Question

Which of the following phylum has solenocytes or flame cells as excretory structures?
A. Echinoderms
B. Annelids
C. Platyhelminthes
D. Molluscs

Answer 1

Hint: Solenocyte is an elongated cell derived from the mesoderm which constantly moves along with flagellum. It forms the excretory system of the flatworms. Bundles of flame cells are called protonephridia. The function of the solenocyte is the removal of nitrogenous waste from the body.

Complete answer: The simplest freshwater invertebrates, which includes flatworms, rotifers, and nemertean consist of a specialized type of excretory cell known as flame cells. They are also called solenocytes. The flame cell possesses a body with a nucleus along with a cup-shaped projection and the inner surface of the cup is covered by flagella. Solenocyte regulate the function of maintaining the osmotic pressure in worms and also maintain the ionic balance. Platyhelminthes or the flatworms are the invertebrates whose body is unsegmented, soft, and bilateral. Platyhelminthes are acoelomates that mean it does not have a body cavity. They do not possess a specialized respiratory system or cardiovascular system and the exchange of oxygen takes place by diffusion through their body. An organ called nephridia is a tube coiled like structure which performs the function of filtering waste out of the body. It forms the excretory system of most annelids and molluscs. Removal of waste in echinoderms takes place through the finger-like extension of coelom which is called papulae.
So, option C is the correct option.

Note: The flame cell can be distinguished from the solenocyte as the flame cell possesses cilia whereas the solenocyte has a flagellum. Branchiostoma is an example of an organism in which excretion is performed by the solenocytic protonephridia. The function of a flame cell is similar to a kidney which involves removing waste materials.