Observations: Pyrosomes and Squid Eggs

Pyrosome from Pantar blennywatcher
What was this mysterious tube floating by?

Today on Blennywatcher, I’m sharing images of two things that are not related, but caused us some confusion a few years ago. In Beangabang Bay, Indonesia, Ned and I encountered what we were certain was a very large squid egg case. It turned out not to be so, but at that moment we were certain that was what we had. It was long and tubular, similar in color and shape to the Diamond Squid egg case we’d seen in photos.

Ned DeLoach and pyrosome
It was a pyrosome, a colonial tunicate!

We videotaped and photographed it and returned to the boat, beside ourselves with excitement. But as we reviewed the video and started discussing it, we became less and less convinced. For example, it was firm to the touch – more like a plastic bathtub toy; definitely not like the soft squid eggs of smaller species that we knew. Also, it seemed to move on its own, like it had some internal propulsion system; that didn’t seem likely for eggs. Back home, a few minutes of searching revealed that what we observed was a pyrosome, a colonial tunicate made up of many individuals called zooids that form a tube with their joined bodies. Each individual takes in water, extracting plankton for food and expelling the water into the tube. The water flowing out the open end of the tube creates a sort of jet propulsion. So, while we hadn’t captured images of eggs of some sort of giant squid, we had in fact observed something rarely seen by divers.

A couple of months ago in Bali, we saw what looked more like the squid egg mass – it was tubular, purplish red and floating, but other than that really didn’t look much like the pyrosome. It occurred to me that unlike the finger-sized egg capsules of the much smaller reef squid, there were no visible embryos in the large egg mass. Back home, I found this paper about Diamond Squid egg masses that includes photos, so we have an idea of just how tiny the hatchlings are (and they are cute). So I think, this time, we did see a real squid egg mass.

Now that we have seen both in person, the differences are obvious! For comparison, here is video with both the pyrosome and what we think is a Diamond Squid egg mass: