Swimming behaviour of females and males: case study Keratella cochlearis

Rotifer locomotion is tightly connected to food acquisition. While females swim and feed, males do generally not feed and only swim to find a mating partner. Here, we filmed females and males, respectively, of Keratella cochlearis and analysed their swimming behaviour with Bemovi, an open-source software to extract behaviour and morphology from videos. The application of this recently developed software opens up the opportunity to apply movement ecology to plankton. Males of K. cochlearis swam slower (ca. 1.7 mm sec-1) than females (ca. 2.3 mm sec-1). Visual inspection of data indicated that females showed a more uniform swimming pattern, while males showed a much more varied swimming pattern ranging from circling within a restricted area, swimming in a straight line, and any combinations of these patterns. We, further, classified the swimming pattern of males and females as a hidden Markow model (HMM) to unravel different swimming states. First results indicated that females did not vary between swimming states while males effectively showed a mixture between two movement states as indicated by HMM. Here, we showed how filming and video analysis advances our understanding of rotifer ecology.