Sponges are the members of the phylum porifera. There are approximately 5000 living sponges species in the world. These are divided into 3 different groups based on the presence or composition of spicules or spongin.
What Is Sycon?
Sycon is a marine sponge which is found attached to the rocks, corals and shells of molluscs. Let us know more about sycon, its structure, scientific classification, characteristics, canal system, their nutrition, respiration and nutrition.
The classification of sycon is given below.
Structure of Sycon
Sycon is in the form of branched cylinders, all these branches are attached to the same base.
Even though the body has firm consistency they are slightly flexible.
They have minute openings called pores or ostia.
At the end of each branch it has an opening called osculum.
The wall of the sycon is lined by cells called pinacocytes.
Characteristics of Sycon
The length of the sycons vary from 2.5cms to 7.6cms.
Their bodies are radially symmetrical or asymmetrical.
They have the capability to regenerate their lost parts.
Needle-like spines called spicules cover their body.
Canal System of Sycon
The body of sycon contains pores and canals which results in the formation of a canal system of sycon. This canal system is used to draw watercurrent inside the body. The food and oxygen is transported inside the body through the water current.
The composition of canal system of sycon is as follows:
Ostia: The pores present on the body of sycon is called ostia. It sends the water current into the incurrent canals. It also regulates the amount of water entering the body.
Incurrent canals: The dermal pores send water to the incurrent canal which is narrow from inside. These are lined by pinacocytes. The inner end of the canal is closed. There is a presence of small aperture called prosopyles in between the incurrent canal and radial canal.
Prosopyles: The prosopyles helps to move the water inside the radial canal.
Radial canals: The radial canal is lined up by choanocytes or flattened cells. These choanocytes help to move the water inside the body. These are closed externally and opened by a small aperture called apopyle.
Apopyle: The connection between the radial canal and the excurrent canal is called apopyle. These are surrounded by myocytes.
Excurrent canal: The excurrent canal is lined by pinacocytes. This canal connected to spongocoel through an opening called gastric ostium.
Spongocoel: Spongocoel is a narrow cavity lined by pinacocytes. It opens out through the osculum.
In sycon reproduction we can observe both sexual and asexual modes.
In asexual mode they produce buds and in some cases it produces special structures called gemmules.
In sexual mode, the female gametes and male gametes are produced from the archaeocytes present in mesoglea. The sperm cells have long tails and can swim freely in the water current. The ova can wander in mesoglea.
The sperm cell does not enter the ova directly. But the sperm moves nearer to the egg by the assistance of choanocyte.
The early development is seen inside the mother sponge. When the development is complete, it is moved to a radial canal and from there it emerges out.
The sycon respiration is carried out by a simple diffusion process.
This diffusion causes the exchange of gases in between sponge cells and the water.
The oxygen is dissolved in the water and is diffused into the cells. This diffusion causes oxidation of protoplasmic molecules with the release of energy in the form of ATP.
The sycons feed on the microorganisms which enter the body through water current.
These microorganisms are moved into amoeboid cells by choanocytes. The digestion takes place here and the assimilated products are transferred to the various parts of the body.
Hence the nutrition is holozoic and the digestion process is intracellular.