LONG legs aren鈥檛 all they are cracked up to be 鈥� at least not if you鈥檙e a toad.
Cane toads are a hugely problematic invasive pest in Australia. Last year, a team led by Rick Shine of the University of Sydney found that the toads leading the invasion have evolved longer legs, enabling the front line to move three times as fast as in the early years of colonisation (New 杏吧原创, 18 February 2006, p 21).
Now it turns out those long legs come at a cost. When Shine and his colleagues dissected toads, they found that 10 per cent of the long-legged toads at the invasion front in the Northern Territory had severe spinal arthritis, with bony growths fusing some of their vertebrae. Smaller toads were not afflicted (Proceedings of the National Academy of Sciences, ). The worst-affected joints were towards the back end of the toad, suggesting that mechanical stress is part of the cause.
Advertisement
The bony growths were infected with a ubiquitous, and normally harmless, soil bacterium. One possibility is that the effort of hopping long distances starves the immune system of energy, so it operates below par, allowing the bacteria to take hold and cause disease.
鈥淭he fact that the toads at the front line are under stress is good news. It suggests that they might be vulnerable to other infectious agents that could be used to control them,鈥� Shine says.
