Bursicon

Definition

A heterodimeric neurohormone in insects that triggers post-ecdysial processes, principally sclerotization (tanning) of the new cuticle and expansion of the wings after adult emergence. Released from neurosecretory cells in the central nervous system, bursicon acts via a G-protein-coupled receptor to stimulate tyrosine metabolism and cross-linking of cuticular proteins, hardening the exoskeleton. It also promotes the plasticization and subsequent resclerotization of the wing cuticle, allowing wings to expand and then stiffen for flight.

Etymology

From Latin bursa (purse, sac), referring to the neurohemal release sites; coined by Gottfried S. Fraenkel and Catherine Hsiao in 1965 upon identifying the hormone in blow flies.

Example

In newly emerged Drosophila melanogaster adults, bursicon release peaks within two hours after eclosion; without it, the cuticle remains soft and untanned, and wings fail to expand beyond their folded pupal configuration.

Synonyms

• tanning hormone

Related Terms

• Ecdysis
• Sclerotization
• Cuticle
• Neurohormone
• ecdysteroid
• Corazonin
• wing expansion
• post-ecdysial behavior

Usage Notes

Bursicon is often contrasted with ecdysteroids, which drive molting and cuticle deposition, whereas bursicon acts after ecdysis to harden and shape the new cuticle. The term refers specifically to the hormone complex (α and β subunits, encoded by genes such as rickets and pburs in Drosophila), not to the neurohemal organs (perisympathetic organs, abdominal ganglia) that release it. In some literature, 'bursicon' loosely denotes the bioassay activity rather than the purified hormone, a distinction now largely historical.