Long period, northwest swell, 10-11 feet, on 16 April 2015
Thursday, April 16, 2015
During the past month, Eric and I have been finding these very distinctive gelatinous animals on the beach. By distinctive I mean they had a definite shape: horseshoe-shaped, rounded at one end and coming to two points at the other end. There's a little more to it than that, but I'll let you see for yourself:
We've only found a few of them, but all of them were this exact shape. The pictures I'm showing tonight are of the most recent one found on 10 April 2015. We estimate it was about 20-22 mm across.
Below is another angle, showing the points at one end — they almost look like small "horns." If you look very closely, you'll also see another important characteristic — four raised knobs in an arc at the rounded end (it's easier to see them in the first picture).
We hadn't seen this animal before, so at first we just started calling them "horseshoes." We'd be walking along the beach, and when the sun glinted off one and we were close enough to see the shape, one of us would say, "Oh, there's another horseshoe!" They were very different than a nondescript blob on the beach.
Well, you know me...it wasn't enough to call something so distinctive a "horseshoe" and not know what it was. My best guess was that it was part of a siphonophore, so I started looking up possibilities. I was struggling, so I gave in and requested help from Phil Pugh in the U.K. Phil was very generous and responded with an identification of this siphonophore:
What a great name! Here's an illustration of the nectophore or swimming bell of Hippopodius, along with one of my pictures to match the same orientation:
From A Synopsis of the Siphonophora by A.K. Totton (1965)
I mentioned that this is one nectophore, i.e., it's just one part of the whole colonial siphonophore. Hippopodius has many nectophores that fit together tightly around a long central stem (see below). The nectophores are used for swimming while the stem supports structures used for feeding and defense (e.g., stinging cells) and reproduction.
Modified from Jacobs, W. 1937. Beobachtungen über das Schweben der Siphonophoren. Z. vergl. Physiol. 24: 583-601; and Totton (1965), see above.
There are a couple of really fun facts that I can't help sharing:
- The name Hippopodius means "horseshoe"! It's very appropriate.
- Hippopodius is a warm-water species. It's rare to find them in northern California.
- Hippopodius is known for being bioluminescent — I think even the lone nectophores would light up in response to stimulation. If we find another one, we'll have to look for it.
P.S. For introductory information about siphonophores, review the posts from 23 January 2012 and 3 April 2013.
P.P.S. Since Hippopodius is somewhat long, we started calling it "Hippo" for short, leading to the title of this post.
Wednesday, April 15, 2015
On 9 April 2015, we noticed a blue crate washed ashore covered with pelagic gooseneck barnacles (Lepas sp.):
We didn't have a lot of time, but we noticed that some of the barnacles had an unusual purple coloration between their plates:
For the record, here's a close-up (see below). We're not sure if the purple had actually been incorporated into the plates, or if there was an internal structure with that color that was strong enough to show through the plates. Do you have ideas about what could cause this coloration?
I don't know if they have responded to the warmer water during the past year, but there have been impressive numbers of pelagic gooseneck barnacles on objects washing ashore during the past month.
Monday, April 13, 2015
Last week we noticed quite a few small sand dollars — or perhaps they should be called sand quarters or sand dimes? — washed up on Salmon Creek Beach.
So this was intriguing. Eric and I guessed that the sand dollars we saw ranged in size from smaller than a dime, to as large as a quarter, with the average size being about dime-sized. The true range we measured was 10 to 23 mm in diameter, with an average size of about 17 mm.
How well did they match the measurements of the coins? I had never measured the coins before, but tonight I measured them — a quarter is 23 mm across and a dime is 17 mm across. Amazing! Our estimates were pretty darn good relative to the coins! But we've both measured a lot of things for many years, and used a lot of coins, too, so I guess that shows you the value of practice and repetition (...or we just got lucky).
I wrote about sand dollar skeletons a few years ago, so if you'd like to learn more about them, you can review the post called "Petals and grooves".
Sunday, April 12, 2015
Here's a seaweed puzzler. I think I've figured it out, but this one had me wondering at first...which was fun! I learned some things while trying to identify it, and now I have some questions.
This is what I found washed up on the beach:
This is what I found washed up on the beach:
If you need something for scale, here's a picture with my field notebook. (My notebook is about 4 5/8" x 7".)
I realize this might be difficult because some of the characters used to identify algae are better experienced in-the-hand, e.g., color subtleties, texture, and flexibility.
Perhaps you can see that this seaweed is leaning towards golden brown? It's not always true, but in this case I thought the color probably was a clue pointing towards a member of the brown algae (i.e., not a green or a red algae).
