Biol326: Experimental Biology Of Invertebrates

Hi, I’m your host Kai G. and today we’ll be exploring the home of the common woodlouse celebrity rapper O. A$ellu$.

Yo! What-up MTV! I’m O. A$ellu$, and welcome to my crib.

This 30-bedroom home is located under a fallen log in Pacific Spirit Regional Park, Vancouver, BC. Here, take a look under the roof:

This house is off the hook and has a few things that make it perfect for my lifestyle. Firstly, it’s dark and secluded, which is perfect for keeping me out of the way of my predators and haters who are always crampin’ my style. Secondly, it’s nice and damp under here which I need so that I can breathe. I don’t have lungs like you, I have gills instead (like fish) which need to stay wet to work properly, ya feel? Lastly, I never run out of food since I can eat the decomposing log around me. It’s dope. I also love to hang out here with my homies, as you can see in the picture above. We get a lot of benefits from living together, click here for a complete scientist’s explanation:

Benefits of aggregation in woodlice

I used to have a crib down the road, but humans came and messed everything up in the ‘hood. In fact, researchers at UBC compared the number of woodlice in an area of forest where tree-cover had been recently removed by humans, to the number before the disturbance and found that the abundance of my species was significantly lower afterwards! They also compared the disturbed site to a separate, unaffected site and found the disturbed site to have fewer woodlice, and fewer downed logs to use as homes. That’s whack. How would you feel if someone came to your neighborhood with bulldozers and tore up your home?

In my spare time I do a lot of charity work helping to decompose dead plants and recycle their nutrients back into my community. If I can’t live in an environment because of humans destroying my habitat, the whole ecosystem suffers. Without us, the soil has less recycled nutrients for plants to use to grow. Because plants are at the bottom of the food chain, if they suffer, EVERYONE suffers. So, if you want a healthy, happy ecosystem where everyone can thrive, keep your bulldozers out of our ‘hood!

Humans actively destroying our homes isn’t the only problem. My species is also really sensitive to changes in temperature and moisture. With the rapidly changing global climate, it’s going to make environments like this harder for us to survive in. See below for a scientist’s experiment looking at what might happen:

Effects of climate on isopods

Well that’s all for today folks, thanks for joining me. Don’t forget to tune in for the next episode where you’ll be shell-shocked by our next host – Leonardo daPinchi, and his crab house!

Have you ever gone out to the docks and peered into the ocean just at the edge of the wooden planks? If you have not, you will be surprised to know that there is quite a bit of wildlife right under your feet!

Last week we paid a visit to the Royal Vancouver Yacht Club at Jericho Beach on a mission to look for sea squirts (aka tunicates), and any other native species that may also be present.

The forecast called for rain but thankfully the weather was pretty moderate that day.

Tunicates are a species of marine invertebrates that are often seen stuck to the side of boats, docks, or many other hard surfaces. Also, these little sea creatures can be found in solitary, colonies, or even drifting in the ocean. They generally have two openings, called siphons, that allow water to enter and leave in order for these creatures to filter feed.

Our mission was to set up 1 meter transects along the dock and count the number of tunicates, number of other native species, and the relative number of mussels (percentage cover) that could be observed attached to the edge of the dock by looking into the water. Unfortunately, during our trip down to Jericho we were unable to spot any tunicates. Instead we were able to find mostly mussels attached to the docks, as well as a possible sponge species.

 

 

The main goal of this field lab was to find out whether the presence of mussels and/or other marine invertebrates could have an effect on the tunicate abundance in an area. It is possible for different species to either facilitate one another, which is a positive relationship, or for species to compete against one another for scarce resources, which is a negative relationship. For example, an instance of facilitation could be when a plant releases nutrients that make the soil around them more habitable for other plant species. While an example of competition is when different species must compete for the same prey, thus limiting the food resource. We want to explore whether these types of relationships were occurring in our research.

Other classmates had gone to a dock in Coal Harbour to look for tunicates and other species as well. However, they did not have much luck in finding tunicates there either. Only a few classmates managed to spot a couple of tunicates at Coal harbour. The data we collected from Jericho was compared to the data from Coal Harbour. We statistically concluded that there is no significant difference between tunicate abundance at Jericho compared to Coal harbour.

 

Looks like it was a bad time to be looking for tunicates!

