As we approach Christmas I wanted to write about a marine animal with a festive link and what better than the humble starfish, an iconic symbol of the sea?
Starfish belong to a strange group of animals that includes sea urchins and sea cucumbers, all animals without eyes or even a head!
They are Echinoderms meaning spiny-skinned. Starfish normally have 5 arms but some British species can have up to 14, and they have some remarkable characteristics. Having no ‘front end’ they can move in any direction, leading with any of their arms without having to turn round. They glide over the sea floor using an army of tube feet on their underside. These are hydraulically operated, often with little suckers on the end to enable vertical movement over rock faces. But they can have a more macabre function too. Some starfish feed on shellfish such as mussels and clams using their tube feet to pull open the two halves of the shell with a force equivalent to 5kg. As soon as a tiny opening appears the starfish inserts its stomach through the crack and starts to digest the mollusc inside, at which point the fight is over. When digestion is complete the stomach is re-swallowed.
Another trick up the starfish’s spiny sleeve is its ability to re-grow lost arms.
Individuals can often be seen with various sized arms as new ones grow. In fact a whole starfish can regenerate from a single arm as long as it still has part of the central body. Any slow-moving animal in the sea is prone to having other life attach and grow on its surface but the starfish deals with this in an unusual way. Between its spines, which aren’t necessarily long or sharp, are special structures called pedicellariae. Through a magnifier they look like a miniature pair of jaws on a stalk and will grip and kill anything trying to settle within their reach, thus keeping the starfish clean of unwanted hitch-hikers.
Marine curiosities are collected around the world for jewellery, souvenirs and ornaments, often with little understanding of the impact this harvesting has on the ecosystem.
Globally there is a huge trade selling a wide range of animals including turtles, corals, shark jaws and sea shells. Because of their tough spiny skins starfish retain their shape and structure when dried, making them ideal as decorations in the home. Dried tropical starfish are commonly found in gift shops and gift packs in the UK with no explanation of how they were caught. They have even been used on top of Christmas trees. While some animals are taken as a by-product of fishing or by small-scale collection from beach strandlines, many live animals are deliberately taken and this can result in declining populations and local extinctions. Removal of key species can upset the balance of an ecosystem with severe knock-on effects for other species.
At this festive time of year spare a thought for the starfish, inhabitant of rockpools, mussel beds and sea-floors throughout our British seas, and symbol of the outstanding marine wildlife we are blessed with.
Marine Awareness Officer
Dorset Wildlife Trust
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Working for a secure future for Dorset’s wildlife enriching the quality of life
Dorset Wildlife Trust is part of the Natural Weymouth and Portland Partnership; connecting people with nature.
Dorset Wildlife Trust works to champion wildlife and natural places, to engage and inspire people and to promote sustainable living. Founded in 1961, DWT is now the largest voluntary nature conservation organisation in Dorset, with over 25,000 members and over 40 nature reserves. Most are open daily and there are visitor centres providing a wealth of wildlife information at Brooklands Farm, Lorton Meadows, Kingcombe Meadows and Brownsea Island Nature Reserves, The Purbeck Marine Wildlife Reserve and the Urban Wildlife Centre at Upton Heath Nature Reserve. DWT plays a key role in dealing with local environmental issues and leads the way in establishing the practices of sustainable development and engaging new audiences in conservation, particularly in the urban areas.