This project has received funding from the COST Association (Food and Agriculture COST Action FA1205: AQUAGAMETE, and the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie project IMPRESS (GA No 642893). We would like to thank the scientific team of PROiSER, specifically to the student Alberto Vendrell Bernab&#233;u, for his active participation in the video recording of this project.

Procedures involving animal subjects have been approved (2015/VSC/PEA/00064) by the General Direction of Agricultural Production and Livestock at the Universitat Polit&#232;cnica de Val&#232;ncia.
1. Collect Sperm from Mature European Eels in Captivity
NOTE: Use European eel males maintained in tanks with seawater and a recirculation system at constant temperature (20 &#176;C). Treat with hormones through weekly intraperitoneal injection (human chorionic gonadotropin (hCG); 1.5 IU per g of fish body weight). Acclimatize fish gradually starting with 3 days in freshwater followed by replacement with seawater (1/3 of the total water in the tank) every 2 days until reaching a salinity of 37.0 g/mL.
<ol>
	<li>Anesthetize the eel 24 h after hormone injection to obtain samples with better sperm quality.
	<ol>
		<li>Prepare the anaesthesia beforehand: add 300 mg of benzocaine to 100 mL of 70% ethanol. Mix well and store at 4 &#176;C.</li>
		<li>Dilute benzocaine in a flexible bucket with 5 L of system water to get a final concentration of 60 mg/L and mix properly.</li>
		<li>Transfer the fish to the bucket with system water and benzocaine. Wait a few minutes until the fish calm down.</li>
	</ol>
	</li>
	<li>Clear the genital area with water and dry with absorbent paper to avoid contamination of sperm samples by faeces, urine or seawater.</li>
	<li>Apply gentle pressure in the abdominal area and collect the sperm samples into 15 mL plastic tubes using the vacuum pump. Sperm volume up to 6-7 mL, depending on the male.</li>
	<li>Keep sperm samples at 4 &#176;C for at least 1 h until motility analysis is carried out.</li>
</ol>
2. Refrigerate and Dilute the Sperm Samples
<ol>
	<li>Prepare the diluter solution beforehand. 
	NOTE: The sperm samples should be diluted in the extender solution specific for each species.
	<ol>
		<li>Prepare the non-activator medium for eel sperm samples (P1 medium). Add 0.42 g of sodium bicarbonate, 1.828 g of sodium chloride, 0.127 g of magnesium chloride, 0.56 g of potassium chloride and 0.037 g of calcium chloride to 250 mL of distilled water. Mix well to dissolve. Store at 4 &#176;C.</li>
	</ol>
	</li>
	<li>Set the cooler block at 4 &#176;C to maintain samples at a constant temperature. Wait until the temperature stabilizes.</li>
	<li>Dilute the sperm samples using the diluter solution specific for each species. 
	NOTE: The dilution ratio is species specific and must be defined to standardize the protocol. First, estimate sperm concentration based on the concentration obtained in the pre-analysis of motility using software, as explained in steps 3 and 4. With this analysis, it is also possible to select the best sperm samples based on the percentage of motility. After this, the researcher can start to collect data for the experiment using the best samples with the correct concentration.
	<ol>
		<li>Dilute eel sperm samples in the P1 medium with a ratio of 1:50. To prepare 500 &#181;L of eel diluted sperm, add 50 &#181;L of the fresh sperm sample and 450 &#181;L of P1. Mix well.</li>
	</ol>
	</li>
</ol>
3. Evaluate the Sperm Motility Parameters
<ol>
	<li>Set-up the Motility Module of the Software
	<ol>
		<li>Set the cooler stage at 4 &#176;C and wait until it stabilizes.</li>
		<li>Open the software and select Motility Module. Create username and password if necessary.</li>
		<li>Select Properties and choose the desired parameters before starting the sperm analysis.
		<ol>
			<li>Click on Species | Fish.</li>
			<li>Select the Frames Per Second and Number of Images, depending on the best technical conditions for each species. Set both options at 120 images per second.</li>
			<li>Choose negative contrast. It is mandatory for accurate reconstruction of the spermatozoa trajectories16.</li>
			<li>Select the corresponding Counting Chamber and Scale of the video camera. Calibrate the video camera for the magnification lens used in the experiment. Set SpermTrack10 as counting chamber and 10X scale. 
			NOTE: In general, a depth of 10 &#181;m in the counting chamber and a magnification lens of 10X are the recommended conditions since they provide better focusing of all spermatozoa and capture the highest number of cells. However, it is recommended to make a previous study of the optimal conditions for motility analysis of each species.</li>
			<li>Adjust the Particle Area and Connectivity for each species. Set minimum particle area at 2 &#181;m2 and connectivity at 7 &#181;m. 
			NOTE: For fish, the minimum value of particles area ranges between 2-5 &#181;m, and connectivity depends on the spermatozoa velocity and the frame rate.</li>
			<li>Save the set-up.</li>
		</ol>
		</li>
		<li>Select Capture.</li>
	</ol>
	</li>
	<li>Analyze European Eel Sperm with Software
	<ol>
		<li>Prepare the activator solution (artificial seawater) by adding 0.946 g of commercial salt to 25 mL of distilled water with 2% BSA.</li>
		<li>Take 500 mL of activator solution (artificial seawater) and place in the cooler block. 
		NOTE: In general, fish sperm is activated by an osmotic shock event, although for some species the ion concentration could also be important. For freshwater species, the activator medium should have hypotonic osmolality, while for marine species the medium should be hypertonic.</li>
		<li>Put the counting chamber under the cooling stage and wait until the temperature stabilizes to 4 &#176;C.</li>
		<li>Mix the activator and diluted sperm to activate spermatozoa and start the motility video recording between 5-10 s after activation.
		<ol>
			<li>Take 4 &#181;L of activator solution and place in the counting chamber.</li>
			<li>Gently homogenize the diluted sperm by shaking the microcentrifuge 3 times to avoid damage in spermatozoa cells.</li>
			<li>Take 0.5 &#181;L of diluted sperm, mix with the activator, and put the cover in the counting chamber quickly. 
			NOTE: This step should not take more than 5 s to start the analysis as soon as possible.</li>
			<li>Focus on the spermatozoa cells and find the best visual area, which is defined by a low number of spermatozoa (150 to 200 cells) to avoid interception between cells (Supplemental Figure 1A). Select Capture Video to obtain the spermatozoa tracks, which are separated according to speed.</li>
			<li>Select Capture to obtain 3 to 7 fields, which are the optimal interval to obtain a lower variability in the results, and proceed as before. Record videos until 120 s post-activation in order to avoid condensation on the cover of the counting chamber.</li>
			<li>Select Exit to have a general view of all the fields.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
4. Obtain Motility Data
<ol>
	<li>Select Fields | Partial | Save and choose a file name. Click Save. 
	NOTE: The spreadsheet provides mean values of partial data, charts and images of spermatozoa tracks.</li>
	<li>Select General Data | File Name | Save. 
	NOTE: The data provide kinetic values for individual spermatozoa of all fields.</li>
</ol>

