It’s the shuddery stuff of nightmares for some, but for a select group who admire extending ladders, giraffes and the Odyssey, one of the longest animals in the world is bound to appeal.This creature is nneither the blue whale, nor a lion’s mane jellyfish but the humble bootlace worm, Lineus longissimus, one of the most remarkable marine invertebrates of them all.It can stretch out longer than an Olympic swimming pool. In fact, one worm, found washed ashore after a storm at St Andrews, was recorded at an incredible 55 metres in length. Worm-sceptics suggest it may have been stretched out, because the species is also very elastic. A more usual length is a mere 15 metres. Its width is just 5–10mm.When threatened, the bootlace worm discharges a poisonous mucus. Photograph: Nature Photographers Ltd/AlamyThis slender, super-long superworm has a second superpower: it can fire toxic slime. When threatened, the blackish-brown bootlace worm discharges a poisonous mucus which may remind you of the smell of sewage if you pick up a beached worm.Although the Swedish archbishop and naturalist Olaus Magnus first noted its toxic slime back in 1555, it wasn’t until 2018 that the worm’s toxins were fully described by (Swedish) scientists. Its mucus was designed to paralyse and kill crabs.Researchers have discovered the toxins, known as alpha-nemertides, can also kill cockroaches but have little impact on mammals, leading to the possibility that they could be the basis for new insecticides. There are likely to be many more useful chemicals and medicines still to be discovered within the invertebrate world.The bootlace worm is one of many little-known nemerteans – ribbon or proboscis worms. The phylum contains more than 1,250 described species of worms which are found everywhere from intertidal zones to great ocean depths – a little-heralded but rich and vital branch of the tree of life.This record-breaking and yet rather overlooked worm is a voracious and extremely effective predator, enjoying nothing more than swallowing annelids (soft-bodied, segmented worms) whole. It was nominated by a reader who says it is “a neglected but quite amazing branch on the tree of life. The longest of all wormy creatures (up to 15m?!) and only a few mm wide.” He loves “a worm that can stretch and stretch and stretch” and argues that it is one of the “many amazing creatures contributing to Britain’s coastal heritage”.skip past newsletter promotionSign up to Down to EarthThe planet’s most important stories. Get all the week’s environment news – the good, the bad and the essentialafter newsletter promotionLong, slimy and lethal – what’s not to love? Vote bootlace worm!
It’s invertebrate of the year again! From 3-12 August, every day we will profile one of the thousands of amazing invertebrates that our readers have nominated. And then, when you’ve heard about all of them, we’ll open the voting so you can choose your favourites. Don’t hesitate to get in touch with thoughts and ideas: email us at environment.desk@theguardian.com with Invertebrate in the subject line.