phylum poriferaStudents develop academic skills not just inside a classroom but beyond it. This is why when a potential academic issue in Biology’s Porifera Phylum arises, students should rather look outside classrooms for reliable help. And timely academic help from the right experts is one such ideal help that incorporates both essential learning and academic success.

Porifera is described as a phylum within the Kingdom Animalia which comprises species of sponges. Categorized as the simplest animals on our planet, porifera sponges are believed to have evolved from the species of the first multi-cellular organisms that later evolved into animals. Porifera sponges were first proved animals by Robert Grant and Ellis.

The phylum porifera however signifies the only phylum of the Parazoa branch of Kingdom Animalia. It mainly constitutes true tissues, which soon gets separated from its lineage right when the evolution of multi-cellularism from colonial protists occurs.


Despite most porifera sponges are considered as radially symmetrical, they are not really ‘radially symmetrical’ as they don’t have true tissues. Most sponges comprise of three layers of cells.

* The outermost layer contains compacted cells with many pores. The layer of cells constitutes both mobile and skeletal cells.

* Skeletal cells are flexible protein, mineral particles, or sponging. They are responsible to give shapes to the sponges.

* The third and the innermost layer is made up of choanocytes. Choanocytes are cells with rings covering the base of flagella used to run water in and out through the pores of the sponges porifera into the central body cavity. It uses central opening to run water out though. Choanocyte also absorb food (bacteria) by phagocytosis.

Amoebocytes is the name given to mobile cells in the center layer, which can easily move to pick up food by using pseudopodia. It also functions as a nutrient supplier and helps in digesting the food vacuoles from the choanocytes. They supply oxygen to other cells, dispose waste products, uphold the structure of the sponge, and, more importantly, transform into another cell types whenever required.

Sponges bear striking resemblance to features of protists despite being animals. And the main reason for such a striking similarity of sponges porifera with Kingdom Protists is their common ancestors—choanoflagellate.

Choanoflagellates is a colonial protest dwelling at the bottom of shallow water. It comprises a small group of flagellated cells that are very similar to choanocyte. This similarity explains that sponges porifera originally evolved from the colonial protist.  


Three Classes of Phylum Porifera

Phylum porifera is divided into three classes on the basis of endoskeleton:

a) Calcarea

b) Hexetinillida

c) Demospongia


Calcareaphylum porifera

The first class of phylum porifera is called calcarea or class calcarea. It constitutes sponges with calcium carbonate of three or four rays. Body plans are visible in calcarean sponges and the group is completely marine. Most of these porifera species are dull-colored and shorter than 4 mm. calcarean sponges comprise Leucosolenia and Sycon (as shown in the image below).  

Porifera examples of calcarea are:

1. Scypha

2. Leucosolenia

3. Sycon



Hexetinillida is the second class of phylum porifera. They are deep-sea sponges void of epidermal covering. Their skeletons comprise spicules of silica. Always pale in color, glass sponges are either cup or basket shaped. The spongocoel is large and the osculum is covered by a grillwork of united spicules.

The cylindrical skeletons normally have the shape of the spun glass when the living tissue is removed. The glass shaped sponge is called Venus’s flower basker or Euplectella in a more biological term. The body plan of Hexactinellida is between syconoid and leuconoid.

Hexetinillida or Glass Sponges

The examples of Porifera Hexetinillida

1. Pheronema

2. Hyalonema

3. Euplectella


DemospongiaCharacteristics of phylum porifera

Demospongia is a class third category which comprises most of the sponges. It mainly constitutes sponges of silicon containing spicules or spongin fibers or both. Demospongiae vary in size and masses. Brightly colored, they are all leuconoid. It includes freshwater sponges and is mostly green due to algae dwelling in amoebocytes.

The fibrous sponges are also categorized into this class. Common bath sponges such as Hippospongia communis and Spongia officinalis are also included and used commercially. The boring sponges can bore into calcareous and mollusk shells as larvae.


Characteristics of phylum porifera

By drawing an idea from the explanation above, we can sum up the porifera characteristics as:

1. Phylum porifera represents cellular level of organization without true tissues.

2. Adult phylum porifera represent radial symmetry or are asymmetrical.

3. They constitute totipotent cells.

4. They also constitute flagellated cells like choanocytes, which create water flow through water current system.

5. In phylum porifera, outer and inner cell layers are void of a basement membrane.

6. In phylum porifera, outer and inner cells layers are separated by a noncellular layer—Mesohyl containing cells and skeletal material.

7. Phylum porifera gets body support (skeleton) which is offered by spicules containing calcium carbonate or silicon.

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