This publication was funded by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642893 (IMPRESS), the COST Office (COST Action FA 1205, AQUAGAMETE), and the Research Centre of Excellence - 1476-4/2016/FEKUT.

All procedures for working with European eel described in this protocol were approved by the Committee of Ethics of Animal Experimentation at the Universitat Polit&#232;cnica de Val&#232;ncia, following the Spanish laws and regulations controlling the experiments and procedures on live animals.
1. Fish Maintenance
<ol>
	<li>Bring the European eels to a research facility and put them in a 200 L aquaria with a recirculation system. Use thermostats and coolers to maintain a constant 20 &#176;C ...

<ol>
	<li>ICES_Working_Group_on_Eels. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Report of the 2011 Session of the Joint EIFAAC/ICES Working Group on Eels. , 246 (2011).</li><li>Moriarty, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=European+Catches+of+Elver+of+1928-1988.">European Catches of Elver of 1928-1988.</a> Int. Rev. Hydrobiol. 75 (6), 701-706 (1990).</li><li>Dekker, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+fractal+geometry+of+the+European+eel+stock.">The fractal geometry of the European eel stock.</a> ICES J. Mar. Sci. 57 (1), 109-121 (2000).</li><li>Jacoby, D., Gollock, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Anguilla anguilla. The IUCN red list of threatened species. Version 2014.2. , (2014).</li><li>Asturiano, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+hCG+as+spermiation+inducer+on+European+eel+semen+quality.">Effects of hCG as spermiation inducer on European eel semen quality.</a> Theriogenology. 66 (4), 1012-1020 (2006).</li><li>P&#233;rez, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+maturation+and+spermiation+in+the+male+European+eel:+assessment+of+sperm+quality+throughout+treatment.">Induction of maturation and spermiation in the male European eel: assessment of sperm quality throughout treatment.</a> J. Fish Biol. 57 (6), 1488-1504 (2000).</li><li>Gallego, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+the+effects+of+thermal+regime+and+alternative+hormonal+treatments+on+the+reproductive+performance+of+European+eel+males+(Anguilla+anguilla)+during+induced+sexual+maturation.">Study of the effects of thermal regime and alternative hormonal treatments on the reproductive performance of European eel males (Anguilla anguilla) during induced sexual maturation.</a> Aquaculture. 354, 7-16 (2012).</li><li>Asturiano, J. F., S&#248;rensen, S. R., P&#233;rez, L., Lauesen, P., Tomkiewicz, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=First+Production+of+Larvae+Using+Cryopreserved+Sperm:+Effects+of+Preservation+Temperature+and+Cryopreservation+on+European+Eel+Sperm+Fertilization+Capacity.">First Production of Larvae Using Cryopreserved Sperm: Effects of Preservation Temperature and Cryopreservation on European Eel Sperm Fertilization Capacity.</a> Reprod. Domestic Anim. 51 (4), 485-491 (2016).</li><li>Di Biase, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Co-treatment+with+androgens+during+artificial+induction+of+maturation+in+female+eel,+Anguilla+anguilla:+Effects+on+egg+production+and+early+development.">Co-treatment with androgens during artificial induction of maturation in female eel, Anguilla anguilla: Effects on egg production and early development.</a> Aquaculture. 479, 508-515 (2017).</li><li>Lokman, P., Wylie, M. J., Downes, M., Di Biase, A., Damsteegt, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Artificial+induction+of+maturation+in+female+silver+eels,+Anguilla+australis:+The+benefits+of+androgen+pre-treatment.">Artificial induction of maturation in female silver eels, Anguilla australis: The benefits of androgen pre-treatment.</a> Aquaculture. 