Meeting Abstract
The lymphatic system in teleost fish has similar genetic and developmental origins to the mammalian lymphatic system, which is involved in immune response and fluid homeostasis. Here, we show that the lymphatic system of tunas functions in swimming hydrodynamics. Specifically, a musculo-vascular complex is involved in the hydraulic control of median fins for maintaining swimming stability. This specialization of the lymphatic system is associated with the scombrid fishes and may have evolved in response to the demand for stability control in these high-performance species. The unique feature of the musculo-vascular complex described here in tuna fins is that, unlike other known examples of animal hydraulics, it is formed by the integration of the lymphatic vessels and muscles having skeletal support. The complex is comprised of the three elements of a canonical hydraulic system: muscles that may serve as a hydraulic pump to pressure the lymphatic fluid, vascular vessels to guide and control the system, and fin rays acting as actuators to convert pressure energy into mechanical energy. The hydraulic system of tuna fins is similar to an engineer’s design of the control surface. Tuna are of comparable size and speed to autonomous underwater robotic vehicles, which are currently used extensively worldwide to perform the wide range of ocean survey and inspection applications. The advantages of hydraulic force generation and transmission, as well as the ability to change dynamically their stability properties during transient motion by altering fin sweep, make this strategy a solution of choice for bio-inspired aquatic robotics.