The authors have nothing to disclose.

The sperm analysis software used in this protocol has been used by researchers worldwide for different species, including fish. However, fish have some specific features that can affect the sperm assessment. Fish spermatozoa showed high speed in the moment of activation which declines quickly and leads to a short time of motility after activation. Besides, the temperature of reproduction is species-dependent and, in some cases, could be around 4 &#176;C2,4,8,12. Thus, it is necessary to make some adaptations to improve the efficiency of a computerized system for fish sperm analysis. The basic principle of the motility parameter is the acquisition and analysis of successive images of motile spermatozoa. Most systems use standard frame rates (16, 25, 30, 50 or 60 fps) due to limitations of hardware and software17,18,19,20,21,22. However, some studies showed that a higher frame rate increases some velocity parameters, such as VCL, STR, BCF15,23,24. This is particularly important when it is necessary to evaluate the hyperactivation of spermatozoa and find the maximum velocity of spermatozoa11,17,18,19,25. In relation to the temperature of analysis, a cooling plate for the optical microscope, and a new technology to refrigerate samples at constant temperature could also improve the analysis over time. The present work offers an approach to solve two of the main problems associated with the fish sperm motility analysis and temperature sensibility. Despite the results focusing on some freshwater species, this methodology could be used for marine species, although the activation medium should be adapted for each species.
In the market, there are a range of products or even different versions of the same product. Even if the systems may have the same principle, each one has different details resulting in the incompatibility of results26,27,28. Besides, the evaluation of fish sperm quality could still have methodological and technical limitations. The sperm activation technique and the time of analysis after activation are two essential factors that affect sperm quality evaluation29,30. The time between the activation of sperm samples and the stabilization of image for video recordings should be around 5 s since the first seconds (time interval of 5-20 s) provides the most useful data2,4. The time of sperm analysis may be limited due to condensation problems on the glass slide. However, fish spermatozoa remain active with a vigorous movement for less than two minutes2. At a technical level, it is necessary to know the "optimal" frame rate to obtain detail information that gives an accurate reconstruction of the spermatozoa trajectories15. At lower frame rates, the details of the trajectory are lost, particularly for fast and nonlinear spermatozoa, whereas at higher frame rates, the information becomes redundant15,31. For some fish species, the frame rate (up to 250 fps) could not be enough to find the maximum velocity of spermatozoa for some fish species, such as Grayling and Salmon. This variation is species specific and must be defined for each species to standardize the protocol and obtain reliable results15,23,24. The depth of counting chamber may limit the movement of the large flagellum of fish and the spermatozoa could not reach maximum speed11,32,33. Besides, the software may have some limitations in the detection of the real spermatozoa when there is an intersection of cells.
Classical assessment of sperm quality is a subjective analysis based on the estimation of concentration and percentage of motility, which can produce variability on the results. However, a computerized system provides rapid, accurate and quantitative measurements of motility parameters. This objective analysis gives a large amount of data and reduces the variability of results34,35,36,37. The response of sperm motility behavior depends on the temperature of the analysis and varies among species38,39,40. Optimal temperature of the sperm analysis could provide sperm velocity and duration of the motility period similar to the natural conditions of reproduction38,40. Therefore, sperm analysis software with cooling devices improves the evaluation of fish sperm quality.
The results of sperm quality analysis could improve the knowledge about fish sperm characteristics and quality based on sperm subpopulations, which may be the future of sperm evaluation in all animal species41,42. At a practical level, this technique could be an indicator of high-quality breeders and helps to get more information about sperm selection process, seminal doses calculation for artificial insemination, sperm competition based on velocity and progressivity and fertility potential. All this knowledge can be applied to different research fields including aquaculture and conservation programs, which stimulated the interest in fish sperm storage and cryopreservation in the last decades2,13. Toxicological effects are also getting special interest due to environmental problems, as well as studies the development of phylogenetical studies based on sperm motility characteristics43,44.
This work has shown how the optimization of an automatic software for fish sperm motility analysis improves the results. Standardization of the protocol must take into account the temperature of analysis and the frame rate, which could be different depending on the species. However, the analysis of fish sperm motility has two critical steps that the researcher should pay attention. Sperm collection is the first critical step that can destroy the sample due to contaminations by faeces, urine and water (seawater or freshwater). The other critical point is associated with the moment of sperm activation and the beginning of video recordings. This step should be done as soon as possible to collect data when the spermatozoa have vigorous movement.

