It's been an interesting week learning about Pelagic Red Crabs (Pleuroncodes planipes). It's made me think about how much fun it is to watch and wonder about an animal that you've read about or seen pictures of but have never encountered before.
Pelagic Red Crabs are very rare in northern California. According to the records we can find, this is only the second time they've made it this far north. The last time was over 30 years ago (in 1985, following the 1982-1983 El Niño)!
On 24 January 2017, we collected some of the live Pelagic Red Crabs that washed up on the beach and put them into an aquarium.
Observation #1 — The crabs didn't float at the surface, but instead settled to the bottom. They often sat in a "tip-toe" position, elevated off the bottom, raised up on their long legs. (We learned that even though they're often called Pelagic Red Crabs, much of their life is spent on the bottom.) Observation #2 — They're excellent swimmers and adopt a very streamlined profile when jetting through the water using "tail-flips." After swimming to the surface, sometimes they passively drift down through the water column with their legs spread wide (some descriptions liken this to a parachute).
Observation #3 — The crabs use a variety of feeding methods, but they spend a lot of time suspension-feeding, i.e., filtering plankton from the water. They use small mouthparts to generate a water current (drawing water towards their mouth) and then sweep noticeably setose appendagesthrough the water (like fine nets) to capture food particles (in photo below, see center appendages with tufts of fine bristles):
And then when we put one of the crabs in a bowl of seawater to take a look through the microscope, Eric noticed something else:
Observation #4— They have "hitchhikers!"
Remember the mystery photo from last night? (see below)
The claws are covered with dense setae (hair-like bristles). These long bristles increase surface area and slow sinking rates (an adaptation for spending time near the ocean surface and in the water column). But there was another animal there, too, growing among the setae:
This is the hydroidObelia, possibly Obelia dichotoma. Obelia has a life cycle that includes a sessile stage (a colony of feeding polyps that lives attached to an object) and a free-swimming medusa stage (similar to a jellyfish).
Modified from The Light & Smith Manual (2007)
Eric was recording some video footage of a crab when a little medusa swam by! The tiny medusa had just been released from one of the hydroid colonies.
So you can see for yourself, here's a collection of video clips showing some of the above. Watch for (1) sweeping, brush-like mouthparts, (2) large compound eyes, (3) long claw with hydroids growing on it, (4) close-ups of the hydroids, (5) close-up of the setae (long, hair-like bristles), (6) swimming medusa (in the background starting at about 51 seconds).
[If you're receiving this via e-mail and can't see the video clip, click on the title of the post above to go directly to the web page.]
It's fun to think about what it would be like to be a hydroid living on a Pelagic Red Crab and all of the things you'd encounter while drifting along!
Most of them were ~9-10 cm long (with the tail tucked underneath):
Here's a view from above:
And one in my hand (Note: they can pinch!):
It was very exciting to see them alive. It appeared that they were just washing in this evening, having just been left behind by the receding waves.
Let me know if you see any on beaches near you!
For the record, we also found a half a dozen Purple Sea Snails (Janthina umbilicata) today:
This was somewhat unexpected. The water has cooled down this year, and we haven't seen any Janthina in Bodega Bay since last spring. [Interestingly, the our firstsighting ofJanthinalast year was on 19 January 2016. To review information about Janthina, click here.] We have a lot to learn about the movements of these tropical species to northern waters.
For the record, here are a few more photos from the 20-21 January 2017 storm:
When the waves reach heights of over 20 feet, one of the most noticeable things about the ocean is how white it is close to shore. (It's challenging to photograph!) Below is one example with a large set approaching just offshore:
And here's what it looked like in the rocky intertidal zone. This "liquid foam" reminded me of the middle stages of whipped cream:
Another example of the foamy waves splashing onto the beach (with a drift log in the foreground):
And sloshing up over the rocks:
And "exploding" against the rocks:
I think I've said this before, but this is the closest we get to snow in Bodega Bay!
Yesterday I spent a little time trying to document the large wave event that occurred on 20-21 January 2017. Below is a selection of photos showing various aspects of the storm.
I find it hard to photograph large waves from shore in a way that reveals their size. Here's an example that doesn't include anything for scale:
And here's a similar photo that includes one gull (likely a Western Gull):
Knowing an approximate wingspan (58") and length (25") of the gull, we worked through an estimate for the wave height. As you can see, the gull is at an angle, which made this calculation difficult. Coming up with a point for the top of the wave was easy, but we had to do our best to decide on a point for the bottom of the wave. We feel safe saying that this wave was at least 30 feet high, but it could have been higher. (The NWS forecast had predicted breaking waves of 30-40 feet near the coast.)
