Question

Juvenile hormone in insects is released from
A) Protocerebrum
B) Corpora Cardiaca
C) Corpora Allata
D) Thoracic gland

Answer 1

Hint:It is an organ that induces the liquid substances secretion on the body surface in insects that corresponds to the pituitary gland. It is an endocrine gland which plays a significant role in metamorphosis.

Complete answer:
First we should know about Juvenile hormone (JH) to answer this question. Throughout insect life, JH controls growth, reproduction, diapause, polyphenism, and behaviour. Juvenile hormones have many roles, and the primary purpose of JH in insect growth is to modulate the activity of ecdysone. Juvenile hormone retains the present activity of the tissues and cells, while ecdysone induces the moult to induce both pre differentiated and differentiative cellular activities. Thus, a molt to a larval stage happens when Juvenile hormone is present. If at the start of the molt, Juvenile hormone is absent, metamorphosis occurs.
Now, let us find the solution from the options-
Protocerebrum produces brain hormone (BH) that accumulates in the corpora allata and this brain hormone is known as prothoracicotropic hormone (PTTH) or ecdysiotropin. Therefore, the option (A) is incorrect.
The hyperglycemic hormone that induces a sudden rise in blood levels of trehalose, this insect's blood sugar, is secreted by the corpora cardiaca. Often it is referred to as the hypertrehalosemic hormone. Therefore, the option (B) is incorrect.
Corpora allata is the endocrine gland of insects which secretes juvenile hormones. It is a gland found in the head of insects that is essential for the secretion of juvenile hormone which retains the characteristics of the larval at each molt before adult metamorphosis occurs.
The thoracic gland is a diffuse endocrine organ producing ecdysone in the thoracic area of insects. Therefore, the option (D) is incorrect.

Thus, the correct answer is option (C) Corpora Allata.

Note:In the 1930s, juvenile hormone (JH) was first identified as a component that is secreted and prevents the metamorphosis of insects. In 1967, the chemical composition of the first JH was resolved, and to date at least eight JHs have been recognised.