Control of puberty in farmed fish

91 p., il., y bibliografía. Geir Lasse Taranger [et al.]Puberty comprises the transition from an immature juvenile to a mature adult state of the reproductive system, i.e. the individual becomes capable of reproducing sexually for the first time, which implies functional competence of the brain-pituitary-gonad (BPG) axis. Early puberty is a major problem in many farmed fish species due to negative effects on growth performance, flesh composition, external appearance, behaviour, health, welfare and survival, as well as possible genetic impact on wild populations. Late puberty can also be a problem for broodstock management in some species, while some species completely fail to enter puberty under farming conditions. Age and size at puberty varies between and within species and strains, and are modulated by genetic and environmental factors. Puberty onset is controlled by activation of the BPG axis, and a range of internal and external factors are hypothesized to stimulate and/or modulate this activation such as growth, adiposity, feed intake, photoperiod, temperature and social factors. For example, there is a positive correlation between rapid growth and early puberty in fish. Age at puberty can be controlled by selective breeding or control of photoperiod, feeding or temperature. Monosex stocks can exploit sex dimorphic growth patterns and sterility can be achieved by triploidisation. However, all these techniques have limitations under commercial farming conditions. Further knowledge is needed on both basic and applied aspects of puberty control to refine existing methods and to develop new methods that are efficient in terms of production and acceptable in terms of fish welfare and sustainability.Peer reviewe

Efectos de la restricción calórica sobre el inicio de la pubertad y la calidad del esperma en la lubina europea (Dicentrarchus labrax)

Ponencia presentada en el XIII Congreso Nacional de Acuicultura celebrado en Barcelona del 21 al 24 de noviembre de 2011.This study reports the effects induced by a long fasting protocol on the reproductive performance of male sea bass during the first reproductive season. Two different treatments of food deprivation were carried out from July to March, one feed 1/4 and another feed 1/8 of the ration given to the control group (1/4C, 1/8C and C). Both restricted feed regimes resulted in a deep impact over the weight, length and growth rate indexes. Also, the fat visceral index decreased dramatically in November in both feed restricted groups (1/4C and 1/8C). Interestingly, both restricted and controls had similar gonadosomatic index values in November (IGS= 0.4-0.7%). Moreover, the histological analysis revealed the presence of a high number of death cell bodies in testis of those animals kept under both restricted feed regimes. Furthermore, we evaluated the sperm quality along the reproductive season (December-March) and it was shown that a long-term fasting affects sperm quality parameters of pubertal male sea bass such as, density (nº spz cells/ml) and quantity (ml/kg wt), although no differences were observed in motility (µm/seg). Additionally, no statically differences in 11KT plasma levels were observed among experimental groups. Our study evidences that a shortage on energy store is not enough to abolish partially or totally the puberty onset of prepubertal male sea bass.Proyecto Europeo LIFECYCLE (FP7-222719-1) y Generalitat Valenciana (PROMETEO/2010/003). S.E. disfrutó de una beca JAE-Predoc CSIC y M.S. disfrutó de una beca CIHEAM.Peer Reviewe

The GnRH systems of perciform fish: and in situ hybridization and immunohistochemical study in the European sea bass; Dicentrarchus labrax

Trabajo presentado en el 4th International Symposium on Fish Endocrinology, celebrado en Seattle, WA (Estados Unidos), del 31 de julio al 3 de agosto de 200

Novel galanin receptors in teleost fish: identification, expression and regulation by sex steroids

In fish, the onset of puberty, the transition from juvenile to sexually reproductive adult animals, is triggered by the activation of pituitary gonadotrophin secretion and its timing is influenced by external and internal factors that include the growth/adiposity status of the animal. Kisseptins have been implicated in the activation of puberty but peripheral signals coming from the immature gonad or associated to the metabolic/nutritional status are also thought to be involved. Additionally, there is evidence that the galaninergic system in the brain and testis of pre-pubertal male sea bass is a possible mediator involved in the translation of somatic signals leading to gonadal maturation. Here, the transcripts for four galanin receptors (GALR), named GALR1a, 1b, 2a and 2b, were isolated from European sea bass, Dicentrarchus labrax. Phylogenetic analysis confirmed the previously reported duplication of GALR1 in teleost fish, and unravelled the duplication of GALR2 in teleost fish and in some tetrapod species. Comparison with human showed that the key amino acids involved in ligand binding are present in the corresponding GALR1 and GALR2 orthologues. Transcripts for all four receptors are expressed in brain and testes of adult fish with GALR1a and GALR1b abundant in testes 15 and hardly detected in ovaries. In order to investigate whether GALR1 dimorphic expression was dependent on steroid context we evaluated the effect of 11-ketotestosterone and 17β-estradiol treatments on the receptor expression in brain and testes of pre-pubertal males. Interestingly, steroid treatments had no effect on the expression of GALRs in the brain while in the testes, GALR1a and GALR1b were significantly up regulated by 11KT. Altogether, these results support a role for the galaninergic system, in particular the GALR1 paralog in fish reproductive function