As I mentioned last night, the storm waves pushed a lot of foam onto shore. It created a rather surreal landscape...like liquid snow!
Waves breaking on the beach showed unusual patterns of splashing and sloshing:
This effect was even more dramatic along the rocky shore:
And when I said "a lot" of foam, I meant a lot. Check out this picture of the foam on top of the bluff (with Eric for scale!).
Okay, the foam was deep, but not quite that deep. We staged that picture for fun, but in some places the foam was at least 2 feet deep.
Okay, here we go — the answer to last night's mystery. This story started during a beach walk on 12 January 2017. And I'll admit, it has to do with something that drives me crazy — walking by an animal on the beach that I can't identify. Especially when it seems like it should be identifiable, e.g., when you see the same obvious and distinctive structures over and over again. For example, we kept encountering these clear blobs on the beach. Each of them was about the same size, and each had a noticeable purple teardrop-shaped globule. Here are two examples:
See what I mean? It had to be something. It appeared to be part of an animal of some kind. It wasn't just a random bit of goo on the sand.
I was a little frustrated that I couldn't tell what it was, but I kept looking and hoping that we would fine one with more "parts" that would reveal the identity of the animal.
And then Eric decided to place one of the blobs in some water. They were incredibly thin and fragile and difficult to pick up, but this step was critical. Here are two pictures of the blobs when floating:
These specimens were tattered after having come through the surf, but I hope you can see that we now had more clues. In water the blob expanded into defined structures — broad wings, with a latticework-like design!
This brought to mind an illustration which you might recall from a post in 2012:
Modified from The Light & Smith Manual: Intertidal Invertebrates from Central California to Oregon (2007)
Yes, this is the pteropod Corolla spectabilis. And the blobs observed during our beach walk on 12 January 2017 represented my first close look at Corolla's wings. I know many of you have been finding Corolla pseudoconchs on the beach this winter. The wings are easily separated from the pseudoconch, and they're probably torn apart in rough seas, so they're not often seen on the beach.
[In the illustration above, also note the "viscera." The purple globule attached to the wings is a part of the gut (included in the viscera).]
For some reason, quite a few Corolla wings were washed up on 12 January, so it was a rare opportunity to observe them and the muscles in the wings. [Remember that Corolla and other pteropods are sometimes called "sea butterflies."]
Here's the close-up again from last night's post, showing the fascinating muscle bands running through the wings:
Having seen these specimens and the pattern of the muscle bands under the microscope, can you tell what's missing from the illustration shown above? Although there are muscle bands drawn in two directions, there's a third set at a different angle. For the drawing to be accurate, you'd need to add one more set of muscle bands. The latticework of muscles may be important in achieving the upstroke and downstroke of the large wings as the pteropod swims through the water.
Mystery solved! And now if we see these blobs washed up on the beach again, we'll know what they are.
P.S. Click here to watch a video of Corolla wings in action.
P.P.S. And here's a reminder about the more commonly encountered Corolla pseudoconch:
Okay, I know some of you have probably been waiting for me to show the 2017 Pantone Color of the Year. ;) Well, I've been trying to find a good match. That is, until I photographed something that would be a good representation of the color known as "greenery." Although it's not a perfect match, today I think I came close enough. Here's a nice patch of moss on a stone with some late afternoon sun (photographed in Petaluma on 15 January 2017):
Carol mentioned she had seen a Bald Eagle near Spud Point Marina this afternoon. So I kept an eye out for it when I went to the post office. I didn't think I was going to see it, but then I noticed the eagle in my rear-view mirror perched on a utility pole.
I turned around and pulled up nearby and started taking some photos from the car (see below). Then the eagle took off and flew over Bodega Harbor. I think the eagle was chasing an Osprey (hoping to force it to drop a fish), but then, amazingly, I could see the eagle flying straight back towards the same pole that it had started on. The picture above is of the eagle just before landing.
While perched, the eagle spent some time preening:
Here's one more picture from the end of the preening session:
Thanks to Carol quite a few people were able to enjoy great views of this bird! Maybe it will stay around for a little while.