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Characterization of pikeperch (Sander lucioperca) milt collected with a syringe and a catheter
Aquaculture 450 (2016) 14–16
Contents lists available at ScienceDirect
Aquaculture journal homepage: www.elsevier.com/locate/aqua-online
Short communication
Characterization of pikeperch (Sander lucioperca) milt collected with a syringe and a catheter Beata Sarosiek a,⁎, Katarzyna Dryl a, Sławomir Krejszeff b, Daniel Żarski b,c a b c
Department of Gamete and Embryo Biology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Tuwima Str. 10, 10-748 Olsztyn, Poland Department of Lake and River Fisheries, University of Warmia and Mazury in Olsztyn, Poland Department of Aquaculture, Szent István University, Gödöllő, Hungary
a r t i c l e
i n f o
Article history: Received 17 March 2015 Received in revised form 23 June 2015 Accepted 24 June 2015 Available online 30 June 2015 Keywords: Sander Milt Catheter Urine contamination Motility
a b s t r a c t Collection of fish milt by stripping risks contamination with urine, which may negatively influence milt characteristics and quality. Urine contamination of milt may be avoided by using a catheter for sperm collection. The objective of this study was to compare basic pikeperch milt parameters, i.e., sperm concentration (SC), pH, osmolality of seminal plasma (OSM), and motility parameters of spermatozoa analyzed with a CASA system (Computer Assisted Sperm Analysis), collected either with a syringe (as the standard method of sperm collection) or with a catheter. Every parameter of pikeperch milt collected with a catheter was significantly higher (P b 0.05; SC = 12.31 ± 3.81 × 109 ml−1, pH = 9.04 ± 0.07, OSM = 311 ± 16 mOsm kg−1) than that collected with a syringe (SC = 8.05 ± 3.04 × 109 ml−1, pH = 8.93 ± 0.09, OSM = 228 ± 51 mOsm kg−1), which clearly suggests urine contamination of milt collected with the standard procedure. Moreover, milt collected with catheter was characterized by higher spermatozoa motility parameters, e.g., motility rate of sperm collected with a catheter was 73% whereas the motility rate of sperm collected with a syringe did not exceed 35%. The results obtained in this work indicate that the milt collected with the standard procedure is likely to be exposed to contamination with urine, which may cause a significant reduction of quality parameters. Collection of sperm with a catheter was proven to effectively reduce the contamination of sperm with urine. Therefore, it is recommended to collect pikeperch sperm using a catheter. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Research on fish sperm quality often shows high diversification of the analyzed parameters, such as spermatozoa concentration or motility (Bokor et al., 2007; Cejko et al., 2008). Individual differences may be the result of genetic diversity of males used for reproduction, their age, and the method used to obtain semen (Rana, 1995). In most fish species, it is difficult to avoid urine contamination during the standard method of milt collection via massaging of the abdominal parts of the fish. Fertilization efficiency largely depends on the quality of sperm and oocytes. Apart from factors such as photoperiod, temperature, nutrition, and the type of hormonal stimulation (Hajirezaee et al., 2010), the method of obtaining gametes is also of great importance. During the process of collecting milt, it is important to ensure that it is not contaminated with urine to a great extent. Many authors have indicated the influence of the pikeperch sperm quality on the percentage of fertilized eggs (Casselman et al., 2006; Cejko et al., 2008; Rinchard et al., 2005). Nevertheless, the abovementioned studies were based on sperm collected with a syringe or directly into a dry beaker. The data on the methods
⁎ Corresponding author. E-mail address: [email protected] (B. Sarosiek).
http://dx.doi.org/10.1016/j.aquaculture.2015.06.040 0044-8486/© 2015 Elsevier B.V. All rights reserved.
