This week in lab we went to Pacific Spirit Park in search of terrestrial isopods (AKA Sowbugs or Pillbugs). The goal: to compare the number of isopods found on top of logs to the number found underneath the logs. After flipping each log, my lab partner and I would spend ten minutes or so pouring unrequited love and praise onto the disgruntled invertebrates. Among them were isopods, termites, spiders, bright red centipedes, millipedes, and a small bundle of eggs. My attention was immediately diverted to the eggs.
They looked like little shiny pearls, about 5mm in diameter, clear, gelatinous, and perfectly round. A gelatinous egg like this could belong to a fish, an amphibian, or an invertebrate. Using my post-secondary expertise, I concluded the eggs were not likely from a fish. The only amphibians capable of laying eggs on land are from family “Plethodontidae”, or the lungless salamanders. Lungless salamanders can lay their eggs on land because their young are born as tiny salamanders, rather than water-dwelling tadpoles. I looked up a list B.C. salamanders from the B.C. Frogwatch website and found no lungless salamanders whose habitat or range matched the location of our eggs. So these eggs must have been from an invertebrate!
So what invertebrate could possibly lay such large eggs? Here are some clues:
- B.C. is home to the world’s second largest species of this animal.
- Known for their kinky sex lives, these hermaphrodites are notorious for their tendency to commit “apophalation”, which means biting off someone’s penis. Also, their genitalia come out of their head.
- Some species are known to produce a small amount of neurotoxin, just enough so that if you lick them, your tongue goes numb!
You guessed it, the slug! B.C.’s temperate rainforests are the perfect habitat for a variety of slug species. The three most common species are the Leopard Slug (Limax maximus), the European Black Slug (Arion Ater) and the Pacific Banana Slug (Ariolimax Columbianus). The latter two species are introduced from Europe, but have become extremely common in B.C. Only the Banana slug is native, and it is the second largest slug in the world after the European Black Keel-Back Slug (Limax cinereoniger). If you’re an adventurous type, you might want to try licking a banana slug, the mild toxin they excrete gives the tongue a tingling numbness. Just don’t lick its head; those weird genitals I mentioned are real.
As for the eggs, I eliminated the possibility of them coming from a banana slug because their eggs are oval-shaped, whereas our eggs were perfectly round. Unfortunately this is as far as I got. I couldn’t find much on the difference between black slug and leopard slug eggs, but based on the pictures I saw online, my best guess is that these eggs are from a leopard slug.You can check out slug factsheets with this Terrestrial Mollusk Tool and decide for yourself!