437, 111-119 (2015).</li><li>Mylonas, C. C., Duncan, N. J., Asturiano, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hormonal+manipulations+for+the+enhancement+of+sperm+production+in+cultured+fish+and+evaluation+of+sperm+quality.">Hormonal manipulations for the enhancement of sperm production in cultured fish and evaluation of sperm quality.</a> Aquaculture. , (2016).</li><li>Ohta, H., Izawa, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diluent+for+cool+storage+of+the+Japanese+eel+(Anguilla+japonica)+spermatozoa.">Diluent for cool storage of the Japanese eel (Anguilla japonica) spermatozoa.</a> Aquaculture. 142 (1-2), 107-118 (1996).</li><li>Pe&#241;aranda, D. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=European+Eel+Sperm+Diluent+for+Short-term+Storage.">European Eel Sperm Diluent for Short-term Storage.</a> Reprod. Domestic Anim. 45 (3), 407-415 (2010).</li><li>Ohta, H., Kagawa, H., Tanaka, H., Unuma, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+by+the+environmental+concentration+of+ions+of+the+potential+for+motility+in+Japanese+eel+spermatozoa.">Control by the environmental concentration of ions of the potential for motility in Japanese eel spermatozoa.</a> Aquaculture. 198 (3), 339-351 (2001).</li><li>Asturiano, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Media+and+methods+for+the+cryopreservation+of+European+eel+(Anguilla+anguilla)+sperm.">Media and methods for the cryopreservation of European eel (Anguilla anguilla) sperm.</a> Fish Physiol. Biochem. 28 (1), 501-502 (2003).</li><li>Asturiano, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physio-chemical+characteristics+of+seminal+plasma+and+development+of+media+and+methods+for+the+cryopreservation+of+European+eel+sperm.">Physio-chemical characteristics of seminal plasma and development of media and methods for the cryopreservation of European eel sperm.</a> Fish Physiol. Biochem. 30 (3), 283-293 (2004).</li><li>Szab&#243;, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryopreservation+of+European+eel+(Anguilla+anguilla)+sperm+using+different+extenders+and+cryoprotectants.">Cryopreservation of European eel (Anguilla anguilla) sperm using different extenders and cryoprotectants.</a> Acta. Biol. Hung. 56 (1-2), 173-175 (2005).</li><li>M&#252;ller, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryopreservation+of+sperm+of+farmed+European+eel+Anguilla+anguilla.">Cryopreservation of sperm of farmed European eel Anguilla anguilla.</a> J World Aquac Soc. 35 (2), 225-231 (2004).</li><li>Pe&#241;aranda, D. S., P&#233;rez, L., Gallego, V., Jover, M., Asturiano, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improvement+of+European+eel+sperm+cryopreservation+method+by+preventing+spermatozoa+movement+activation+caused+by+cryoprotectants.">Improvement of European eel sperm cryopreservation method by preventing spermatozoa movement activation caused by cryoprotectants.</a> Cryobiology. 59 (2), 119-126 (2009).</li><li>Marco-Jim&#233;nez, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryopreservation+of+European+eel+(Anguilla+anguilla)+spermatozoa:+effect+of+dilution+ratio,+foetal+bovine+serum+supplementation,+and+cryoprotectants.">Cryopreservation of European eel (Anguilla anguilla) spermatozoa: effect of dilution ratio, foetal bovine serum supplementation, and cryoprotectants.</a> Cryobiology. 53 (1), 51-57 (2006).</li><li>Asturiano, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+sperm+cryopreservation+on+the+European+eel+sperm+viability+and+spermatozoa+morphology.">Effect of sperm cryopreservation on the European eel sperm viability and spermatozoa morphology.</a> Reprod. Domestic Anim. 42 (2), 162-166 (2007).