Abstract
We report a high-throughput technique for characterising the motility of spermatozoa using differential dynamic microscopy. A movie with large field of view (∼10mm2) records thousands of cells (e.g. ≈ 5000 cells even at a low cell density of 20 × 106 cells/ml) at once and yields averaged measurements of the mean () and standard deviation (σ) of the swimming speed, head oscillation amplitude (A0) and frequency (f0), and the fraction of motile spermatozoa (α). Interestingly, we found that the measurement of α is facilitated because the swimming spermatozoa enhance the motion of the non-swimming population. We demonstrate the ease and rapidity of our method by performing on-farm characterisation of bull spermatozoa motility, and validate the technique by comparing laboratory measurements with tracking. Our results confirm the long-standing theoretical prediction that for swimming spermatozoa.
Highlights
Sexual reproduction in all metazoans relies on the fertilisation of an ovum by a motile spermatozoon, which has to migrate through a variety of external or internal liquid environments to reach its destination
We demonstrate that differential dynamic microscopy (DDM) is a high-throughput on-farm technique to measure population averaged values of α, VAP, amplitude of lateral head oscillations (ALH) and beat cross frequency (BCF) immediately after semen collection, and validate our method by comparing DDM with tracking measurements in the laboratory
We have demonstrated that DDM is a high-throughput technique for characterising bull semen motility that can be applied to both fresh samples on farm and thawed samples in the laboratory
Summary
Sexual reproduction in all metazoans relies on the fertilisation of an ovum (egg) by a motile spermatozoon, which has to migrate through a variety of external or internal liquid environments to reach its destination. Motility is of the essence of spermatozoon function, and the description of motile spermatozoa goes back to the earliest days of scientific microscopy [1]. Spermatozoon phenotype is hugely variable across different phyla, both in terms of morphology and swimming characteristics, possibly as a result of co-evolution with the female reproductive tract [2]. Major adaptations were needed in the spermatozoon when marine vertebrates relying on external fertilisation evolved into terrestrial dwellers reproducing by internal fertilisation [3]. In both cases, the composition and properties of the seminal fluid in which spermatozoa are released help determine reproductive success [4]
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