April 30, 2014 | 3
Spiders and I have a tortured relationship. I know they play a crucial role in their respective ecosystems, and they hunt mosquitos and cockroaches in and around my house. And I know that most of them aren’t aggressive and that you’d have to be really, really unlucky to get bitten by one. But I also live in the city after which this guy was named, so irrational or not, my fear of spiders isn’t going anywhere soon.
But comical cartwheeling spiders do help, if only a little bit.
In the latest edition of ZooTaxa, Peter Jäger from the Senckenberg Research Institute in Frankfurt, Germany describes a new species of spider native to the Erg Chebbi desert of southeastern Morocco. Named Cebrennus rechenbergi, its genus contains 13 known species, most of which are found in the arid region that stretches from Morocco to Turkmenistan. These desert spiders are nocturnal and elusive, spending most of their time hidden under rocks or buried in their long, silken burrows, which means there’s very little known about their biology or ecology. But what we do know, thanks to Jäger’s recent observations, is that one of them is an expert ‘flic-flacker’.
One of the strangest defense mechanisms ever observed in nature, flic-flacking, as it’s known in the scientific literature, is essentially cartwheeling to avoid danger. It’s been observed in a handful of animals around the world, including the larvae of the southeastern beach tiger beetle (Cicindela dorsalis), the American mantis shrimp (Nannosquilla decemspinosa) and caterpillars of the moth species Pleurotya ruralis and Cacoecimorpha pronubana. And then there’s the golden wheel spider (Carparachne aureoflava), which you can read about in one of my earlier blog posts here.
Native to the steep sand dunes of the Namib Desert in Southern Africa, the golden wheel spider is a small, cream-coloured species of huntsman. It lives in constant fear of the parasitic Pompilid wasp – a particularly nasty predator that goes to great lengths to snare its prey. To get at a golden wheel spider, a Pompilid wasp will sniff one out in its underground burrow, which can plunge 50 cm below the surface of the sand dunes, and shift up to 10 litres of sand to get at it. It will then paralyse the golden wheel spider by injecting it with venom, and drag it into another underground burrow it prepared earlier. Here the Pompilid wasp will lay a single egg in the spider’s abdomen before sealing it inside the burrow. When the egg hatches, the wasp larva will have an enormous supply of food waiting for it. Severely paralysed but not yet dead, the golden wheel spider will be eaten alive from the inside out.
So you can’t really blame the golden wheel spider for coming up with the world’s most ridiculous getaway plan to avoid literally the worst possible way to die. Using the steep slip-faces of the sand dunes to its advantage, an agitated golden wheel spider will curl its legs up around its body to make a ball and roll itself down the slope at speeds of up to one metre per second.
Until this week, the golden wheel spider and its close relative, Carparachne alba, were the only known species of spider to engage in cartwheeling behaviour. But now C. rechenbergi can be added to the list. According to Jäger, when disturbed, this spider will first turn around the threaten its agitator. If further provoked, it will cut its losses and run, and in about half the cases he witnessed, the fleeing spiders would curl themselves up and cartwheel themselves away. Most of the time the cartwheel was performed forwards, Jäger reports, but some spiders managed to do it backwards. It was performed on flat ground, on a downwards slope, and even in an uphill direction.
What separates the cartwheeling C. rechenbergi from the golden wheel spider is how much energy is required to perform the behaviour. While the golden wheel spider uses the slope of the hill to propel it away from its predators, C. rechenbergi does all the work to achieve its locomotion. And this can exhaust it so much, reports Jäger, that it can sometimes cartwheel itself to death. “In contrast to the wheeling behaviour in Carparachne aureoflava, it is an active energy-consuming movement, which can lead to the death of the individual when performed some times in succession.”
What remains a mystery is exactly what threat the C. rechenbergi spider is cartwheeling from when it’s not Jäger. Whatever it is, if it’s even half as terrifying as what the golden wheel spider has to deal with, maybe death by cartwheels isn’t so bad after all.