Sonography of the Heart of Weatherfish Misgurnus fossilis at the Prelarval Stage of Development

Abstract

The article describes a method for hearts of lower vertebrates in the early stages of their development. To achieve sufficient spatial resolution, the method uses an acoustic microscope with mechanical scanning of a focusing ultrasound transducer, the received signal of which is recorded as a function of spatial coordinates and time. The heart of weatherfish Misgurnus fissilis at the prelarval stage of development was examined with a pulsed acoustic microscope. The center frequency and duration of the envelope of the recorded reflected pulses were 70 MHz and 30 ns, respectively. Processing of the recorded spatiotemporal signal made it possible to visualize movement of tissues of the ventricle, atrium, and valves in the ventricular region of the heart, determine the period of heartbeats, and identify heart rhythm phases. It is shown that the characteristic sizes of the ventricle and atrium are 150–300 µm. The responses of moving blood elements were identified and the speed of their movement in different areas of the heart were measured as a function of time. It was found that the blood flow rate reaches a maximum of 2.5 mm/s in the diastolic period in the ventricular region of the heart. In other regions, peaks in the diastolic and systolic periods range from 1.5 to 0.8 mm/s. In accordance with the principle of high-power Doppler sonography, the change in density of moving blood elements was visualized as a function of time.