</li><li>Mordenti, M., Di Biase, A., Sirri, R., Modugno, S., Tasselli, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+Sexual+Maturation+in+Wild+Female+European+Eels+(Anguilla+anguilla)+in+Darkness+and+Light.">Induction of Sexual Maturation in Wild Female European Eels (Anguilla anguilla) in Darkness and Light.</a> Isr. J. Aquac. 64, (2012).</li><li>Ohta, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Artificial+induction+of+maturation+and+fertilization+in+the+Japanese+eel,+Anguilla+japonica.">Artificial induction of maturation and fertilization in the Japanese eel, Anguilla japonica.</a> Fish Physiol. Biochem. 17 (1), 163-169 (1997).</li><li>Tanaka, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+cryopreservation+of+sperm+of+Japanese+eel.">Long-term cryopreservation of sperm of Japanese eel.</a> J. Fish Biol. 60 (1), 139-146 (2002).</li><li>Gallego, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Subpopulation+pattern+of+eel+spermatozoa+is+affected+by+post-activation+time,+hormonal+treatment+and+the+thermal+regimen.">Subpopulation pattern of eel spermatozoa is affected by post-activation time, hormonal treatment and the thermal regimen.</a> Reprod. Fertil. Dev. 27 (3), 529-543 (2015).</li><li>Asturiano, J. F., Cabrita, E., Horv&#225;th, &. #. 1. 9. 3. ;. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progress,+challenges+and+perspectives+on+fish+gamete+cryopreservation:+A+mini-review.">Progress, challenges and perspectives on fish gamete cryopreservation: A mini-review.</a> Gen. Comp. Endocrinol. , (2016).</li><li>Kime, D. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computer-assisted+sperm+analysis+(CASA)+as+a+tool+for+monitoring+sperm+quality+in+fish.">Computer-assisted sperm analysis (CASA) as a tool for monitoring sperm quality in fish.</a> Comp. Biochem. Physiol. C Toxicol. Pharmacol. 130 (4), 425-433 (2001).</li><li>Rurangwa, E., Kime, D. E., Ollevier, F., Nash, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+measurement+of+sperm+motility+and+factors+affecting+sperm+quality+in+cultured+fish.">The measurement of sperm motility and factors affecting sperm quality in cultured fish.</a> Aquaculture. 234 (1-4), 1-28 (2004).</li><li>Verstegen, J., Iguer-Ouada, M., Onclin, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computer+assisted+semen+analyzers+in+andrology+research+and+veterinary+practice.">Computer assisted semen analyzers in andrology research and veterinary practice.</a> Theriogenology. 57 (1), 149-179 (2002).</li><li>Magnotti, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cryopreservation+and+vitrification+of+fish+semen:+a+review+with+special+emphasis+on+marine+species.">Cryopreservation and vitrification of fish semen: a review with special emphasis on marine species.</a> Rev. Aquacult. , (2016).</li><li>Dziewulska, K., Rzemieniecki, A., Czerniawski, R., Domaga&#322;a, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Post-thawed+motility+and+fertility+from+Atlantic+salmon+(Salmo+salar+L.)+sperm+frozen+with+four+cryodiluents+in+straws+or+pellets.">Post-thawed motility and fertility from Atlantic salmon (Salmo salar L.) sperm frozen with four cryodiluents in straws or pellets.</a> Theriogenology. 76 (2), 300-311 (2011).</li><li>Babiak, I., Bolla, S., Ottesen, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suitable+methods+for+cryopreservation+of+semen+from+Atlantic+halibut,+Hippoglossus+hippoglossus+L.">Suitable methods for cryopreservation of semen from Atlantic halibut, Hippoglossus hippoglossus L.</a> Aquac. Int. 16 (6), 561-572 (2008).</li><li>M&#252;ller, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Japanese+eel+(Anguilla+japonica+Temminck+&amp;+Schlegel,+1846)+propagation+using+cryopreserved+sperm+samples.">Japanese eel (Anguilla japonica Temminck &amp; Schlegel, 1846) propagation using cryopreserved sperm samples.</a> J. Appl. Ichthyol. 33 (3), 550-552 (2017).</li></ol>

