On the way home from work tonight, I noticed a Killdeer (Charadrius vociferus) flying low over a field. It reminded me of this Killdeer nest that I photographed a couple of years ago. The patterning on the eggs looked remarkably similar to the little pieces of granite scattered around the nest site.
White-crowned Sparrow (Zonotrichia leucophrys) bathing on 5 April 2018. We often notice a lot of bird activity at the bird bath when it starts to rain. I'm not exactly sure why?
Sounds like we're due for quite a bit of precipitation tomorrow. We've received ~20 inches so far this winter, but the average annual rainfall total in this area is closer to ~31 inches, so a little more would be welcome!
It's been in the upper 70s during the last few days, and butterflies have been passing through our yard. Yesterday (1 April 2018), a Gulf Fritillary (Agraulis vanillae) landed in a fruit tree for a few seconds. I didn't get a great shot, but here's one for the record:
This triggered a memory of finding Gulf Fritillary caterpillars and chrysalids a couple of years ago (June 2016) while we were in the line for SF Giants Ferry. The dock is in Larkspur, and I noticed a passionflower vine (Passiflora sp.) just before boarding:
Looking more closely, there were several Gulf Fritillary caterpillars(below)— with bold stripes and prominent spikes!
And there were also a few chrysalidsattached to the frame supporting the passionflower vine:
You might remember when I was photographing colors in spider webs last summer (see posts from 17 July 2017 and 31 July 2017 for examples). I walked around the backyard yesterday (30 March 2018) and found a few colorful strands, including one with some of the pastel colors I often associate with Easter. This spider web was built along an old fence. I found the resulting photo somewhat reminiscent of a paper collage:
Black-tailed Jackrabbits (Lepus californicus)have been uncommon on Bodega Head for years now. But here's a fun look back at an older Easter-related post called "Special delivery" from 7 April 2012.
Happy Easter! Happy Passover! Happy Blue Moon! Happy April Fools' Day! (Happy Birthday, Jen!)
If you've looked closely at a porcelain crab, you've probably noticed that it has a large pair of claws and three pairs of striped walking legs. The photo below shows the Chocolate Porcelain Crab (Petrolisthes manimaculis). They're found under cobbles and boulders in the rocky intertidal zone.
It's easy to overlook that porcelain crabs also
have a 5th pair of limbs that are greatly reduced in size relative
to the walking legs.Porcelain crabs
along with some other types of crabs (such as hermit crabs, mole crabs, and
pelagic red crabs) belong to a taxonomic group called the Anomura.Unlike Cancer
crabs, kelp crabs, and other “true crabs,” anomuran crabs never use their last
(or 5th) pair of limbs for walking.In the drawing below, the 5th pair of limbs are marked with
Modified from Fleischer,
J., M. Grell, J.T. Hoeg, and J. Olesen. 1992. Morphology of grooming limbs in
species of Petrolisthes and Pachycheles (Crustacea: Decapoda:
Anomura: Porcellanidae): a scanning electron microscopy study. Marine Biology 113: 425-435.
These appendages are small enough that they are easy to miss. The close-up photo below shows this 5th pair of limbs marked with black arrows:
Given the small size of these appendages, one might wonder
if they are vestigial structures that no longer serve a useful function?
Well, it turns out that in porcelain crabs, these appendages
are actually important for grooming.The
slender grooming limbs can be folded up like a jackknife when not in use, but
they are remarkably long and flexible when extended.As you can see in Siena’s drawing below, the
grooming limbs end in a claw.They are
also covered with several types of bristles (or setae).
Drawing by Siena
Watson. Modified from Fleischer et al. 1992.
The grooming limbs are used both to clean the gills within
internal chambers and to clean the external surface of the crab of detritus,
debris, parasites, and other attached organisms.The bristles act as cleaning brushes, whereas
the toothed claw is well equipped to remove objects that are more firmly
attached.Some of the bristles on the
claw are sensory structures that appear to allow the crab to both feel and
taste the objects that are encountered during grooming.
Eric captured some nice video of the grooming limb of a porcelain crab in action. Porcelain crabs are suspension feeders. Near the beginning of the video you will see the crab sweeping its specialized fans through the water to capture food. Then the crab starts using one of its grooming limbs (white arrow at ~15 seconds) to vigorously scrub around its back, eyestalks, and long red antenna! It is amazing to see the flexibility and dexterity of the limb as it diligently cleans and grooms.
for not posting more this week. I'm recovering from surgery on Monday,
and my ability to stay upright is more limited than I had hoped. I'm feeling better now
though, and I hope to resume more frequent postings in the near future.
For now, Eric offered to help put together the information for a really fun
post. Many thanks to Eric and Siena!]
