Question

Excretory organs of protochordate Amphioxus are
A) Malpighian tubules
B) Protonephridia
C) Kidney
D) None of the above

Answer 1

Hint:Chordata group is divided into many subphylums that includes cephalochordata, urochordata, vertebrates, and hagfishes. They cover four percent of the organisms in Earth as chordata has had necessary evolutionary success.

Complete answer
To answer this question, we have to know about the Amphioxus. Amphioxus belongs to the subphylum Cephalochordata. These are the marine animals in the chordata group, they have thin laterally compressed bodies that are transparent and about five to seven centimeter in size. The skin of these animals consist of a layer of prismatic cells along with the mucus followed by the dermis and the basal lamina. Mostly notochord and the cells are surrounded by paramyosin and actin, these consist of neurons. The Amphioxus can swim as they have many fins like dorsal, vesicles, caudal, and anal. The caudal fin extended to the atriopore from where water leaves the body. The anal fin has two sheets and form two folds to stabilize them and is termed as metapleural folds. They do not have heart in their circulatory system rather they consist of two circuits; the ventral and the dorsal circuit. The circulatory liquid moves to the pharynx fissures to get oxygenated not its lack of respiratory pigments; therefore respiration takes place through diffusion.
Now, the excretory organ of Amphioxus is nephridium that has the similar function as that of kidney in vertebrates. This cell is found in pared form and expels the wastes from the body cavity to the exterior.

Hence, the correct answer is ‘B’. Protonephridia.

Note:In some cases excretory systems are formed by solenocytes that involve in the filtration of blood from arteries and connect the atrium to the channel. The channel allows the excretory products to move out of the body along with the water in the atrium.