 

 

Here are some links for more information on tunicates:

 

https://depts.washington.edu/fhlk12/links/StudentProjects/Tun.biology.html

 

https://www.britannica.com/animal/tunicate

 

Crabs are arguably some of the most well-known and photogenic critters in the intertidal. I mean just look at this little guy! They are a type of crustacean that are found in all different types of environments, from the deep sea to terrestrial habitats.

One of my favourite activities as a young wannabe marine biologist was flipping over rocks at low tide in search of shore crabs. I loved watching them scatter towards shelter, claws (which I now know to be called chelipeds) up in defense as the sped away on their eight walking legs. If you’ve ever been out exploring tide pools in the Pacific Northwest like myself, then you’re probably familiar with this small species of crab, Hemigrapsus oregonensis, commonly known as the green shore crab. Don’t worry, I don’t know the scientific name off the top of my head either.

See an example of this behaviour by clicking here!

When tasked with designing and carrying out an experiment to investigate the behaviour of these crabs in our BIOL 326 class, my mind went back to those little crabs scurrying to shelter as my pre-teen-self towered over them. In that situation, I was their potential predator and they were seeking protection from me in the form of a sheltered habitat.

With little knowledge of their behaviour besides this and the warning that they “can pinch hard when they have to” from our professor, my partner and I developed a research question: what are the effects of predator cues on their feeding and habitat choice? The predator cue that we used in this instance was pheromones from a predator of the green shore crabs, the big scary Dungeness crab. You know this guy, it’s the most commonly harvested crab in B.C.! Delicious when dipped in butter but a bit more threatening to the small shore crab.

To test this question, we set up a type of experiment known as a choice experiment. Basically, this means we gave the crabs two options from which to choose from: food or habitat. We predicted that in the presence of Dungeness pheromones, the shore crabs would choose to hide in the shelter of seaweed rather than staying exposed to feast on mussels.

This experiment took the form of three medium-sized fish tanks, each with seaweed on one end and mussels on the other. We filled the tanks with varying amounts of smelly predator water from the Dungeness tank then placed our shore crabs in the middle of the tanks (between the two choices) and recorded whether they chose to eat or to hide.

So what did we find? Anything interesting? Well, define sort of…the crabs chose to hide regardless of the predator cue. In other words, the results didn’t match our prediction but hey, that’s science. Clearly crabs choose habitat independently of predator pheromones. Why might this be? We’re not exactly sure but it’s possible that these crabs just weren’t that hungry or maybe their response was influenced by the big humans that were picking them up. Either way, we can only find out by asking more questions and designing new experiments.

To learn more about green shore crabs check out this link or check them out on iNaturalist!

The intertidal zone: the area where the high tides cover and low tides expose; the interface between terrestrial and marine ecosystems; the home for rich communities of crabs, limpets, snails, barnacles, and more.

The rocky shore houses these communities (Image 1) where all these animals face the same challenges and stresses of intertidal life. These invertebrates need water to respire and survive, yet they are exposed to air twice a day, isolated in pools, and experience large fluctuations in temperature and salinity, extremes in wave action, as well as predation from land animals (and us!).

To learn more about the amazing properties and life in the intertidal zone, visit https://www.crd.bc.ca/education/our-environment/ecosystems/coastal-marine/intertidal-zone

This is a lot for such small creatures to go through, and they have become strong and adapted to these extreme conditions over time. Yet life throws them another curve-ball, that is, global warming.

As a result of global warming, large amounts of CO₂ enter the ocean and through different reactions, increases the acidity of the seawater. Ocean pH averages at 8.1, but in the intertidal it can reach as low as 7.6 pH and is expected to reach lows of 7.2 pH in 2100. These changes of 0.1 pH affect our intertidal species incredibly, and I took it upon myself to study one of the most beloved intertidal organisms, the checkered periwinkle Littorina scutulata (Image 2).

Learn more about ocean acidification and implications: https://www.nationalgeographic.com/environment/oceans/critical-issues-ocean-acidification/

I set out on my adventure to Tower Beach, UBC Vancouver in early March of 2019. These guys love to hide in broken barnacle shells on top of rocks and graze on algae and sea weed. After collecting them in containers with sea weed to keep them happy, I divided them into three seawater treatments (pH 7.6, pH 7.7, pH 7.9) and let them sit for two days before experiments.

My hypothesis:

Snails will have a lower thermal tolerance at a lower pH.

My reasoning:

When put under acidity stress, the snail will suffer internally, inhibiting proper function and balance of its body’s pH, causing it to perform worse under high temperature.

