Inflation-induced motility for long-distance vertical migration

Area of Science:

• Marine Biology
• Biogeochemistry
• Cell Biology

Background:

• Vertical migrations of pelagic organisms are vital for marine ecosystems and global biogeochemical cycles.
• Some single-cell protists migrate vertically over 50m without motility structures, a mechanism previously unknown.
• Density regulation has been hypothesized as a key factor for non-motile cell migration.

Purpose of the Study:

• To investigate the mechanism by which non-motile protists achieve large vertical migrations.
• To elucidate the role of cell density regulation in planktonic movement.
• To understand the cellular adaptations enabling rapid volume and density changes.

Main Methods:

• Utilized the dinoflagellate Pyrocystis noctiluca as a model organism.
• Observed and quantified rapid cell inflation post-cell division.
• Developed a mathematical framework to model cell-cycle-driven density regulation and migration.

Main Results:

• Discovered a rapid 6-fold cell volume expansion within 10 minutes post-division in Pyrocystis noctiluca.
• Demonstrated that this cellular inflation is the primary driver of density control, enabling upward migration.
• Identified a unique reticulated cytoplasmic architecture facilitating rapid volume increase without cytoplasmic dilution.

Conclusions:

• Non-motile plankton employ a novel strategy of self-regulated cellular inflation for vertical migration.
• Precise control over cell size and density allows plankton to evade sedimentation and undertake long-distance migrations.
• This mechanism provides new insights into the ecological strategies of planktonic organisms in stratified marine environments.