I don't think I'll ever get tired of looking at these colorful bubbles! They seem to be at their best when there's a lot of foam during spring upwelling (=windy) conditions. A few self-portaits below. Same bubble, over a span of ~3 minutes. Photographed 24 March 2018. In gold:
While looking for Polydora
on the surface of the hydrocoral Stylantheca papillosa, Eric noticed a small
raised blister (~3 mm long) with an opening at one end. The antennae of a tiny worm were barely visible in the darkened doorway. [I think the little blister is reminiscent of a pink igloo! :) ]
We were curious about this worm, and eventually found a reference to a little-known syllid polychaete, Proceraea penetrans, first discovered living on the subtidal hydrocoral Stylaster californicus in southern California (Wright and Woodwick 1977).
In response to the worm, the hydrocoral creates a "blister" that serves as a home for the worm. Eric was able to coax this worm out of its home for a closer look and it turns out that it was indeed Proceraea penetrans! Many thanks to Leslie Harris for confirming this identification.
This appears to be the first record of Proceraea penetrans living on the intertidal
hydrocoral Stylantheca papillosa, and also the first record of this species north of the Channel Islands.
Note that Proceraea penetrans is tiny (see photos below). [Its small size is likely one of the reasons it has been observed so rarely.] We don't believe any photographs of a live specimen have been published before. With this post, you get to see photos and a video!
The entire individual was only ~5 mm long:
Here's a magnified view of the anterior end, with 2 pairs of red eyes:
Another fascinating aspect ofProceraea penetrans is its life history. Some polychaete worms, including this species, produce
reproductive individuals called epitokes. Epitokes are specialized for
swimming to the surface of the ocean, often in response to lunar cues,
where they release eggs or sperm with other
epitokes during mass spawning events.
To facilitate this journey,
epitokes often have enlarged eyes and modified setae (bristles) on
their appendages that aid in swimming. In some species the entire adult
worm transforms into an epitoke. But in other species,
including Proceraea penetrans, the adult worm produces epitokes
asexually, as genetically-identical buds attached at its posterior end (see photos below).
When the lunar cues are right, the mature epitoke separates from the
posterior end and takes a one-way journey to the surface to spawn while the adult worm (formally called an atoke) remains safe and
sound on the bottom.
Proceraea penetrans produces just a single epitoke at a time.
Below, here are two views of the epitoke. In the first, note the adult worm (the atoke) in the lead, and the epitoke developing at the posterior end of the atoke. Look for one set of eyes at the head end of the atoke (bottom of photo), and a second set of eyes at the head end of the epitoke (top of photo).
It looks odd to see eyes in what appears to be the mid-section of the worm. Remember that the portion in front is the benthic adult and the second set of eyes belongs to the reproductive epitoke that will separate and swim to the surface to spawn.
Eric was lucky to capture a short video clip (probably the first ever of this species). Note that the epitoke is longer than the atoke — watch how long it takes for the epitoke to pass through the view!
Amazingly, some closely-related syllid polychaetes in the same family (Autolytinae) as Proceraea produce a chain of multiple epitokes at one time. The photo below of
Myrianida pachycera from the Indo-Pacific (and introduced to Southern California) is a particularly
beautiful species and a striking example of this phenomenon. Thanks to
Leslie Harris for sharing her wonderful photo.
I was sitting down to think about what I might post about tonight, when I noticed a movement out of the corner of my eye. A jumping spider appeared on the edge of my computer screen! Not a digital one, a real one!
It was a good opportunity for a few close-ups. The spider was upside down, but it was a great view of those beautiful eyes! And I love the little rim of hairs wrapping around the perimeter of the eyes. (Do the hairs help keep the eyes clean, like eyelashes?)
Then the spider went on a journey across the table (before being escorted outside). Here it is on a napkin:
And a dorsal view on a place mat:
I appreciated the timely visit from this charismatic spider.
P.S. I think I first wrote about the Red-backed Jumping Spider (Phidippus johnsoni) on 30 January 2013— see the post called "Zip line".
A few nights ago, I posted some photos of the hydrocoral, Stylantheca papillosa (See "Hello, hydrocoral!"). I also referenced a post from 2012 called "The hydrocoral and the worm." Well, we have a friend who is interested in the worm that is associated with the hydrocoral, so we made an effort to obtain better documentation (including live video!) of this interesting spionid polychaete.
As a reminder, here's a photo I shared from the research paper that first described Polydora alloporis:
From Light, W.J. 1970. Polydora alloporis, new species, a commensal spionid (Annelida, Polychaeta) from a hydrocoral off Central California. Proceedings of the California Academy of Sciences 37: 459-472.
And here's your first view of a worm living in Stylantheca papillosa:
This worm is thought to live exclusively in hydrocorals. [Note the earlier paper discovered the worm in a different species of hydrocoral, Stylaster (formerly Allopora) californica.]
