5. Insect endocrine system
Structures and functions of the endocrine systems in insects.
Like other animals, insects possess an
array of hormones that regulate their
diverse physiological and biochemical
Hormonal sources in insects include the
the corpora allata,
the prothoracic glands,
and epitracheal glands.
Other endocrine cells are also found in the gut and ovaries.
The neuroendocrine system consists of
nerve cells that secrete hormones.
Neurosecretory cells are located mainly
in the brain,
the ventral nerve cord,
and the corpora cardiaca.
They are also
found in association with other nervous tissues
located throughout the body.
Neurohormones are the master regulators
and control most physiological and
metabolic processes including regulating
secretion of the hormones that control
metamorphosis and reproduction.
Neurohormones also regulate the
synthesis of blood lipids, carbohydrates
and proteins and control energy
metabolism related to flight.
also control other basic physiological
functions such as feeding activity and
Corpora cardiaca are major
neuroendocrine structures attached to the brain,
Neurosecretory cells located
in the brain synthesize and transport
neurohormones to the corpora cardiaca from which the brain hormones are stored and released.
In addition, corpora cardiaca contain intrinsic neurosecretory cells
that also synthesize and release neurohormones.
The corpora allata are structurally
associated near the corpora cardiaca,
but they are not part of the neuroendocrine system.
Corpora allata synthesize and secrete juvenile hormone.
Juvenile hormone prevents immature insects from undergoing metamorphosis
into premature adults during molting.
Juvenile hormone also stimulates egg
formation in most adult female insects.
The prothoracic glands are a grape-like
cluster of cells surrounding the trachea
in the first thoracic segment.
These glands secrete ecdysone a hormone that
stimulates the molting events necessary
for insect growth.
Prothoracic glands deteriorate in adult insects because
adult insects no longer molt.
Like the prothoracic glands, epitracheal glands
are groups of secretory cells associated with the trachea.
They secrete hormones
that regulate molting behavior.
Endocrine cells are also found in the
gut and may affect feeding activity