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2CIBIO
Research Centre in Biodiversity and Genetic Resources, InBIO,
Universidade do Porto, Campus Agrário de Vairão, 4485-661
Vairão, Vila do Conde, Portugal. |
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Scorpion
venom is a complex mixture of toxins. A lot of work is being
done on the biochemical properties of the scorpions venom and
not that much of work has yet been performed on the
biomechanical aspects of scorpion venom delivery. The amount of
venom released during different stings is known to be different.
Scorpions, just like snakes and spiders, have the ability to
meter the amount of venom they want to expel. Production is an
expensive metabolic investment. In scorpions metabolic rate gets
up to 39%, for milked specimens compared to the unmilked ones.
Factors like the amount of total venom present in the scorpion's
venom glands at that moment and the perceived level of threat to
the scorpion, can influence the released venom volumes. In this
study the level of threat was manipulated in order to test its
influence on the volume of released venom. Hadrurus
arizonensis, was the species chosen for the experiment. Two
hypothesis where formed. The first one defends that scorpions
are able to meter the amount of venom they expel. The second one
states that larger quantities of venom are expected to be
released by the scorpions, as the level of threat increases. Our
results show that during ten consecutive attacks to which
scorpions were exposed in rapid succesion, venom volume released
on each attack is being controlled by the scorpion, changing the
amount of released venom between the attacks. Overall, the
amount of venom released on consecutive attacks decreases, but
there is high inter-individual variability. The number of dry
stings, where no venom is released whatsoever, increases with
the number of consecutive threats, and also varies by
individual. By the end, we did accept the first hypothesis, and
reject the second one. |
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