Newborn scorpions hitch a ride on their mother’s back for protection, and at this early stage in their lives cannot eat, excrete or sting. But scientists have found that they still accumulate venom, enabling them to catch prey and defend themselves as soon as they go it alone after shedding their first exoskeleton.
Such speedy development of venom production helps to explain scorpions’ remarkable survival ability since their ancient aquatic ancestors swam the seas more than 400 million years ago, surviving even mass extinction events, say the researchers behind the finding.
at Wuhan University in China and his colleagues studied two-day old Chinese scorpions (Mesobuthus martensii), which are translucent and still embryo-like, and found they already had venom stored in the end of their tail, or telson. However, their stinger was blunt and venom exit ducts were blocked, enabling the toxin to pool inside the tail.
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“It makes sense that they start producing venom so early. It takes a lot of energy and some days to fill venom glands,” says evolutionary biologist at the University of Porto, Portugal, who wasn’t involved in the study. “I imagine the venom gland cells will start producing venom as soon as they are fully [developed].”
Li and his colleagues peeled off the outer layer on telson samples with tweezers and observed the sharp stinger had already formed beneath. This would ordinarily be revealed when scorpions naturally moult for the first time around 10 to 20 days after birth, enabling them to inject venom.
The scientists also looked at telsons in older, more developed scorpions – which use muscle contractions to control venom release – and found that these animals don’t have blocked venom ducts. This suggests that newborns haven’t yet developed the required muscular control of their venom and so their ducts are initially blocked to prevent venom loss, say the researchers.
Since a newborn scorpion’s orifices, including the mouth and anus, are all closed before their first moult, van der Meijden suggests a further advantage. “Keeping unneeded orifices closed until they are needed will allow a longer time for their tissues to develop, and perhaps even protect from [entry] of dirt or pathogens.”
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