Toward welfare indicators: leg condition and aversive stimuli modulate defensive behavior in Opilones

In Prionostemma sp. 1, aversive squeezing and substrate cues did not produce substrate preference or avoidance, while fleeing dominated responses across 5 days.

• Why it matters: Welfare indicators are needed for invertebrates, but behavioral links to welfare states are poorly validated across taxa, especially in wild arachnids.
• What they did: Field-collected harvestmen with intact, missing 1–2 legs, or missing sensory legs were tested with an aversive squeeze-and-release on rock or sand, with food on the alternate substrate.
• The result: After aversive stimulation, fleeing was consistently most common over 5 days, bobbing increased and escaping decreased across trials, and leg condition only weakly predicted escape.

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