Above: Seawash Ball © Julie Hatcher
Below: Grey Triggerfish © Paul Parsons, Pink sea fan © Mike Markey
Seawash balls, so named because sailors once used them to wash with, are the egg cases of common whelks. Washed up on the beach it may appear like a lump of bubble wrap but is actually hundreds of egg capsules bunched together. The female whelk attaches up to 2000 of these capsules to rocks and other hard surfaces and it is several months before the young snails hatch. Some especially large egg masses may have been deposited by several females which laid them together. Each capsule contains around 1000 eggs! However the vast majority of these young whelks will never fully develop and will be eaten by their brothers and sisters. This source of energy gives the lucky few young that survive, around 10-15 per capsule, the best possible start in life. At this time of year the young are still developing inside their capsules so there may be a colour variation in the seawash balls you find washed up on the shore. Greyish masses are old empty shells where all the young have already crawled out, whereas yellow ones may have been ripped from the rocks in stormy weather and probably still have some eggs inside.
Those lucky enough to visit tropical coral reefs may be familiar with a family of fish called triggerfish. Triggerfish get their name from an unusual adapatation they have to help them evade predators. Their front dorsal fin is formed by three spines which can be held erect but are normally laid flat inside a groove along the fish’s back. The first spine can be locked into place and enables the fish, which is very narrow in shape, to wedge itself into narrow cracks and crevices in the reef, safe from the grasping jaws of predators.There are around 40 different varieties around the world and one of these species can be found here in Dorset the grey triggerfish (Balistes capriscus).
Over the last 20 years increasing numbers of this visitor have turned up in late summer, living in shoals through the autumn months, around wrecks, piers and rocky outcrops. On some ship wrecks they can be reliably found at this time of year by divers and anglers, such as the wreck of the Adelaide off Chesil Beach. However, although a few may survive the chilly sea temperatures of a mild winter, most perish and their bodies can often be found washed up on the strandline at this time of year.
Pink seafan skeletons
Pink seafans are an exotic looking coral that are found just off the Dorset coast. Although they look plant-like they are actually a colony of tiny animals called polyps that appear similar to anemones. They are highly branched and their colour comes from pigments within the polyps: ranging from white to a deep orangey-pink. Growing perpendicular to fairly strong currents, they use their stinging tentacles to catch microscopic particles of food that are swept by. Pink seafans can grow up to 100cm wide and live for up to 50 years! These extremely slow growing corals are vulnerable to damage, especially from mobile fishing gear such as beam trawling and scallop dredging. You can find them washed up on beaches after storms. Ones that have broken off fairly recently are normally white in colour as they have a chalky calcium carbonate layer with lots of small warty lumps which the polyps live in. More weathered seafan skeletons are brown and look just like twigs, because the chalky layer has been removed- this core structure is made of a flexible protein called gorgonin.