BIOL 326: Experimental biology of invertebrates

“What was the coolest thing you saw at the beach today?”

The answer to that question is rarely, if not ever, “The barnacles!!”

You might think there’s nothing to these seemingly boring white rock decorations, but believe me, they are having an absolute party underneath those white calcareous plates.

What even are they?

Barnacles are related to crabs! They are in the same subgroup (subphylum), Crustacea, under the group (phylum) Arthropoda. A distinctive overlying trait of arthropods is segmentation of the body and jointed appendages, such as legs. This trait is very apparent in most organisms in this group like insects, shrimps, spiders, crabs, and lobsters.

So how the heck do these things, belong in the group Arthropoda? Where are its jointed appendages?

To get to the bottom of this mystery, we will have to rewind time a bit to when this barnacle was just a wee zooplankton (baby).

Baby Barnacles!

Barnacles like most marine invertebrates start off as tiny little zooplankton.

Below, is an an early larval stage of an acorn barnacle moments after hatching, this stage is called the naupliar stage.

WOAH! LOOK AT ALL THOSE JOINTED LEGS AND SEGMENTED BODY SECTIONS!!

As you can see by this nauplius larvae trying its best to swim in a microscope slide, this stage is what allows barnacles to disperse, and get to where we eventually see them on rocks and docks.

Here is a more complete look at the life cycle of barnacles to get a better picture of how they go from babies to adult barnacles. (If you are interested in a more in depth exploration of the life cycle, check out this video!)

What happened to all those segmented legs in the naupliar stage?

If you spend a little quality time with adult barnacles under water, you may start to see them feed!

The fan-like appendages coming out to feed are actually their legs and they are called cirri!

You may be wondering things like, “What are they eating?” and “I don’t really see the cirri catching anything??”

That’s because they catch tiny plankton in the water by filtering and combing the water. We can’t really see what they’re catching because most of the plankton they’re feeding on are microscopic.

Here is a picture of their moult to get a better look at their structure! Take a look at the hairs coming off the cirri. They are there to maximize the capturing of plankton. MMMMM yummy.

(Barnacles also have another incredibly long thin appendage used for something very different. If you’re interested in barnacle copulation, check out this video!)

Thanks, barnacles!

Barnacles provide services that support the maintenance and creations of other ecosystems. Just by existing, adult barnacles create habitats for other organisms that need a place to settle. They also help purify the water as they feed on suspended dead materials in the water in addition to plankton through their filter feeding!

Barnacles are important to our ecosystems, so we want them to stick around. Climate change however, could pose a potential threat to barnacle populations. To better understand how climate change would affect barnacles, we exposed adult barnacles to higher temperature water to see how it would affect their feeding rate. (Here’s a picture of us observing their feeding rate)

Hopefully by better understanding the how climate change would affect barnacles, we will be better equipped to deal with the effects and make sure that our barnacle friends are doing well 😀

You know that feeling when you put your snail down for a snail race only to have it hide in its shell and never move the entire time? Well, I can’t say I’ve participated in many snail races, but boy do I have a solution for you.

A few weeks ago in lab, we were talking about TMIIs (which does not stand for Too Much Information with an extra i). TMIIs are Trait-Mediated Indirect Interactions — but what does that mean, do you ask? Well, it means that I’m about to solve all your snail-racing worries.

If your fastest little snail was chomping on some lettuce with all its might, then you can say that the snail is directly impacting the lettuce, and the lettuce is not having a good time.

Now what if a crab suddenly decided to join the party and decided that your speediest snail looked tasty? Well, your snail would zoom right out of there for fear of being chomped on (see where this is going?). Then you can say that the crab has a direct effect on your zoomiest guy.

But what about the lettuce that was left behind? Since the crab scared away your speedster, the lettuce can chill out and… do whatever it is that lettuce does when it’s not being eaten. In this way, you can say that the crab has an indirect effect on the lettuce. And in the same way, crabs can have an indirect effect on your next snail racing championship.

