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EFFECT OF THERMAL REGIMES AND HORMONAL TREATMENTS Abstract Since 1960, the European eel (Anguilla anguilla) has suffered a dramatic reduction in natural stocks. Breeding in captivity is considered an alternative, but obtaining high quality sperm seems basic on this regard. The main objective of this study was to assess the effects of three thermal regimes (two of them variable: T10 and T15; and one of them constant: T20) and three hormonal treatments with different hormones (hCG, hCG rec and PSMG) on the induction of maturation in European eel males. In the case of the thermal regimes, our results demonstrated that the onset and progression of spermiation are strongly influenced, and perhaps closely regulated, by water temperature. T20 demonstrated the best results in all the sperm parameters (volume, density, motility, kinetic features, etc.) throughout most weeks of treatment, becoming a reliable and productive method for inducing spermiation in this species. In the case of hormonal treatments, the onset and progression of spermiation in European eel males were influenced by the hormone used. In this respect, hCG rec produced the best results in all the sperm parameters including volume, density, motility, kinetic features, etc., throughout most weeks of treatment, thus becoming an effective alternative treatment to the standard hCG treatment used to induce spermiation in eel species. Moreover, hCG rec gave rise to the best economical profitability, making it possible to obtain good quality sperm samples at a lower price than by using the other two hormonal treatments. 1. Introduction The European eel (Anguilla anguilla) is a teleost fish with a peculiar life cycle: prepubertal eels migrate across the Atlantic Ocean for supposedly 6– 7 months to reach the spawning area, in the Sargasso Sea (Tesch, 1978; Van Ginneken and Maes, 2005). In the last years the European eel has suffered a dramatic reduction in its population mainly due to varying factors including overfishing, habitat reduction and contamination (Feunteun, 2002). Therefore, breeding in captivity is the only alternative to save this species, 49
CHAPTER 2 reducing the pressure on natural populations, and meeting the demands of eel farms. A good tool for a breeding captivity program is obtaining high quality sperm during a large number of weeks with the aim of synchronizing the gamete maturation and fertilizing the ova produced throughout the breeding season (Jørstad and Navdal, 1996; Roldan and Gomendio, 2009). In some fish species, reproduction in captivity can be controlled exclusively by environmental factors such as temperature, photoperiod or salinity. However, sometimes it is impractical or even impossible to simulate the environmental factors of the breeding process (i.e., spawning migration, depth, pressure, etc.) so the use of exogenous hormones is the only effective way of inducing maturation and spermiation (Asturiano et al., 2002; Boëtius and Boëetius, 1967; Kagawa et al., 2009; Ohta et al., 1996; Pérez et al., 2000). Eels (Anguilla spp.) do not mature spontaneously in captivity, so the maturation of males must be induced with long-term hormonal treatments (Asturiano et al., 2005; Huang et al., 2009; Ohta et al., 1997; Pérez et al., 2000). However, in several studies it has been described that the sexual maturation of non-treated males could be stimulated indirectly by treated males, suggesting the existence of chemical communication (pheromones) between them (Huertas et al., 2006). Despite the effectiveness of these long-term hormonal treatments, little attention has been paid to factors such as the duration of spermiation periods, which has been limited in time, or the variations in sperm quality parameters (Asturiano et al., 2005; Miranda et al., 2005; Mylonas et al., 1998). A high number of environmental and procedural factors can affect the gonadal development and, consequently, the gamete quality (Mylonas et al., 2010). With regard to environmental factors, the water temperature plays a key role in the gonadal development in many fish species (García- López et al., 2006; Lim et al., 2003; Van Der Kraak and Pankhurst, 1997). In the case of the European eel, the temperature of the hypothetical spawning area is around 20 °C (Boëtius and Boëtius, 1967), and this is probably the reason why both males and females of this species have been matured at this constant water temperature (Asturiano et al., 2006; Pedersen, 2003; 50
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SPERM PHYSIOLOGY AND QUALITY IN TWO
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ACKNOWLEDGEMENTS Muchos años han p
Page 6 and 7: aunque tiene una alcachofa en la ca
Page 8 and 9: TABLE OF CONTENTS SUMMARY 1 RESUMEN
Page 10 and 11: SUMMARY SUMMARY The conservation st
Page 12 and 13: RESUMEN RESUMEN Las especies objeto
Page 14 and 15: RESUM RESUM Les espècies objecte d
Page 16: GENERAL INTRODUCTION 7
Page 19 and 20: GENERAL INTRODUCTION who postulated
Page 21 and 22: GENERAL INTRODUCTION 2. Sperm physi
Page 23 and 24: GENERAL INTRODUCTION Finally, the a
Page 25 and 26: GENERAL INTRODUCTION 3. Sperm quali
Page 27 and 28: GENERAL INTRODUCTION in fish (Kime
Page 29 and 30: GENERAL INTRODUCTION However, for s
Page 31 and 32: GENERAL INTRODUCTION future applica
Page 33 and 34: GENERAL INTRODUCTION With regards t
Page 36: OBJECTIVES The chapters presented b
Page 40 and 41: STANDARDIZATION OF SPERM MOTILITY E
Page 56: CHAPTER 2 Study of the effects of t
Page 61 and 62: CHAPTER 2 ongoing task in order to
Page 63 and 64: CHAPTER 2 To measure sperm density,
Page 65 and 66: CHAPTER 2 Spermiating males (%) 100
Page 67 and 68: CHAPTER 2 100 80 60 I II III IV A 4
Page 69 and 70: CHAPTER 2 3.2 Hormonal treatments P
Page 71 and 72: CHAPTER 2 With regard to the sperm
Page 73 and 74: CHAPTER 2 Relative volume (%) 80 I
Page 75 and 76: CHAPTER 2 In this respect, it is we
Page 77 and 78: CHAPTER 2 treatment to that of the
Page 79 and 80: CHAPTER 2 Our results demonstrate t
Page 82 and 83: 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
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CHAPTER 4 although the activation m
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CHAPTER 4 dilution ratio and an opt
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CHAPTER 4 2006). Several studies in
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CHAPTER 4 5. Conclusions Some concl
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RELATIONSHIP BETWEEN SPERM MOTILIY
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GENERAL DISCUSSION 1. Improvements
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GENERAL DISCUSSION profiles induced
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GENERAL DISCUSSION more studies on
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GENERAL DISCUSSION sperm motility p
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CONCLUSIONS 133
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CONCLUSIONS vii. The coefficients o
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REFERENCES Aarestrup K, Økland F,
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REFERENCES Beirão J, Cabrita E, P
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REFERENCES Cabrita E, Robles V, Cu
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REFERENCES De Vos A, Van De Velde H
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REFERENCES Gallego V, Pérez L, Ast
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REFERENCES sperm competition and fe
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REFERENCES Liu QH, Li J, Xiao ZZ, D
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REFERENCES Mortimer ST. Effect of i
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REFERENCES Peñaranda DS, Marco-Jim
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REFERENCES Rurangwa E, Volckaert FA
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REFERENCES Tesch F. Telemetric obse
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REFERENCES Wong PYD, Lee WM, Tsang
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