Barnacle brains

Windy ride

By  Nicole Webster

I was on the east side of Vancouver island last weekend and noticed an interesting phenomenon on some barnacle rocks:

A brainy barnacle (not quite) boulder

A brainy barnacle (not quite) boulder

The barnacles in the centre of a bump are taller than the others.

The barnacles in the centre of a bump are taller than the others.

Here's a single barnacle extruded

Here’s a single barnacle extruded

This was wide spread across the rocks in this area, but not universal.

This was wide spread across the rocks in this area, but not universal.

What is going on here? Have you seen this before?

I had a thought relating to competition and/or the boundary layer. Barnacles are particle feeders, scooping tasty treats from the water column. They also can come (as seen here) in very high densities. If you and your neighbour are both trying to steal the same nutritious blobs, there’s a problem. If you are just a little bit taller, you can reach out that little bit further and get the scoop. The same explanation fits when you look at fluid dynamics.

Water is a sticky substance, that’s how the meniscus is formed on your water glass or graduated cylinder. This causes a big problem for some aquatic animals, especially small ones, because the water sticks to every surface, including yourself. This creates a layer of highly viscous water covering everything – the boundary layer. This water is slow moving, and for a particle/filter feeder, is quickly emptied off all its foods. Thus animals need to reach out further from themselves to reach the faster moving water that is constantly refreshed with particulate matter/snacks. This is a simplistic explanation, and doesn’t touch on all the effects of a boundary layer on organisms, but will suffice here.

This might explain why some barnacles are so tall in the center, trying to reach out beyond the boundary layer for food.

Neither of these ideas help the barnacles in the grooves, which don’t seem to be unhealthy (although I did not complete a thorough survey to test this). Speculation: Perhaps the winding grooves act as ‘wind tunnels’, increasing the turbulence of the water (a factor which reduces the thickness of boundary layers), producing more flow in the depths of the brain as well….

Hrm..

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Barnacle Sperm Casting

By Marjan Barazandeh

Whenever you go to intertidal shores in almost any island in Barkley Sound, you will find hundreds of calcareous shells, ranging from less than 1 cm to 10 cm, attached to the surface, on bare rocks or on mussel beds. Believe it or not, they are not mollusks! They are barnacles, a group of crustaceans that have amazed evolutionary biologists, including Darwin, for more than 150 years.

The typical and most familiar barnacles are acorn barnacles. They usually have 6 fixed calcareous plates surrounding their body that are permanently cemented to the substrata and 2 pairs of moveable plates at the top (Fig 1).

Fig1. Different species of acorn barnacles: Semibalanus cariosus (the largest ones), Balanus glandula (the white-yellow smaller ones) and Chthamalus dalli (the brown smallest ones). Credit: M. Barazandeh

Fig1. Different species of acorn barnacles: Semibalanus cariosus (the largest ones), Balanus glandula (the white-yellow smaller ones) and Chthamalus dalli (the brown smallest ones). Credit: M. Barazandeh

The gooseneck (stalked) barnacles are the less familiar group. They attach to the substrata by a long fleshy stalk and the two valves, usually made of 5 plates, are at the top of the stalk (Fig 2). I have never tried them, but there are a lot of people who eat stalked barnacles and claim they are delicious.

Fig 2. Clump of Pollicipes polymerus, a gooseneck barnacle. Credit: A.R. Palmer

Fig 2. Clump of Pollicipes polymerus, a gooseneck barnacle. Credit: A.R. Palmer

The organisms inside the shells are shrimp-like animals, which lie on their back, with the head attached to the bottom surface, and grab food from the water using their feathery legs. Except for a few species, most barnacles are hermaphrodites, so they are able to act as both males and females.

Well, there are many cool facts about barnacles, but the most famous one is perhaps their long penises, which in some species could extend up to eight times their body length. You can imagine how advantageous this would be to sessile organisms. They can copulate with several neighbors and release their sperm into their mantle cavity. But is that true for all types of barnacles?

Pollicipes polymerus is an intertidal gooseneck barnacle with a relatively short penis, which is less than their body length, even when extended (Fig 3). It’s not a disaster for this species since they are usually found in tight clumps (Fig 2).

Fig 3. a) Balanus glandula penis length versus b) Pollicipes polymerus penis length. Credit: C.J. Neufeld

Fig 3. a) Balanus glandula penis length versus b) Pollicipes polymerus penis length. Credit: C.J. Neufeld

But what about those individuals that don’t have any neighbors in their penis range? How sad their love life would be! Well, some species have overcome this problem by self-fertilization; however, P. polymerus is presumed incapable of self fertilization. Yet, there are several isolated individuals that have fertilized egg masses (Fig 4). How did they get fertilized? That was the initial motivation to my study. The first possibility: maybe, they are able to self-fertilize!