The efficacy of reproduction depends on the quality of both gametes (eggs and sperm)1,2. This is the major factor that contributes to successful fertilization, allowing the development of viable offspring3,4. The convenient evaluation of gamete quality is the best tool for defining the fertility potential of a specimen. 
Mixing sperm from multiple males is a common practice in the production of many aquatic commercial species4. However, the sperm variability between males can lead to sperm competition and, consequently, not all the males are equally contributing to the gene pool5. In this sense, the correct evaluation of individual ejaculate/spermatozoa features, such as motility, is fundamental to obtain discriminatory information regarding individual male fertility potential. Direct observation of sperm motility can produce inaccurate and subjective data as it requires time and experience, which leads to a lack of consistency and incompatibility of results6,7. However, there are many innovative, rapid and quantitative techniques that can provide a reliable sperm quality analysis2,4. 
Computer-assisted sperm analysis was developed to offer accurate data about sperm quality8. This technology includes the development of software associated with a phase contrast microscope that allows the assessment of sperm motility. However, a limiting factor of motility parameter is the frame rate of the video camera. Individual spermatozoa trajectories are based on spermatozoa head centroid position in consecutive frames of video recordings, which is correlated with the flagellar movement patterns3,9,10,11. The main kinetic parameters measured are the straight-line velocity (VSL), curvilinear velocity (VCL) and average path velocity (VAP). VSL is the distance between the start and end-point taken by the spermatozoa divided by time. VCL is the real velocity along the precise trajectory taken by the spermatozoa. VAP is the velocity along a derived smoothed path of trajectory. These parameters allow additional kinetic information, including linearity (LIN), straightness (STR), wobble (WOB) and beating measurements like amplitude of lateral head movement (ALH) and beat-cross frequency (BCF)4,10.
The sperm analysis system was originally used for mammalian species, and one of the requirements for the system is to operate at the body temperature of the donor (about 37 &#176;C). This software could also be used for fish species; although, it is necessary to make some adaptations to reduce the error of sperm analysis results. In some fish species, such as salmonids and eel8,12, fertilization occurs at low temperature (around 4 &#176;C)2,4. Thus, cooling devices should be developed to avoid uncomfortable working conditions. In addition, fish spermatozoa are immotile in seminal fluid and require an osmotic shock to activate motility. For freshwater species, the activator medium should have hypotonic osmolality, while for marine species the medium should be hypertonic. However, for some species, as salmonids, the ion concentration could also be important3,4,9. After activation, fish sperm is characterized by a rapid decrease of motility (less than 2 min)13,14 and high velocity, being vital to determine the optimal frame rate to obtain reliable data15.
The objectives of this study are to design and apply refrigeration systems for fish sperm samples. In addition, this protocol defines how to determine the optimal frame rates for the establishment of standard protocols depending on the species. The use of this protocol opens new doors in the context of fish seminal evaluation, using the European eel as a model.

