Question

'Lasso cells' are present in
A. Ctenophora
B. Nematoda
C. Porifera
D. Protozoa

Answer 1

Hint: Lasso cells are found in the tentacles of the organism. Each one of these has two protruding filaments, one straight and one spiraled, with adhesive heads used to capture prey.

Complete Answer:
- Ctenophores include the many marine invertebrates that make up the Ctenophora phylum. The name of the phylum is derived from the series of vertical ciliary combs on the surface of the animal.
- Ctenophores have eight "comb rows" of fused cilia arranged down the side of the animal. These cilia beat synchronously and drive the ctenophores through the water. Some animals move with the flapping motion of their lobes or the undulation of the body. Some ctenophores have two long tentacles, but others have no tentacles at all.
- The colloblast, also known as lasso cells, is present only in ctenophores. These cells produce a sticky substance that prey species stick to when in contact with them. Colloblasts form a spiral coiled filament embedded in the epidermis and an axial filament with a granular dome.
- The apical surface of these cells comprises eosinophilic granules, which are considered to be the basis of adhesion. Upon touch, the granules rupture and release the adhesive to the prey. The spiral filament absorbs the force of the rupture, stopping the snarled prey from fleeing.

Thus the correct answer is option A i.e., Ctenophora.

Note: Like cnidocytes of cnidarians, colloblasts are released from the tentacles and used to trap prey. However, unlike cnidocytes, which are poisonous cells, colloblasts attach to their prey rather than sting their prey.