Ups and downs: copepods reverse the near-body flow to cruise in the water column.

Autor: Tack NB; School of Engineering, Brown University, 345 Brook St, Providence, RI 02912 USA., Oliveira Santos S; School of Engineering, Brown University, 345 Brook St, Providence, RI 02912 USA., Gemmell BJ; Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, FL 33620 USA., Wilhelmus MM; School of Engineering, Brown University, 345 Brook St, Providence, RI 02912 USA.
Jazyk: angličtina
Zdroj: Marine biology [Mar Biol] 2024; Vol. 171 (11), pp. 207. Date of Electronic Publication: 2024 Oct 10.
DOI: 10.1007/s00227-024-04531-1
Abstrakt: Copepods are negatively buoyant organisms actively participating in large-scale vertical migrations as primary consumers in marine ecosystems. As such, these organisms need to overcome their own weight to swim upwards, incurring extra energy costs that are not offset by any mechanism intrinsic to drag-based propulsion. While copepod vertical migrations are well documented, it is still unclear how they achieve extensive upward cruising despite this limitation. In this study, we found suction to be a compensatory mechanism enhancing thrust in upward-swimming copepods. Using experimentally derived velocity and pressure fields, we observed that copepods pull water in front of them to generate sub-ambient pressure gradients when cruising upward, thereby inducing an upstream suction force to complement the thrust produced by the legs. Contrary to expectations that drag always dominates the leg recovery phase, we found that the upstream suction generates net thrust for about a third of the recovery stroke. In contrast, downward-swimming copepods push rather than pull on water and do not benefit from thrust-enhancing suction effects during the recovery stroke. Differences in the induced flows are associated with contrasting leg kinematics, indicating a response to the body orientation rather than a fixed effect. These results offer insights into an important swimming mechanism that can inform the role mesozooplankton play in biogenic hydrodynamic transport and its impact on marine biogeochemistry.
Competing Interests: Conflict of interestThe authors declare no competing interests.
(© The Author(s) 2024.)
Databáze: MEDLINE