chapter 3 - RiuNet

GENERAL INTRODUCTION
in fish (Kime et al., 2001; Fauvel et al., 2010; Boryspholets et al., 2013).
However, the most used technique to assess sperm motion has been
subjective evaluation, and some problems have emerged from this method.
In this respect, the subjective assessment depends on an experienced
observer, and several aspects such as sperm density, sperm velocity, drift,
etc. can cause over- or underestimation readings. Therefore, the low
reproducibility of this motility analysis through subjective evaluation, which
can result in variations of 30 to 60% from the same sample, often makes it
difficult to interpret and compare the results between labs (Verstegen et
al., 2002; Rosenthal et al., 2010). In this sense, the gradual appearance of
computerized techniques has provided us with an objective and rapid
method for obtaining a correct and accurate evaluation of sperm motion
features (Rurangwa et al., 2004, Cabrita et al., 2011).
3.2 New tools to determine sperm quality
The appearance of Computer Assisted Sperm Analysis (CASA) systems has
made it possible to estimate a higher number of sperm motion parameters
using an objective, sensitive and accurate technique. These systems are the
evolution of multiple photomicrography exposure and video-micrography
techniques for spermatozoa track, using a computer equipped with imaging
software (Rurangwa et al., 2004). This technique was first introduced in the
80´s in mammalian sperm and only in the last few years have modern CASA
systems been adapted for fish spermatozoa studies (Van Look et al., 2000;
Wilson-Leedy and Ingermann, 2007). The differences in the biology of fish
and mammalian spermatozoa may explain the delay in the release of
adequate tools for the measurement of sperm motility in fish. To date,
these systems have been used and validated in a wide range of animal
groups such as marine invertebrates (Gallego et al., 2013), birds (Kleven et
al., 2009), marine mammals (Montano et al., 2012), reptiles (Tourmente et
al., 2011) or even insects (Al-lawati et al., 2009).
A long time ago and by subjective assessment, the experimented observer
was only able to estimate two sperm motion traits: the percentage of
motile sperm cells and the total duration of spermatozoa movement. Then,
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