From the scale, you can tell that this blade is fairly large. So I started to wonder about a kelp. The problem was, it didn't look like any of the local kelps I am familiar with.
(Note also that this blade was reproductive — the dark brown patches on the left end are reproductive structures, not shadows.)
Here's another angle:
After a little more time, I realized something was throwing me off — the narrow "branches" at the bottom of the blade. At first I didn't give these too much thought and I passed over them as a possible stipe, i.e., where the blade connects to a holdfast (the attachment to the substrate).
But there were things about this blade that were familiar — the color and texture — and those reproductive patches. And then it hit me — what if those little branches at the bottom weren't part of a stipe at all? What if they connected the blade to something else, like a float (also called a pneumatocyst)?
You can see a hint of what I mean in this picture from Big Sur:
Is it possible that Bull Kelp (Nereocystis luetkeana) blades grow to be as wide as the blade I found today? I hadn't seen them this size before. As mentioned, my field notebook is 4 5/8" (11.7 cm) wide. I measured the blade, and at its widest it was 16 cm across.
I went to the Marine Algae of California and started reading. Sure enough, Bull Kelp blades are reported to at least 15 cm wide. So the size of the blade I found today is at the extreme end of the range, but possible for a large Bull Kelp blade.
And is it possible that Bull Kelp is reproductive this early in the year? Generally, I think of Bull Kelp being very early in its annual growth cycle during the spring (see next photo of very young Bull Kelp from 24 March 2015).
The Marine Algae of California reports that Bull Kelp's reproductive season is from early May through December. Well, if my identification is correct, I can now add early April to that description!
But I still have questions. Although this large, reproductive Bull Kelp blade washed up on Bodega Head on 12 April 2015 — did it grow locally, or did it start growing somewhere else, break free, drift, and then wash ashore here far from its origin?
And what conditions cause Bull Kelp blades to grow so wide? Have you seen them this wide before, and if so, are there certain conditions under which you expect to find wider blades?
Saturday, April 11, 2015
I'm used to seeing Gulf Fritillaries (Agraulis vanillae) in Florida and other parts of the southeastern U.S. (The "Gulf" in their name refers to the Gulf of Mexico.) I was surprised at first to learn that they occur in California.
This is a tropical/subtropical species, occurring from the southern U.S. through Mexico, the West Indies, and South America. Gulf Fritillary caterpillars feed on Passionflower vines (Passiflora spp.), none of which are native to California. However, where the plants have been used in landscaping, the butterflies may follow, as long as temperatures allow (they're apparently sensitive to temperatures below ~22°F).
Note that Gulf Fritillaries are not "true fritillaries" — that is, they are not related to butterflies in the genus Speyeria with which they share a common name. Gulf Fritillaries are in the subfamily of butterflies sometimes known as "longwings." It's hard to see this feature in my pictures, but if you encounter this species in person, look for the very long, narrow forewings.
Although I cropped the pictures above so you could see the butterfly up close, this butterfly was very well camouflaged while resting high in the branches of this shrub. Can you find it in the picture below?
The Gulf Fritillary is just below and right of center.
To learn more about the history of Gulf Fritillaries in California, read Art Shapiro's summary here.
Friday, April 10, 2015
Eric and I came across a large flock of Whimbrel on Salmon Creek Beach tonight. In fact, it was the largest number of Whimbrel I've seen since moving here in 2005.
I didn't manage to photograph all of them in one picture. However, I came relatively close, documenting about 2/3 of them. If you'd like to count yourself, here's one picture with a good number of Whimbrel. You can click on the picture for a larger version. (I'll reveal the count below the image.)
There are 42 Whimbrel in the picture above. There's one "trick" bird that you have to ignore — a Marbled Godwit, about 5 birds in from the left side (feeding in the wet sand). I counted 20 more Whimbrel in addition to the individuals in this image, for a total of 62 birds tonight.
I wondered how this number compared to other high counts in Sonoma County. Below I've listed the top five high counts for Whimbrel as recorded in the Birds of Sonoma County California:
- 100 on 4/29/89 at a wet field near Petaluma
- 88 on 5/3/03 at a pond near Carmody Road
- 50+ on 7/5/81 at Bodega Harbor
- 50+ on 4/24/99 at the Bodega Farm Pond
You can see that the 62 birds we documented tonight is a fairly high count for the County.
There have been an abundance of Mole Crabs on Salmon Creek Beach this year, and I'm guessing the number of birds frequenting the area might be related to this food source. (We saw at least two Whimbrel catch Mole Crabs while we were there.)