Tracking sperm in three-dimensions.
Sperm motility, crucial for fertilization, has been mostly studied in two dimensions (2D) by recording their swimming trajectories near a flat surface. However, spermatozoa swim in three-dimensions (3D) to find eggs, with their speed being the main impediment to track them under realistic conditions. Here, we describe a novel method allowing 3D tracking and analysis of the trajectories of multiple free-swimming sperm. The system uses a piezo-electric device displacing a large focal distance objective mounted on a microscope to acquire 70 image stacks per second, each stack composed of 60 images that span a depth of 100 microm. With this method, 3D paths of multiple sperm in the same field could be visualized simultaneously during 1 s. Within the same sample we found that surface-confined sperm swam 25% slower, produced 3-fold fewer circular revolutions per second, and had trajectories of 134% greater radius of curvature than those sperm swimming freely in 3D.
Unidad de Microscopía Avanzada, Laboratorio de Imágenes y Visión por Computadora, Instituto de Biotecnología, Universidad Nacional Autónoma de México (UNAM), Apdo. Postal 510-3, Cuernavaca, 62250 Morelos, Mexico. corkidi@sgima.ceingebi.unam.mx
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Corkidi
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Taboada
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Wood
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Guerrero
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Darszon
D000818:Animals; D021621:Imaging, Three-Dimensional / Q000295:instrumentation* / Q000379:methods*; D008297:Male; D018715:Microscopy, Video; D013081:Sperm Motility; D013094:Spermatozoa / Q000166:cytology* / Q000502:physiology*; D047269:Strongylocentrotus