Ultrastructure of Colloblast
Ctenophores are a group of animals found in all the world’s seas, from coastal
areas to the deep sea and from the tropics to the poles (Hyman, 1940). They are
sometimes called “comb jellies” because they have a jelly-like appearance and
distinctive rows of comb plates (ctenes) that are used for locomotion. The
presence of an ectomesoderm, and the presence of special adhesive cells
known as “colloblasts”, “Klebzellen”, “collocytes”, or “lasso cells”, instead of
venomous cells “nematocytes” or “cnidoblasts” of Cnidaria.
Colloblast Organization:
Still, little is known about the development, function, and bonding mechanisms
of the colloblasts. Early light microscope studies (Chun, 1880; Hertwig, 1880;
Komai, 1922; Hyman, 1940) were complemented by electron microscopy
investigations performed by Hovasse and de Puytorac (1962, 1963). More
recently, Bargmann et al. (1972), Carré and Carré (1993), and Eeckhaut et al.
(1997) published detailed ultrastructural studies on the adhesive structures in
ctenophores.
(In general, colloblasts have a hemispherical head (collosphere) and a conical
stalk (collopod). The stalk is surrounded by a helical thread, which is coiled in
the form of a helix and ends in the mesoglea by a root (Weill, 1935a). The
colloblast head is decorated by external granules, attached outside the plasma
membrane in a regular manner.
Head (Collosphere) and Spheroidal Body:
The head of the colloblast has a bulb- to kidney-like shape. Its cytoplasm
consists of loose, fine-grained material and contains typical cell organelles such
as mitochondria, endoplasmic reticulum, Golgi network, and microtubules. Very
specific structures are two granule types and the spheroidal body. The latter
forms the end of the spiral filament and is located close to the stalk. From its
center, fibers composed of about 20 filamentous sub-units, the so called radii,
stream toward the head periphery and end at a stamp-like fibrillar pad adjacent
to the internal granules. A small plate, consisting of small rods, connects this
pad to one granule. To date, the function of the spheroidal body remains
unresolved. Carré and Carré (1993) suggest that it serves as a “nucleation
Ctenophores are a group of animals found in all the world’s seas, from coastal
areas to the deep sea and from the tropics to the poles (Hyman, 1940). They are
sometimes called “comb jellies” because they have a jelly-like appearance and
distinctive rows of comb plates (ctenes) that are used for locomotion. The
presence of an ectomesoderm, and the presence of special adhesive cells
known as “colloblasts”, “Klebzellen”, “collocytes”, or “lasso cells”, instead of
venomous cells “nematocytes” or “cnidoblasts” of Cnidaria.
Colloblast Organization:
Still, little is known about the development, function, and bonding mechanisms
of the colloblasts. Early light microscope studies (Chun, 1880; Hertwig, 1880;
Komai, 1922; Hyman, 1940) were complemented by electron microscopy
investigations performed by Hovasse and de Puytorac (1962, 1963). More
recently, Bargmann et al. (1972), Carré and Carré (1993), and Eeckhaut et al.
(1997) published detailed ultrastructural studies on the adhesive structures in
ctenophores.
(In general, colloblasts have a hemispherical head (collosphere) and a conical
stalk (collopod). The stalk is surrounded by a helical thread, which is coiled in
the form of a helix and ends in the mesoglea by a root (Weill, 1935a). The
colloblast head is decorated by external granules, attached outside the plasma
membrane in a regular manner.
Head (Collosphere) and Spheroidal Body:
The head of the colloblast has a bulb- to kidney-like shape. Its cytoplasm
consists of loose, fine-grained material and contains typical cell organelles such
as mitochondria, endoplasmic reticulum, Golgi network, and microtubules. Very
specific structures are two granule types and the spheroidal body. The latter
forms the end of the spiral filament and is located close to the stalk. From its
center, fibers composed of about 20 filamentous sub-units, the so called radii,
stream toward the head periphery and end at a stamp-like fibrillar pad adjacent
to the internal granules. A small plate, consisting of small rods, connects this
pad to one granule. To date, the function of the spheroidal body remains
unresolved. Carré and Carré (1993) suggest that it serves as a “nucleation
