30 August 2010

Photo essay: Jellyfish – ancient ocean drifters

Helen Lockhart and Ingrid Sinclair
Photo courtesy KimNowacki

In the open oceans, some 2 000 species of jellies pulsate with life as they drift with the ocean currents. The variety of designs and the luminescent colours of these otherworldly creatures will astound even the most fertile of imaginations. The blue jellyfish, pictured above, is not always blue – but its long tentacles differentiates it from its family member, the moon jelly.

Photo courtesy Natascha Spargo

It is said that some of the weird futuristic designs of space ships seen in science fiction movies are inspired by the body structures of jellies. Simple in form and of fragile make-up, these animals have survived some 650 million years on this watery planet with little change to their lifestyles or forms. Moon jellyfish (pictured above), which can be seen at the Oceans of Contrast: Atlantic Ocean Gallery, have short tentacles that are armed with stinging cells – fortunately their sting lacks the toxic, painful punch of other jellies.

Photo courtesy Ottie

Jellies move gracefully through their tranquil environment. Some time is spent simply drifting with the ocean currents, but they do actually swim by contracting the muscles on the rim of the bell or “umbrella”. The movement resembles that of an umbrella being opened and closed very slowly. These box jellyfish, which are often encountered in swarms by scuba divers, are a real treat to watch at the Oceans of Contrast: Atlantic Ocean Gallery and visitors often stand in awe in front of the exhibit for many, many minutes.

Photo courtesy Sivan Miller

Jellies don’t have any specialised organs for respiration, so they have neither lungs nor gills. It can almost be said that jellies breathe with their entire bodies through osmosis. The walls of the body and tentacles are so thin that oxygen and carbon dioxide can easily pass through. The senses in jellies are fairly limited, but they make adequate use of their tentacles as touch receptors. This gorgeous image of a blue jellyfish shows how thin their bodies really are.

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