A focus-stacked echidna.

And now or something quite different - a focus-stacked photograph of the rear end of a Tasmanian spiny ant-eater, or echidna! The echidna is lying flat on his back with his hind legs in the air. Besides the formidable array of spines there are a couple of other interesting (at least to me!) things to see.

Spiny ant-eaters are monotremes, mammals that lay eggs instead of giving birth to live young as do marsupials and placental mammals. The only surviving monotremes are found Australia and New Guinea and consist of the duck-billed platypus and four species of spiny-anteaters. The word monotreme comes from the Greek μονός, monos, meaning single, and τρῆμα, trema, meaning hole. The name derives from the fact that their urinary, defaecatory, and reproductive systems all open into a single opening, called the cloaca. You can see the cloaca in the photograph as a slit like structure, central and towards the top.

The second interesting structure is the spur that you can see at the base of the right leg, the leg on the left in the photograph. Monotreme legs bear a spur on both ankles; the spur is non-functional in echidnas, but contains a powerful venom in the male platypus.

My short-nosed spiny ant-eater is of course, stuffed. He came from Tasmania and probably dates from the second half of the nineteenth century. I bought him in 1964 from a dealer operating from a converted bus in a lay-by near to the village Durness in northern Scotland. It was offered for sale as a hedgehog with a price-tag of £1. However, the dealer was easily persuaded that it was a very badly stuffed hedgehog indeed and he reduced his price to 12s 6d!

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