The Endocrine System Of Arthropods

Arthropods are animals with jointed legs and segmented bodies. They include insects, spiders, crustaceans, centipedes, millipedes, scorpions, and lobsters.

The Endocrine System Of Arthropods

Arthropods have advanced endocrine systems. The hormones regulate growth maturation and reproduction in arthropods.

The Endocrine System Of A Crustacean:

Its example is crayfish. Its hormone controls the functions like ecdysis (molting) sex determination, and color changes. Following endocrine glands control the process of ecdysis:

• X-organs: They are neurosecretory tissues. These are present in the eye Stalks of the crayfish.

• Sinus gland: It is associated with each X-organs. It stores and releases the secretions of the X-organ.

• Y-organs: These are present at the base of maxillae.

 X-organs and Y-organs control ecdysis. The X-organ produces a molt-inhibiting hormone (MIH) in the absence of a stimulus. The sinus gland releases it. The target of this hormone is the Y-organ. The Y-organ becomes inactive in the presence of high concentrations of MIH. Some internal and external stimuli stop the secretion of MIH. Now the Y-organs become active. It releases the hormone ecdysone. It causes molting or ecdysis.

Endocrine System In Insects:

Insets have similar hormones to crustaceans. But molt inhibiting hormone is absent in them. They have the following endocrine glands:

1. Corpora cardiaca: These are mass of neurons associated with the brain. They produce thoracoscopic hormones. It is carried to the prothoracic

2. Prothoracic glands: They produce and release ecdysone. Ecdysone induces molting. It controls the reabsorption of some of the old cuticles and the development of a new cuticle.

3. Some other neurosecretory cells in the brain and nerve cords produce the hormone bursicon Bursicon influences epidermal development like tanning. The hardening and darkening of the chitinous outer cuticle layer are called tanning. Tanning is completed several hours after each molt. Corpora allata: It is present just behind the brain of an insect. It produces

4. Juvenile hormone (JH): This hormone is also involved in molting. High concentrations of JH in the blood inhibit differentiation. The corpora allata decreases the JH production in the absence of an environmental stimulus. It differentiates the insect larva into a pupa. The pupa then forms a cocoon to spend winter. JH is stopped in the spring. Therefore, the amount of ecdysone again transforms the pupa into an adult moth.