My experiment run-down:

Each snail was placed in its own falcon tube with the same seawater as their treatment. After attaching to the wall of the tube, I slowly heated the water and recorded when the periwinkle would detach itself from the tube wall. Escargot anyone? Just kidding! The high heat temperature only induced a heat coma on the snail, so they fainted rather than became a meal.

Experiment findings?

I did not find any significant effect of pH on snail thermal tolerance, perhaps because these periwinkles have already adapted to these pH levels in their normal environment. What I did find, however, was that with larger shell size the snail’s thermal tolerance was lower. This could be due to the added stress of its shell weight to its already lowered metabolism and respiration under acidic stress.

Ocean acidification poses a lot of stresses on periwinkles, including weakened and impaired shell growth and reduced metabolism, which together cause them to be less protected and more vulnerable to disease. If my hypothesis is true in more severe acidic conditions, this could mean periwinkle populations would be impacted, and without them the marine ecosystem would not function the same.

For more information on the periwinkle species of BC and where to find them, see here: https://www.thecanadianencyclopedia.ca/en/article/periwinkle

Okay, I didn’t mean that exactly, but I’m pretty sure that you, and almost everyone else on this planet, are making the world’s oceans more acidic. Let me explain.

Many of the things that we do, as we go about our daily lives, contribute greenhouse gases to the atmosphere. In fact, our vehicles and industrial activities generate about 24 billion tons of carbon dioxide per year, which is 120 times the amount produced by all of the world’s volcanoes! The oceans have been able to absorb as much as half of the carbon dioxide that we have put into the atmosphere. So, if carbon dioxide leads to climate change and rising temperatures, and if the ocean can remove it for us, then we’re all good, right?

If only things in life were that simple… The carbon dioxide that is dissolved in the oceans goes through a series of chemical reactions, eventually increasing the concentration of hydrogen ions in the ocean. The more hydrogen ions, the lower the pH, and the more acidic the oceans become. 

Ocean acidification has many negative consequences, such as making it harder for shellfish, sea urchins, and corals to build and maintain their shells or skeletons. Difficulty forming skeletons isn’t the only consequence for corals!

What about other creatures that call the ocean home? Get ready to learn about how too much “crabon” dioxide in the water affects our crabby friends!

As an aside, if you’re ever on a beach, try flipping over some of the larger rocks. You might be amazed at what you discover! 

The green shore crab is one of the animals you’re likely to find on the West Coast. They are scavengers that can be found from Alaska all the way down to Baja California, and are what I studied for my independent project.

I found that the crabs weren’t affected very much by low pH. It turns out that they may be more tolerant to ocean acidification than I thought. Here’s some research on how ocean acidification is expected to impact marine crustaceans (the diverse group of ocean-dwelling animals that includes crabs, but also, lobsters, barnacles, isopods, and more) by 2100. Luckily, many of them aren’t too sensitive to low pH and will likely be okay! Sadly, the same doesn’t hold for many other oceanic life forms.

The devastating impacts of ocean acidification don’t stop there! Check out this video to learn how we humans will be affected! 

We dug for treasure, and boy did we find it!

This past March, the Experimental Biology of Invertebrates class went to the beautiful community of Bamfield, on the west coast of Vancouver Island. Anyone interested in visiting should make a point of getting out there! Beware the journey though… it’ll be 90 minutes up a gravel road. The destination is completely worth the journey!

Our first taste of the Bamfield life was a trip on the “Alta,” captained by the amazing Janice! We were all buzzing with excitement as we were suited up in PFDs and boarded! After a short ride, we were introduced to our first critter of the trip, Steller sea lions! While they weren’t exactly invertebrates, they were certainly stellar, and I’m not sea lyin’.

After our quick visit with the sea lions, Captain Janice took us to the treasure trove in Barclay sound, where we would search for our loot. Once there, she deployed our treasure digging shovel, in this case a dredge net. Ten minutes or so of digging and we were ready to pull up our prize. We definitely hit pay dirt!

What we found was beyond our wildest dreams! We found dozens of species of fish, invertebrates, creepy crawlies, spiny creatures and slimy things!

One of the most beautiful creatures we found was the purple ring top snail. What a gem! It’s hard to believe that this is a real animal and not a gem stone! The one in the photo below is small, but some can get up to 30 cm tall. Can you imagine how spectacular that would be?

Another beautiful creature we found in the dredge was the vermillion sea star seen below! Can you guess how it got its name? These beauties can be from California, all the way up to Alaska! Sadly, they are subtidal sea stars, so you’re not likely to find them while beach combing.