You can see the "double-barreled" tube that the worm lives in. A pair of tentaculate palps emerges from one opening, and the disc-shaped pygidium (or tail end) is sometimes visible in the other opening (see below):
The tentaculate palps are the most visible feature. They're very active and are used to explore the surroundings and to capture food. There is a prominent groove that runs down the middle of each palp. When a food particle is captured— either from the water or the surrounding surface— the particle is moved down the food groove towards the mouth by cilia. You can see particles in the food grooves below (white arrows):
Here's an explanatory diagram(below). Note that the food groove is deeper in the middle of the palp and shallower near the base of the palp.
Modified from Dauer, D.M., C.A. Maybury, and R.M. Ewing. 1981. Feeding behavior and general ecology of several spionid polychaetes from the Chesapeake Bay. J. Exp. Mar. Biol. Ecol. 54: 21-38.
As particles get closer to the base, they "ride up" into the shallower section of the groove and accelerate towards the mouth. You can see this for yourself in the video below.
Watch for the following: (1) exploring palps, (2) food particles moving along the food grooves (from ~18-28 seconds and ~29-32 seconds), and (3) the posterior end appearing near the surface of the tube.
We have lots of questions about the relationship between the worm and the hydrocoral. Does the worm steal food particles from the hydrocoral (from the surface or even from within the hydrocoral pores)? Does the feeding activity of the worm help keep the hydrocoral free of debris? How do the larval worms find the hydrocorals? Do the juvenile worms take over an established hydrocoral pore?
Just a quick note about a couple of recent observations:
There were thousands of By-the-wind Sailors (Velella velella) washed up on Salmon Creek Beach on 16 March 2018. Most were between 10-20 mm long (those are millimeter marks on the ruler in the photo), but many were smaller than that. With a storm coming mid-week, there might be more Velella washed ashore.
We also spotted a few Purple Sea Snails (Janthina umbilicata) on 16 March 2018:
Although we haven't seen many Purple Sea Snails during 2017-2018, we remain curious about what oceanographic conditions are driving these pelagic snails onshore two years after an El Niño event (with which their appearances here are more often associated).
I've always been drawn to our local hydrocoral, Stylantheca papillosa. It appears as bright pink patches growing on rocks in the low intertidal zone:
Now that I have a waterproof camera, I thought it might be interesting to photograph Stylantheca under water. During a very low tide in February, I found a patch that was submerged, plunged my camera under water, held the camera in front of the patch and took some pictures. (Note that I couldn't really see what I was photographing at the time.)
This was one of my first pictures. (Each pore is ~1 mm across.)
Interesting! And can you see those very slender thread-like things in front of the colony (especially in the lower right corner)?
I thought there might be something drifting in the water, so I moved the camera and tried again, this time a little closer:
With this view I could tell that those "threads" probably weren't random debris. They looked like they could be tentacles associated with the colony. At this point I realized how little I knew about this species. Were those really tentacles? They're so long!
I took more pictures, then the tide came in and I had to leave. Here's another example of what I captured:
I was really puzzled about these tentacle-like structures and decided to do some reading about Stylantheca to learn what they were. Well, it turned out this was not an easy question to answer! I had trouble finding good descriptions of Stylantheca anatomy. Eventually I found a couple of older papers from 1879 and 1938 that helped.
Hydrocorals (a type of hydrozoan) are colonial animals made up of different units with specialized functions, e.g., defense or feeding. These long tentacle-like units are involved in protecting the colony and are called dactylozooids. Note that their tips are slightly but noticeably swollen:
Since they have a defensive function, you would expect the dactylozooids to have a high concentration of stinging cells (like jellyfish or sea anemones). To confirm this, we clipped one of the dactylozooids and looked at the tip under a high-powered microscope.
Check it out (below)! The entire surface is packed with stinging cells (oval shapes). At the lower right are three stinging cells dislodged from the surface. When triggered, the cells rapidly fire tiny coiled harpoons called nematocysts, which appear as the long dark threads emanating from the battery of stinging cells.
Note that the dactylozooids are not always expanded. Often they're retracted and look like short tentacles tucked inside the pores:
While learning about the dactylozooids, I read that the hydrocorals have feeding units (called gastrozooids) in the center of their pores. So I went back and took more pictures, hoping I could capture an image of a gastrozooid:
And there they were! In the center of the pores, can you see the little rounded polyp with tiny tentacles (nubs) around the perimeter? The gastrozooids can withdraw to the bottom of the cavity, but they can also extend upward to the rim. The gastrozooids have little mouths — they'll open up to ingest food (either caught by their own tentacles, or possibly passed to them from the dactylozooids).
It took me a while to sort out all of this. In the process, I decided to try to sketch what I was seeing and learning. In case it's helpful, here's an example from my notebook to summarize:
For such a striking species, I was surprised how hard it was to find out more about it. I hope this makes information about Stylantheca papillosa a little more accessible!