Hold on Tight: Little Isopods in Big Waves Part II

We’re in our second directed studies week at Bamfield Marine Sciences Center which is devoted solely to research projects. My partner Sam and I have big plans for this week, and although they seem to change every day we’re working hard and getting some interesting results. Our study organism is Idotea, a small isopod, and we’re investigating the biomechanics of the hooks on their legs. As I mentioned in my previous post, our overall question is:

“By what morphological and behavioural mechanisms do Idotea survive wave action while grazing effectively?” 

A baby Idotea under a microscope, you can see the little hooks on the ends of its legs. They are darker in the adults.

Sam preparing the Idotea for part of our experiment: a dislodgment cycle

One way we’re approaching this question is by dislodging Idotea from various substrata. We’re measuring dislodgment force between four seaweeds and comparing them to rock as a baseline. We’ve been running the idotea through dislodgment cycles all week: We tie dental floss “leashes” onto them then randomly assign them to Ulva, Fucus, Macrocystis, Porphyra, or a rock and give them time to attach. Different seaweeds have different material properties, some of which may make better habitat in high velocity waves, and others are preferred because they have high nutritional value. We think that the difference in material properties will make it easier for Idotea to hold on to tougher seaweeds, which may not be as nutritionally valuable. Once the Idotea are attached we measure the dislodgment force by pulling them off the substrate (seaweed or rock) with a spring scale. Each individual Idotea is dislodged from each substrate.

Fun in the field: Sam looking for idotea at Scott’s Bay

We’ve collected from two separate sites, a sheltered area on Wizard Islet and an exposed area at Scotts Bay. So far we’ve had a lot of fun out in the field collecting. We’ve noticed that those from the sheltered site were usually found under Ulva (a thin sheet like green seaweed) on rock but at the exposed site they were almost always on fucus (a thick branched brown seaweed). They seem to be showing differences in dislodgement force between sites, for example the individuals from Scotts Bay hold on to rock with more force than the individuals from Wizard.

Our collection sites: Wizard Islet and Scotts Bay (also called Eagle Bay)

This observation has sparked a lot of new questions. We’re now planning to put out dynamometers to measure maximum wave force at both sites, double our sample size so we can really compare differences between sites, and possibly even find more sites with exposed and sheltered areas.

Two adult Idotea being prepped for dislodgement with their dental floss “leashes”

It’s fun working with someone who has the same ADHD all over the place thought patterns as I do. We’ve revised our project so many times I hardly recognize our proposal and neither of us is particularly attached to previous ideas when new and more interesting ones come up. We’ve been working pretty long days, thinking a lot and analyzing data as we go, but I managed to get a quick surfing break in yesterday! And really, I can’t complain about fun and interesting field and lab work.

Off to learn how to use the flume for another mini experiment, then run some dislodgment trials! I’ll talk more about our work with the flume in another post, assuming all goes according to plan.

Until next time!
Christina

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5 thoughts on “Hold on Tight: Little Isopods in Big Waves Part II

  1. Hey, sounds like things are working out well for you guys. Are you going to do any feeding trials in the lab to see what their preferred prey is in the absence of wave action? It might be cool to see if the little guys from the exposed site switch from Fucus to Ulva…And how do you know which seaweeds are more “nutritious”?

  2. Hey, your project sounds awesome; I loved reading your post! Do you think that the difference in dislodgement force between the two sites could be due to a difference in the hook morphology, similar to the phenotypic plasticity exhibited by barnacle penis lengths in differing levels of wave action? Perhaps hook measurements between the two sites would show that longer hooks are better at grabbing the substrate/algae or vice versa. Are you doing experiments to measure substrate preference? Those results could also be really interesting to your project. Lastly, a bit of a silly (but necessary?) question that you probably already thought of. Is the dental floss you’re using flavoured? I feel like mint dental floss may negatively affect the performance of your Idotea.

    • Thanks for the feedback Nic! We have considered that and looked into the differences in dislodgment forces between our two sites. We’ve now doubled our sample size and have found no difference in dislodgment force between the two sites except for in fucus. Fucus has shown the highest dislodgment force, so this finding suggests that the maximum force they can exert may differ between sites, and could definitely be a result of hook morphology. If we have time that would definitely be something interesting to investigate!

    • And we used unflavored dental floss for all trials, we ran out and almost had to use mint for a few but wanted to be consistent so we waited for more unflavored.

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