A story with a point

Last September I wrote about a fascinating predator-prey interaction that involved an inducible defense.  The bryozoan responds to being preyed upon by a nudibranch by growing significant spines.  I showed the nudibranch and the bryozoan, but I didn't have pictures of the spines.  Are you ready to see them now?  

To review, here's the nudibranch, Corambe steinbergae, and the bryozoan, Membranipora sp.  The nudibranch is so well camouflaged that you'll need to look carefully along the left side of the image to find it.  The darker zooids (members of the bryozoan colony) just behind the nudibranch have probably been eaten.

 

Below is a close-up of the nudibranch, showing its head that was exposed while it was probing the bryozoan colony:

 

And now for the spines.  First, here's an illustration to help you know what to look for.  The inset shows a close-up of a single zooid with elongated spines at the corners and numerous smaller spines along the edges.

 

Modified from Harvell, C.D.  1990.  The ecology and evolution of inducible defenses.  The Quarterly Review of Biology 65: 323-340.

Now here's the real thing, from two different angles:

 

Would those spines deter you from eating this bryozoan?

Eric is so impressed with this nudibranch-bryozoan interaction that he filmed some video and set it to music.  This has to be one of his best invertebrate music videos.  Follow the link below to watch it on YouTube — you don't want to miss it!

"Nudibranch predator (Corambe steinbergae) and bryozoans"

P.S.  For the record, these bryozoans and nudibranchs were found on kelp blades washed up on Salmon Creek Beach on 8 August 2014.

Time with a tattler

A few pictures of a juvenile Wandering Tattler (Tringa incana), photographed on Bodega Head, 13 August 2014.  (Note the white tips to the feathers.)


Showing the habitat along the rocky outer coast:

 

Roosting:

 

Preening:

 

Searching for prey among the mussels:

 

Red-sided and blue-bellied

 

I debated about showing these pictures, but then I decided to go ahead.  It's an opportunity to praise and share images of one of the most beautiful local snakes — a California Red-sided Garter Snake (Thamnophis sirtalis infernalis). 

The unfortunate part is that this was a road-killed animal.  I'll be selective and I won't show you the entire snake.  But I hope you can appreciate how handsome it was.

 

 

Although the blue of the belly scales was much brighter in person, I think you'll be able to see the keels on the scales in the following close-ups:

  

  

Perhaps this snake will serve as a reminder to all of us to slow down and always watch for wildlife.

To learn more about California Red-sided Garter Snakes, check the California Herps web page.

The lion feeds tonight

 

Are you familiar with this animal?  The species name is "leonina," referring to a "lion" and the mane-like appearance of its oral hood and the peripheral tentacles.

Here's the entire animal viewed from below:

 

You can see that the oral hood is very large relative to the rest of the body.  Also visible is a long slender foot, and rounded, leaf-like cerata extending out to either side of the foot.

This is Melibe leonina, sometimes called the Lion Nudibranch or Hooded Nudibranch.

This nudibranch has some very unusual features.  Along with the impressive oral hood used to capture prey (such as small crustaceans), look for the interesting rhinophoral processes (flap-like or ear-like) and the small, grooved rhinophores at their tips — see images below.

 

 

Melibe inhabits kelp forests (especially Giant Kelp, Macrocystis pyrifera) and eelgrass beds (Zostera marina).  They are occasionally found in Bodega Harbor.

We were somewhat surprised to find two small Melibe in a Bull Kelp (Nereocystis luetkeana) holdfast washed up on Salmon Creek Beach on 13 August 2014.  

Here's a picture of the Bull Kelp holdfast.  I photographed it because there was also a small Five-ribbed Kelp (Costaria costata) attached to it, and I still have yet to find Five-ribbed Kelp growing on Bodega Head.

 

When we looked closely at the holdfast, Eric noticed an unusual brown blob.  This is what Melibe looked like on the holdfast, out of the water.  It's just below the tip of Eric's forceps:

 

 

It makes sense, but it made me smile to see this description from a paper written in 1923: 

"The body-substance of Melibe leonina appears as a mass of brown jelly, when the animal is alive or freshly caught..."  

Kudos to Eric for realizing this bit of "brown jelly" in the holdfast was worth looking at.  Who knew it would turn out to be a lion!

P.S.  The quote above is from Agersborgh, H.P. von Wold Kjerschow. 1923. The morphology of the nudibranchiate mollusk Melibe (syn. Chioraera) leonina (Gould). Q. J. Microsc. Sci. 67: 507-592.

Nesting along the creek -- confirmed

This is a follow-up to the post a few days ago about Common Mergansers nesting along Salmon Creek.  I inquired whether anyone knew if mergansers had actually nested along the creek somewhere.  Thankfully, Skip Hand responded and also shared this wonderful picture:

 

Although this image is from June 2011, it documents an adult female with a brood of very young Common Mergansers resting on a log in Salmon Creek.  The ducklings in Skip's photo are too young to fly, providing strong evidence that the mergansers nested somewhere nearby (or at least upstream).