of sperm collection and its effect on sperm characteristics in pikeperch are scarce. Collection of fish milt by stripping risks contamination with urine, and this may seriously influence milt characteristics and quality (Rana, 1995). The research done on carp semen showed that the addition of even a low volume of urine causes a significant decrease in sperm motility parameters (Poupard et al., 1998). A small addition of urine also causes lower freezing efficiency (i.e., a lower percentage of motile spermatozoa obtained after thawing). This in turn accounts for a lower percentage of achieved low percentage of fertilized eggs (Bokor et al., 2007). Urine contamination of milt may be avoided by using a catheter for sperm collection. Glogowski et al. (2000) indicated that rainbow trout sperm collected with a catheter showed good motility parameters and low inter-individual variability. Bokor et al. (2008) also reported catheter usefulness. Even though it has already been suggested that the collection of pikeperch sperm with a catheter may have a significant effect on the urine contamination level (Grozea et al., 2008), there is no data regarding the comparative analysis of milt of pikeperch collected with the standard procedure (stripping into a dry syringe) and with a catheter. The objective of this study was to compare basic pikeperch milt parameters collected either with a syringe (as the standard method of sperm collection) or with a catheter.
B. Sarosiek et al. / Aquaculture 450 (2016) 14–16 Table 1 Concentration, pH and osmolality of pikeperch sperm collected either with a syringe or a catheter. (n = 12). Different letters (a, b) indicate statistically significant differences between milt collected with a syringe or a catheter (t-test; p b 0.05 for pH value, and p b 0.001 for sperm concentration and osmolality values). Parameters
Milt collected by a syringe (mean ± SD)
Milt collected by a catheter (mean ± SD)
Milt concentration (×109 ml−1) Range (×109 ml−1) pH Range Osmolality (mOsm kg−1) Range (mOsm kg−1)
8.05 ± 3.04a 4.04–14.73 8.93 ± 0.09a 8.78–9.08 228 ± 51a 129–301
12.31 ± 3.81b 6.77–17.58 9.04 ± 0.07b 8.91–9.10 311 ± 16b 289–342
15
parameters were analyzed: VCL (total spermatozoa velocity; μm s−1), VSL (spermatozoa velocity in a straight line; μm s−1), MOT (percentage of motile spermatozoa; %) and PRG (percentage of spermatozoa with forward progression; %). Additionally, the pH and osmotic pressure were determined in seminal plasma after milt centrifugation (10 min, 8000 ×g). Osmolality of seminal plasma was measured on a Löser apparatus, manufactured by Minitüb, Abfüll-und Labortechnik GmbH&Co.KG. Statistical analyses were conducted with GraphPad Prism software (GraphPad Software Inc., USA). The differences between experiment treatments were determined with paired t-tests at a level of significance of p ≤ 0.05 for pH value and p ≤ 0.001 for sperm concentration and osmolality values. 3. Results
2. Materials and methods Fish (n = 12) were wild caught from Blanki Lake (NE Poland) and were transported to the laboratories of the Department of Lake and River Fisheries, University of Warmia and Mazury, Olsztyn (Poland), in April 2013. The average fish weight was 1.25 ± 0.4 kg. Water temperature was 12 °C. Fish were anesthetized, and then semen was collected by massaging the abdominal parts of the body. Milt was collected first with the use of a syringe and just after using a catheter (flexible cannula) from the same individual (maximum 1 ml was collected with each method). First 1 ml of stripped sperm was rejected in order to avoid the effect of excessive contamination of the first portion of sperm. The catheter was inserted about 1–2 cm into the sperm duct, and sperm were collected directly into Eppendorf tubes. The samples were transported on ice (2–4 °C) to the Department of Gamete and Embryo Biology laboratory, Olsztyn (Poland). Sperm concentrations were estimated using a spectrophotometric method (Ciereszko and Dabrowski, 1993) and by motility parameters (CASA system, Image House CRISMAS Company Ltd.) within 2 h of collection. Sperm motility was documented for 5–7 s after activation in 40 mM of NaHCO3, 20 mM of Tris, and 0.5% albumin, pH 8.5. Sperm motility was documented for 2–3 s after the activation using a Basler 202K digital camera integrated with an Olympus BX51 microscope. The following sperm motility
200
