East Greenland
Friends, we are on the east Greenland continental margin, at the westernmost point of our expedition. We've actually crossed the prime meridian and are in the western hemisphere. Of course lines of longitude are super close together at the poles, so you really don't have to travel far to see a change in your longitudinal position. There are four stations over here that are sampled regularly as part of the HAUSGARTEN Long-Term Ecological Research observatory and plenty of new discoveries to be made.
Our larval samples in east Greenland have included three new types: a trochophore (swimming ciliated sphere), a nectochaete (grows up to be a worm), and a very young pluteus (grows up to be a sea urchin or a brittle star). The pluteus kind of looks like a space ship – a baby Millennium Falcon.
Probably the most exciting thing we've found, though, is a baby crinoid. Some of you may recall that crinoids are related to sea stars, brittle stars, sea urchins, and sea cucumbers. They come in two types: sea lilies that live on stalks as adults, and feather stars that swim around right above the seafloor. When feather stars go through their development, they initially grow on a stalk but then the head breaks off and swims away. I found a couple hundred of those young, stalked feather stars on a long-term recruitment experiment in 2017, and I used them to describe development in the deep-sea feather star Poliometra prolixa.
Now that I'm more aware of what baby feather stars look like, I've been watching for them everywhere. As it turns out, they really like moorings. We found a couple dozen feather stars (young ones in their stalked phase) on mooring floats at about 200 m depth in east Greenland, and they're not Poliometra. There's another species of feather star in this area that lives in shallower water, down to a couple hundred meters, which I think these specimens might belong to. It's called Heliometra glacialis.
Here's the cool part: I think the two species might have completely opposite reproductive strategies. When I found all those Poliometra specimens, they were in dense clusters on the experiment frame, right next to their parents. The ROV video showed several adult Poliometra resting on the lander frame when we recovered it. This suggests to me that Poliometra larvae don't go very far. The adults might just come to rest on a big rock, dump out their larvae, and then the young attach right there. There's one species of feather stars in the tropics whose larvae start crawling on the substrate as soon as they're released from the mother. I can't say for sure if Poliometra does the same thing, but it seems the larvae settle close to home.
Heliometra larvae (if that's what I found on the mooring – another thing to verify when I get home) seem to travel farther afield. I found them at 200 m depth at a station where the seafloor is all the way down at 1000 m. In order to find the mooring, they had to be drifting along in the water column, probably far away from their benthic-bound mamas.
My ideas are pure speculation right now, but sometimes, that's how progress is made. You record observations, draw inferences, and continue to test the validity of your hypothesized explanation whenever new data become available.
In the meantime, there was another really cool thing on the crinoid stalks: small, clear anemones. I've seen many anemones living on crinoid stalks in the deep sea (they actually love stalks of the sea lily Bathycrinus carpenterii), but I didn't know they would colonize the stalk of a young feather star all the way up in the water column. It's a pretty neat find!
Our larval samples in east Greenland have included three new types: a trochophore (swimming ciliated sphere), a nectochaete (grows up to be a worm), and a very young pluteus (grows up to be a sea urchin or a brittle star). The pluteus kind of looks like a space ship – a baby Millennium Falcon.
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| A stalked feather star on the mooring |
Now that I'm more aware of what baby feather stars look like, I've been watching for them everywhere. As it turns out, they really like moorings. We found a couple dozen feather stars (young ones in their stalked phase) on mooring floats at about 200 m depth in east Greenland, and they're not Poliometra. There's another species of feather star in this area that lives in shallower water, down to a couple hundred meters, which I think these specimens might belong to. It's called Heliometra glacialis.
 |
| One of the feather stars broke away from its stalk in the lab |
Here's the cool part: I think the two species might have completely opposite reproductive strategies. When I found all those Poliometra specimens, they were in dense clusters on the experiment frame, right next to their parents. The ROV video showed several adult Poliometra resting on the lander frame when we recovered it. This suggests to me that Poliometra larvae don't go very far. The adults might just come to rest on a big rock, dump out their larvae, and then the young attach right there. There's one species of feather stars in the tropics whose larvae start crawling on the substrate as soon as they're released from the mother. I can't say for sure if Poliometra does the same thing, but it seems the larvae settle close to home.
Heliometra larvae (if that's what I found on the mooring – another thing to verify when I get home) seem to travel farther afield. I found them at 200 m depth at a station where the seafloor is all the way down at 1000 m. In order to find the mooring, they had to be drifting along in the water column, probably far away from their benthic-bound mamas.
 |
| Anemone on a crinoid stalk |
My ideas are pure speculation right now, but sometimes, that's how progress is made. You record observations, draw inferences, and continue to test the validity of your hypothesized explanation whenever new data become available.
In the meantime, there was another really cool thing on the crinoid stalks: small, clear anemones. I've seen many anemones living on crinoid stalks in the deep sea (they actually love stalks of the sea lily Bathycrinus carpenterii), but I didn't know they would colonize the stalk of a young feather star all the way up in the water column. It's a pretty neat find!
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