Tuesday 20 August 2019

Dinoflagellates a fascinating group of life forms

The sea turns an orangey-red colour during a red tide.
The sea turns an orangey-red colour during a red tide.

By Jim Hurley - Nature Trail

Dinoflagellates is not a word you hear every day of the week. In fact, many people probably get through their entire lives without ever coming in contact with the word. Yet, the dinoflagellates are a large group of over 2,000 life forms that we share the planet with.

The reason most people are not aware of them is that they are all microscopic in size. Before the microscope was invented in the late sixteenth century, nobody was aware that dinoflagellates existed. It was not until the nineteenth century that microscopes became powerful enough to name individual species.

We now know that when dinoflagellates occur in vast numbers in the sea that some species can stain the water an orangey-red resulting in the rare phenomenon known as a red tide. Other species cause the equally rare phenomenon of bioluminescence. In the past people could not explain red tides or strange blue lights seen flickering in the sea at night.

All dinoflagellates live in water with more occurring in seawater that in freshwater. Some colonise sea-ice and some even survive in snow. In water, they get lumped in under the umbrella term plankton. Plankton literally means the drifting life as opposed to the creatures that swim. Planktonic creatures cannot swim and are carried about by currents, tides and other moments in the watery world that inhabit.

We are all used to the terms 'plant' and 'animal' and the differences between them are immediately apparent as, for example, the clear distinction between a cow and the grass she grazes on. Dinoflagellates are not as clear cut in that they cannot be immediately pigeonholed as plant or animal. Some of them make their own food like plants. Others hunt and eat prey like animals. Yet others are parasites. These life forms challenge us to re-examine our simple 'plant' and 'animal' classification system.

Some of them also defy the definition that holds that planktonic creatures don't swim in that they have whip-like appendages that they use to move upwards and downwards. Some even have light-sensitive spots that tell them where the sun is. One species has such a sophisticated light-sensitive spot that it is credited with having the simplest eye known to science.

All in all, dinoflagellates are a fascinating group of life forms born like Thomas Gray's flowers to blush unseen but unlike Thomas Gray's flowers they certainly do not exist to waste their sweetness on the desert air.

Wexford People

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