Abstract
We report observations of marine parasitic isopods Gnathia marleyi and coral larvae Orbicella faveolata in an aquatic olfactometer where individuals can respond to chemical signals from host fish species and crustose coralline algae, respectively. We complement these observations with a gradient search model inspired by the theory of Braitenberg vehicles.Videos are available in .mp4 format. Positional data were extracted from videos using ImageJ and EthoVision XT software. The videos were digitized and the positional data were saved in .xlsx or .csv format, respectively. The python codes contain the numerical implementations of our mathematical models.