Ontogenetic changes in swimming performance of a freshwater calanoid copepod

Most studies of copepod swimming have focused on marine adults. Here we studied in detail the changes in morpho-kinematics properties of swimming throughout the entire life cycle of a freshwater calanoid copepod, Sinodiaptomus sarsi, to provide information on the adaptive significance of metamorphosis. We investigated how the swimming speed of nauplii (N1 to N6) and copepodites (C1 to C6) changes with body size and shape, the size and number of limbs involved in movement, and with the stroke frequency and angular amplitude of the limbs using high-speed video filming. The speed of routine swimming in nauplii decreased during growth due to a disproportionate increase in body size relative to the length of the appendages. All three pairs of appendages were used by nauplii only during escape jumps reaching a frequency and relative speed of 240 Hz and 100 body lengths per second, respectively. Copepodites swimming speed increased with body size and the number of thoracic swimming legs and reached up to 300 body lengths per second during escape jumps. Our comparative kinematic analysis showed that nauplii and copepodites represent two different morpho-kinematic types of locomotion organization, well adapted to their body size and the corresponding hydrodynamic swimming regime