Sorting plankton is a bit like a game of Where’s Waldo, except that Waldo is moving and translucent, and the entire background scenery is moving along with him.
In my case, the Waldos I am looking for are appendicularians. I separate them from the commotion of the background plankton by their distinctive shape and motion. They are easily confused with the transparent rod-shaped body of chaetognaths (“arrow worms”)—but have a more pronounced, football-shaped head—and the sinusoidal wriggling of a nematode—yet less fitful. Their motion can be hard to detect amidst the darts and jolts of the ever-abundant calanoid copepods.
Some days my sample (collected from the net in the figure below) is filled with so many Waldos I cannot possibly pipette them all. Some days I can sort for hours and never find a single one. Usually it is one extreme or the other: no goldilocks plankton here.
My task for this term is establishing cultures of appendicularians at our lab on the main campus of the University of Oregon in Eugene—60 miles from the ocean and 120 miles from the collection site. It is rather daunting, particularly since my appendicularians are smaller than copepods—barely visible even when backlit and examined by the squinting, trained eye. Their life cycle is about six days, depending on temperature. Scientifically speaking, they progresses from external fertilization of the egg to embryogenesis to organogenesis to metamorphosis to somatic growth to maturation and reproduction. Less scientifically, they grow from an egg to a little tadpole to a bigger tadpole to a tadpole with a disproportionally large head (yellow for females, blue for males) and then, once her and his heads fills with eggs and sperm, their gamete-brains explode and a new generation begins.
I have yet to raise appendicularians through their full life cycle. For the time being, my efforts are focused on keeping adults alive inland for a few days at a time, which necessitates to a lot of driving back and forth between Eugene and the coast. On the days when hours of scanning yields only Waldo-less samples, I wonder: is it too late to study copepods?