Every parameter of pikeperch milt collected with a catheter was significantly higher than those collected with a syringe (Table 1). The lowest concentration value for the sperm collected with a syringe was 4.04 × 109 ml−1, while the lowest concentration for the sperm collected with a catheter was 6.77 × 109 ml−1. The lowest plasma osmolality value observed in sperm collected with a syringe was 129 mOsm kg−1, whereas the lowest plasma osmolality in sperm collected with a catheter was 289 mOsm kg−1. All motility parameters of the pikeperch spermatozoa were significantly higher (p b 0.05) for the sperm obtained with a catheter in comparison to the standard method of syringe collection (Fig. 1). 4. Discussion and conclusion These data prove for the first time that the use of a catheter to collect pikeperch milt significantly improved its quality. It is very important to optimize the procedures used during fish reproduction, because the spawning effectiveness depends on many factors. After researching the walleye (Sander vitreus), Casselman et al. (2006) showed that the percentage of fertilized eggs dropped drastically due to low spermatozoa concentration. Cejko et al. (2008) reported that spermatozoa concentration in pikeperch ranged between 4.28 and 5.26 × 109 ml−1. However, the data obtained in this study show that collection of the sperm with
b
80
150
a
VSL (µm /s)
VCL (µm/s)
b
100
100
50
60
a
40
20
0
0
120
15
b
b
100
10
a
PRG (%)
MOT (%)
80 60 40
a 5
20 0
0
syringe
catheter
syringe
catheter
Fig. 1. Pikeperch spermatozoa motility parameters: VCL (total spermatozoa velocity; μm s−1), VSL (spermatozoa velocity in a straight line; μm s−1), MOT (percentage of motile spermatozoa; %) and PRG (percentage of spermatozoa with forward progression; %), (n = 12). Different letters (a, b) indicate statistically significant differences between milt collected with a syringe and with a catheter (t-test; p b 0.01).
16
B. Sarosiek et al. / Aquaculture 450 (2016) 14–16
the catheter can assure the concentration of 12.3 × 109 ml−1 on average (Table 1). The significantly lower sperm concentration when sperm was collected with a syringe suggests that sperm was ‘diluted’ while being collected with the standard method. Cejko et al. (2010) reported that the low osmolality value in tench (Tinca tinca) seminal plasma was an indicator of urine contamination. They showed that there were strong relationships between seminal plasma osmotic pressure and sperm concentration, as well as sperm motility. Therefore, the lower spermatozoa concentration reported for pikeperch in the study of Cejko et al. (2008) may indicate urine contamination, which has been confirmed by the osmolality values reported, which ranged between 178 and 227 mOsm kg−1. Similarly, Kowalski et al. (2003) described that the pikeperch seminal osmolality was 221–287 mOsm kg−1. In our work, these values were much higher, especially when we obtained semen with the catheter. The value of seminal plasma osmotic pressure appears to be an indicator of semen contamination with urine. Cejko et al. (2008) reported that the lower osmotic pressure of fish seminal plasma was accompanied by lower spermatozoa motility parameters. A similar relationship was observed in this paper. Presumed urine contamination also negatively affected spermatozoa motility parameters (Fig. 1), which is an important indicator of milt quality (Bobe and Labbe, 2010). It has to be emphasized that both sperm motility and sperm density determine the fertilizing capacity of spermatozoa and are often used to estimate milt quality (Krol et al., 2006; Linhart and Billard, 1994). Bokor et al. (2008) were the first to use a catheter for pikeperch milt collection. They obtained a similar value of sperm motility (63% ± 10%) to that described in our work. Therefore, it may be concluded that urine contamination of pikeperch sperm observed in this study significantly reduces the quality of sperm. The results obtained in our work indicate that the milt quality collected with a catheter was significantly higher. Thus, it is advisable to pay special attention to the method of collecting pikeperch sperm for both scientific analyses and for fertilization. The average concentration value of spermatozoa collected with a catheter was 50% higher than the concentration of sperm obtained using the traditional method. In view of these results, collecting pikeperch sperm using a catheter is recommended. Acknowledgments This work was supported by the National Centre of Sciences, No. N 311 525 640.
