My two feline buddies bring me a never-ending supply of geckos. I frequently find tails and bodies separated, as tails can be shed for defence and regrown if escape is successful. However, I was surprised to find a lone tail that has two bifurcations. Can anyone explain this?
• Of all the lizard families, geckos rely most heavily on of the tail. In most species, muscular contractions break the tail at a plane of weakness passing through the middle of a vertebra, rather than between vertebrae. This produces a clean break and little bleeding. A papilla of tail-growing tissue then forms in the break and develops into a replacement, although it is visibly different to the original. Internally, the replacement spinal column is not formed of bony vertebrae, but a tube of cartilage.
It is complicated to grow such an elaborate organ with its properly organised skin, muscles, nerves and blood vessels, so if anything interferes with that papilla, things go wrong. For example, the tissue-organising process can lose coherence and produce two tails or even more.
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Another outcome is possible and seems to have happened twice in this specimen: a tail might break only part way through, after which a new tail may grow from each lesion. By examining the skin, one can tell what has happened; if both tines of the fork look the same, two new tails had grown after autotomy, otherwise an extra tail must have emerged from a partial break.
Jon Richfield, Somerset West, South Africa