The authors declare that they have no competing financial interests.

This protocol describes the complete process for European eel maturation, handling and sperm cryopreservation. The husbandry conditions described here are optimal for fast maturation and production of high volumes of high-quality sperm in this species 6,7,25. The success of this cryopreservation protocol and its potential use for fertilization after thawing depend greatly on the quality of fresh sperm 26....

Over the last 25 years, the number of European eels (Anguilla anguilla) arriving at the European coast have decreased steadily by 90% 1,2,3. There are several factors that explain this drastic drop including pollution, infections, overfishing and habitat destruction. All of this has had a profound effect on this species, leading to the inclusion of the European eel on the International Union for Conservation of Nature (IUCN) list as critical endangered 4. Consequently, the development of techniques and protocols for reproduction in captivity are necessary.
The maturation of the European eel in captivity is acheived by hormonal treatment 5,6,7 but the production of gametes in both sexes is difficult to synchronize 8. Even though the development of new androgen implants has shown to accelerate oogenesis in eels 9,10, the timing of final maturation in females is still highly variable and difficult to control 11. Therefore, short-term storage of sperm 12,13,14 and cryopreservation techniques are necessary for reproduction management, making gamete synchronization unnecessary 8.
Cryopreservation of European eel sperm has been developed since 2003 15,16. Several researchers designed successful protocols using either dimethyl sulfoxide (DMSO) or methanol as cryoprotectants 16,17,18,19,20. Although both protocols have been successfully used, the obtained cell viability of thawed sperm cryopreserved with DMSO is lower than with methanol 20,21. Moreover, eel sperm is activated on contact with DMSO and requires more tedious sperm manipulation 19, therefore methanol is a more suitable cryoprotectant for European eel sperm than DMSO.
Here, the protocol for optimal handling and hormonal treatment of the European eel will be described below. In addition to this, the best European eel sperm cryopreservation protocol using methanol as a cryoprotectant and a protocol for the assessment of sperm quality in this species will also be described.

<table border="0" cellpadding="0" cellspacing="0" width="538">
	<tbody>
		<tr height="19">
			<td height="19" style="height:19px;width:151px;">AQUACEN BENZOCA&#205;NA +D2A2:D24</td>
			<td style="width:128px;">AQUACEN</td>
			<td style="width:119px;">3394ESP</td>
			<td style="width:141px;">Benzocaine</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">NaCl</td>
			<td>Avantor&#160;</td>
			<td>3624-19</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Syringe</td>
			<td>BD Plastipak</td>
			<td>305501</td>
			<td>Syringe 1 mL</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">FC500</td>
			<td>Beckman Coulter</td>
			<td></td>
			<td>Flow cytometer</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Air pump 100</td>
			<td>EHEIM</td>
			<td>4011708370032</td>
			<td>Modified for suction</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Eppendorf 1.5</td>
			<td>Eppendorf</td>
			<td>175508</td>
			<td>Plastic tubes 1.5 mL</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Falcon tubes</td>
			<td>Falcon</td>
			<td>175747</td>
			<td>Plastic tubes 15 mL</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Flexible bucket</td>
			<td>Fiel</td>
			<td>1040101</td>
			<td>40 L, Black color.</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Ethanol</td>
			<td>Guinama SL</td>
			<td>Mg96270</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Cyopreservation straws&#160;</td>
			<td>IMV Technologies</td>
			<td>14550</td>
			<td>500 &#181;L straws</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Live/Dead Sperm Viability Kit</td>
			<td>Invitrogen</td>
			<td>L7011</td>
			<td>Cytometer Kit</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Modelling clay</td>
			<td>JOVI</td>
			<td>Art 30</td>
			<td>4 different colors</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Precision scale PCB</td>
			<td>KERN &#38; Sohn GmbH</td>
			<td>PCB35002</td>
			<td>Digital scale</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Saline solution Vitulia 0.9%</td>
			<td>Laboratorios Ern, S.A.</td>
			<td>C.N. 999790.8</td>
			<td>Saline solution</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Forceps</td>
			<td>Levantina de Lab. SL</td>
			<td>3710025</td>
			<td>30 cm metal forceps</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Scissors</td>
			<td>Levantina de Lab. SL</td>
			<td>3700014</td>
			<td>Scissors 14cm</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Ovitrelle (r-hCG)</td>
			<td>Merck SL</td>
			<td>EMEA/H/C/000320</td>
			<td>Human chorionic gonadotropin</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Nikon Eclipse 80i</td>
			<td>Nikon</td>
			<td></td>
			<td>Microscope</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">CaCl2</td>
			<td>Panreac Quimica SAU</td>
			<td>2112211210</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Na2SO4</td>
			<td>Panreac Quimica SAU</td>
			<td>3257091611</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">NaHCO3</td>
			<td>Panreac Quimica SAU</td>
			<td>1416381210</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">782M Camera</td>
			<td>Proiser</td>
			<td>782M</td>
			<td>Camera for CASA</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">ISAS v1</td>
			<td>Proiser</td>
			<td>ISAS v1</td>
			<td>CASA software</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">SpermTrack-10</td>
			<td>Proiser</td>
			<td>SpermTrack-10</td>
			<td>Countig chamber for CASA</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Beaker Pyrex 3L</td>
			<td>PYREX</td>
			<td>2110668</td>
			<td>Glass beaker 3L</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Flask Pyrex 250 GL-45</td>
			<td>PYREX</td>
			<td>21801365</td>
			<td>Glass flask 250 mL</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">KCl</td>
			<td>Scharlab SL</td>
			<td>PO02000500</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Methanol</td>
			<td>Scharlab SL</td>
			<td>ME03061000</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">MgCl2</td>
			<td>Scharlab SL</td>
			<td>MA00370500</td>
			<td></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">BSA</td>
			<td>Sigma Aldrich</td>
			<td>05482</td>
			<td>Bovine serum albumina</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;">Styrofoam box</td>
			<td></td>
			<td></td>
			<td>34x34x30 cm and 5cm thick</td>
		</tr>
	</tbody>
</table>