<table border="0" cellpadding="0" cellspacing="0" style="width:745px;" width="745">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Human Chorionic Gonadotropin</td>
			<td style="width:179px;">Argent Chemical Laboratories</td>
			<td style="width:151px;">hCG</td>
			<td style="width:167px;">Hormone</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Benzocaine</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">E1501 Sigma</td>
			<td>Anesthesia</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">sodium bicarbonate</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">S5761 Sigma&#160;</td>
			<td style="width:167px;">P1 medium</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:21px;width:249px;">sodium chloride</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">1.06406 EMD Millipore</td>
			<td style="width:167px;">P1 medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">magnesium chloride</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">1374248 USP</td>
			<td style="width:167px;">P1 medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">potassium chloride</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">P3911-500G</td>
			<td style="width:167px;">P1 medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">calcium chloride</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">C7902-500G</td>
			<td style="width:167px;">P1 medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">commercial salt</td>
			<td style="width:179px;">Aqua Medic&#160;</td>
			<td style="width:151px;">Meersalz</td>
			<td>Activator solution&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">BSA</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">05470 Sigma</td>
			<td>Activator solution&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Falcon tubes 15 ml</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">T1943-1000EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Falcon tubes support</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">R5651-5EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Eppendorfs</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">T9661-1000EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Micropipet 20 &#181;l</td>
			<td style="width:179px;">Gilson</td>
			<td style="width:151px;">PIPETMAN&#174; Classic</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Micropipet 10 &#181;l</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">Z683787-1EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Tips for micropipets 20 &#181;l</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">Z740030-1000EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Tips for micropipets 10 &#181;l</td>
			<td style="width:179px;">Merck</td>
			<td style="width:151px;">Z740028-2000EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Spermtrack</td>
			<td style="width:179px;">PROiSER</td>
			<td style="width:151px;">Counting chamber</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">TruMorph</td>
			<td style="width:179px;">PROiSER</td>
			<td style="width:151px;">TruMorph</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Microscope UB 200i Serie</td>
			<td style="width:179px;">PROiSER</td>
			<td style="width:151px;">Microscope</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Cooler plate</td>
			<td style="width:179px;">PROiSER</td>
			<td style="width:151px;"></td>
			<td>Prototype</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:249px;">Cooler block</td>
			<td style="width:179px;">PROiSER</td>
			<td style="width:151px;"></td>
			<td>Prototype</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ISAS v1</td>
			<td style="width:179px;">PROiSER</td>
			<td style="width:151px;">ISAS</td>
			<td>Software</td>
		</tr>
	</tbody>
</table>

fish sperm assessment using software and cooling devices

For gamete quality evaluation, there are innovative, rapid, and quantitative techniques that can provide useful data for aquaculture. Computerized systems for sperm analysis were developed to measure several parameters and one of the most commonly measured is the sperm motility.
Initially, this computer technology was designed for mammalian species, although it can also be used for fish sperm analysis. Fish have specific features that can affect sperm assessment such as a short motility time after activation and, in some cases, adaptation to lower temperatures. Thus, it is necessary to modify both software and hardware components to make motility analysis more efficient for fish sperm analysis. For mammalian sperm, the heating plate is used to maintain optimal temperatures of spermatozoa. However, for some fish species, it is advantageous to use a lower temperature to prolong the duration of motility, since the sperm remain active for less than 2 min. Therefore, cooling devices are necessary to refrigerate samples at constant temperature over the time of analysis, including on the optical microscope. This protocol describes the analysis of fish sperm motility using software for sperm analysis and new cooling devices to optimize the results.

