Invertebrate Distractions

The major goal of the IcyInverts team on this cruise is to collect specimens of cumaceans and other peracarid crustaceans for two National Science Foundation-funded projects (see: here and here for details). However, given the expense and effort it takes to sample in Antarctica, we try to preserve specimens of as many of the organisms that come up in our nets as possible. Another group my lab studies is the worm-like aplacophoran mollusks (see previous IcyInverts blog posts about this group from our 2023 and 2020 cruises and a video on why we study these animals). When not photographing and processing peracarid samples, aplacophorans have been another major focus of mine. Today's post is about a different invertebrate distraction, though.

One really exciting thing that happened was the collection of dozens of colonies of the pterobranch hemichordate Cephalodiscus hodgsoni. Check out a blog post by Mike Tassia from our 2020 cruise to learn more about these weird animals here. Pterobranch hemichordates are fascinating because they offer a unique glimpse into early deuterostome evolution. These small, colonial, tube-dwelling animals are relatives of acorn worms and share features with both echinoderms and chordates, making them key to understanding our own evolutionary history. Despite their significance, pterobranchs remain poorly known, with many species yet to be described and their biology still largely mysterious. Their unusual body plan, suspension-feeding lifestyle, and rarity in collections make them especially intriguing to evolutionary biologists and invertebrate zoologists.

I was really excited to see so many colonies come up in the dredge and rushed nearly half a 5-gallon bucket of colonies inside to get them into cold water. The colonies were *teeming* with animals! Below are some photos and details on how I isolated zooids (individuals from the colony) and preserved them for future studies. We're pretty busy just sampling the peracarids but this was an exciting find, if a distraction.

You never know what you'll find in Antarctica!

Dr. Kevin Kocot
University of Alabama