Movilidad espermática en salmónidos

Abstract

El objetivo de este trabajo es realizar una descripción completa y objetiva de la dinámica de espermatozoides de salmónidos. Se realizó una caracterización de su morfología, así como un análisis de sus trayectorias para calcular diferentes parámetros de movilidad. Las distribuciones de velocidad presentaron valores iniciales de alrededor de 200 μm/s, que disminuyeron a menos de 50μm/s en 30 segundos. Similar para la frecuencia de cabeceo, con valores iniciales de 120Hz que decaen a alrededor de 50Hz. Finalmente, la amplitud de cabeceo, con un valor medio de 0.8μm. Con estos parámetros se propuso un modelo fenomenológico de su dinámica y se realizaron simulaciones con Dinámica de Langevin. El modelo resulta una buena aproximación y muestra concordancia teórica-experimental, dejando paso a nuevos estudios y predicciones de la dinámica de estos micronadadores.

Few detailed studies on the dynamics of fish sperm can be found. Such cells present several differences compared to mammalian spermatozoa. A complete and objective description of their dynamic would be beneficial for both ecological applications and the aquaculture industry, as it would contribute to a better understanding of the reproduction of these animals and improved assessment of sperm quality. This thesis, both theoretical and ex- perimental, is the result of a collaboration between experimental biochemists from Chile and theoretical physicists from FAMAF-UNC. Regarding the experimental side, videos were recorded at 400 fps to observe the mobility of these cells. A careful tracking of the spermatozoa from the videos was made to qualitatively analyze the behavior of the cell path and measure different motility parameters. A morphological characterization of the cell bodies was also performed. Based on the obtained parameters, a first approached phenomenological model of the sperm dynamics was proposed, and its theoretical predictions were validated against experimental results through Langevin Dynamics simulations. The velocity distributions exhibited a significant temporal variability, with initial high values of approximately 200µm/s rapidly diminishing to less than 50µm/s within a mere 30-seconds interval. A similar trend was observed for head frequency, which started at 120Hz and decreased to approximately 50Hz. The third parameter assessed was head amplitude, which displayed minimal temporal fluctuations around a mean value of 0.8µm. In all cases the sperm population exhibited a high heterogeneity of values, requiring the development of an adaptive program to automatically analyze the trajectory of each track. The obtained results were of the same order as in studies done with shorter tracks and fewer frames per second. This work aimed to provide an objective description, independent of the software configuration used for the analysis, as well as handling a larger amount of data to make our contribution more realistic and precise along the full cells’ life. The model provides a good approximation, achieving good theoretical-experimental agreement. It paves the way for further studies and predictions of the dynamics of these microswimmers, with potential applications in marine ecology conservation and progress in techniques for more sustainable aquaculture.