Food Preferences of Idotea: Little Isopods in Big Waves

It’s that time of year: the temperature is dropping, the trees are changing colour, and students everywhere are submerging themselves in their textbooks and hunkering down for the winter. At Bamfield Marine Sciences Center we have just started our research projects and my classmate Sam and I have decided to team up!

Me, Sam and Rihana out for a hike at Cape Beale

We have three separate weeks throughout the term set aside for our research projects, but can work on them in our free time as well. Sam is interested in algae and has been involved with the Martone lab at UBC researching seaweed biomechanics and I am interested in invertebrates and biomechanics. So we began talking to other scientists around the marine station and brainstorming.

Waves in a rocky exposed site at Cape Beale near Bamfield

Life in the intertidal is very stressful for many reasons. Some of them are chemical, as I discussed in my research this summer, and some are physical. Waves in the intertidal can be huge and put a lot of selective pressure on both animals and algae living there. One problem with these wave forces is dislodgement. If you are an alga or animal trying to live in these high flow areas you have to be able to hold on or you could easily be swept out to sea.

An Idotea: Cute may be an exaggeration, but they are pretty awesome. Note the hooks on the end of their legs which are assumed to be used for attachment. *photo from marLIN

There are these cute little isopods called Idotea that feed on algae in the intertidal. They are important herbivores in the intertidal and can be found at wave exposed sites. These animals are obviously well adapted to hold on for dear life in high water flow. Sam and I had many thoughts and questions, so we sat down and packed them all up into one overall question:

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

One of our smaller questions within this involves the trade off between food choice and habitat. In life there are always trade offs. Just as we have to balance love of chocolate and daily caloric intake, herbivores in the intertidal have to balance nutritional value and safety from wave forces causing dislodgement. There are many different algae in the intertidal offering different protection and nutritional advantages.

Ulva lactuca, a thin green bladed algae common in the intertidal

Fucus distichus, a brown algae commonly found in the intertidal

We want to test the trade offs involved in feeding and habitat preferences of Idotea. We’re using the algae MacrocystisFucusPorphyra, and Ulva in our study. We believe Ulva, a thin green blade like algae, will be a preferred food source due to it’s high nutritional value, but Fucus, a thicker branched brown algae or the kelp Macrocystis will be preferred as habitat. Idotea may be able to attach with more force to Fucus or Macrocystis than Ulva and, in the case of Fucus, be more protected from wave forces.

Over the next few weeks we will be grinding up algae and feeding it to Idotea to see which they prefer as a food source as well as placing Idotea in tanks with un-ground algae in flow and seeing which algae they prefer as habitat.

In the field, the best place to observe and decide what to do next . Photo credit: Rhian Tate

As far as our other hypothesis and experiments go we have quite a few ideas and I think we are going to get some very interesting results. Hopefully we’ll even get to play around with the flume!

I hope everyone enjoyed their Thanksgiving weekend!


3 thoughts on “Food Preferences of Idotea: Little Isopods in Big Waves

  1. Another way to get at the form vs. herbivory question would be to make ‘algae’ out of non-edible material (like rubber or latex). If the same preference was observed in the inedible ‘algae’ as the natural algae, then it would suggest morphology as the underlying cause for the preference.

  2. Pingback: Data Collection and a Million Questions | The Transient Biologist

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