Questions & Answers

Function of malpighian tubules of cockroach is of
A. Digestion
B. Respiration
C. Excretion
D. Reproduction

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Hint: Periplaneta americana is a native of tropical America. The cockroach is more active in summer. It is nocturnal i.e., comes out of its hiding places at night to feed. It remains concealed in cervices and under various objects during the daytime. They are omnivorous.

Complete answer: Excretion and osmoregulation are brought about by malpighian tubules that open into the ileum. The tubules are lined by glandular, cuboidal brush bordered cells that extract nitrogenous waste matter from the haemolymph and discharge it into the ileum as uric acid (uricotelism). Excretion via guts conserves water by reabsorption from waste matter. This is necessary because cockroaches cannot drink water. Some waste matter is deposited in the fat body, cuticle, and nephrocytes (pericardial cells). This is excretion by storage.
So, the correct answer is option C, i.e., Excretion.

Additional information:
The alimentary canal of a cockroach shows 3 regions: foregut (stomodaeum), midgut (mesenteron), and hindgut (proctodaeum). The foregut and the hindgut are lined by ectodermal epithelium that secretes a coat of cuticle outside it. The midgut is lined by endodermal epithelium and cuticle. The respiratory system comprises a network of white, shining tubes, the trachea, that opens out by 10 pairs of lateral apertures, the stigma or spiracles. The circulatory system of cockroaches is open type. Sexes are separate and distinguishable externally (sexual dimorphism).

Note: Hindgut comprises a very short, narrow ileum; a long wide, coiled colon, and a short, wide rectum. The rectum opens out by the anus located below the 10th tergum. A ring of about 150 fine, yellowish, thread-like malpighian tubules is joined to the beginning of the ileum. These tubules have an excretory role.