Define canal system. give an account of canal system in porifera ?
Answers
Your answer is =>
Canal system is the transport system through which metabolic transports within the body of poriferans takes place i. e. the transport of nutrients, excretory products, etc.
Now, the different types of canal systems are =>
Canal systems refer to method of water flow throughout the sponge
There are three different types of canal sysrem: -.-
⚜ Simple (asconoid) =>
Water cntcrs spongocoelby incurrcnt openings of the pore cells. Cells lining the spongocoeI absorb the nutrients and oxygen and left over wateris expelled through the osculum.
⚜ Advanced (Syconoid) =>
the body wallis folded:accomodating more pores without increasing the site of the sponge.
⚜ Complex (Leuconoid) =>
This canal systemis extensively branched.and thus more complex
Understanding Canal System
It's a distinguish characteristic of porifera in which water moves in (ingression) and out (exgresssion) of the body flowing through a certain canal system inside the animal body.
● It's maintained by flagella of collar cells.
● minute opening called ostia for ingression of water.
● water moves out through single osculum.
● spongocoel is the inner mesenchyme large cavity lined by choanocytes/flagellated collar.
● Canal system depends on water movement.
Function: Helps in exchange of gases, nutrition, osmoregulation and excretion.
TYPES OF CANAL SYSTEM IN SPONGES/PORIFERA
1. Ascon:
- simplest form of canal system.
- water enters through ostia by ingression.
- moves inside body via porocytes.
- enters spongocoel.
- due to beating of flagella water moves out through osculum.
Water flow:
Ingressing water -> ostia -> spongocoel -> osculum -> outside
Example: Leucosolenia
2. Sycon:
- more complex pores and canals.
- forms by horizontal folding in ascon walls.
- It includes two more canals: Radial canal and Incurrent canal.
- Both are parallel-alternate to each other.
- Prospyles connects them.
- Incurrent canals are lined by pinaco-derm (un-flagellated) but Radial canals are lined by choanocytes (flagellated) like spongocoel.
- Apopyles connect the spongocoel with the Radial Canal.
Water Flow:
Ingressing water -> ostia -> Incurrent canal -> prospyles -> Radial canal -> Apopyles -> Spongocoel -> Osculum -> outside
Example: Scypha and Grantia
3. Leucon:
- most complicated canal system.
- no radial symmetry unlike last two.
- spongocoel disappears into excurrent canal due to formation of many flagellated chambers lined by choanocytes in place of radial canals.
- All other places lined by pinaco-derm.
Water Flow:
Ingressing water -> ostia -> incurrent canals -> prospyles -> flagellated chambers -> Apopyle -> Excurrent canal -> osculum -> outside
Example: Spongilla
Based on addition of canals, Leucon is of three types:
A. Eurypylous: no additional of extra canal.
B. Aphodal: Apopyle is drawn out as a narrow canal called aphodus connecting flagellated chambers.
C. Dipodal: In addition to aphodus, prosodus is present between incurrent canal and flagellated chambers.
Rhagon Type: It's a special type of canal system shown in larval stages of Demospongiae.
Spongocoel is surrounded by flagellated chambers open into wide apopyles with osculum opening. It's absent in adult stages.
