freshwater and marine water.
• they have a Leuconoid type canal system.
• The skeleton system comprises of spongin fibers and siliceous spicules. 
• They are asymmetrical
• This category includes a lot of commercial sponges used in cleaning and bathing products. The Bath Sponge (Spongia officinalis) and the Barrel Sponge are two examples.
• More Examples: Cliona, Spongia, Spongilla, Chalina

Examples of Phylum Porifera

Phylum Porifera consists of wide variety o sponges with different traits. Few of these have been explained in detail below:

Sycon

These are marine sponges present either in solitary or in colonial form which are attached to rocks. The flagellated cell is made from a radial canal. From the Ostia, water enters the body and reaches radial canals via prosopyles. Sycon reproduces both sexually and asexually.

Barrel Sponge

The class Demospongiae includes barrel sponges, which can be found in a variety of marine habitats, including coral reefs.They can be identified by their huge size and characteristic barrel or cylinder shape with an opening at the top (osculum). They help different marine organisms by providing habitat.

Cliona

They are also called Boring Sponges, found in coral skeletons, mollusk shells, and other calcareous articles. They are green, purple, or light yellow in colour. The canal system is one of the main characteristics of leuconoid sponge. They reproduce both sexually and asexually.

Euplectella

These are also called Venus flower baskets and are present in marine water. These are long cylindrical and curved present on the mud of the upper surface of the sea. They show a simple synconoid canal system. Their skeleton consists of silicious spicules which are fused around their tips and form a 3-D structure.

Spongilla

They are majorly found in ponds, lakes, streams. The body is covered with thin dermis, and small pores i.e., Ostia are present on the surface. Rhagon-type canal systems are present in Spongilla. They reproduce via both modes. 

FAQs on Phylum Porifera

1. Give few Examples of Kingdom Porifera.

Answer:

Spongilla, Grantia, Barrel Sponge, Euplectella,Bath Sponge are some examples of Phylum Porifera.

2. What are the 3 Characteristics of Phylum Porifera?

Answer:

Following are the three characteristics of Phylum Porifera:

• They are pore-bearing animals
• They show a Holozoic mode of nutrition.
• They show a very high rate of regeneration

3. What are the 3 Different Classes of Phylum Porifera?

Answer:

The 3 classes of Phylum Porifera based on their endoskeleton are:

1. Calcispongiae
2. Hexactinellida
3. Demospongiae 

4. Which Category of Porifera has the Highest number of Sponges?

Answer:

The class Demospongiae contains the greatest number of species of Porifera. Within the Phylum Porifera, Demosponges are the largest and most varied class. It contains a large range of sponge species, making up roughly 80–90% of all documented sponge species.

5. What do you Mean by Porifera?

Answer:

The scientific term for the phylum of aquatic creatures known as sponges is “Porifera”. It is a phrase used in biology to describe a certain class of multicellular, primarily marine animals that are distinguished by their straightforward body plans and distinctive feeding strategies.