APPLICATION OF SWIMMING IN JUVENILE MALE SEA BASS (DICENTRARCHUS LABRAX) TO PREVENT PRECOCIOUS SEXUAL MATURATION Raúl Benito*¹, Josep V. Planas¹ and Arjan P. Palstra² ¹ Departament de Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, 08028 Barcelona (Spain). ² IMARES Wageningen UR, Korringaweg 5, 4401 NT Yerseke (The Netherlands). E-mail: [email protected] ; [email protected]; [email protected] http://planaslab.wordpress.com/ Current culture conditions of the European sea bass (Dicentrarchus labrax) promote rapid growth that results in the advancement of puberty. Precocious sexual maturation in males is an economically important problem. To date, efforts to control the onset of puberty in sea bass have concentrated on manipulating the photoperiod (Begtashi et al., 2004; Rodriguez et al., 2012). In other species, such as the European eel (Anguilla anguilla) and the rainbow trout (Oncorhynchus mykiss), swimming has been shown to delay ovarian development (Palstra et al., 2010a; Palstra et al., 2010b). However, nothing is known regarding the possible modulatory effects of swimming on reproduction in the European sea bass. • To apply sustained swimming as a way to reduce gonadal development in male sea bass and address the issue of precocious male maturation in this species. We used a 3,600 L oval swim gutter as RAS with two chambers (Fig. 1), one for the swimmers (N=100; swimming at their optimal speed or Uopt) and another one for the resting controls (N=100; minimal flow of 0.10 m/s to assure good water quality). Water temperature was set at 25 ºC, salinity at 30.1‰, pH at 7.7 and light intensity at 40-50 lux at the water surface. Initial sea bass body weight was 3.91±0.22 g (mean ± s.e.m.). Uopt was measured every 4 weeks by respirometry in 123 L swim-tunnels (3 times in total; courtesy of Dr. G. van den Thillart, Leiden University; Fig. 2). Fish in the flume swam for a total of 10 weeks and were sampled every 2 weeks (5 samplings; N=15 fish per chamber) to record weight (g), standard length (cm), gonadosomatic index (GSI; %), 11-ketotestosterone (11-KT) levels in plasma and histology of the testes. Fig. 1. Swim gutter. M, motor. Fig. 2. Blazka-type swim tunnels. • Weight, length and GSI increased over time in both groups. However, we did not find differences in size between swimmers and resters at any of the sampling points (Figs. 3-5). • At week 10, male sea bass from the swimmers group had a significantly (p<0.05) lower GSI than the control group (Fig. 6) but no differences in 11-KT plasma levels were observed between resters and swimmers (Fig. 7). • Histological analyses of testes samples at week 10 showed delayed development in the swimmers compared to the resters (Fig. 8). Fig. 8. Histological analysis of testicular samples from resters (A) and swimmers (B). Spermatogonia A (SgA) and B (SgB) are indicated by arrows. Cysts are delineated by circles. Representative images of paraffin-embedded testes sections stained with hematoxylin and eosin are shown. Sustained swimming at Uopt caused a gradual increase in length and weight of fish throughout the study but no differences were observed between swimmers and resters. No differences in GSI were observed between swimmers and resters when males and females were combined. Males at week 10 that were subjected to sustained swimming at Uopt showed evidence for decreased testicular development: - GSI was lower in the swimmers when compared to the resters. - Reduced presence of type-B spermatogonia in testes from swimmers. No differences in 11-KT plasma levels were observed between swimmers and resters, even though it has been postulated that 11-KT may be a firm candidate for the regulation of the onset of puberty (Rodríguez et al., 2005). For the first time in this species, we provide evidence that swimming may delay testicular development in juvenile sea bass. These results are highly indicative of the promise of swimming induction for the control of reproductive development in sea bass and, specifically, to address the issue of precocious male maturation in this species. We would like to acknowledge the support by the AQUAEXCEL grant SWIMBASS and grant AGL2012- 40031 (Spanish Ministry of Economy and Competitiveness) to