handling and treatment of male european eels (anguilla anguilla) for hormonal maturation and sperm cryopreservation

During the last years, several research groups have been working on the development and improvement of new protocols for the European eel handling and maturation. As of yet, weekly injections of human chorionic gonadotropin (hCG) have proved to maturate males after just 5-6 weeks of treatment, producing high volumes of high-quality sperm during several weeks. In addition, sperm cryopreservation protocols using different extenders, cryoprotectants and cooling and thawing times have been previously described for European eel. Here, we show that Tanaka&#180;s extender solution can be directly used for fertilization or for cryopreservation, making unnecessary the usage of different types of solutions and dilutions. Furthermore, the use of methanol as a cryoprotectant makes this protocol easy to use as methanol has low toxicity and does not activate the sperm. The sperm does not need to be cryopreserved immediately after the addition of the cryoprotectant, and it can be used long after being thawed. Moreover, sperm motility is still high after thawing although it is lower than that of fresh sperm. The aim of this work is to show the best available protocol for European eel handling, maturation, and sperm cryopreservation.

Sperm from 18 eels with a sperm motility of 70% or higher, was selected for this study. The results showed a reduction in all quality parameters after thawing compared to those from fresh sperm (Table 1 and Figure 2). The motility results (mean &#177; S.E.M., n=18) showed a higher total motility and a progressive motility in fresh sperm than the total motility and progressive motility found in the post-thaw sperm samples.
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Watch this Scientific Journal Video about Handling and Treatment of Male European Eels Anguilla anguilla for Hormonal Maturation and Sperm Cryopreservation at JoVE.com

Handling and Treatment of Male European Eels Anguilla anguilla for Hormonal Maturation and Sperm Cryopreservation

Protocols for European eel maturation and sperm cryopreservation have been improved over the last years. This article describes the best protocol available using human chorionic gonadotropin (hCG) for inducing maturation and methanol as cryoprotectant.

Handling and Treatment of Male European Eels (Anguilla anguilla) for Hormonal Maturation and Sperm Cryopreservation

During the last years, several research groups have been working on the development and improvement of new protocols for the European eel handling and ...

Hi, my name is Juan Asturiano from the Polytechnic University of Valencia, and we are with some of our colleagues from the Szent Istv

handling-treatment-male-european-eels-anguilla-anguilla-for-hormonal

Research

JoVE Journal

Developmental Biology

7.8K Görüntüleme.  Universitat Politècnica de València. Hi, my name is Juan Asturiano from the Polytechnic University of Valencia, and we are with some of our colleagues from the Szent Istv