Fat body

Definition

A metabolically active tissue distributed throughout the insect hemocoel, composed primarily of trophocytes (storage cells) that accumulate lipids, glycogen, and proteins. Functionally analogous to both mammalian adipose tissue (energy storage) and liver (metabolism, detoxification, and biosynthesis), but additionally serving as a major endocrine organ, an immune effector site producing antimicrobial peptides, and a source of vitellogenin for oocyte development. The fat body responds dynamically to nutritional state, metamorphic hormones, and infection, making it central to insect physiology.

Etymology

Example

In Drosophila melanogaster larvae, the fat body stores triacylglycerols during feeding; upon pupariation, juvenile hormone and ecdysone trigger lipolysis to fuel metamorphosis, while the same tissue simultaneously secretes immune peptides like drosomycin in response to fungal infection.

Synonyms

• adipose body
• corpus adiposum

Related Terms

• hemocoel
• trophocyte
• Vitellogenesis
• antimicrobial peptide
• Juvenile hormone
• Ecdysone
• Metamorphosis
• adipokinetic hormone

Usage Notes

The term is specific to arthropods, especially insects; 'fat body' should not be used for vertebrate adipose tissue. In arachnids, homologous tissue exists but is less structurally defined. The singular/plural distinction matters: 'fat body' refers to the collective tissue system, while 'fat bodies' may emphasize discrete lobes or regional deposits. Contrast with 'pericardial cells' (nephrocytes), which are adjacent but functionally distinct.