References Bobe, J., Labbe, C., 2010. Egg and sperm quality in fish. Gen. Comp. Endocrinol. 165 (3), 535–548. Bokor, Z., Muller, T., Bercsenyi, M., Horvath, L., Urbanyi, B., Horvath, A., 2007. Cryopreservation of sperm of two European percid species, the pikeperch (Sander lucioperca) and the volga pikeperch (S. volgensis). Acta Biol. Hung. 58 (2), 199–207. Bokor, Z., Horvath, A., Horvath, L., Urbanyi, B., 2008. Cryopreservation of pike perch sperm in hatchery conditions. Isr. J. Aquacult. 60 (3), 168–171. Casselman, S.J., Schulte-Hostedde, A.I., Montgomerie, R., 2006. Sperm quality influences male fertilization success in walleye (Sander vitreus). Can. J. Fish. Aquat. Sci. 63, 2119–2125. http://dx.doi.org/10.1139/F0. Cejko, B.I., Glogowski, J., Kowalski, R.K., Kucharczyk, D., Targońska, K., 2008. Description of pikeperch, Sander lucioperca (L.), semen obtained from males held under different rearing conditions. Arch. Pol. Fish. 16 (1), 93–100. Cejko, B.I., Żarski, D., Targońska, K., Krejszeff, S., Kucharczyk, D., Glogowski, J., 2010. Osmolality of seminal plasma as an indicator of milt contamination with urine based on the example of the tench Tinca tinca (L.). Pol. J. Nat. Sci. 25 (3), 287–298. Ciereszko, A., Dabrowski, K., 1993. Estimation of sperm concentration of rainbow trout, whitefish and yellow perch using a spectrophotometric technique. Aquaculture 109, 367–373. Glogowski, J., Kwasnik, M., Piros, B., Dabrowski, K., Goryczko, K., Dobosz, S., Kuzminski, H., 2000. Characterization of rainbow trout milt collected with a catheter: semen parameters and cryopreservation success. Aquacult. Res. 31, 289–296. Grozea, A., Telea Ada, Korbuly, B., Banatean-Dunea, I., Osman, A., 2008. Preliminary study regarding the efficiency of different hormones on pikeperch spermiation. Zootehnie si Biotehnologii Timisoara 42 (2), 59–64. Hajirezaee, S., Amiri, B.M., Mirvaghefi, A., 2010. Fish milt quality and major factors influencing the milt quality parameters: a review. African J. Biotechnol. 9 (54), 9148–9154. Kowalski, R., Glogowski, J., Kucharczyk, D., Goryczko, K., Dobosz, S., Ciereszko, A., 2003. Proteolytic activity and electrophoretic profile of proteases from seminal plasma of teleost. J. Fish Biol. 63, 1008–1019. Krol, J., Glogowski, J., Demska-Zakes, K., Hliwa, P., 2006. Quality of semen and histological analysis of testes in Eurasian perch (Perca fluviatilis L.) during a spawning period. Czech J. Anim. Sci. 5, 220–226. Linhart, O., Billard, R., 1994. Spermiation and sperm quality of European catfish (Silurus glanis L.) after GnRH implantation and injection of carp pituitary extracts. J. Appl. Ichthyol. 10, 182–188. Poupard, G.P., Paxion, Ch., Cosson, J., Jeulin, C., Fierville, F., Billard, R., 1998. Initiation of carp spermatozoa motility and early ATP reduction after milt contamination by urine. Aquaculture 160, 317–328. Rana, K., 1995. Preservation of gametes. In: Bromage, N.R., Roberts, R.B. (Eds.), Broodstock Management and egg and Larval Quality. Blackwell, Oxford, pp. 53–75. Rinchard, J., Dabrowski, K., Van Tassell, J.J., Stein, R.A., 2005. Optimization of fertilization success in Sander viterus is influenced by the sperm: egg ratio and ova storage. J. Fish Biol. 67, 1157–1161.