JVP. References Begtashi I, Rodríguez L, Moles G, Zanuy S, Carrillo M. 2004. Long-term exposure to light inhibits precocity in juvenile male European sea bass (Dicentrarchus labrax, L.). I. Morphological aspects. Aquaculture 241: 539-559. Palstra A P, Schnabel D, Nieveen M C, Spaink H P, van den Thillart G. 2010a. Swimming suppresses hepatic vitellogenesis in European female silver eels as shown by expression of the estrogen receptor 1, vitellogenin1 and vitellogenin2 in the liver. Reprod Biol Endocrinol 8: 27. Palstra A P, Crespo D, van den Thillart G E, Planas J V. 2010b. Saving energy to fuel exercise: swimming suppresses oocyte development and downregulates ovarian transcriptomic response of rainbow trout Oncorhynchus mykiss. Am J Physiol Regul Integr Comp Physiol 299: 486-499. Rodríguez L, Begtashi I, Zanuy S, Carrillo M. 2005. Long-term exposure to continuous light inhibits precocity in European male sea bass (Dicentrarchus labrax, L). Gen Comp Endocrinol 140: 116–125. Rodríguez R, Felip A, Cerqueira V, Hala E, Zanuy S, Carrillo M. 2012. Identification of a photolabile period for reducing sexual maturation in juvenile male sea bass (Dicentrarchus labrax) by means of a continuous light regime. Aquacul Int, 20: 1071–1083. Fig. 6. Weight, length and GSI values from control and swimming males at the last sampling week (week 10) for the swimming experiment. Values are means ± s.e.m.; N, number of sea bass. In each row, * = P<0.05. Fig. 7. 11-KT plasma levels in male rester and swimmer sea bass at sampling week 10. Fig. 3. Temporal changes in body weight. Columns sharing a letter are statistically similar (a posteriori ANOVA test; P<0.05). Fig. 4. Temporal changes in length. Columns sharing a letter are statistically similar (a posteriori ANOVA test; P<0.05). Fig. 5. Temporal changes in GSI. Columns sharing a letter are statistically similar (a posteriori ANOVA test; P<0.05). Introduction Materials and methods Results Conclusions Results (Cont.) Objectives
AQUAEXCEL POSTER Raúl Benito AE2014
Aug 12, 2015
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APPLICATION OF SWIMMING IN JUVENILE MALE SEA BASS (DICENTRARCHUS LABRAX) TO PREVENT PRECOCIOUS SEXUAL MATURATION
Raúl Benito*¹, Josep V. Planas¹ and Arjan P. Palstra²
¹ Departament de Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, 08028 Barcelona (Spain). ² IMARES Wageningen UR, Korringaweg 5, 4401 NT Yerseke (The Netherlands).
E-mail: [email protected] ; [email protected]; [email protected]
http://planaslab.wordpress.com/
Current culture conditions of the European sea bass (Dicentrarchus labrax) promote rapid growth that results in the advancement of puberty. Precocious sexual maturation in males is an economically important problem. To date, efforts to control the onset of puberty in sea bass have concentrated on manipulating the photoperiod (Begtashi et al., 2004; Rodriguez et al., 2012). In other species, such as the European eel (Anguilla anguilla) and the rainbow trout (Oncorhynchus mykiss), swimming has been shown to delay ovarian development (Palstra et al., 2010a; Palstra et al., 2010b). However, nothing is known regarding the possible modulatory effects of swimming on reproduction in the European sea bass.
• To apply sustained swimming as a way to reduce gonadal development in male sea bass and address the issue of precocious male maturation in this species.
We used a 3,600 L oval swim gutter as RAS with two chambers (Fig. 1), one for the swimmers (N=100; swimming at their optimal speed or Uopt) and another one for the resting controls (N=100; minimal flow of 0.10 m/s to assure good water quality). Water temperature was set at 25 ºC, salinity at 30.1‰, pH at 7.7 and light intensity at 40-50 lux at the water surface. Initial sea bass body weight was 3.91±0.22 g (mean ± s.e.m.). Uopt was measured every 4 weeks by respirometry in 123 L swim-tunnels (3 times in total; courtesy of Dr. G. van den Thillart, Leiden University; Fig. 2). Fish in the flume swam for a total of 10 weeks and were sampled every 2 weeks (5 samplings; N=15 fish per chamber) to record weight (g), standard length (cm), gonadosomatic index (GSI; %), 11-ketotestosterone (11-KT) levels in plasma and histology of the testes.
