A brief foray into another type of invertebrate

This blog is pretty much about insects because that is what I am interested in and what I love taking photos of. However, we’ve recently had a pretty crazy experience involving another type of invertebrate, and it was just too weird not to put up here.

A little over a month ago, we got a salt water fish tank (clearly a dog, two cats, and 6 chickens is not enough pets). We got the tank on Craiglist from a person who didn’t have time anymore to deal with it. It was a fully set up  6-8 year old, 30 gal tank with two fish, two snails, a shrimp, lots of mushroom coral, a torch coral, and two smaller unidentified corals.

There was also about 10 lbs of live rock. Live rock, which it not actually alive, houses all sorts of tiny beneficial organisms that act as a biological filter in the tank. These days much live rock you might buy is made in ‘captivity’, meaning that it was not harvested from the ocean. But this did not used to be the case. Our tank had been set up with this rock 6-8 years ago, and it’s safe to say that this rock came from the ocean. How do I know that? Well, the rock was not the only thing from the ocean in the tank. And I am not talking about the fish, which I knew were there of course.


One night I happened to glance at the fish tank on my way out of the living room and saw a blur of motion that disappeared into a hole in the rock. I thought I’d seen legs and nothing in the tank should have had that many legs… so I got a flashlight and tried to look into the hole. I could just make out something that look kind of like shrimp antennae, but the shrimp was in a different part of the tank. After some internet research, I thought maybe we had a large bristle worm… but they don’t have antennae like appendages so I wasn’t convinced.

Every morning I’d creep into the living room to see if I could get a glimpse of the thing before it knew I was there. And eventually I did! It was, indeed, not a bristle worm. It looked like a large underwater centipede. SO MANY LEGS. Further internet research seemed to indicate that what we had was actually an Eunice aphroditois, also known as a bobbit worm. This realization was quickly followed by a plan to get it out of the tank before it started eating the fish and coral. And also the realization that I had TOUCHED it’s house when arranging the fish tank! I haven’t put my hand in the tank without gloves since.

Like many many ocean creatures, we don’t actually know all that much about E. aphroditois. The have been found in relatively shallow to somewhat deep water (10m to 40m). They are ambush predators that bury themselves in rock or sand. They sense fish and other prey with the five tentacles on their head (the things that I thought looked like antennae). They catch fish with their sharp jaws and drag them back into their burrow. Here is a cool, if somewhat overdone, video of it https://www.youtube.com/watch?v=5_bzyAlspNI (not one I took). The worm has a powerful bite and can cut fish in half. Some sources say that they can cause permanent paralysis to humans (I touched it’s house!). They are believed to be broadcast spawners, but no one is really sure about what the eggs look like or where they develop. Some scientists also believe that what we call E. aphroditois is actually a number of different species (differentiating species can be really really hard). This means that identifying its exactly behaviors and life cycle is even harder because there could be multiple species with different traits.

Removing a bobbit worm from a tank is hard. So we blocked out 6 hrs on Saturday evening for the challenge. Luckily some lovely friends wanted to join in the process, which certainly made it more fun. We put it’s rock in the a bucket of tank water in the dark basement because the worms only come out when it’s dark. We created a red light flashlight to use because the worms cannot see red light.


We started by trying to lure it out into a trap with shrimp bits. It came out about 4 inches but wouldn’t go into the trap. Then we tried to lure it into a lasso. It would go through the lasso and grab the shrimp bait but it was too fast to catch. Even if we had caught him, they are really hard to get out of their holes because they dig their back legs in. People have created very elaborate pulley systems to pull them out of their rock holes. That seemed impossible in our case. So we then resorted to our final option: break the rock apart with a chisel.


Somewhat amazingly we managed to keep it alive through out the process. We got it back into salt water in a Tupperware pretty quickly. Actually once it was partially exposed, we got it out by putting it’s head in the water. It then slithered out.


And then in full nature-nerd mode, we watched it for a while. Here is a video of it https://youtu.be/mjfVXKYw0W4.

It is pretty creepy (and very crawly!) but that’s kind of my style. It was a rainbowy shimmery color and had so so so many leg appendages. Really a very cool creature.


We might have kept the worm if we wanted a second tank (and it didn’t possibly cause permanent paralysis). But instead we gave it to the Denver aquarium. To me, it’s a reminder that there are so many animals/plants/organisms out there that we do not know much about. The world is an incredible place, and there is a lot of exploration left to do!



About keviclaire

I recently graduated from the Department of Environmental Science, Policy and Management at UC Berkeley. My research interests are focused on biological control and how to increase it's use in agriculture and home gardens. I am also an avid gardener and insect photographer. I'm using this blog as a place to share those interests!

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