Fig 4. Pollicipes polymerus, an isolated individual (left) and an isolated pair (right). Credit: A.R. Palmer

Fig 4. Pollicipes polymerus, an isolated individual (left) and an isolated pair (right). Credit: A.R. Palmer

On the other hand, by doing a close survey in the field, we found a lot of P. polymerus leaking some white liquid out of their opercular plates at low tide (Fig 5). Is that the sperm? If it is, then what would be the fate of it? Could that be captured by other individuals? Nobody has ever suggested this could happen in any crustacean.

Fig 5. Pollicipes polymerus leaking sperm at low tide. Credit: M. Barazandeh

Fig 5. Pollicipes polymerus leaking sperm at low tide. Credit: M. Barazandeh

That’s when my supervisor (Rich Palmer), my ex-labmate (Chris Neufeld) and I went out to a few beautiful islands in Barkley Sound and collected as many isolated fertilized individuals as we could (Fig 6). We also collected some isolated pairs, where there were two adjacent individuals, not having any other barnacles around, and at least one of them was fertilized.

 Fig 6. Chris and I, Seppings Island, August 2009. Credit: A.R. Palmer

Fig 6. Chris and I, Seppings Island, August 2009. Credit: A.R. Palmer

I brought them back to the UofA, where I had access to all molecular tools I needed and to the experts that could help me with developing genetic markers for my species, Dave Coltman and Corey Davis. The plan was genotyping both the adults and the egg masses to see if there are any alleles in the egg masses that are not present in the adults. Those must have been obtained from water.

I spent more than a year developing microsatellites for P. polymerus without any success (sigh…). Then I switched to Single Nucleotide Polymorphisms (SNP). I developed 16 SNPs and got whatever I needed in a month! I don’t regret the time I spent on microsatellites because I learned a lot during the troubleshooting process and I’m pretty sure I can use all those experiences some time in the future.

So, the results were fascinating or as Rich Palmer says: “Darwin would be thrilled by this!” All of the egg masses of isolated individuals had at least one allele, not present in the parent. Even in isolated pairs, there were alleles that belonged to neither of the two adults. So, that’s official! They are able to spermcast! It doesn’t mean that they don’t copulate, but at least we now know that they also capture sperm from the water. This is the first example of spermcast mating in aquatic arthropods, which makes us re-think barnacles’ reproductive biology and all the previous reports on self-fertilization in barnacles. This could also have a major impact on previous barnacle population studies that assumed no spermcast mating!

Our results were just published last week (Jan 16, 2013) in Proceeding of the Royal Society B: Biological Sciences (http://dx.doi.org/10.1098/rspb.2012.2919) and surprisingly, we received a lot of media attention about that paper. We were bombarded with emails asking questions and requests for interviews. Honestly, I wasn’t expecting this at all. Like most of other projects, there were lots of disappointing moments during this study, but at the end it was worth all the effort we made. We have a web page for this study, including the media coverage and some of the brilliant headlines used in articles: http://www.biology.ualberta.ca/palmer/pubs/13PRSL/13PRSL.htm

So, the take-home message is we should always be curious about what we observe and have the courage to question the old beliefs.

A spongy habitat

By Danielle Ludeman

The world is full of organisms, living on organisms, that are living on other organisms.  You just have to take a moment to think about the complexity of life that can occur to start to appreciate all of the life around us.  Take a tree in your front yard – at first glance you may just see a tree, but when you start to look closer you notice the bird nest that will be home to baby chicks in the spring, and the squirrel that runs up and down the branches.  Then you notice all the different types of moss, lichen, and mushrooms that are growing on the tree.  And upon closer inspection you realize that this creates even more space for a variety of spiders and insects to thrive.  And we can keep going on and on to include all of the life that we need a microscope to see. And this is just on a single tree!

This summer, while doing some field studies at Bamfield, I began to appreciate all of the life that can be found on a single sponge.  Now it is well known that sponges can be very important habitat for many organisms, with some species being obligate commensals of sponges, meaning they can ONLY live on a sponge to survive.  But when I started to look closer at some of the sponges in my studies, I began to realize just how many other organisms call a sponge its home!  One species of sponge in particular – Suberites sp.  that I collected off of Brady’s beach – seemed to have a surprise guest visiting every time I looked at it!  I managed to photograph a few of these, and thought I would share these with you in the slideshow below!

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Tight living spaces for life in the intertidal zone of Tapaltos Beach

Amanda loves tide pools

By Amanda Kahn
Sometimes, students may feel like they’ve had to share close quarters, sharing apartments or dorms or rooms with multiple roommates and generally feeling like there just isn’t enough space.  Animals, plants, and algae that live in the intertidal zone have to deal with that feeling all the time!  Below is a photo of the “mussel zone” at Tapaltos Beach.  Can you count how many blue-black mussels there are in that photo?!  I count at least 70, and it looks like there are even more white, scaly-looking gooseneck barnacles!

Intertidal organisms of Tapaltos Beach

Intertidal animals and algae compete for space at Tapaltos Beach. Credit: D Ludeman 2011

I guess we humans have another advantage beyond the tighter quarters the animals have to share…at least when sharing an apartment, it’s arguably all one species sharing the space!  How many different animals, plants, or algae can you recognize in this picture?