Barnacles are small, seemingly inconspicuous little animals, especially when compared to some of the more charismatic animals of the intertidal such as crabs and flatworms. Yet they are surprisingly important for us to study, as they have both economic and ecological impacts on their environment, being common biofoulers. They are dependent upon upwelling and other seasonal conditions for larvae dispersal and feeding, and once settled for the second half of their life history, they cannot crawl away when the environment changes or becomes too stressful, so they must be prepared to adapt.
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Chthamalus barnacles in the intertidal
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They are dependent upon upwelling and
other seasonal conditions for larvae dispersal and feeding, and once settled
for the second half of their life history, they cannot crawl away when the
environment changes or becomes too stressful, so they must be prepared to adapt.
We have evidence suggesting that tidal cycles and seasons affect when they
recruit, but rainfall may not be important.
What we don’t know are how individual variables, (like temperature, food
supply, salinity, light exposure, etc), affect their growth, development, and
reproduction. To investigate these, there are two possible approaches: field
experiments that monitor all variables and suss them out via statistics, and
lab experiments that isolate one variable at a time at the cost of being
realistic to nature. Because I was raised as a molecular biologist first, I
think in terms of controlling variables individually, so I embarked on a small
project to establish an in-lab culture of “white” barnacles from the field for
the Collin lab to experiment on.
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A tiny juvenile
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Because there is not much published information on techniques for culturing our local barnacle species from larvae through adulthood and reproduction, I had to start at square one. This meant investigating basic food supplies to find the optimal concoction for growth. I started with some juveniles from a separate field experiment, I kept their temperature, volume of water, and salinity constant, and floated them on plates face down in individual dishes that got fed and water changed three days a week.
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The algae I used to feed the barnacles
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Half of the juveniles were fed just one type of algae (Isochrysis), and the other half got a mixture of two kinds (Isochrysis and Rhodomonas), to see if a combination was more nutritious than just one type. To feed, I first centrifuged our algae to remove the F/2 medium that might be toxic to juvenile barnacles. Then I resuspended them in a small amount of seawater, and counted them on a hemocytometer. (Because I used different kinds of algae, we took relative volumes into account—a bigger cell=more food than a smaller one! We fed twice as many cells worth of Isochrysis as Rhodomonas, to make up for Rhodomonas being about 2x as big as Isochrysis) Then I agitated the algae one last time and added the desired amount by pipet to the dishes. If you try this method out and check on your barnacles periodically under a dissecting microscope, you might be able to notice them growing as time goes on! (If you’re lucky. Or you might also be able to see them feeding, which is super fun and cute!).
