Invertebrate Biology

Velvet Worms and Hydrostatic Locomotion

Velvet worms use hydrostatic pressure and slime jets to hunt, raising questions about the welfare of ancient lineages.

Key Facts

Velvet worms (Onychophora) are among the oldest animal lineages, dating back over 500 million years
They hunt by spraying adhesive slime from oral papillae up to 30 cm to immobilize prey
Their bodies are soft and flexible, relying on hydrostatic pressure rather than a rigid skeleton
They are found in humid leaf litter and forest floors across tropical and southern hemisphere regions
Velvet worms show apparent distress responses when handled or dried out

Welfare Considerations

While research on velvet worm sentience is limited, their ancient nervous systems and responsive behaviors suggest they may experience some form of aversive state. Dehydration appears particularly harmful and should be avoided in captive or research settings.

What You Can Do

Support habitat preservation for tropical forest floors where velvet worms live
Avoid disturbing leaf litter and soil in biodiversity-rich forests
Advocate for invertebrate welfare considerations in biological research ethics