Thursday, April 15, 2010

Water Walking Animal

Anurida maritima

The intertidal area of the shoreline is subject to high intensity of wave action, with the result that many of the flora and fauna present have had to adapt to this often harsh environment. Molluscs and arthropods present have tough, durable shells (e.g. mussels, whelks, sea slaters) and/or cling tightly to the rocks (e.g. limpets, barnacles) while algae present is tightly bound to the rock by holdfasts. Even the seemingly soft bodied anemones have a strong attachment to the rock via their pedal discs.

It is therefore quite surprising to find an animal in quite abundance that has neither of these attributes. Anurida maritima is a small (c. 3 mm), blue coloured springtail (Collembola) that scavanges for dead or dying matter in the intertidal zone. Interestingly, it cannot hypo-regulate its ionic concentration in water with less than 50% salt water, meaning it cannot survive in fresh water conditions. Collembolans are of terrestrial origin, meaning A. maritima is an amazing example of an animal of terrestrial origin that has become physiologically tied to a saline environment (Witteveen et al. 1987 Journal of Insect Physiology 33 pp. 59-66).

What is even more startling about A. maritima is its ability to walk on water. Its body is covered in hydrophobic hairs that allow it to walk with some ease across intertidal pools in search of food.

Anurida maritima walking on water

Anurida maritima walking on water

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