Question

Juvenile hormone in cockroach is secreted by:
А. Corpora cardiaca
B. Prothoracic gland
C. Corpora allata
D. Corpora bigemina

Answer 1

JH (formerly known as neotenin) is a group of hormones found in insects that ensure larval growth while preventing metamorphosis. Insects grow by successively losing their exoskeletons, which is due to their rigid exoskeleton (a process known as molting). JHs are a class of acyclic sesquiterpenoids that control a variety of aspects of insect physiology. Vincent Wigglesworth was the first to discover a JH.

Complete answer:
Option A: Both the paired cardiac corpora (singular, corpus cardiac), together with the paired corpora allata, are neurohemal organ storage and contain endocrine cells in the brain.
So, option A is incorrect.
Option B: The prothoracic glands are a pair of endocrine glands that control molting in some insects.
So, option B is incorrect.
Option C: The corpora allata secretes youth hormones, a pair of endocrine glasses behind the brain. JHs are also essential for female insects to produce eggs. The corpora allatum is an endocrine gland that produces juvenile hormone and is essential for metamorphosis. The surgical removal of this gland will result in an immature larvae pupating at its next molt, resulting in a miniature arachnid.
So, option C is correct.
Option D: The corpora bigemina is a bilateral single swelling of the embryonic midbrain’s roof plate that later develops into a superior and inferior colliculus.
So, option D is incorrect.

Hence, Option C is the correct answer.

Note:
The corpora allata of insects produces juvenile hormones. JH can spread across the haemolymph and function on tissues that are immune to it. Juvenile-hormone esterase (JHE) or juvenile hormone epoxide hydrolase are the enzymes that primarily degrade JH (JHEH). JHE and JHEH both cause JH signalling and response to be suppressed. One or both of these enzymes can be generated by JH-responsive tissues.
Adult males’ accessory glands are stimulated by JH, which promotes gland growth and accessory gland secretion. JH also stimulates the development of eggs (vitellogenesis) in female ovaries. JH can also influence both sexes’ reproductive behaviour.