A CINEMATOGRAPHIC COMPARISON OF BEHAVIOR BY THE CALANOID COPEPOD CENTROPAGES-HAMATUS LILLJEBORG - TETHERED VERSUS FREE-SWIMMING ANIMALS

Many previous cinematographic studies of copepod behavior have used animals tethered to dog or cat hairs to keep them in focus. We compared behavior of tethered and free-swimming specimens of the calanoid copepod Centropages hamatus Lilljeborg using cinematographic methods. Precise quantification was made of the time allocated to four modes of behavior: slow-swim (movement of feeding appendages only), break (no appendages moving), fast-swim (posteriorally-directed movement of first antennae and pereiopods), and groom (brushing of first antennae through feeding appendages). Ten copepods each were used for tethered and free-swimming filming. Under both experimental regimes, copepods spent < 1 % of total amount of time in fast-swimming and grooming behavior. Most of the time (50.7-95.5%) animals were on break. The rest of the time (3.8-48.9%) animals were in the slow-swimming mode, moving only feeding appendages. There were no significant differences between tethered and free-swimming animals in mean time allocations to slow-swimming and break behavioral modes. However, individual variability of tethered animals was higher than that of free-swimming ones. We conclude that, while mean time allocation to slow-swimming and break behaviors were similar between free-swimming and tethered animals, the variability between tethered individuals is a factor to be considered when designing experiments.