Effects of animal density, volume, and the use of 2D/3D recording on behavioral studies of copepods

Abstract

Studies on the behavior of copepods require both an appropriate experimental design and the means to perform objectively verifiable numerical analysis. Despite the growing number of publications on copepod behavior, it has been difficult to compare these studies. In this study, we studied two species of copepods, Eurytemora affinis and Pseudodiaptomus annandalei, and employed recently developed scaling and non-scaling methodology to investigate the effects of density and volume on the swimming behavior of individual organisms in still water. We also compared the results of two-and three-dimensional projections of the swimming tracks. A combination of scale-dependent and scale-independent analysis was found to characterize a number of behavioral observations very effectively. We discovered that (i) density has no effect except to increase the time spent in the swimming state of ''breaking'', (ii) smaller volumes resulted in more complex trajectories, and larger volumes, like density, increased the time spent in the swimming state ''breaking'', and (iii) three-dimensional projections gave a more accurate estimation of speed and the time spent cruising. When only a vertical 2D projection was used, ''cruising'' could be confused with ''sinking''. These results indicate that both experimental conditions and the selection of 2D or 3D projection have important implications regarding the study of copepod behavior. The development of standardized procedures with which to compare the observations made in different studies is an issue of particular urgency.

Unexpected Regularity in Swimming Behavior of Clausocalanus furcatus Revealed by a Telecentric 3D Computer Vision System

“…Advances in video camera performance and computer vision algorithms have made it possible to reach greater levels of accuracy in reconstructing swimming patterns and measuring motion activity of single individuals. For small animals that live and perform in the water column, only 3D observations allow swimming patterns to be described precisely [31], thus providing the correct positions and speed measurements [21]. However, 3D observations require a more complex experimental system.…”

Pseudodiaptomus marinus Sato, 1913, a new invasive copepod in Lake Faro (Sicily): observations on the swimming behaviour and the sex-dependent responses to food

“…Lower swimming speeds and longer time spent swimming in males may also indicate a possible common mating strategy for the two species. Mating experiments performed on P. annandalei (Dur et al 2011b(Dur et al , 2012Lee et al 2011) showed that this species perceives stimuli from the mate mainly through chemical cues. Morphological analyses of the antennulae (A1) of male P. marinus revealed the presence of numerous aesthetascs.…”

Three‐dimensional tracking of multiple aquatic organisms with a two camera system

“…In most applications, however, it is unclear to what extent the strongly restricted motion and ubiquitous presence of rigid boundaries in thin aquariums, cells, or Petri dishes (Untersteiner et al 2005;Lovern et al 2007;Watson et al 2007) affect or bias the observed swimming behavior and kinematics. Only few studies were conducted in relative large volumes observing all three components of the swimming velocity and hence allow distinguishing between motions close to or far away from a boundary (Doall et al 1998;Strickler 1998;Dur et al 2011). Such three-dimensional observations had been conducted using multiple cameras (Leptos et al 2009) or only a singular camera in combination with mirrors (Doall et al 1998;Strickler 1998;Brausch et al 2011).…”