TY - JOUR
T1 - Human sperm swimming in a high viscosity mucus analogue
AU - Ishimoto, Kenta
AU - Gadelha, Hermes Augusto Buarque
AU - Gaffney, Eamonn A.
AU - Smith, David
AU - Kirkman-Brown, Jackson
PY - 2018/3/9
Y1 - 2018/3/9
N2 - Remarkably, mammalian sperm maintain a substantive proportion of their progressive swimming speed within highly viscous fluids, including those of the female reproductive tract. Here, we analyse the digital microscopy of a human sperm swimming in a highly viscous, weakly elastic mucus analogue. We exploit principal component analysis to simplify its flagellar beat pattern, from which boundary element calculations are used to determine the time-dependent flow field around the sperm cell. The sperm flow field is further approximated in terms of regularized point forces, and estimates of the mechanical power consumption are determined, for comparison with analogous low viscosity media studies. This highlights extensive differences in the structure of the flows surrounding human sperm in different media, indicating how the cell-cell and cell- boundary hydrodynamic interactions significantly differ with the physical microenvironment. The regularized point force decomposition also provides cell-level information that may ulti- mately be incorporated into sperm population models. We further observe indications that the core feature in explaining the effectiveness of sperm swimming in high viscosity media is the loss of cell yawing, which is related with a greater density of regularized point force singularities along the axis of symmetry of the flagellar beat to represent the flow field. In turn this implicates a reduction of the wavelength of the distal beat pattern – and hence dynamical wavelength selection of the flagellar beat – as the dominant feature governing the effectiveness of sperm swimming in highly viscous media.
AB - Remarkably, mammalian sperm maintain a substantive proportion of their progressive swimming speed within highly viscous fluids, including those of the female reproductive tract. Here, we analyse the digital microscopy of a human sperm swimming in a highly viscous, weakly elastic mucus analogue. We exploit principal component analysis to simplify its flagellar beat pattern, from which boundary element calculations are used to determine the time-dependent flow field around the sperm cell. The sperm flow field is further approximated in terms of regularized point forces, and estimates of the mechanical power consumption are determined, for comparison with analogous low viscosity media studies. This highlights extensive differences in the structure of the flows surrounding human sperm in different media, indicating how the cell-cell and cell- boundary hydrodynamic interactions significantly differ with the physical microenvironment. The regularized point force decomposition also provides cell-level information that may ulti- mately be incorporated into sperm population models. We further observe indications that the core feature in explaining the effectiveness of sperm swimming in high viscosity media is the loss of cell yawing, which is related with a greater density of regularized point force singularities along the axis of symmetry of the flagellar beat to represent the flow field. In turn this implicates a reduction of the wavelength of the distal beat pattern – and hence dynamical wavelength selection of the flagellar beat – as the dominant feature governing the effectiveness of sperm swimming in highly viscous media.
U2 - 10.1016/j.jtbi.2018.02.013
DO - 10.1016/j.jtbi.2018.02.013
M3 - Article
SN - 0022-5193
VL - 446
SP - 1
EP - 10
JO - Journal of Theoretical Biology
JF - Journal of Theoretical Biology
ER -