In vivo

Definition

Performed or occurring within a living, intact organism, as opposed to isolated tissues, cell cultures, or acellular preparations. In entomology and arachnology, the term distinguishes whole-organism experiments—such as behavioral assays, host–parasite interactions, or pesticide toxicity trials on intact insects or spiders—from in vitro studies using homogenates, primary cell lines, or explanted organs. In vivo conditions preserve systemic physiology, natural immune responses, and organismal behavior, but introduce greater complexity and variability than controlled laboratory preparations.

Etymology

Latin, literally 'within the living'.

Example

Researchers tested the in vivo efficacy of a fungal entomopathogen by exposing live Colorado potato beetle larvae to conidia on foliage, rather than measuring spore germination rates on artificial media alone.

Synonyms

• whole-organism
• intact-system

Related Terms

• In vitro
• ex vivo
• in situ
• organismal biology
• toxicology
• behavioral ecology

Usage Notes

Often contrasted with in vitro (isolated biological components) and ex vivo (tissues or cells removed from the organism but kept alive). In vivo does not necessarily imply the natural environment; it includes laboratory-maintained living organisms. The term is sometimes stretched to include gnotobiotic or axenic systems, though purists reserve it for conventional intact hosts. In medical entomology, in vivo vector competence studies assess pathogen transmission by live mosquitoes or ticks feeding on susceptible hosts.