Analysis of the time effect on sperm motility
In the case of the European eel, the percentage of static spermatozoa increased from 15 s to 120 s after activation (from 24.4% to 40.7%), and the percentage of mobile progressive spermatozoa decreased (from 36.9% to 20.9%) (Figure&#160;1A and 1B). Based on speed, spermatozoa cells showed a decrease in velocity over time (Figure&#160;1C and 1D) decreased. The percentage of spermatozoa with rapid velocity decreased about 23% (from 49.4% to 26.6%) and the percentage of spermatozoa with medium velocity increased around 7%.
The effect of the frame rate and counting chamber
Different species require different frame rates for optimal results. Russian sturgeon requires 150 frames per second (fps; Figure 2A); common carp requires 100 fps (Figure 2B); and for the grayling, 200 fps was not enough to obtain optimal kinetic results (Figure 2C). These results were not dependent on the depth of the counting chamber tested (Figure&#160;2A-2C).
Sperm subpopulations structure
The identification of sperm subpopulation is based on statistical analysis. The first step is the determination of principal components (principal component analysis; PCA) from the complete set of motility data. Then, the clustering procedures are performed with the sperm-derived indices obtained after the PCA.
For this study, we used Atlantic salmon sperm which showed four different subpopulations, named: slow nonlinear (low LIN, STR and VCL), fast nonlinear (lower STR, high VCL), fast linear (high LIN, STR and VCL) and fastest linear (highest LIN, STR, and VCL). The distribution of these subpopulations varied along generations from wild animals to farmed ones (Figure 3).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56823/56823fig1.jpg" /> 
Figure 1: Effect of time post-activation on the progressivity and motility of European eel sperm. A and B) Percentage of progressivity at 15 and 120 s, respectively; and C and D) the percentage of motility based on speed over time (15 and 120 s post-activation, respectively). The progressivity was divided in three groups: progressive motile cells (white; VCL mean value &#177; SD: 114.5 &#177; 18.2 and 101.4 &#177; 34.5 &#181;m/s for 15 and 120 s, respectively), no progressive motile cells (grey; VCL mean value &#177; SD: 84.8 &#177; 17.4 &#181;m/s for 15 s and 84.6 &#177; 16.5 &#181;m/s for 120 s), and static spermatozoa (black). The spermatozoa velocity was divided into 4 groups: rapid (VCL mean value &#177; SD: 119.3 &#177; 13.7 &#181;m/s for 15 s and 118.9 &#177; 13.3 &#181;m/s for 120 s; white), medium (VCL mean value &#177; SD: 79.7 &#177; 15.5 &#181;m/s for 15 s and 79.6 &#177; 15.5 &#181;m/s for 120 s; light grey), slow (VCL mean value &#177; SD: 32.9 &#177; 6.5 &#181;m/s for 15 s and 32.6 &#177; 6.6 &#181;m/s for 120 s; dark grey) and static (black). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56823/56823fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56823/56823fig2.jpg" /> 
Figure 2: The effect of the frame rate and the counting chamber in three freshwater fish species: (A) Russian sturgeon (B) Common carp and (C) Grayling.&#160;Sperm analysis was made at 50, 100, 150 and 200 fps, using two commercial counting chambers with different depths (10 and 20 &#181;m). The black circle represents the best frame rate for each species. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56823/56823fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56823/56823fig3.jpg" /> 
Figure 3: Sperm subpopulations structure of three generations of Atlantic salmon: wild males (F0), and the first two generations produced in captivity (F1 and F2). After cluster analysis, four subpopulations were observed: slow nonlinear spermatozoa (low LIN, STR and VCL; cluster 1; black), fast nonlinear spermatozoa (lower STR, high VCL; cluster 2; dark grey), fast linear spermatozoa (high LIN, STR and VCL; cluster 3; intermediate grey) and fastest linear spermatozoa (highest LIN, STR, and VCL; cluster 4; light grey). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56823/56823fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Supplemental Figure 1" src="/files/ftp_upload/56823/56823figsup1.jpg" /> 
Supplemental Figure 1. Different visual areas from the motility analysis of European eel sperm defined as (A) best and (B) worst cell concentration. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56823/56823figsup1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Fish Sperm Assessment Using Software and Cooling Devices at JoVE.com

Fish Sperm Assessment Using Software and Cooling Devices

The present protocol describes a procedure of fish sperm assessment using computer-assisted sperm analysis and cooling devices. The software gives a rapid, accurate and quantitative analysis of fish sperm quality based on spermatozoa motility, which can be a useful tool in aquaculture to improve reproduction success.

For gamete quality evaluation, there are innovative, rapid, and quantitative techniques that can provide useful data for aquaculture. Computerized systems ...

fish-sperm-assessment-using-software-and-cooling-devices

Nanyang Technological University

Research

JoVE Journal

Biology

8.7K Views.  PROiSER R+D S.L.. The present protocol describes a procedure of fish sperm assessment using computer-assisted sperm analysis and cooling devices. The software gives a rapid, accurate and quantitative analysis of fish sperm quality based on spermatozoa motility, which can be a useful tool in aquaculture to improve reproduction success.

Video: Fish Sperm Assessment Using Software and Cooling Devices

Harvesting Sperm and Artificial Insemination of Mice

Rodents of the genus Peromyscus (deer mice) are the most prevalent native North American mammals. Peromyscus species are used in a wide range of research including toxicology, epidemiology, ecology, behavioral, and genetic studies. Here they provide a useful model for demonstrations of artificial insemination. 

Methods similar to those displayed here have previously been used in several deer mouse studies, yet no detailed protocol has been published. Here we demonstrate the basic method of artificial insemination. This method entails extracting the testes from the rodent, then isolating the sperm from the epididymis and vas deferens. The mature sperm, now in a milk mixture, are placed in the female&#x2019;s reproductive tract at the time of ovulation. Fertilization is counted as day 0 for timing of embryo development. Embryos can then be retrieved at the desired time-point and manipulated.

Artificial insemination can be used in a variety of rodent species where exact embryo timing is crucial or hard to obtain. This technique is vital for species or strains (including most Peromyscus) which may not mate immediately and/or where mating is hard to assess. In addition, artificial insemination provides exact timing for embryo development either in mapping developmental progress and/or transgenic work. Reduced numbers of animals can be used since fertilization is guaranteed. This method has been vital to furthering the Peromyscus system, and will hopefully benefit others as well.

