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GENERAL DISCUSSION profiles induced by each thermal treatment (Peñaranda et al., in preparation). After selecting the best thermal regime (T20), the kind of hormone used for the induction of maturation was chosen as the second factor for the improvement of reproductive performance. Although successful maturation and spermiation by hCG has been reported by several authors in the last half century (Boëtius and Boëtius, 1967; Bleniarz and Epler, 1977; Amin, 1997), scarce attempts have been made to optimize previously used hormonal treatments (Asturiano et al., 2005). Our results have shown that the type of hormone used significantly affects the onset and progression of spermiation in European eel males, and a recombinant version of the hCG (hCG rec ) produces the best results in almost all the sperm parameters. Until the present study, only Asturiano et al. (2005) had carried out trials with the aim of achieving shorter induction treatments, longer spermiation periods and/or higher sperm quality. In their experiment, five hormonal treatments based on hCG, modifying both the doses and timing of injection, were tested for the induction of maturation and spermiation in male European eels, reaching a good reproductive performance. Even so, the results produced by the hCG rec treatment in the present trial far exceed those reached by Asturiano et al. (2005), thus making it an effective and alternative treatment for inducing spermiation in male European eels. To sum up, a new hormonal treatment which improves the reproductive performance of male European eels has been set up and is ready for applying in eel hatcheries. This treatment, based on the weekly administration of hCG rec under a constant temperature regime of 20 °C, has been able to induce a high percentage of spermiating males with good quality samples for a high number of weeks. In addition, other tools such as short and long-term sperm storage methods have specifically been developed for this species in recent years (Peñaranda et al., 2008, 2009, 2010). With regards to short-term sperm storage methods, recent studies have come up with good results in terms of fertilized eggs and hatched larvae during in vitro fertilization trials. However, although it was possible 127
GENERAL DISCUSSION to obtain the first European eel “cryolarvae”through cryopreserved spermatozoa, the low percentages achieved in terms of fertilization and hatching rates mean that some improvements in the cryopreservation techniques for this species are necessary (Asturiano et al., 2013). However, new methods are needed to enable the production of viable eggs and larvae from broodstock in a regular and predictable way. In this respect, further challenges include the identification of suitable larval rearing conditions and initial feed in order to establish feeding cultures of European eel larvae. 2. Sperm quality biomarkers: which, how and where to apply? The use of high quality gametes from both males and females in the field of aquaculture is essential in order to achieve a production of viable fertilized eggs and larvae from broodstock. In this respect, sperm quality biomarkers have proven themselves a powerful tool which is ready to use, making itossible to predict fertilization rates in IVF trials. In this thesis, we have demonstrated that both the number of spermatozoa and their “swimming” parameters (time, velocity, direction, etc.) have a great influence on fertilization and hatching success in pufferfish, thus sperm motion parameters can be used as sperm quality biomarkers in this species. However, it is important to note that although certain sperm quality biomarkers can be used in different fish species, sometimes spermatozoa motion features are species-specific and depends on spawning microenvironment, reproductive strategy, etc., thus more studies on different fish species are necessary to analyze the specific requirements of each one in order to define their own sperm quality biomarkers. On the other hand, a single sperm biomarker by itself often does not provide enough data, and a complete assessment of several biomarkers generates the right information. In fact, we have shown how sperm/egg ratio and sperm motion must be taken into account as unique factors, making it possible to apply a successful combination of high/low quality sperm in low/high volumes in order to achieve fertilized oocytes. There are 128
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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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ROLE OF IONS IN THE SPERM ACTIVATIO
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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 138 and 139: GENERAL DISCUSSION more studies on
Page 140 and 141: GENERAL DISCUSSION sperm motility p
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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