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GENERAL DISCUSSION sperm motility patterns and the period of fertility (Billard, 1978). However, our data has shown that sperm motility parameters do not improve when using partly diluted seawater in pufferfish, so the common activation medium (not diluted seawater) is recommended when carrying out reproduction trials in this species. Regarding the ion composition of the activation media, we have reported that despite the fact that pufferfish spermatozoa were able to initiate movement without any ion in the activation medium, the presence/absence of Ca 2+ and K + affected kinetic parameters such as velocities. We also observed that spermatozoa velocities (VCL, VSL and VAP) were highly correlated to the fertilization success and hatching rates. It can therefore be assumed that the presence of these ions in the activation media helps the fertilization process, thus the proper ion composition of the activation/fertilization media should be taken into account in order to reach suitable fertilization and hatching rates in both laboratory trials and commercial hatcheries. However, while in the majority of marine fish species studied sperm motility can be induced by hyperosmotic non-ion solutions (using sugars, i.e.), in species such as tilapia (Oreochromis mossambicus) certain ions such as calcium are essential for sperm activation (Linhart et al., 1999). Thus, it seems clear that there is a wide interspecific variability in terms of the role of extracellular ions and their effect on the sperm motion parameters, so more studies focusing this topic are necessary in order to understand the sperm motility activation process in marine fish. On the other hand, although it is widely accepted that firstly, the osmolality, and secondly, the ion composition of the activation media are the main factors triggering sperm motility in marine fish, little is known about the molecular mechanisms that enable environmental stimuli to determine the activation of the axoneme and the intracellular ion changes occurring after sperm activation (Zilli et al., 2012). In this thesis we have reported that when using an ion-rich medium (seawater) for activation of the sperm, intracellular Ca 2+ and K + increased both in European eel and 131
GENERAL DISCUSSION pufferfish spermatozoa, as occurs in other marine fishes (Oda & Morisawa, 1993; Morisawa, 2008). However, when using a free-ion activating medium, there was an increase in [K + ] i but not in [Ca 2+ ] i , even when motility started, and the same has recently been observed in European eel sperm (data not published). These results pose a tricky question because nowadays, the widely accepted model regarding sperm not only from fish, but also from mammals and marine invertebrates (see Darszon et al., 2005, 2011; Espinal et al., 2011), indicates that an increase in intracellular Ca 2+ is necessary for sperm motility activation. However, in the case of pufferfish (see Chapter 4) and European eel (unpublished results), this intracellular calcium increase seems unnecessary, at least for triggering motility, thus other mechanisms could be involved in the initiation of sperm motility in this species. On the other hand, seawater also contains significant amounts of other ions such as Cl - , HCO3 - , Na + and Mg 2+ , and all of them have important functions in cell biology, and can affect sperm motility in marine fish. For example, Na + has been studied in freshwater fish sperm (Alavi & Cosson, 2006), and preliminary studies in European eel also suggest that Na + fluxes happen at motility activation. In mammals, sperm motility hyperactivation involves the activation of sperm-specific Ca 2+ , and K + channels (CatSper, KSper), a specific Na + /HCO3 co-transporter (sNHE), a proton channel (Hv), and a Na + /Ca 2+ channel (Darszon et al., 2011; Krasznai et al., 2006). In sea urchin, sperm motility involves the participation of at least 8 different ion channels, controlling Ca 2+ , K + , Cl - , Na + , and H + fluxes in the sperm membrane (Espinal et al., 2011). We are far from having a similar understanding of sperm activation in marine fish, where a complex universal mechanism for sperm motility initiation does not seem to exist, and different species-specific activation mechanisms could be acting among marine species. Therefore, new studies involving the use of specific channel blockers, the intracellular measure of other ions (like Na + , Cl - , HCO 3 - ), and the use of patch-clamp techniques would help to understand the specific mechanisms which occur during motility activation in marine fish sperm. 132