Fig. 1. Swim gutter. M, motor. Fig. 2. Blazka-type swim tunnels.
• Weight, length and GSI increased over time in both groups. However, we did not find differences in size between swimmers and resters at any of the sampling points (Figs. 3-5).
• At week 10, male sea bass from the swimmers group had a significantly (p<0.05) lower GSI than the control group (Fig. 6) but no differences in 11-KT plasma levels were observed between resters and swimmers (Fig. 7).
• Histological analyses of testes samples at week 10 showed delayed development in the swimmers compared to the resters (Fig. 8).
Fig. 8. Histological analysis of testicular samples from resters (A) and swimmers (B). Spermatogonia A (SgA) and B (SgB) are indicated by arrows. Cysts are delineated by circles. Representative images of paraffin-embedded testes sections stained with hematoxylin and eosin are shown.
Sustained swimming at Uopt caused a gradual increase in length and weight of fish throughout the study but no differences were observed between swimmers and resters.
No differences in GSI were observed between swimmers and resters when males and females were combined.
Males at week 10 that were subjected to sustained swimming at Uopt showed evidence for decreased testicular development:
- GSI was lower in the swimmers when compared to the resters.
- Reduced presence of type-B spermatogonia in testes from swimmers.
No differences in 11-KT plasma levels were observed between swimmers and resters, even though it has been postulated that 11-KT may be a firm candidate for the regulation of the onset of puberty (Rodríguez et al., 2005).
For the first time in this species, we provide evidence that swimming may delay testicular development in juvenile sea bass. These results are highly indicative of the promise of swimming induction for the control of reproductive development in sea bass and, specifically, to address the issue of precocious male maturation in this species.
We would like to acknowledge the support by the AQUAEXCEL grant SWIMBASS and grant AGL2012-40031 (Spanish Ministry of Economy and Competitiveness) to JVP.
References Begtashi I, Rodríguez L, Moles G, Zanuy S, Carrillo M. 2004. Long-term exposure to light inhibits precocity in juvenile male European sea bass (Dicentrarchus labrax,
L.). I. Morphological aspects. Aquaculture 241: 539-559. Palstra A P, Schnabel D, Nieveen M C, Spaink H P, van den Thillart G. 2010a. Swimming suppresses hepatic vitellogenesis in European female silver eels as shown by
expression of the estrogen receptor 1, vitellogenin1 and vitellogenin2 in the liver. Reprod Biol Endocrinol 8: 27. Palstra A P, Crespo D, van den Thillart G E, Planas J V. 2010b. Saving energy to fuel exercise: swimming suppresses oocyte development and downregulates ovarian
transcriptomic response of rainbow trout Oncorhynchus mykiss. Am J Physiol Regul Integr Comp Physiol 299: 486-499. Rodríguez L, Begtashi I, Zanuy S, Carrillo M. 2005. Long-term exposure to continuous light inhibits precocity in European male sea bass (Dicentrarchus labrax, L).
Gen Comp Endocrinol 140: 116–125. Rodríguez R, Felip A, Cerqueira V, Hala E, Zanuy S, Carrillo M. 2012. Identification of a photolabile period for reducing sexual maturation in juvenile male sea bass
(Dicentrarchus labrax) by means of a continuous light regime. Aquacul Int, 20: 1071–1083.
Fig. 6. Weight, length and GSI values from control and swimming males at the last sampling week (week 10) for the swimming experiment. Values are means ± s.e.m.; N, number of sea bass. In each row, * = P<0.05.
Fig. 7. 11-KT plasma levels in male rester and swimmer sea bass at sampling week 10.
Fig. 3. Temporal changes in body weight. Columns sharing a letter are statistically similar (a posteriori ANOVA test; P<0.05).
Fig. 4. Temporal changes in length. Columns sharing a letter are statistically similar (a posteriori ANOVA test; P<0.05).
Fig. 5. Temporal changes in GSI. Columns sharing a letter are statistically similar (a posteriori ANOVA test; P<0.05).
Introduction
Materials and methods
Results Conclusions
Results (Cont.)
Objectives
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