Predator worms, spines with eyeballs, and a mystery
I’m Hannah Blair, a graduate student at Stony Brook University, aboard the NOAA Ship Henry Bigelow for the 2017 sea turtle and cetacean cruise. This trip is my first foray into the world of zooplankton identification. Each night, we sift through the contents of targeted zooplankton trawls, pull individual plankton out of each sample collected by the nets, and measure and photograph what we find. I’ve slowly been learning to recognize the categories these tiny animals belong to. For example, we pull up lots and lots of chaetognaths, or arrow worms, a group of predatory worms!
We find many kinds of gelatinous animals, such as jellyfish, as well as a number of crustaceans, like these adorable bug-eyed megalops, an early crab life stage.
We also find fish larvae of various sizes and shapes, from the wide and flat larvae of flounder to fish so small they look like spines with eyeballs. After going through a few hauls, you start to recognize what animal belongs with what category.
And then, this guy appeared:
The first time we saw it, we dismissed it as an unidentifiable piece of another animal. But then we got another, and another. When, on the third night, we got six in one haul, we had to stop and take a closer look.
As someone who’s spent many an hour identifying species, whether for classes or for surveys (or for fun), I am familiar with the frustration of not being able to figure out what species an animal or plant is, and the satisfaction of finally pinning it down. However, at first we couldn’t even determine what group of animals we should start narrowing down from! Was it a flatworm? Some type of echinoderm (starfish and relatives) larva?
After spending hours searching through identification keys and checking our trusty friend Google Images, our resident marine zooplankton expert Betsy Broughton was able to track it down. Meet Phylliroe bucephala, a free-swimming nudibranch!
Nudibranchs are a type of sea slug, and are a highly varied group. Searching the term (which I highly recommend, I love these guys) will bring up many photos of brightly-colored tropical sea slugs, crawling around on the ocean floor. But Phylliroe is pelagic, which means it lives up in the water column, swimming much like a fish as it searches for tasty jellyfish prey. Check out this link to see images and even a video of them swimming through the water!
We’ve found a lot of cool animals in our trawls, but this one is definitely my favorite so far.
Oceanography Team, aboard the NOAA ship Henry B. Bigelow