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The Ear-like Shell of Abalone

© Esther Wullschleger

A snail with quite an unusual shell is the abalone: Its shell has a form similar like a human ear, because the last whirl is always much extended, compared to the previous ones, and grows into a longish form. One species is appropriately called ass's ear abalone (Haliotis asinina) obviously, it is long enough to resemble a donkey's ear. Even more extraordinarily, the last whirl of abalone shells has a row of little holes in it. There is not much known about the origin of these holes, but the snails seem to use the front most holes to put tentacles through them, and the older ones to get rid of their waste water.

Like the limpets (Patellidae), abalones (Haliotidae) belong to the Order of Diotocardia or Archaeogastropoda, which is the group of the most primitive snails that occur today. What is unusual among contemporary gastropods: These primeval snails still have mother-of-pearl as an inner structure of their shells. This, together with their reputation of being ancient and something particular, certainly makes the shells of some species attractive to collectors.

On the inside of the shell, most abalone species have a glossy layer of mother-of-pearl in a variety of colors. Also from the outside, some of these shells look quite decent, at least, if the outermost layer is removed. Abalone shells may reach lengths up to 20 centimetres. They are well demanded, but not extremely expensive, since there are abalone species that do still occur commonly. If buying an abalone shell, it is important to make sure that it stems from a common species, as with every shell in commercial trade.

Luckily, abalones aren't as much demanded as their less lucky relative of the genus Pleurotomaria: a cone-like shell that got the nickname "millionaire's snail", because it was traded at extraordinarily high prices. The snail itself lives at depths around 100 to 3000 metres, and it is unknown how common it actually is, since some locations where it was found seem to be kept secret.

There are about one hundred abalone species, which occur around the world, mainly though in the Southwestern Pacific (around Japan and Australia), at the Southern African and the Californian coast. They are inhabitants of the upper coast and lower tidal zone, where they attach firmly on stony ground with their extraordinarily muscular foot, and live from grazing algae.

Abalone are also collected for their meat, and at least some Californian species have been severely decimated, so that the American abalone fishing industry today is controlled by the State. The California Department of Fish and Game warns that abalone is easily over fished, because they have a slow growth rate and a high mortality of small animals. Abalone is also vulnerable to fishery-related injuries, and they need high densities for a successful reproduction.