Simplest type of canal system is
1) sycon type
2) leucon type
3) ascon type
4) rhagon type
Answers
Type of spongocoel/canal system found in Leu
A. Ascon type or Asconoid canal system: It is the simplest type of canal system found in asconoid sponges like Leucosolenia. It is the only canal system in which spongocoel is lined by choanocytes. The ostia are represented by cells called porocytes. These cells have intracellular canal inside them. The cells extend radially into the mesenchyme and open directly into the spongocoel.
B. Sycon type or Syconoid canal system: This type of canal system develops from asconoid type due to horizontal folding of asconoid body wall. The spongocoel is lined by pinacoderm and the choanocytes are restricted to small chambers which are called radial chambers. Besides radial chambers, incurrent canals are also there. Incurrent canals open into radial chamber through prospoyle and radial chamber opens into spongocoel through apopyle. Spongocoel is very narrow and opens to outside through osculum.
C. Leucon type or Leuconoid canal system: It is the most complicated canal system. It develops from syconoid type due to folding of walls of radial canals. This type of canal system is found in leuconoid sponges. The radial symmetry of body is lost and thus, the canal system becomes very irregular. A characteristic feature of this type of canal system is the presence of excurrent canals.
D. Rhagon type of canal system is found in sponges of class Demospongiae. This type of canal system forms during embryonic development. Each chamber directly opens out at body surface by a prosopyle and into spongocoel by an apopyle.
So, the correct answer is 'Ascon'.
Type of spongocoel/canal system found in Leu
A. Ascon type or Asconoid canal system: It is the simplest type of canal system found in asconoid sponges like Leucosolenia. It is the only canal system in which spongocoel is lined by choanocytes. The ostia are represented by cells called porocytes. These cells have intracellular canal inside them. The cells extend radially into the mesenchyme and open directly into the spongocoel.
B. Sycon type or Syconoid canal system: This type of canal system develops from asconoid type due to horizontal folding of asconoid body wall. The spongocoel is lined by pinacoderm and the choanocytes are restricted to small chambers which are called radial chambers. Besides radial chambers, incurrent canals are also there. Incurrent canals open into radial chamber through prospoyle and radial chamber opens into spongocoel through apopyle. Spongocoel is very narrow and opens to outside through osculum.
C. Leucon type or Leuconoid canal system: It is the most complicated canal system. It develops from syconoid type due to folding of walls of radial canals. This type of canal system is found in leuconoid sponges. The radial symmetry of body is lost and thus, the canal system becomes very irregular. A characteristic feature of this type of canal system is the presence of excurrent canals.
D. Rhagon type of canal system is found in sponges of class Demospongiae. This type of canal system forms during embryonic development. Each chamber directly opens out at body surface by a prosopyle and into spongocoel by an apopyle.
So, the correct answer is 'Ascon'.
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