Porifera Characteristics

Remember SpongeBob SquarePants? Yes, he is a sponge that lives under the sea! He and other sponges come from the Phylum Porifera – derived from Latin words porus for pore and Ferre to bear. Members from this family are all invertebrates (no backbone). Sponges look pretty simple in their structure, but have certain characteristics that no other possesses. It is essential to learn about the features of this class of animals as they constitute more than half of the biomass in the marine reefs and have been in existence for almost 600 million years. There are nearly 5000 different species of sponges that have become a very interesting topic of study. Did you know? The volume of water passing through a sponge daily is as much as 20000 times the volume of the sponge itself! Being ubiquitous in nature, they occur in rivers to rock pools to deep oceans and even in the frozen and tropical seas. Some of the important characteristics of Phylum Porifera are as given below.

Characteristics of Phylum Porifera

Sponges have a variety of shapes. Some form crusts, some are simple tubes, some are vase shape while others can be cup shaped, massive clumps, fan shaped, finger like bulges, treelike or even bushy. They maybe soft, brittle or hard.
They do not have a definite symmetry. Majority of the sponges are asymmetrical. Some are radially symmetrical which means the body parts can be arranged around a central axis.
Sponges have hollow bodies. They are made up of a jelly-like substance where collagen forms an important component. Spicules also make up the skeletal structure where they interlock to form a delicate framework of tubes inside and outside the body.
Members of this Phylum are multicellular and possess a few tissues with no organs. They have no true body cavity and all the cells and tissues surround a water filled space.
The three main layers of their body structure are: a layer of flattened epidermal cells, a semi fluid matrix and a layer of flagellated collar cells. Though mostly sessile, some have the presence of a whip-lash flagella for locomotion that can help them move only uni-directionally.
Nutrition in sponges is done by the presence of ostia that is found on top of the sponge as a pore or opening. There are numerous pores by means of which water and other plankton enter the sponge body. They are also used to control water flow through the spongocoel (body cavity). Hence, they are called filter feeders.
A characteristic feature of the sponges is the presence of a water canal system. There are three types of canal systems – asconoid, syconoid and leuconoid. Poriferans are sessile (live attached) suspension-feeding animals that possess flagellated (for locomotion) cells to circulate water through a unique system of water canals.
The power of cell aggregation is tremendous in sponges. If cut into a million minute pieces, they can still come together and re-form into a fully functional sponge.
The Poriferans do not possess a proper digestive, nervous or circulatory system. Despite this, they can respond to stimuli by the closure of ostia.
Excretion (primarily ammonia) and respiratory gas exchange occur by simple diffusion. Most cells of freshwater sponges contain contractile vacuoles for osmoregulation.
Reproduction can be asexual or sexual. Asexual reproduction is either by fragmentation, budding or gemmules. Sexual reproduction is by the production of sperms from the choanocytes and eggs in the mesohyl. Sponges are generally hermaphroditic, but can be only one gender at a time, being either male or female or neutral.

Sponges have some of the most varied characteristics and are interesting species of the Phylum Porifera under the sea!

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