PARK WATCH Article March 2025 |

Evan’s Sea Spider (Anoplodactylus evansi)

It might look like a spider, scuttle like a spider, and… well, maybe not quack like a spider – but sea spiders aren’t just underwater versions of their land-loving cousins. Sure, they’ve got eight legs and belong to the arthropod club (the largest animal phylum, named after their jointed legs – arthron meaning ‘joint’ and podos meaning ‘leg’). But that’s where the family resemblance ends. Sea spiders have been doing their own thing, evolution-wise, for at least 500 million years. Talk about a long-distance relative!

Here in Victoria, we’ve got a few species of sea spiders, but none get me as pumped as spotting an Evan’s. Half of my excitement is because they’re rare to find, and the other half? Well… I really want to witness one slurp on a sea slug. Morbid? Maybe. But watching any kind of predation in action is pretty cool.

Despite their tiny size (a mere 1 cm body with a 3 cm leg span), these little folks can feed on prey six times their size. How? They use their front-leg claws to grab hold of their victim, then whip out their proboscis to slurp up the internal soup. Delicious, right? They’re known to dine on at least 13 different types of sea slugs, but their favourite seems to be the sea hare Aplysia parvula.

So, if you ever spot one of these elusive hunters, do me a favour – let out a little squeal of excitement (optional but encouraged) and follow it! I’d love to see a photo of anything besides another sea slug munching on a sea slug… but hey, that’s a salty science story for another day.

Fun Fact: Evan’s Sea Spider has neither lungs nor a bum! Instead, they diffuse gases and wastes through their cuticle (skin), especially through their legs.

Kade Mills is ReefWatch Coordinator