This protocol demonstrates methods for extracting sperm from the testes of males and then inseminating female mice. This procedure is useful when precise time is needed in developmental studies as well as transgenic work.

Rodents of the genus Peromyscus (deer mice) are the most prevalent native North American mammals.  Peromyscus species are used in a wide range of research ...

Fluorescence in situ hybridization (FISH) Protocol in Human Sperm

Aneuploidies are the most frequent chromosomal abnormalities in humans. Most of these abnormalities result from meiotic errors during the gametogenic process in the parents. In human males, these errors can lead to the production of spermatozoa with numerical chromosome abnormalities which represent an increased risk of transmitting these anomalies to the offspring.
For this reason, the technique of fluorescence in situ hybridization (FISH) on sperm nuclei has become a protocol widely incorporated in the context of clinical diagnosis. This practice provides an estimate of the frequencies of numerical chromosome abnormalities in the gametes of the patients that seek for genetic reproductive advice.
To date, the chromosomes most frequently included in sperm FISH analysis are chromosomes X, Y, 13, 18 and 21.
This video-article describes, step by step, how to process and fix a human semen sample, how to decondense and denature the sperm chromatin, how to proceed to obtain sperm FISH preparations, and how to visualize the results at the microscope. Special remarks of the most relevant steps are given to achieve the best results.

Fluorescence in situ hybridization FISH Protocol in Human Sperm

This video-article describes, step by step, how to process a semen sample to achieve good-quality fluorescence in situ hybridization on human spermatozoa. Preparations obtained can be used for aneuploidy screening in the context of clinical diagnosis.

Aneuploidies are the most frequent chromosomal abnormalities in humans. Most of these abnormalities result from meiotic errors during the gametogenic ...

Isolation and In vitro Activation of Caenorhabditis elegans Sperm

Males and hermaphrodites are the two naturally found sexual forms in the nematode C. elegans. The amoeboid sperm are produced by both males and hermaphrodites. In the earlier phase of gametogenesis, the germ cells of hermaphrodites differentiate into limited number of sperm - around 300 - and are stored in a small 'bag' called the spermatheca. Later on, hermaphrodites continually produce oocytes1. In contrast, males produce exclusively sperm throughout their adulthood. The males produce so much sperm that it accounts for &gt;50% of the total cells in a typical adult worm2. Therefore, isolating sperm from males is easier than from that of hermaphrodites.
Only a small proportion of males are naturally generated due to spontaneous non-disjunction of X chromosome3. Crossing hermaphrodites with males or more conveniently, the introduction of mutations to give rise to Him (High Incidence of Males) phenotype are some of strategies through which one can enrich the male population3.
Males can be easily distinguished from hermaphrodites by observing the tail morphology4. Hermaphrodite's tail is pointed, whereas male tail is rounded with mating structures.
Cutting the tail releases vast number of spermatids stored inside the male reproductive tract. Dissection is performed under a stereo microscope using 27 gauge needles. Since spermatids are not physically connected with any other cells, hydraulic pressure expels internal contents of male body, including spermatids2.
Males are directly dissected on a small drop of 'Sperm Medium'. Spermatids are sensitive to alteration in the pH. Hence, HEPES, a compound with good buffering capacity is used in sperm media. Glucose and other salts present in sperm media help maintain osmotic pressure to maintain the integrity of sperm.
Post-meiotic differentiation of spermatids into spermatozoa is termed spermiogenesis or sperm activation. Shakes5, and Nelson6 previously showed that round spermatids can be induced to differentiate into spermatozoa by adding various activating compounds including Pronase E. Here we demonstrate in vitro spermiogenesis of C. elegans spermatids using Pronase E.
Successful spermiogenesis is pre-requisite for fertility and hence the mutants defective in spermiogenesis are sterile. Hitherto several mutants have been shown to be defective specifically in spermiogenesis process7. Abnormality found during in vitro activation of novel Spe (Spermatogenesis defective) mutants would help us discover additional players participating in this event.

Isolation and In vitro Activation of Caenorhabditis elegans Sperm

A protocol for isolating and activating spermatids from male C. elegans is described here. Cutting the posterior end of male releases spermatids. The spermatids can be activated by addition of protease.

Males and hermaphrodites are the two naturally found sexual forms in the nematode C. elegans. The amoeboid sperm are produced by both males and ...