Contents lists available at ScienceDirect
Aquaculture journal homepage: www.elsevier.com/locate/aqua-online
Short communication
Characterization of pikeperch (Sander lucioperca) milt collected with a syringe and a catheter Beata Sarosiek a,⁎, Katarzyna Dryl a, Sławomir Krejszeff b, Daniel Żarski b,c a b c
Department of Gamete and Embryo Biology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Tuwima Str. 10, 10-748 Olsztyn, Poland Department of Lake and River Fisheries, University of Warmia and Mazury in Olsztyn, Poland Department of Aquaculture, Szent István University, Gödöllő, Hungary
a r t i c l e
i n f o
Article history: Received 17 March 2015 Received in revised form 23 June 2015 Accepted 24 June 2015 Available online 30 June 2015 Keywords: Sander Milt Catheter Urine contamination Motility
a b s t r a c t Collection of fish milt by stripping risks contamination with urine, which may negatively influence milt characteristics and quality. Urine contamination of milt may be avoided by using a catheter for sperm collection. The objective of this study was to compare basic pikeperch milt parameters, i.e., sperm concentration (SC), pH, osmolality of seminal plasma (OSM), and motility parameters of spermatozoa analyzed with a CASA system (Computer Assisted Sperm Analysis), collected either with a syringe (as the standard method of sperm collection) or with a catheter. Every parameter of pikeperch milt collected with a catheter was significantly higher (P b 0.05; SC = 12.31 ± 3.81 × 109 ml−1, pH = 9.04 ± 0.07, OSM = 311 ± 16 mOsm kg−1) than that collected with a syringe (SC = 8.05 ± 3.04 × 109 ml−1, pH = 8.93 ± 0.09, OSM = 228 ± 51 mOsm kg−1), which clearly suggests urine contamination of milt collected with the standard procedure. Moreover, milt collected with catheter was characterized by higher spermatozoa motility parameters, e.g., motility rate of sperm collected with a catheter was 73% whereas the motility rate of sperm collected with a syringe did not exceed 35%. The results obtained in this work indicate that the milt collected with the standard procedure is likely to be exposed to contamination with urine, which may cause a significant reduction of quality parameters. Collection of sperm with a catheter was proven to effectively reduce the contamination of sperm with urine. Therefore, it is recommended to collect pikeperch sperm using a catheter. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Research on fish sperm quality often shows high diversification of the analyzed parameters, such as spermatozoa concentration or motility (Bokor et al., 2007; Cejko et al., 2008). Individual differences may be the result of genetic diversity of males used for reproduction, their age, and the method used to obtain semen (Rana, 1995). In most fish species, it is difficult to avoid urine contamination during the standard method of milt collection via massaging of the abdominal parts of the fish. Fertilization efficiency largely depends on the quality of sperm and oocytes. Apart from factors such as photoperiod, temperature, nutrition, and the type of hormonal stimulation (Hajirezaee et al., 2010), the method of obtaining gametes is also of great importance. During the process of collecting milt, it is important to ensure that it is not contaminated with urine to a great extent. Many authors have indicated the influence of the pikeperch sperm quality on the percentage of fertilized eggs (Casselman et al., 2006; Cejko et al., 2008; Rinchard et al., 2005). Nevertheless, the abovementioned studies were based on sperm collected with a syringe or directly into a dry beaker. The data on the methods
⁎ Corresponding author. E-mail address: [email protected] (B. Sarosiek).
http://dx.doi.org/10.1016/j.aquaculture.2015.06.040 0044-8486/© 2015 Elsevier B.V. All rights reserved.