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SPERM PHYSIOLOGY AND QUALITY IN TWO
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ACKNOWLEDGEMENTS Muchos años han p
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aunque tiene una alcachofa en la ca
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TABLE OF CONTENTS SUMMARY 1 RESUMEN
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SUMMARY SUMMARY The conservation st
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RESUMEN RESUMEN Las especies objeto
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RESUM RESUM Les espècies objecte d
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GENERAL INTRODUCTION 7
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GENERAL INTRODUCTION who postulated
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GENERAL INTRODUCTION 2. Sperm physi
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GENERAL INTRODUCTION Finally, the a
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GENERAL INTRODUCTION 3. Sperm quali
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GENERAL INTRODUCTION in fish (Kime
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GENERAL INTRODUCTION However, for s
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GENERAL INTRODUCTION future applica
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GENERAL INTRODUCTION With regards t
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OBJECTIVES The chapters presented b
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STANDARDIZATION OF SPERM MOTILITY E
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CHAPTER 2 Study of the effects of t
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CHAPTER 2 reducing the pressure on
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CHAPTER 2 ongoing task in order to
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CHAPTER 2 To measure sperm density,
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CHAPTER 2 Spermiating males (%) 100
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CHAPTER 2 100 80 60 I II III IV A 4
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CHAPTER 2 3.2 Hormonal treatments P
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CHAPTER 2 With regard to the sperm
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CHAPTER 2 Relative volume (%) 80 I
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CHAPTER 2 In this respect, it is we
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CHAPTER 2 treatment to that of the
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CHAPTER 2 Our results demonstrate t
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ROLE OF IONS IN THE SPERM ACTIVATIO
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Page 90 and 91: ROLE OF IONS IN THE SPERM ACTIVATIO
Page 92: CHAPTER 4 Study of pufferfish (Taki
Page 95 and 96: CHAPTER 4 2002) so Takifugu niphobl
Page 97 and 98: CHAPTER 4 carrying out sperm collec
Page 99 and 100: CHAPTER 4 Table 1. Activation media
Page 101 and 102: CHAPTER 4 TM (%) 100 A a a Und-PD a
Page 103 and 104: CHAPTER 4 TM (%) 80 60 40 20 0 A a
Page 105 and 106: CHAPTER 4 TM (%) 80 A ASW100 GLU 60
Page 107 and 108: CHAPTER 4 although the activation m
Page 109 and 110: CHAPTER 4 dilution ratio and an opt
Page 111 and 112: CHAPTER 4 2006). Several studies in
Page 113 and 114: CHAPTER 4 5. Conclusions Some concl
Page 116 and 117: RELATIONSHIP BETWEEN SPERM MOTILIY
Page 130: RELATIONSHIP BETWEEN SPERM MOTILIY
Page 134 and 135: GENERAL DISCUSSION 1. Improvements
Page 136 and 137: GENERAL DISCUSSION profiles induced
Page 138 and 139: GENERAL DISCUSSION more studies on
Page 142: CONCLUSIONS 133
Page 145 and 146: CONCLUSIONS vii. The coefficients o
Page 148 and 149: REFERENCES Aarestrup K, Økland F,
Page 150 and 151: REFERENCES Beirão J, Cabrita E, P
Page 152 and 153: REFERENCES Cabrita E, Robles V, Cu
Page 154 and 155: REFERENCES De Vos A, Van De Velde H
Page 156 and 157: REFERENCES Gallego V, Pérez L, Ast
Page 158 and 159: REFERENCES sperm competition and fe
Page 160 and 161: REFERENCES Liu QH, Li J, Xiao ZZ, D
Page 162 and 163: REFERENCES Mortimer ST. Effect of i
Page 164 and 165: REFERENCES Peñaranda DS, Marco-Jim
Page 166 and 167: REFERENCES Rurangwa E, Volckaert FA
Page 168 and 169: REFERENCES Tesch F. Telemetric obse
Page 170 and 171: REFERENCES Wong PYD, Lee WM, Tsang
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