Imaging C. elegans Embryos using an Epifluorescent Microscope and Open Source Software

Cellular processes, such as chromosome assembly, segregation and cytokinesis,are inherently dynamic. Time-lapse imaging of living cells, using fluorescent-labeled reporter proteins or differential interference contrast (DIC) microscopy, allows for the examination of the temporal progression of these dynamic events which is otherwise inferred from analysis of fixed samples1,2. Moreover, the study of the developmental regulations of cellular processes necessitates conducting time-lapse experiments on an intact organism during development. The Caenorhabiditis elegans embryo is light-transparent and has a rapid, invariant developmental program with a known cell lineage3, thus providing an ideal experiment model for studying questions in cell biology4,5and development6-9. C. elegans is amendable to genetic manipulation by forward genetics (based on random mutagenesis10,11) and reverse genetics to target specific genes (based on RNAi-mediated interference and targeted mutagenesis12-15). In addition, transgenic animals can be readily created to express fluorescently tagged proteins or reporters16,17. These traits combine to make it easy to identify the genetic pathways regulating fundamental cellular and developmental processes in vivo18-21. In this protocol we present methods for live imaging of C. elegans embryos using DIC optics or GFP fluorescence on a compound epifluorescent microscope. We demonstrate the ease with which readily available microscopes, typically used for fixed sample imaging, can also be applied for time-lapse analysis using open-source software to automate the imaging process.

Imaging C. elegans Embryos using an Epifluorescent Microscope and Open Source Software

The C. elegans embryo is a powerful system for studying cell biology and development. We present a protocol for live imaging of C. elegans embryos utilizing DIC optics or fluorescence using readily available epifluorescent microscopes and open-source software.

Cellular processes, such as chromosome assembly, segregation and cytokinesis,are inherently dynamic. Time-lapse imaging of living cells, using ...

Mouse Sperm Cryopreservation and Recovery using the I&middot;Cryo Kit

Thousands of new genetically modified (GM) strains of mice have been created since the advent of transgenesis and knockout technologies. Many of these valuable animals exist only as live animals, with no backup plan in case of emergency. Cryopreservation of embryos can provide this backup, but is costly, can be a lengthy procedure, and generally requires a large number of animals for success. Since the discovery that mouse sperm can be successfully cryopreserved with a basic cryoprotective agent (CPA) consisting of 18&#37; raffinose and 3&#37; skim milk, sperm cryopreservation has become an acceptable and cost-effective procedure for archiving, distributing and recovery of these valuable strains.
 Here we demonstrate a newly developed I&bull;Cryo kit for mouse sperm cryopreservation. Sperm from five commonly-used strains of inbred mice were frozen using this kit and then recovered. Higher protection ratios of sperm motility (&gt; 60&#37;) and rapid progressive motility (&gt; 45&#37;) compared to the control (basic CPA) were seen for sperm frozen with this kit in 5 inbred mouse strains. Two cell stage embryo development after IVF with the recovered sperm was improved consistently in all 5 mouse strains examined. Over a 1.5 year period, 49 GM mouse lines were archived by sperm cryopreservation with the I&bull;Cryo kit and later recovered by IVF.

Here we demonstrate the newly developed I&#x2022;Cryo kit for mouse sperm cryopreservation. Two-cell stage embryo development with frozen-thawed sperm was improved consistently in 5 mouse strains with the use of this kit. Over a 1.5 year period, 49 genetically modified mouse lines were archived by sperm cryopreservation with the I&#x2022;Cryo kit and later successfully recovered by IVF.

Thousands of new genetically modified (GM) strains of mice have been created since the advent of transgenesis and knockout technologies.  Many of these ...

Assessing Differences in Sperm Competitive Ability in Drosophila

Competition among conspecific males for fertilizing the ova is one of the mechanisms of sexual selection, i.e. selection that operates on maximizing the number of successful mating events rather than on maximizing survival and viability 1. Sperm competition represents the competition between males after copulating with the same female 2, in which their sperm are coincidental in time and space. This phenomenon has been reported in multiple species of plants and animals 3. For example, wild-caught D. melanogaster females usually contain sperm from 2-3 males 4. The sperm are stored in specialized organs with limited storage capacity, which might lead to the direct competition of the sperm from different males 2,5.
Comparing sperm competitive ability of different males of interest (experimental male types) has been performed through controlled double-mating experiments in the laboratory 6,7. Briefly, a single female is exposed to two different males consecutively, one experimental male and one cross-mating reference male. The same mating scheme is then followed using other experimental male types thus facilitating the indirect comparison of the competitive ability of their sperm through a common reference. The fraction of individuals fathered by the experimental and reference males is identified using markers, which allows one to estimate sperm competitive ability using simple mathematical expressions 7,8. In addition, sperm competitive ability can be estimated in two different scenarios depending on whether the experimental male is second or first to mate (offense and defense assay, respectively) 9, which is assumed to be reflective of different competence attributes.
Here, we describe an approach that helps to interrogate the role of different genetic factors that putatively underlie the phenomenon of sperm competitive ability in D. melanogaster.

Assessing Differences in Sperm Competitive Ability in Drosophila

Differential sperm competitive ability among Drosophila males with distinct genotypes can be ascertained through double-mating experiments. Each of these experiments involves one of the males of interest and a reference male. Readily identifiable markers in the progeny allow inference of the fraction of individuals fathered by each male.

Competition among conspecific males for fertilizing the ova is one of the mechanisms of sexual selection, i.e. selection that operates on maximizing the ...

