Spiders can reach their top running speeds again soon after self-amputating a limb 鈥� a trick that could inspire robots that can move more effectively when they are damaged.
When threatened by a predator, spiders can detach their legs in a process called autotomy 鈥� up to 40 per cent of wild spiders have missing legs as a result. Their legs fully grow back when they moult, which can be within one to two months for juveniles.
聽at Haverford College in Pennsylvania and her colleagues wanted to find out how spiders adjust their running style after losing legs. They recorded high-speed videos of Guatemalan tiger rump tarantulas (Davus pentaloris) running with all their legs intact, then immediately after losing two legs and again one day later.
Advertisement
To coax the spiders into dropping two legs simultaneously, the researchers anaesthetised them by cooling them on ice. 鈥淥nce they were sluggish and not moving, we would glue the two legs we wanted them to drop to an index card,鈥� says , a team member at Temple University in Philadelphia. 鈥淲hen they woke up, we would gently poke them with a fine-tip paintbrush until they would drop those legs at almost the same time.鈥�
Kane says the spiders typically ran at around 0.38 metres per second with all eight legs, but some clocked in at over 0.6 metres per second. After amputation, the team found the spiders almost immediately recovered their full speed.
They compensated for limb loss so quickly that the final running trials from the day of limb loss were practically indistinguishable from the trials recorded a day later, says Hsieh.
鈥淲hat makes this particularly cool is that they are doing this by immediately changing the strategy with which they run,鈥� she says. 鈥淭hey move the remaining limbs to fill in the space the autotomised limbs used to occupy and they even switch up the synchronisation patterns of the remaining legs to achieve the greatest running stability and performance.鈥�
at the Australian Museum in Sydney says the study shows that spiders have a lot of flexibility built into their nervous system and they can make dynamic adjustments to their gait very quickly. 鈥淵ou can see why robot engineers could be very interested in this study,鈥� he says.
bioRxiv
