Expedition log by Graduate Student Collaborator Ethan Kahn, Yale University

I’m a new graduate student in the Dunn Lab at Yale University, where we are interested in the biology and evolution of siphonophores, a group of long, slender jellies. In the past couple of months, I’ve read a lot about these animals, but because they mostly live far from shore in the open ocean, I had never seen one in person. Being invited to join an MBARI expedition on R/V David Packard has been an incredible chance for me to encounter live siphonophores and learn about their anatomy, taxonomy, behavior, and environments.

My first challenge: figuring out what in the world I’m looking at. Siphonophores have many specialized body units, called zooids, which are connected by a linear stem. Multi-zooid siphonophores evolved from ancestral solitary forms, and within the siphonophore, each individual zooid functions like an organ, specialized to help the animal swim, feed, defend itself, or reproduce. These zooids are often densely packed on the stem, and it takes a microscope plus a specialized eye to distinguish the various bumps and growths and recognize their functions. As I encounter specimens, I am preserving tissues for research—some samples will provide crucial data for ongoing projects, while others will be deposited in a natural history museum collection as a permanent record of the biodiversity we encountered on this expedition. 

Using MBARI’s remotely operated vehicle (ROV) Doc Ricketts, we’re able to collect deep-sea siphonophores that live hundreds or even thousands of meters underwater. After a full day of exploring, Doc Ricketts returns to the ship in the evening, and then my work can really begin. I scoop and ladle the delicate jellies into a photo tank, keeping them submerged at all times. Any time out of the water can introduce air bubbles or cause the temperamental animals to fragment. After photographing the full body, I look at each siphonophore under a dissecting microscope, where I can view each zooid individually, tracing ridges and noting colony arrangements that help identify each species. Some days, I work into the wee hours of the morning, while on others I only have a couple of specimens to process and can turn in by 10:00 p.m., but either way I’m up early the next day to watch the ROV dive back into the near-freezing ocean depths.

It is especially cool to see how our knowledge is constantly expanding. For example, a new study coauthored by MBARI Senior Scientist Steve Haddock and members of my lab at Yale described two new siphonophore species in the genus Bargmannia, which we have been able to see on this cruise. This publication came out just in time to help me identify specimens that can provide important data for future phylogenetic and biochemical studies on these now-distinct species. Our expedition opens a small window into a strange and vast world, and I’m grateful to be along for the ride, witnessing and documenting an ecosystem that is too alien and too beautiful to be found anywhere else in the known universe.