Project 1
Ontogenetic Changes in Swimming Squid: An Integrative Examination of Jet Structure and Muscle Mechanics.
Pulsed jetting is used by squids of remarkably different sizes, from hatchlings that are only a few millimeters in length to adults that may grow as large as 18 m. Over this wide size range, the physics of fluids plays an important role in the evolution of various jet features (e.g., characteristic vortices known as vortex rings) that are central to propulsive swimming performance. This collaborative project investigates how fluid mechanical constraints shape swimming strategies and muscular mechanics in squid of different life history stages, with the ultimate goal of assessing how propulsive efficiency changes with size. To accomplish this, squids, which vary in total length from < 1 cm as hatchlings to >15 cm as adults, are being trained to swim in a water tunnel containing water seeded with light-reflective particles. As particle-laden water is expelled from the funnel, it is illuminated with lasers and videotaped so that the jet velocity can be determined using a technique known as digital particle image velocimetry (DPIV). These DPIV data provide direct measurements of jet features and propulsive efficiency. Multiple video cameras positioned on a motorized rail system are being used to collect high-resolution images of the mantle and funnel as the squids swim, providing valuable data on swimming behavior. Because the contractile properties of the mantle change with size and have direct effects on jet flows, detailed measurements of isolated bundles of mantle muscle also are being made using standard muscle mechanical techniques in Dr. Thompson's lab. The integration of DPIV, swimming footage, and muscle mechanical data promises to broaden our understanding of propulsive efficiency in jet-propelled organisms, especially at low size ranges where little is known about the jet mechanism, and provide insight into the evolution of ontogenetic changes in musculoskeletal support systems.
Project 2
Role of Fins in Propulsion of the Brief Squid Lolliguncula brevis
Project participants: William J. Stewart and Ian K. Bartol
Although the pulsed jet is the foundation of a squid's locomotive system, the lateral fins also play important roles in swimming, providing thrust, lift, and dynamic stability. Although there is considerable diversity in fin form and function in squids, the locomotive role is not well understood. In this project, several high-speed video cameras are being used to record the kinematics of fin motion, and DPIV is being used to study flows around the fins as they undulate/oscillate over a range of swimming speeds. If successful, these experiments will provide the first data that link fin kinematics with global flow quantification in any cephalopod and provide valuable insight into the locomotive role of fins in squids.
Project 3
Role of the Carapace and Fins of Boxfishes in Stability and maneuverability
Boxfishes are marine fishes having rigid carapaces that vary significantly among taxa in their shapes and structural ornamentation. Using three separate but interrelated approaches (DPIV, pressure distribution measurements, and force balance measurements), we determined that four species of boxfishes produce vortices around their keels that lead to self-correcting trimming forces during swimming. For example, when a boxfish pitches upward in a turbulent environment, spiral flows develop above the keels and are strongest at the posterior edge of the carapace. The low pressures that result from the vortices pull the back-end of the fish upwards, returning it to a level trajectory. This sophisticated self-correcting systems acts quickly and automatically without neural processing and reduces the complexity of boxfish swimming movements, which saves energy and enhances sensory acuity. Interestingly, systems that are stable are generally not very maneuverable because every change in course is counteracted by the stabilizing mechanism. However, boxfishes are unique because they are both stable and maneuverable! Current work on boxfishes focuses on how fins interact with body-induced flows to enhance maneuverabilty.
Results from our work were recently appiled to the development of
Mercedes-Benz's bionic car. and are being used by Navy to make more efficient underwater robots.
Project 4
Application of 3D DDPIV to the Study of Squid Swimming
Collaborators: Dr. Mory Gharib and Emilio Graff
Defocusing digital particle image velocimetry (DDPIV) is a technique that was developed recently in Dr. Mory Gharib's lab at the California Institute of Technology. This emerging technology allows for 3-dimensional quantification of flow fields within a 10 x 10 x 10 cm volume, which is significantly larger than volumes considered in stereo-PIV systems. The DDPIV system collects three separate images of the particle field and uses the shape of the aperture layout as a guide when matching particles among the three images. Once a triplet is identified, the size of the matching pattern is used to calculate the distance of a given particle from the reference plane. DDPIV is now being applied to study the jet features in squids and promises to provide unprecedented 3-dimensional flow quantification around biological systems.
Project 5
Sensory Physiology and Locomotion of Sea Turtles
Collaborators: Dr. Soraya Bartol
(Description of project is coming soon!)