Robust 3D DNA FISH Using Directly Labeled Probes

3D DNA FISH has become a major tool for analyzing three-dimensional organization of the nucleus, and several variations of the technique have been published. In this article we describe a protocol which has been optimized for robustness, reproducibility, and ease of use. Brightly fluorescent directly labeled probes are generated by nick-translation with amino-allyldUTP followed by chemical coupling of the dye. 3D DNA FISH is performed using a freeze-thaw step for cell permeabilization and a heating step for simultaneous denaturation of probe and nuclear DNA. The protocol is applicable to a range of cell types and a variety of probes (BACs, plasmids, fosmids, or Whole Chromosome Paints) and allows for high-throughput automated imaging. With this method we routinely investigate nuclear localization of up to three chromosomal regions.

We describe a robust and versatile protocol for analyzing nuclear architecture by 3D DNA FISH using directly labeled fluorescent probes.

3D DNA FISH has become a major tool for  analyzing three-dimensional organization of the nucleus, and several variations  of the technique have been ...

Assessing Species-specific Contributions To Craniofacial Development Using Quail-duck Chimeras

The generation of chimeric embryos is a widespread and powerful approach to study cell fates, tissue interactions, and species-specific contributions to the histological and morphological development of vertebrate embryos. In particular, the use of chimeric embryos has established the importance of neural crest in directing the species-specific morphology of the craniofacial complex. The method described herein utilizes two avian species, duck and quail, with remarkably different craniofacial morphology. This method greatly facilitates the investigation of molecular and cellular regulation of species-specific pattern in the craniofacial complex.&#160;Experiments in quail and duck chimeric embryos have already revealed neural crest-mediated tissue interactions and cell-autonomous behaviors that regulate species-specific pattern in the craniofacial skeleton, musculature, and integument. The great diversity of neural crest derivatives suggests significant potential for future applications of the quail-duck chimeric system to understanding vertebrate development, disease, and evolution.

This article describes a method to generate chimeric embryos that are&#160;designed to test the species-specific contributions of neural crest and/or other tissues to craniofacial development.

The generation of chimeric embryos is a widespread and powerful approach to study cell fates, tissue interactions, and species-specific contributions to ...

A Protocol for Using Gene Set Enrichment Analysis to Identify the Appropriate Animal Model for Translational Research

Recent studies that compared transcriptomic datasets of human diseases with datasets from mouse models using traditional gene-to-gene comparison techniques resulted in contradictory conclusions regarding the relevance of animal models for translational research. A major reason for the discrepancies between different gene expression analyses is the arbitrary filtering of differentially expressed genes. Furthermore, the comparison of single genes between different species and platforms often is limited by technical variance, leading to misinterpretation of the con/discordance between data from human and animal models. Thus, standardized approaches for systematic data analysis are needed. To overcome subjective gene filtering and ineffective gene-to-gene comparisons, we recently demonstrated that gene set enrichment analysis (GSEA) has the potential to avoid these problems. Therefore, we developed a standardized protocol for the use of GSEA to distinguish between appropriate and inappropriate animal models for translational research. This protocol is not suitable to predict how to design new model systems a-priori, as it requires existing experimental omics data. However, the protocol describes how to interpret existing data in a standardized manner in order to select the most suitable animal model, thus avoiding unnecessary animal experiments and misleading translational studies.

We provide a standardized protocol for the use of gene set enrichment analysis of transcriptomic data to identify an ideal mouse model for translational research. 
This protocol can be used with DNA microarray and RNA sequencing data and can further be extended to other omics data if data are available.

Recent studies that compared transcriptomic datasets of human diseases with datasets from mouse models using traditional gene-to-gene comparison ...

Sperm Collection of Differential Quality Using Density Gradient Centrifugation

In sexual reproduction, a male gamete or sperm cell fuses with a female gamete to bring about fertilization. However, a large number of sperm cells with fertilizing ability are required to interact with a female gamete to ensure fertilization. As such, the fertilizing ability of individual sperm cells is critical for successful reproduction. Density gradient centrifugation has been utilized for several decades as a reproducible, fast, efficient, effective and extremely adaptable method to collect only high-quality sperm to be used in assisted reproductive technology. The protocols we described herein focus on the utilization of the discontinuous Percoll density gradient centrifugation (PDGC) technique to isolate three distinct populations of rooster sperm by their quality. We were able to collect low-, medium- and high-quality sperm. We also describe reproducible protocols that entail determining fertility potential of sperm by assessing their viability, mobility and penetrability. Collection of sperm by their quality using PDGC technique would be useful to accurately and thoroughly characterize sperm with differential fertility potential.

In this paper, we aim to describe the performance of the density gradient centrifugation technique and its application in sperm physiology research.

In sexual reproduction, a male gamete or sperm cell fuses with a female gamete to bring about fertilization. However, a large number of sperm cells with ...