ISLAND CONSERVATION-The first time can be enough for scorpions |25 August 2008

I peered at her where she crouched under a concave piece of bark in the glass terrarium where I keep her. I felt disappointed that I had missed seeing her give birth during the night. She would have raised the front part of her body and held out her claws and first two pairs of legs below her to catch the babies as they emerged one by one. They would then have climbed up her legs and claws to settle on her back. I knew they would remain there for several days without feeding before shedding their “skin” or cuticle (a process called moulting) and finally dispersing.

Nothing particularly unusual in all that, though many people don’t know that scorpions don’t lay eggs but give birth to live young, and that the whole litter stays with the mother until after the first moult. What surprised me was that the female lesser brown scorpion (a gift from one of my nephews) was all alone in the terrarium – she didn’t have a mate – and yet this was the third time she had given birth!

There were only two possible explanations that I could think of. Perhaps the female of the lesser brown scorpion did not need to be inseminated by a male to be able to give birth.

This ability to reproduce by “parthenogenesis” exists among many animals, including the tiny blackish flowerpot snake, which in Seychelles is often mistaken for a worm or a caecilian – indeed, it appears that males of this snake do not exist at all! The other possible explanation was that the scorpion was one of those species able to store sperm – she could have mated before my nephew found her and used her sperm reserve to fertilise the eggs inside her body for all three broods.

I read later in a scientific paper by the renowned scorpion expert Wilson Lourenço of the Muséum National d’Histoire Naturelle in Paris that sperm storage is known to happen among females of a number of scorpion species, including the lesser brown scorpion. Again, this is something that is found among other animals as well, one of them being the barking gecko, which has spread rapidly around Mahé, Praslin and other granitic islands in recent years.

The ability to store sperm helps to explain why such animals are so widespread. In fact, the lesser brown scorpion is the most widespread species of scorpion in the world, being found all over the tropical and subtropical parts of Asia, Africa and America, as well as on islands from Seychelles to Hawaii. Obviously, once a female carrying sperm is introduced somewhere, it can reproduce without having to mate – the presence of males is not necessary.

Moreover, the lesser brown scorpion is able to thrive in habitats where humans are present.

I have found it among old papers inside a drawer in a house at Glacis as well as under the bark of casuarinas trees on Aldabra. Like some geckos, this is a species that must have been carried around the world in shipping (apparently it originated from south-east Asia).

How different from our two endemic scorpions – the tiny Brauer’s scorpion, that lives only in leaf litter in the high altitude mist forests, and the giant black scorpion, that now survives only on Frégate and in the Vallée de Mai on Praslin.

Oh, and in case you are worried about scorpion stings – I must stress that none of the scorpions found in Seychelles is dangerous. As I found out while handling my “pet” one, the lesser brown scorpion can deliver a sting no more painful than that of a honeybee. A bit of ice soon reduced the pain in my finger and within twenty-four hours I could hardly feel anything. I’m back to watching it lovingly, waiting to see if it will give birth to a fourth litter without the slightest need for a male…

by Pat Matyot