British Beasts | Football Jersey Worm
Nemerteans are commonly known as ribbon worms, because of their long, often compressed and featureless shape; or as proboscis worms, because of their interesting feeding apparatus. They are common in the sea but are often overlooked, as many are small, a dull brownish colour and relatively inconspicuous, though some are bright red or yellow. However, the football jersey worm, as its name suggests, has a handsome ‘strip’, the bright white stripes possibly a warning to potential predators that it contains toxins and might not taste good – like a stripy sea snake.
Their capacity for elongation is quite extraordinary. Find one end of a worm underwater and trace it back – you might find the other end a metre or two away, the worm stretched thinly across the sea bed. If disturbed, it can contract rapidly to a fraction of its expanded length, increasing its girth to compensate. Inside is a relatively simple blood system and gut running the length of the body, presumably also very elastic. Food is moved along the gut by small beating hairs (cilia) rather than by muscular contractions. It has no gills, but ‘breathes’ (exchange gases with the surrounding sea water) along its whole body.
The football jersey worm is carnivorous and eats mainly segmented worms, including the peacock fan worm (Sabella pavonina). I have never seen a football jersey worm actually capture a fan worm, so I’m not sure if they can make themselves thin enough to actually reach down the fan worm’s narrow tube, or just go for a fast tackle on the expanded feeding crown.
In the football jersey worm’s head, just above the mouth, is an inverted proboscis in a fluid-filled cavity. As soon as the worm senses prey at close quarters, it contracts muscles to increase the pressure in the fluid, and the proboscis shoots out, like an inverted finger blown out of a rubber glove. This proboscis has quite a kick, is sticky, and coils around the prey, drawing it towards the mouth. Toxins in nemertean tissues, some of them produced by bacteria, may help to subdue prey as well as deter predators. Football jersey worms will also eat detritus from the sea bed.
Nemertean worms have a remarkable capacity for regeneration, and, if nipped in two by a crab or other attacker, each half can grow into a new worm, genetically identical to the original. Football jersey worms have separate sexes, so there is no chance of an own goal (some worms are hermaphrodite, and can, in theory at least, fertilise themselves). Each worm has multiple ovaries or testes, and releases eggs and sperm into the water, the lucky ones producing a small swimming larva that drifts in the plankton to pastures new. No transfer fee involved!
Beast at a glance
FOOTBALL JERSEY WORM: Tubulanus annulatus, Tubulanus superbus
KNOWN HAUNTS: More common at sheltered sites.
BEST PLACE TO SEE: Both species occur all around Britain, but are less common in the east.
LIKELY TO APPEAR: Present all year.
DISTINGUISHING FEATURES: The smooth body of the football jersey worm has unmistakable colouring – striking white transverse rings and longitudinal stripes on a brown background. Sometimes the worms have a purplish tinge. There are two very similar species in British waters: Tubulanus annulatus has around 50 rings and three longitudinal stripes, one on each side and one along the back, while Tubulanus superbus is slightly larger, with up to 200 rings and an extra longitudinal stripe along the underside.
SIZE: These worms are extremely ‘stretchy’, and length measurements are rather meaningless. When contracted, the football jersey worm may be about 30cm long and 5–6mm wide, but can stretch to well over a metre long and only 3mm wide. The related bootlace worm, Lineus longissimus, also common on our shores, is the longest worm so far discovered and is reported to reach lengths of more than 30m.