Colloblast — Safekipedia Discoverer

Colloblasts are special, multi-part cells found in ctenophores, also known as comb jellies. These tiny structures live in the tentacles of ctenophores and help the animal catch its food. Each colloblast has a cell called a collocyte that holds a spiral filament and other important parts.

A bioluminescent Ctenophore.

When a ctenophore uses a colloblast, it shoots it out from its tentacles to catch prey. This works in a different way from the stinging cells of jellyfish, called cnidocytes. Instead of stinging, colloblasts shoot out sticky glue that sticks to the prey, helping the ctenophore hold onto it.

Form and Function

Colloblasts were first described in 1844. They are made of two types of cells: a stalk split into parts called the collosphere and collopod, and many cap cells that put sticky granules on the collosphere's surface. These granules help the colloblast stick to things.

When a colloblast is touched, it breaks away from the tentilla, a part of the creature's tentacles. When it touches prey, the granules burst and release a sticky substance. A spiral filament stays connected to the tentillum, holding the prey in place until it is eaten.

Variation and Occurrence

Colloblasts are found in all ctenophores except those in the order Beroida, which do not have tentacles, and the genus Haeckelia, which uses cnidocytes from cnidarian prey.

The biggest difference among ctenophore groups is the shape of the collosphere. The basal colloblast has a round collosphere, but the orders Cestida, Cydippida, and Lobata have a longer collosphere and no collopod, with the spiral filament attached directly to the collosphere. In these species, the spiral filament is often smaller or missing.

The round collosphere colloblast can be divided into five types based on the size and shape of its spiral filament and radii. Types I, II, and III, found on the front part of a small tentacle, are smaller and have fewer coils, while types IV and V, found on the end part, have more complex spiral filaments and lack certain granules. The reason for this difference in shape is not known.