of sperm collection and its effect on sperm characteristics in pikeperch are scarce. Collection of fish milt by stripping risks contamination with urine, and this may seriously influence milt characteristics and quality (Rana, 1995). The research done on carp semen showed that the addition of even a low volume of urine causes a significant decrease in sperm motility parameters (Poupard et al., 1998). A small addition of urine also causes lower freezing efficiency (i.e., a lower percentage of motile spermatozoa obtained after thawing). This in turn accounts for a lower percentage of achieved low percentage of fertilized eggs (Bokor et al., 2007). Urine contamination of milt may be avoided by using a catheter for sperm collection. Glogowski et al. (2000) indicated that rainbow trout sperm collected with a catheter showed good motility parameters and low inter-individual variability. Bokor et al. (2008) also reported catheter usefulness. Even though it has already been suggested that the collection of pikeperch sperm with a catheter may have a significant effect on the urine contamination level (Grozea et al., 2008), there is no data regarding the comparative analysis of milt of pikeperch collected with the standard procedure (stripping into a dry syringe) and with a catheter. The objective of this study was to compare basic pikeperch milt parameters collected either with a syringe (as the standard method of sperm collection) or with a catheter.
B. Sarosiek et al. / Aquaculture 450 (2016) 14–16 Table 1 Concentration, pH and osmolality of pikeperch sperm collected either with a syringe or a catheter. (n = 12). Different letters (a, b) indicate statistically significant differences between milt collected with a syringe or a catheter (t-test; p b 0.05 for pH value, and p b 0.001 for sperm concentration and osmolality values). Parameters
Milt collected by a syringe (mean ± SD)
Milt collected by a catheter (mean ± SD)
Milt concentration (×109 ml−1) Range (×109 ml−1) pH Range Osmolality (mOsm kg−1) Range (mOsm kg−1)
8.05 ± 3.04a 4.04–14.73 8.93 ± 0.09a 8.78–9.08 228 ± 51a 129–301
12.31 ± 3.81b 6.77–17.58 9.04 ± 0.07b 8.91–9.10 311 ± 16b 289–342
15
parameters were analyzed: VCL (total spermatozoa velocity; μm s−1), VSL (spermatozoa velocity in a straight line; μm s−1), MOT (percentage of motile spermatozoa; %) and PRG (percentage of spermatozoa with forward progression; %). Additionally, the pH and osmotic pressure were determined in seminal plasma after milt centrifugation (10 min, 8000 ×g). Osmolality of seminal plasma was measured on a Löser apparatus, manufactured by Minitüb, Abfüll-und Labortechnik GmbH&Co.KG. Statistical analyses were conducted with GraphPad Prism software (GraphPad Software Inc., USA). The differences between experiment treatments were determined with paired t-tests at a level of significance of p ≤ 0.05 for pH value and p ≤ 0.001 for sperm concentration and osmolality values. 3. Results
2. Materials and methods Fish (n = 12) were wild caught from Blanki Lake (NE Poland) and were transported to the laboratories of the Department of Lake and River Fisheries, University of Warmia and Mazury, Olsztyn (Poland), in April 2013. The average fish weight was 1.25 ± 0.4 kg. Water temperature was 12 °C. Fish were anesthetized, and then semen was collected by massaging the abdominal parts of the body. Milt was collected first with the use of a syringe and just after using a catheter (flexible cannula) from the same individual (maximum 1 ml was collected with each method). First 1 ml of stripped sperm was rejected in order to avoid the effect of excessive contamination of the first portion of sperm. The catheter was inserted about 1–2 cm into the sperm duct, and sperm were collected directly into Eppendorf tubes. The samples were transported on ice (2–4 °C) to the Department of Gamete and Embryo Biology laboratory, Olsztyn (Poland). Sperm concentrations were estimated using a spectrophotometric method (Ciereszko and Dabrowski, 1993) and by motility parameters (CASA system, Image House CRISMAS Company Ltd.) within 2 h of collection. Sperm motility was documented for 5–7 s after activation in 40 mM of NaHCO3, 20 mM of Tris, and 0.5% albumin, pH 8.5. Sperm motility was documented for 2–3 s after the activation using a Basler 202K digital camera integrated with an Olympus BX51 microscope. The following sperm motility
200
