17 February, 2020

Are trichobothria really necessary in scorpion prey capture?

It is a well known fact that the scorpion trichobothria on their pedipalps are very important in how the scorpions sense their environment. They use these small hairs to detect vibrations in the air and in the substrate, but direct behavioral studies on the use of trichobothria and natural prey capture are scarce.

Gabriel Pimenta Murayama and Rodrigo Hirata Willemart have recently published an interresting  study where they tested if the trichobothria are important in prey capture in Tityus serrulatus Lutz & Mello, 1922 (Buthidae). I must admit I assumed the answer was yes, but surprisingly their results suggested that the trichobothria of T. serrulatus was not essential to capture terrestrial prey.

It is important to remember that scorpions do have other types of sensory hairs (sensilla) on different parts of their body and these may play a role in detecting prey in the scorpions vicinity.

Many arachnids rely on substrate-borne vibrations and air displacement to detect prey. Air-flow stimuli may be detected by long setae called trichobothria, which occur on scorpion pedipalps, but seldom have their functions been addressed in these animals. We tested the hypothesis that trichobothria on scorpion pedipalps are important for capturing terrestrial prey in the scorpion Tityus serrulatus. We predicted that scorpions with trichobothria experimentally removed would be less successful in capturing terrestrial prey than the control groups. We also predicted that scorpions without trichobothria would have a higher number of capture attempts, that the latency to detect prey and to the first capture attempts would be higher, and the number of times that scorpions oriented their body towards the prey would be lower. We used an experimental subject and a cricket in an arena with a paper sheet as substrate. We did not find differences in the measured variables between the groups. Other sensory organs, such as basitarsal compound slit sensilla and tarsal hairs would enable scorpions to detect prey by substrate-borne vibrations, compensating for the lack of trichobothria. Our results suggest that the trichobothria of T. serrulatus may not be essential to capture terrestrial prey.

Murayama GP, Willemart RH. Are trichobothria used in terrestrial prey capture by the yellow scorpion Tityus serrulatus Lutz & Mello, 1922 (Buthidae)? Arachnology. 2019;18(3):287-90.

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