But am I really asking you to bring an entire crab to your next race? That sounds like a really good way to get disqualified. No no no, we’re going to be sneakier than that. Now that we know about the indirect interactions part of TMII, let’s look at what trait-mediated means.

Remember when your speedy snail zoomed away from the crab and set the lettuce free? Well, how did your snail know that there was even a crab to run away from? What I neglected to tell you earlier was that all of this was happening under water, and that your snail was actually able to smell the crab as it made its not-so-sneaky approach. And since your snail was able to smell the crab and run away, we call it a trait-mediated interaction.

If your poor snail was eaten by the crab (heaven forbid), we would call that a density-mediated interaction. The lettuce would still be indirectly affected by the crab, but that would be through a Density-Mediated Indirect Interaction (a DMII, if you will) rather than a TMII (have I given you too much information yet?).

With that out of the way, now it’s time for the fun stuff. In the lab, we got a whole bunch of periwinkle snails in a tank (shown below).

We wanted to see just how fast these snails would move if they were placed in water filled with Big Tony smells (Big Tony is a natural predator of these snails, shown in the picture below). One of the ways we did this was by placing them into cups with water from Big Tony’s tank and seeing how long it took for them to crawl out of the water. We also put them in cups of regular sea water just to make sure they weren’t afraid of the water or something. And then we also had cups with starfish-smelling water (another predator) just to see what would happen.

More super scientific testing was done in tanks filled with either Big Tony water, Starfish water, or regular water to measure snail speed. And finally, we placed the snails in dishes with the different waters and some yummy, yummy algae for them to eat to see if the smells in the water affected how much they wanted to eat (to really test those trait-mediated indirect interactions).

So how would you win a snail race using this information? I would recommend letting your snail sit in a bit of crabby water (make sure the crab is a natural predator of your snail!) before the race, and hopefully that will get your zippy guy in a hurry.

But now you might be worried that there is a whole class of scientists out there scheming to take over the snail racing industry, but in reality, we were interested in how these interactions affect ecosystems in the wild. To learn more about how snails, crabs, and algae interact in the wild, take a look at this paper that examines all of the above and more! https://doi.org/10.1098%2Frspb.2016.2590

Happy snail racing!

Have you been considering joining a yacht club in Vancouver? There are many things to consider including quality of food, entertainment, dock neighbours and lets be honest, whether anyone there has a nicer boat than you. But don’t fret, the tunicates are here to help you make this tough decision. The verdict is in and tunicates voted for Coal Harbour over Jericho by a long shot. Keep reading to find out why local invertebrate species are worried about this new invasive species travelling from far and wide to become a member.

We went to both locations and would lay down on the docks and look over the edge to see if tunicates were present, if they were on the sunny or shady side, and how many other species were there. Lets take a look at what coal harbour has to offer that Jericho doesn’t.

Coal Harbour

Pros

• More intertidal friends due to higher salinity
• This is due to Coal Harbour being farther away from the mouth of the Fraser River

Cons

• Far from UBC
• Will have to fight through Downtown Vancouver’s traffic to get there

Jericho

Pros

• Sea angel and nudibranch neighbours

Check out this cute video of a sea angel swimming in circles!

It is safe to say there is a lot of future research that can still be done. So don’t take the tunicates word too seriously if you are a fan of Jericho Yacht club.

Who lives in a pineapple under the sea? If you grew up watching Spongebob Squarepants as often as I did, you’re no doubt familiar with the catchy theme song, the bright yellow square sponge, and his humorous pink starfish friend, Patrick. Patrick is a sea star, commonly known as a starfish. Most of us recognize these iconic marine animals as a key part of our oceans –  a reminder of sunny summer vacations at the beach. But what if I told you that billions of them are perishing? 

Can you guess the culprit? Unsure? So are we. Researchers have tried to narrow down the exact cause of the disease, originally claiming a virus as the cause, but later finding flaws in that conclusion. 