Every parameter of pikeperch milt collected with a catheter was significantly higher than those collected with a syringe (Table 1). The lowest concentration value for the sperm collected with a syringe was 4.04 × 109 ml−1, while the lowest concentration for the sperm collected with a catheter was 6.77 × 109 ml−1. The lowest plasma osmolality value observed in sperm collected with a syringe was 129 mOsm kg−1, whereas the lowest plasma osmolality in sperm collected with a catheter was 289 mOsm kg−1. All motility parameters of the pikeperch spermatozoa were significantly higher (p b 0.05) for the sperm obtained with a catheter in comparison to the standard method of syringe collection (Fig. 1). 4. Discussion and conclusion These data prove for the first time that the use of a catheter to collect pikeperch milt significantly improved its quality. It is very important to optimize the procedures used during fish reproduction, because the spawning effectiveness depends on many factors. After researching the walleye (Sander vitreus), Casselman et al. (2006) showed that the percentage of fertilized eggs dropped drastically due to low spermatozoa concentration. Cejko et al. (2008) reported that spermatozoa concentration in pikeperch ranged between 4.28 and 5.26 × 109 ml−1. However, the data obtained in this study show that collection of the sperm with
b
80
150
a
VSL (µm /s)
VCL (µm/s)
b
100
100
50
60
a
40
20
0
0
120
15
b
b
100
10
a
PRG (%)
MOT (%)
80 60 40
a 5
20 0
0
syringe
catheter
syringe
catheter
Fig. 1. Pikeperch spermatozoa motility parameters: VCL (total spermatozoa velocity; μm s−1), VSL (spermatozoa velocity in a straight line; μm s−1), MOT (percentage of motile spermatozoa; %) and PRG (percentage of spermatozoa with forward progression; %), (n = 12). Different letters (a, b) indicate statistically significant differences between milt collected with a syringe and with a catheter (t-test; p b 0.01).
16
B. Sarosiek et al. / Aquaculture 450 (2016) 14–16
the catheter can assure the concentration of 12.3 × 109 ml−1 on average (Table 1). The significantly lower sperm concentration when sperm was collected with a syringe suggests that sperm was ‘diluted’ while being collected with the standard method. Cejko et al. (2010) reported that the low osmolality value in tench (Tinca tinca) seminal plasma was an indicator of urine contamination. They showed that there were strong relationships between seminal plasma osmotic pressure and sperm concentration, as well as sperm motility. Therefore, the lower spermatozoa concentration reported for pikeperch in the study of Cejko et al. (2008) may indicate urine contamination, which has been confirmed by the osmolality values reported, which ranged between 178 and 227 mOsm kg−1. Similarly, Kowalski et al. (2003) described that the pikeperch seminal osmolality was 221–287 mOsm kg−1. In our work, these values were much higher, especially when we obtained semen with the catheter. The value of seminal plasma osmotic pressure appears to be an indicator of semen contamination with urine. Cejko et al. (2008) reported that the lower osmotic pressure of fish seminal plasma was accompanied by lower spermatozoa motility parameters. A similar relationship was observed in this paper. Presumed urine contamination also negatively affected spermatozoa motility parameters (Fig. 1), which is an important indicator of milt quality (Bobe and Labbe, 2010). It has to be emphasized that both sperm motility and sperm density determine the fertilizing capacity of spermatozoa and are often used to estimate milt quality (Krol et al., 2006; Linhart and Billard, 1994). Bokor et al. (2008) were the first to use a catheter for pikeperch milt collection. They obtained a similar value of sperm motility (63% ± 10%) to that described in our work. Therefore, it may be concluded that urine contamination of pikeperch sperm observed in this study significantly reduces the quality of sperm. The results obtained in our work indicate that the milt quality collected with a catheter was significantly higher. Thus, it is advisable to pay special attention to the method of collecting pikeperch sperm for both scientific analyses and for fertilization. The average concentration value of spermatozoa collected with a catheter was 50% higher than the concentration of sperm obtained using the traditional method. In view of these results, collecting pikeperch sperm using a catheter is recommended. Acknowledgments This work was supported by the National Centre of Sciences, No. N 311 525 640.
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