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What is Sycon?

Sycon is a marine sponge which is found attached to the rocks, corals and shells of molluscs. Sponges are the members of the phylum porifera. There are approximately 5000 living species of sponges in the world. These are divided into 3 different groups based on the presence or composition of spicules or spongin.

  • Calcaria

  • Hexactinellida

  • Demospongiae

Let us know more about sycon, its structure, scientific classification, characteristics, canal system, their nutrition, respiration and nutrition.


Sycon Classification

The classification of sycon is given below.

  • Kingdom: Animalia

  • Phylum: Porifera

  • Class: Calcarea

  • Order: Heterocoela

  • Family: Sycettidae

  • Genus: Sycon


Geographic Range of Sycon

It is a marine sponge found across the world, generally in shallow water but not more than 150 meters deep. They are predominant. Also, they are commonly found in the arctic ocean, pacific ocean, Indian ocean etc. 


Habitat of Sycon

  1. Habitat Region -

  • Temperature - that region of the Earth between 23.5 degrees North and 60 degrees North. 

  • Region - mainly lives in oceans, seas, or other bodies of saltwater.

  1. Aquatic Biomes -

  • Benthic - Lives at the bottom of a body of water.

  • Reef - Reef is the structure produced by the calcium carbonate skeletons of coral polyps.

  • Coastal - It is the nearshore aquatic habitat near the coast.

  1. Other Habitat Features

  • Intertidal or littoral - Littoral is the area of shoreline influenced mainly by the tides.


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 an 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 the 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 the sycon are 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 apertures called prosopyles in between the incurrent canal and radial canal. 

  • Prosopyles: The prosopyles help 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 the spongocoel through an opening called gastric ostium.

  • Spongocoel: Spongocoel is a narrow cavity lined by pinacocytes. It opens out through the osculum. 


Sycon Reproduction

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 the 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.


Sycon Respiration

The sycon respiration is carried out by a simple diffusion process.

  • This diffusion causes the exchange of gasses 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.


Sycon Nutrition

  • 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.


Current of Water in Sycon

The flow of water in sycon is maintained by continuous flagellar beating of choanocytes. So, the water rushes along the external surface and enters inside the body through ostia. Through prosopyle, the water flows inside the radial canal (from the incurrent canal).


Function of water current in this sponge:

  • By means of this current,  exchanges between the sponge body and the external medium takes place.

  • With the help of this water current, food and oxygen is brought into the body.

  • The excreta is taken out of the body by the water current.

  • The water current carries out the reproductive bodies into the body of the sponges .


Answer the following MCQs :

(i) A sycon is a type of marine ______.

(a) plant

(b) sponge

(c) rock

(d) chemical

Ans: (b) it is a type of marine sponge.


(ii) Which of the following sponge is found in the river?

(a) Cliona

(b) Sycon 

(c) Spongilla

(d) Hyalonema

Ans: c) Spongilla


(iii) Sycon belongs to which of the following groups of animals?

(a) multicellular organisms without any tissue organization

(b) multicellular organisms and which a gastrovascular system

(c) multicellular organisms which have tissue organization, but have no body cavity.

(d) unicellular organisms or acellular organisms

Ans: (a)  multicellular organisms without any tissue organization


Answer the following :

(i) What is sycon ciliatum?

(ii) List out the points of differences between sycon and hydra.

Answer: 

(i) Sycon ciliatum is a sycon species (calcareous sponge) which belongs to the family Sycettidaephylum.

 It's specification are:

  • Kingdom - Animalia

  • Phylum - Porifera

  • Class - Calcarea

  • Order - Leucosolenida

  • Family - Sycettidae

  • Genus - Sycon

  • Species - S. ciliatum

It is a type of small purse sponge which grows singly or in a small group from single holdfast. It's length is upto 5 centimeter. It has a covering of fine papillae on its surface. This gives it the furry look. It's skeleton consists of tangential layers of triactines and tetractines. This specie is different from the other species because in this, the choanocyte chambers are free from each other and are not fused. It is commonly found along the coasts of Europe and also seen on the eastern fringes of the Atlantic Ocean.


(ii) Sycon and hydra differ from each other in the following ways :

  • Sycon belongs to the phylum Porifera (which shows cellular level organization) whereas Hydra belongs to the phylum Coelenterata (which has tissue-level organization).

  • Sycons are asymmetric whereas hydra are radially symmetric.

  • Sycons are mostly marine animals (few of them are also freshwater organisms) but Hydra is always a freshwater organism.

  • Sycons eat tiny organic particles that float in the water flow. Hydra are carnivorous and eat small insects and the insects with larvae. 

  • Sycons do not have a mouth whereas hydra have a mouth. 

  • Sycons are found deeper than the hydra plants .

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FAQs (Frequently Asked Questions)

1. Is a sponge diploblastic or triploblastic?

Members of the phylum porifera are neither diploblastic or triploblastic because the organization found in them is cellular. Most of the sponges are asymmetric.

They have 3 layers namely,

  • Dermal Layer -This layer connects the other layers and the nutrition absorbing parts etc.

  • Gastral Layer - It consists of highly specialized flagellated cells called choanocytes.

  • Mesohyl - They are also known as mesenchyme or as mesoglea. It is a gelatinous matrix within a sponge.

Even though they have 3 layers none of the layers act as a tissue.

2. What are the types of canal systems in sycon? Describe each of them in brief.

Canal system in sycon has three types based on the order of increasing complexity, and they are:

  • Asconoid Canal System - It is the simplest and most primitive type of canal system. Here, asconoid type is present. It's body is like a vase and is radially symmetrical. It also has a spongocoel opening (by a narrow osculum at the summit). These pours extend into the mesenchyme. They also open directly into the spongocoel. The water current in the Asconoid Canal System is as follows - Ingressing water -> Ostia -> Spongocoel -> Osculum -> outside.

  • Syconoid Canal System - This type of canal system is the first stage (above Asconoid Canal System type). In this, the walls are pushed towards the outside of an asconoid sponge at regular intervals into radial canals. (finger-like projections). The water current in the Syconoid Canal System is as follows : Ingressing water -> dermal ostia -> incurrent canal -> Prosopyles -> Radial canals -> Apopyles -> Spongocoel -> Osculum -> Outside.

  • Leuconoid Canal System - This is a complex style canal system. It is a type of canal system, loss of radial symmetry is seen due to the complexity of the canal system. The water current Leuconoid Canal System is as follows : Ingressing water ->  dermal ostia ->  incurrent canal ->  Prosopyles ->  Flagellated chambers ->  Apopyles ->  excurrent canals  -> Osculum ->  Outside.

3. What is the function of the sycon type of water current ?

In calcareous sponges, the sycon type of water current system is found. It is characterized by choanocytes which surround fingerlike projections (belonging to the sponge wall). Through pores, water directly enters the projection. This makes its way into the central cavity (spongocoel). After that, it leaves out by the way of an osculum. Hence, it helps the sponges in proper functioning and makes it easy for sponges to survive.

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