Our next treasure is the vermillion star’s cousin. See if you can see any resemblance between the two! This one is the purple urchin. These poky fellas can live for up to 70 years! Urchins can actually move those spines around at will!

The last creature feature for this post is a cute little hermit crab with an unorthodox approach to hermiting. Most hermit crabs use discarded snail shells as their homes. This one decided to do so in what appeared to be a tube worm casing! The little crab seemed pretty comfortable though. They say home is where the heart is, even if it is a little unconventional!

We were so lucky to get to see these critters up close and personal. There were some concerns, however about the effects of dredging on the environment of the sea floor, as it has the potential to be harmful. Turns out the waves coming into Barclay sound from the open Pacific are so powerful that they naturally churn the bottom around anyway, and is actually beneficial for the system. Captain Janice let us know that she has spoken to divers about it. Apparently, later the same day, the divers can’t even tell where the dredge happened.

It was really good to know that our actions were having a limited impact on the environment. In today’s age where it seems like so many species and ecosystems are in peril, it is important that we are always considering our impacts on the nature, species and people around us. Being conscious of our effects, even when they seem small, on our surroundings is a great first step in mitigating such influence on the environment.

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Other cites to check out:

Bamfield marine science center official website: http://www.bamfieldmsc.com/

More information on purple ringed top snail: https://www.centralcoastbiodiversity.org/purple-ringed-topsnail-bull-calliostoma-annulatum.html

More information on the vermillion sea star: http://www.racerocks.com/racerock/eco/taxalab/mediastera/damieng.htm

More information on the purple urchin: https://en.wikipedia.org/wiki/Strongylocentrotus_purpuratus

To learn more about hermit crabs: http://ibis.geog.ubc.ca/biodiversity/efauna/CrabsofBritishColumbia.html

When you take a walk along rocky beaches and lose your balance, it hurts when you fall. The barnacles that cover all the rocks are hard and pointy. At first glance, you wouldn’t assume that they are animals. But they are! They are inside the hard exterior!

Barnacles are arthropods and are actually more closely related to crabs than other animals like mussels! They are very important in the intertidal zone where you can find them. They cover a lot of the space available for other organisms, so they “control” the presence and abundance of other organisms and competition! So if barnacles are affected negatively by climate change factors such as temperature and salinity, then the entire intertidal ecosystem structure can change!

This is why climate change is a serious issue that must be tackled to protect ecosystems and biodiversity! The oceans will get warmer and will get less salty. This will make it difficult for marine organisms to live.

Because of how dangerous climate change is, I wanted to take a look at how temperature and salinity affected barnacles. In order to survive, barnacles must eat like all of us. Therefore, I looked at their feeding rate in response to the stress of different temperatures and salinities. It’s like how right before a big test, humans get too stressed to even think about food! Would barnacles react the same? I wanted to find out.

So the question is: how do barnacles even eat? Especially when they look like shell structures! Well, they have legs called CIRRI! They beat as a cirral fan to bring in food particles from the seawater. The cirri trap food and eventually bring it closer to their mouths. They are filter suspension feeders!

Keeping that in mind, I exposed barnacles to 3 different levels of temperatures and 3 different levels of salinities (INSTANT ocean sea salt was very helpful here!), and counted how many times they flicked their cirri in 1 minute. Sounds simple enough.

Boom! The results were definitely interesting! Less salty water made them feed slower! This means that with climate change making the ocean less salty and more fresh, barnacles might not be successful in being able to EAT! Cold temperatures led to barely any feeding at all! Warmer temperatures actually made them eat faster, because of increased metabolic activity.

However… what if they were in warmer temperatures for longer periods of time? Would they still succeed in feeding? Is that a chance we are willing to take by letting climate change continue its course without trying to fix it? NO! Climate change also makes things super cold in winters while keeping it hot in the summers! So probability of survival via finding food? Not that high.

My little experiment proves that they are going to be affected by climate change and we need to do something to keep the ecosystem in balance! Barnacles are strong and can tolerate a lot of stress but the combined effects of different stressors will eventually run them down! Protect the barnacles and their right to use cirri! It’s cirri-ous!

For some fun facts about barnacles and romance, check out this video:

Here is some information on climate change:
https://www.theglobeandmail.com/canada/article-report-on-climate-change-shows-canada-warming-at-twice-the-rate-of/

Want to learn more about stress and barnacles? Check out this quick link:
https://www.ncbi.nlm.nih.gov/pubmed/26615725