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10 Reasons to Love Slugs
Who are these slimy gastropods that have been gliding across Earth since before the Ice Age? Slugs may look like little more than shell-less snails leaving a mucus trail everywhere they go, but thereâs more to them than meets the eye. There are over 2,000 species of terrestrial and marine slugs (including nudibranchs, sea hares, and the out-of-this-world Elysia chlorotica). This peculiar group has evolved an astonishing array of survival strategies, superpowers, and oddities. They may take a second to arrive and tell you all about themselves. So, in the meantime, here is a list of some of their most impressive qualities.
Theyâre blue-blooded, kinda
Instead of blood, slugs and some other invertebrates have a body fluid known as hemolymph, which is not contained in vessels, but floats around all the organs. In some species, this fluid is blue because copperânot iron, as in humansâis used to carry oxygen throughout the body. Besides the regal sea goddess nudibranch (Felimare picta), however, most slugs are not royal, despite their blue âblood.â
Slugs reduce, reuse, recycle
An essential part of the ecosystems they inhabit, most terrestrial slugs clean and feed on decaying organic material such as dead leaves, animal feces, and moss. They send nutrients back into the carbon and nitrogen cycles. Theyâre so good at recycling that theyâve even been known to eat a dead friend here or thereâŠthose tree-hugging cannibals!
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Their relationship status? Itâs complicated.
Virtually all terrestrial and marine slugs are simultaneous hermaphrodites, meaning they have both female and male reproductive organs throughout their lives. Some can mate with themselves, but many also engage in relations with one another. Certain terrestrial slugs, such as the leopard slug (Limax maximus), do so while dangling from trees, stabbing one another in the process. Nudibranchs often have a less violent coexchange of sperm, though some engage in phallic fights to see who gets to impregnate whom. Depending on the species, a slug can have as many as 90,000 offspring in its lifetime. Thank goodness they do not need to pay university tuition.
They have all-seeing, all-smelling tentacles
Terrestrial slugs have four tentacles: two that serve as eyestalks and two used for smelling. They leave trails with their scent behind so they can find their way back home, like a sluggy Hansel and Gretel. (Only the witches in their story are the beetles, frogs, owls, foxes, toads, and slow worms anxious to gobble them up.) And in case you were wondering, the hole through which they poo is often not that far from their smelling tentacles. Unfortunate, indeed.
Theyâre tasty...?
Adventurous chefs at Californiaâs Russian River banana slug festival once served slug-based dishes to curious diners. Not that you would normally, but please donât eat slugs; most slugs are best appreciated from a distance. Land slugs can carry rat lungworm, a parasite that can cause serious neurological disease in humans, and many sea slugs contain defensive toxins acquired from their prey. Between the potential parasites, the toxins, and the thousands of tiny teeth packed into a slugâs mouth, weâll be skipping the tasting menu. Check, please!
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Theyâre oracles of jelly
Some slugs can predict the near future. If you find a land slug sealing itself in a moist, protective mucus sac, it is in a state of estivationâyou can expect dry weather conditions from here on out. Similarly prophetic, lemon slugs (Malacolimax tenellus) will come out of their underground fungal networks (where they spend 95 percent of their time) only when woodland fungi are fruiting.
Slime is their superpower
Super slime does it all. The slimy mucus of terrestrial slugs keeps them hydrated, lets them gliiiiddeee, cleans them, and tracks their path. The slime of some species also numbs an attackerâs tongue, protecting them from predators. BAM! POW! WHOOOOOSH!
Their heads will roll
Imagine you are a sea slug, stuck somewhere and you canât wriggle out. Or youâve been infected with parasites. Or a predator is about to eat you whole! What do you do?
Well, if youâre a sacoglossan sea slug or an Elysia marginata sea slug, you might try a little self-amputation process called autotomy. In an emergency these slugs can chop off their own head and ditch their body. Their hearts and parapodia (appendages for swimming and crawling) regenerate, and in 17 days the slugs are good as new. Kids, donât try this at home.
Theyâre the muses of great inventions
These remarkable (and sometimes terrifying) abilities of slugs have not gone unnoticed by scientists and inventors. Biomimicked medical glue, inspired by the slime of a common garden slug (Arion subfuscus), can bond to bloody tissue and holds great promise for surgical applications and the treatment of painful lesions. Similarly, banana slugs in the California redwood forest have inspired experimental water-regulating architecture. Sluglike movement holds promise in robots as well. Sluglike...robots...coming...your...way...
Slugs are natureâs reminder to slow down
Have you ever stopped to marvel at a slug? When you look at one for long enough, you begin to experience life at the pace and wonder of one. (Even the Usain Bolt of slugs, Deroceras invadens, moves at a tedious 29 cm [12 inches] per minute.) Next time you see one, donât step on it; take a deep breath instead. Let it serve as a reminder to slow down, even if just for a little bit. Who knows what else youâll notice?