Sequestration

Definition

The active accumulation, isolation, and long-term storage of a substance—typically defensive compounds, nutrients, or toxins—within specialized tissues, cells, or anatomical structures, rendering it biologically unavailable for immediate metabolic use. In arthropods, sequestration commonly involves the uptake and concentration of plant-derived allelochemicals (e.g., cardiac glycosides, pyrrolizidine alkaloids, iridoid glycosides) from host plants into the hemolymph, cuticle, or specialized glands for predator deterrence. The process also encompasses the storage of excess nutrients (lipids, glycogen) in fat body or other depots during diapause preparation, and the immobilization of heavy metals or metabolic waste products in insoluble granules to prevent toxicity.

Etymology

From Latin sequestrare, to set aside or surrender for safekeeping; in biological usage, emphasizing the isolation and protective custody of substances.

Example

Monarch butterfly (Danaus plexippus) larvae sequester cardiac glycosides from milkweed (Asclepias) into specialized cuticular and hemolymph compartments; these compounds persist through metamorphosis, rendering adults unpalatable and emetic to avian predators. In some arachnids, sequestration of dietary heavy metals in intracellular granules allows occupation of contaminated habitats without physiological harm.

Synonyms

• bioaccumulation (partial, when emphasizing uptake)
• storage (general)
• compartmentalization (cellular context)

Related Terms

• defensive secretion
• de novo synthesis
• allochemical
• mimicry
• Batesian mimicry
• Müllerian mimicry
• Fat body
• Diapause
• detoxification
• Excretion
• Granulocyte

Usage Notes

Distinguish sequestration from de novo synthesis (endogenous production of defensive compounds) and from passive bioaccumulation (lacks active transport and specialized storage). Sequestration implies adaptive, often reversible, compartmentalization with potential future deployment—contrasting with permanent excretion or catabolic destruction. In ecological literature, the term also describes ecosystem-level carbon or nutrient locking, but arthropod-focused usage emphasizes organismal physiological mechanisms. Some authors restrict 'sequestration' to exogenous compound uptake, reserving 'storage' for endogenous metabolites; usage varies by subdiscipline.