Common Mergansers are cavity nesters, often utilizing old holes made by Pileated Woodpeckers.  They will also nest on the ground in rock crevices, hollow logs, or holes in the ground.

Females incubate their eggs for ~28-35 days.  After hatching, the young only remain in the nest for 24-48 hours.  They are then led to the water by the female.  The female broods the young for the first few weeks, but they can swim and dive within 1-2 days after leaving the nest.  Although the juveniles form cohesive broods, the female usually leaves them before they can fly at approximately 30-50 days after they hatch.

It's valuable that Skip had photographic evidence of Common Mergansers nesting along Salmon Creek — but he didn't just document them, he also captured a beautiful image of the habitat and a glimpse into "family life" along the creek.


P.S.  Facts above from The Birds of North America account by Mallory and Metz (1999).

Pelagic barnacles attached to a...

Sometimes I'm asked what my favorite invertebrate is.  I can't answer that question, because I'm intrigued by so many of them.  However, pelagic barnacles (Lepas spp.) would definitely make it onto a list of candidate species.  We found some a few days ago washed up on Salmon Creek Beach.  

Pelagic barnacles are often attached to driftwood or floating seaweed, but this time Eric spotted some growing on a different object.  Can you tell what it is?

 

Here's a slightly different angle:

 

And another showing the opposite side with a larger cluster of barnacles:

 

Did you guess what the barnacles were attached to?  

Warning: The next picture will give it away.

  

Yes!  These pelagic barnacles were growing on a feather!

When examined closely, Eric noticed a newly settled barnacle larva, called a cyprid, attached to the feather, too (see below).  You can see it just off to the left of the large cluster of feeding barnacles.

 

Below is a close-up of the cyprid:

 

Although I haven't photographed a cyprid on a feather before, I shared some nice images and an explanation about pelagic barnacle cyprids in 2012.

After Eric spotted the first feather-with-barnacles, I wondered how many we had passed by.  Although we were near the end of our walk, I found one more:

 

After discovering them, we had lots of questions.  For example — Do the barnacles prefer a certain region of the feather?  If so, why?  Do some types of feathers make better floating rafts than others?  How many barnacles would it take to sink a feather? 

Clinging to an eelgrass blade near you

Katie had been seeing these small hydromedusae among the eelgrass (Zostera marina) in Bodega Harbor.  We finally looked at some under the microscope together and believe we identified them as Cladonema californicum. 

There are some amazing things about this species and it has some fun connections to wonderful people and local places, too.

Cladonema californicum was first described by Libbie Hyman in 1947.  To describe the species, she used organisms sent to her that were collected in Tomales Bay (near Dillon Beach) by Frank Pitelka in 1941.

Here are two figures modified from Hyman's paper.  The first shows the most obvious features (that you can identify in the next photo!) and the second highlights the unusual branched tentacles — one branch that ends in a sucker and the other with stinging branches.   

  

Both figures modified from Hyman, L. H.  1947.  Two new hydromedusae from the California Coast.  Trans. Am. Microsc. Soc.  66: 262-268.

Now here's a close-up photo of the living hydromedusae.  Look for all of the parts mentioned above.

 

Can you see how the hydromedusa is using the tentacle branches with suckers to cling to the eelgrass blade?  Many of you are probably used to seeing hydromedusae swimming through the water column (like jellyfish).  This species is unusual in that it has adopted a partially benthic lifestyle.  It holds onto the substrate with adhesive pads and then spreads its stinging tentacles to capture prey (e.g., small crustaceans such as copepods).

The next image highlights the fascinating suckers.  The hydromedusa was crawling to the other side of the eelgrass blade when I took this picture.

 

While watching the hydromedusa, we also observed an interesting behavior.  Occasionally it would draw its stinging tentacles and sucker tentacles into the bell and drag them past the oral tentacles (see next photo). This looked like feeding behavior (like wiping your fingers across your lips), although I'll admit that we didn't actually see the hydromedusa catch any prey and I'd feel more comfortable with more observations to say for sure.

P.S.  Libbie Hyman was one of the most influential invertebrate zoologists in North America.  She single-handedly wrote a six-volume treatise called The Invertebrates between 1940 and 1967.  The format of these books was later adopted by other invertebrate textbooks in use today, and her volumes are still consulted and admired for their depth and comprehensiveness.

Here's a nice photo of Libbie Hyman from the American Museum of Natural History's publication about her:

 

From Libbie Henrietta Hyman: life and contributions.  American Museum Novitates no. 3277 (published in 1999, edited by Judith Winston).