3D-printed Planktonic Observational Setup and Analysis Pipeline TrackmateTaxis

Planktonic organisms are a cornerstone of marine ecosystems. They vary significantly in size and have a repertoire of behaviors to aid them to survive and navigate their three-dimensional environment. One of the most important cues is light. A variety of setups were used to study the swimming behavior of specific organisms, but broader and comparative investigations need more versatile solutions. With the help of 3D printing, we designed and constructed a modular and flexible behavioral observation setup that enables recordings of animals down to 50m or up to a few centimeters. A video analysis pipeline using ImageJ and python allows a quick, automated, and robust tracking solution, capable of processing many videos automatically. A modular light path allows the addition of filters or use of pulse width modulation to equalize photon emission of LEDs or additional LEDs to mix different wavelengths. Optionally, a spectrometer can be installed to enable live monitoring of a stimulus. We tested the setup with two phototactic marine planktonic larvae. First, we investigated the spectral sensitivity of the 7-day old larvae of the polychaete Malacoceros fuliginosus and second, the behavior of the 200m spherical bryozoan coronated larvae of Tricellaria inopinata to ultraviolet light coming from the bottom of the vessel. The setup and pipeline were able to record and analyze hundreds of animals simultaneously. We present an inexpensive, modular, and flexible setup to study planktonic behavior of a variety of sizes.