Donning detective hats and scientist lab coats, we set off on a mission to learn more about this mysterious disease, known as sea star wasting disease (SSWD). We wanted to know if SSWD could be spread among different species of sea stars using various modes of transmission. 

Using sick ochre sea stars, we infected sea stars of two other species known as the leather sea star and the mottled sea star. We tested three modes: water transmission, physical transmission by swab and transmission via injection of bodily fluids. 

As expected, stars started getting sick and resembling the 3 week-old lasagna you forgot was tucked away in the back of your fridge (and the smell was even worse, trust me). We found that all three modes of transmission could transmit SSWD to both the leather and mottled sea stars. Even some of the control stars that were not exposed to any infection started to get sick which suggests they might have been infected before we brought them into the lab. This brings up an important issue in SSWD research – we can’t know the life histories of sea stars collected in the field but stars are also difficult to breed in the lab, making it hard to learn more about this disease. 

Overall, SSWD poses a dire threat to many species of sea stars. Such drastic die-offs have large effects on aquatic food webs and can lead to the collapse of entire ecosystems. More research is needed on the exact cause of the disease and how it is transmitted. 

Want to know more? Watch this 2 minute video from the Hakai Institute on SSWD and how sunflower sea stars in particular have been hit the hardest. Also check out this recent article by the Seattle Times for a great summary of all the details or this paper which touches on SSWD transmission if you have a little bit more time on your hands. 

The sounds of gunshots, dark green slimy liquid, long hairy appendages, and screams of terror (this last bit might be an exaggeration). These frightening things all sound like we were working on the set of a horror movie but turns out, they were all a part of the excitement during our lab this week! 

The focus of this week’s experiments was to look at the impacts of climate change on filter feeding in barnacles as well as in Bay mussels and Pacific oysters, two ecosystem engineers that provide an essential ecosystem service in our oceans. 

Before I delve into the chaos that happened in the lab, let’s define some terms and explain why our work is important!

Filter feeders are organisms that, well it’s in their name, filter water to obtain food particles! They have special structures that allow water to flow through their system and pass over surfaces that capture food particles which they then digest. Here’s an awesome video of filter feeding in sponges:

Ecosystem engineers are organisms that can change the environment they live in. Their presence has a significant effect on resource availability in an environment, therefore they are essential for maintaining healthy and stable ecosystems.

Filter feeding is an important ecosystem service, which is any positive benefit that ecosystems provide and is useful to humans. 

So what’s the point of looking at the impacts of warming temperatures on mussels and oysters? Filter feeders are essential for maintaining our oceans as they help filter out toxins and cycle nutrients for other organisms. Any risk to them would also mean a risk to the health of our oceans. Heat stress, as a result of climate change, can negatively impact the way mussels and oysters can carry out their functions. Therefore, understanding the ways these organisms respond to increasing temperatures is important to help us predict how their behaviour and their ecosystem services will change in the future. 

This video shows just how effective oysters are at filtering water and gives us an idea of their importance in ecosystems!

Now back to the chaos. You might be wondering what could possibly sound like a gunshot inside a laboratory. Well, as it turns out (after experiencing a few scares myself), that’s the surprise you might get if an air tube doesn’t attach properly to an air supply. And what’s with the weird green liquid? Don’t fret as that was simply our algae concoction used to feed our filter feeders! The long hairy appendages, as frightening as they may seem, were actually the amazing structures that barnacles use, called cirri, to feed. And yes, barnacles are living creatures!

Here’s a video I captured of the barnacles in action!

With tubes hanging from the ceiling, grueling minutes of counting tiny algal cells, and looking at hundreds of barnacles feed, BIOL 326 students sure experienced some exciting chaos during our lab but hey, that’s the fun in science!

Want to learn more about filter feeders? Check out this article on the ecosystem services that clams provide in Florida habitats!