Distributed propulsion enables fast and efficient swimming modes in physonect siphonophores

Area of Science:

• Marine Biology
• Biophysics
• Animal Locomotion

Background:

• Fishes exhibit distinct swimming modes for routine and escape behaviors, driven by differing body kinematics.
• Physonect siphonophores, like Nanomia bijuga, possess a decentralized propulsion system using nectophores, enabling varied thrust timing.

Purpose of the Study:

• To compare the swimming performance of synchronous (escape) and asynchronous (routine) swimming in Nanomia bijuga.
• To investigate the influence of colony length on these distinct swimming modes.

Main Methods:

• Combined experimentally derived swimming parameters with a mechanistic swimming model.
• Analyzed swimming performance across a range of colony lengths (number of nectophores).

Main Results:

• Synchronous swimming yields higher mean speeds and accelerations but incurs a greater cost of transport.
• Asynchronous swimming demonstrates lower energy consumption, potentially benefiting vertical migrations.
• Swimming performance varied with colony length in both modes.

Conclusions:

• Synchronous swimming in N. bijuga is advantageous for predator escape due to high speed and acceleration.
• Asynchronous swimming is efficient for routine activities like long-distance vertical migrations.
• Findings suggest principles for designing multi-propulsor underwater vehicles with adaptable thrust timing for speed, efficiency, or acceleration.