Organisation of Body Wall in Scypha
The structural plan of the body wall of Scypha is focused at a cellular level. The cells do not
differentiate into many distinctive types found in higher metazoa. Each cell has quite broad
functional capacities. Sponges as a whole are considered to lack well organised tissues.
The microscopic organisation of body wall shows the presence of a single layer of cells
covering the external surface of the body, designated as the dermal layer and composed of
large pinacocyte cells. The spongocoel is lined by a layer of flattened endodermal
choanocyte cells that are flagellated. The intermediate layer, in between the above two
layer of cells, consists of a gelatinous matrix with spicules and numerous amoeboid cells.
1. Pinacocytes:
(Greek: pinako, plank and kytos, cell) Pinacocytes cover the outer surface and line all
internal canals or spaces that are not covered with choanocytes. Pinacocytes sometime
form a syncytial epitheloid membrane. Externally lying pinacocytes on the outer body
surface are called exo-pinacocytes, while the internal pinacocytes are called endo-
pinacocytes.
The pinacocytes are large, flattened, scale-like cells, closely cemented together by their thin
margins. It contains a somewhat centrally placed nucleus. Pinacocytes are highly contractile
and can either reduce or increase the surface area of the sponge body. Porocytes are
absent in Scypha and the ostia are simple gaps in the pinacocyte layer.
ii. Choanocytes:
(Greek: Choane, tunnel and kytos, cell) Choanocytes are also called collar cells or gastral
cells, having long whip-like flagellum. Each choanocyte has a round or oval body. It
possesses a single nucleus, one or more vacuoles, food vacuoles and reserve food particles.
The free end of the cell body has a comparatively longer flagellum and the base of the
flagellum is surrounded by a contractile transparent collar-like outgrowth of the cytoplasm.
The collars have filtering mechanisms for trapping and engulfing food particles.
Electron microscopic studies reveal that the collar is not a solid structure, but composed of
many delicate, linear, pseudopodia-like microvilli that pass from one microvillus to the next.
The structural plan of the body wall of Scypha is focused at a cellular level. The cells do not
differentiate into many distinctive types found in higher metazoa. Each cell has quite broad
functional capacities. Sponges as a whole are considered to lack well organised tissues.
The microscopic organisation of body wall shows the presence of a single layer of cells
covering the external surface of the body, designated as the dermal layer and composed of
large pinacocyte cells. The spongocoel is lined by a layer of flattened endodermal
choanocyte cells that are flagellated. The intermediate layer, in between the above two
layer of cells, consists of a gelatinous matrix with spicules and numerous amoeboid cells.
1. Pinacocytes:
(Greek: pinako, plank and kytos, cell) Pinacocytes cover the outer surface and line all
internal canals or spaces that are not covered with choanocytes. Pinacocytes sometime
form a syncytial epitheloid membrane. Externally lying pinacocytes on the outer body
surface are called exo-pinacocytes, while the internal pinacocytes are called endo-
pinacocytes.
The pinacocytes are large, flattened, scale-like cells, closely cemented together by their thin
margins. It contains a somewhat centrally placed nucleus. Pinacocytes are highly contractile
and can either reduce or increase the surface area of the sponge body. Porocytes are
absent in Scypha and the ostia are simple gaps in the pinacocyte layer.
ii. Choanocytes:
(Greek: Choane, tunnel and kytos, cell) Choanocytes are also called collar cells or gastral
cells, having long whip-like flagellum. Each choanocyte has a round or oval body. It
possesses a single nucleus, one or more vacuoles, food vacuoles and reserve food particles.
The free end of the cell body has a comparatively longer flagellum and the base of the
flagellum is surrounded by a contractile transparent collar-like outgrowth of the cytoplasm.
The collars have filtering mechanisms for trapping and engulfing food particles.
Electron microscopic studies reveal that the collar is not a solid structure, but composed of
many delicate, linear, pseudopodia-like microvilli that pass from one microvillus to the next.