Neurones à kisspeptine et oestrogènes. Etude chez le poisson zèbre et le loup de mer. Kisspeptin neurones and their relationships with estrogens. Study in two fish species the zebrafish and the sea bass.

Supported by EU Project LIFECYCLE (FP7-222719-1) to OK and SZ, NEMO project to OK and ACOM/2010/086-GV. SE was supported by a JAE-Predoc (CSIC, Spain).Peer Reviewe

Molecular evolution of aphids and their primary (buchnera sp.) and secondary endosymbionts: implications for the role of symbiosis in insect evolution

Aphids maintain an obligate, endosymbiotic association with Buchnera sp., a bacterium closely related to Escherichia coli. Bacteria are housed in specialized cells of organ-like structures called bacteriomes in the hemocoel of the aphid and are maternally transmitted. Phylogenetic studies have shown that the association had a single origin, dated about 200-250 million years ago, and that host and endosymbiont lineages have evolved in parallel since then. However, the pattern of deepest branching within the aphid family remains unsolved, which thereby hampers an appraisal of, for example, the role played by horizontal gene transfer in the early evolution of Buchnera. The main role of Buchnera in this association is the biosynthesis and provisioning of essential amino acids to its aphid host. Physiological and metabolic studies have recently substantiated such nutritional role. In addition, genetic studies of Buchnera from several aphids have shown additional modifications, such as strong genome reduction, high A+T content compared to free-living bacteria, differential evolutionary rates, a relative increase in the number of non-synonymous substitutions, and gene amplification mediated by plasmids. Symbiosis is an active process in insect evolution as revealed by the intermediate values of the previous characteristics showed by secondary symbionts compared to free-living bacteria and Buchnera.The authors thank the Servicio Central de Soporte a la Investigación Científica (Universitat de València) for bioinformatics and sequencing facilities. The work has been supported by grants GV-3216/95 from Generalitat Valenciana (Spain), BFM2000-1383 from MEC (Spain) and FEDER 2FD1997-1006 (Spain).Peer reviewe

Gonadotropin actions in European sea bass: endocrine roles and biotechnological applications

Comunicación presentada en el 10th International Symposium on Reproductive Physiology of Fish, celebrado en Olhao, Portugal, del 25 al 30 de mayo de 2014The follicle stimulating hormone (Fsh) and the luteinizing hormone (Lh) are central endocrine regulators of gonad function in vertebrates. These gonadotropins act by binding and activating their specific receptors that are located in certain cell types of the gonads. In fish, the differential roles of these hormones are being progressively elucidated with the development of different tools for their study. In the case of European sea bass Dicentrarchus labrax, the isolation of the genes coding for the gonadotropin subunits and receptors allowed in first instance for expression studies. Later, to overcome the limitation of native hormones, recombinant dimeric gonadotropins have been generated, which show different functional characteristics depending on the cell system and DNA construct. In addition, single gonadotropin beta-subunits have been produced and used as antigens for antibody production. This last approach has allowed the development of detection methods for native gonadotropins being the European sea bass one of the few species where both gonadotropins can be detected in their native form. The generation of antibodies has also allowed for their cellular localization and co-localization with other factors, helping to a better understanding of their function. By administration of the recombinant gonadotropins to gonad tissues cultured in vitro we have studied their effects on steroidogenesis, the activated intracellular pathways and their target genes. Their administration in vivo has also been tested both for basic studies and as a biotechnological approach. In this frame, it is known from different studies in mammals that exogenous administration of native hormones in cases of deficiency, including assisted reproduction, can be unsatisfactory due to their rapid clearance from circulation or limited availability. Other than the production of recombinant hormones gene-based therapies by using somatic gene transfer are offered as an alternative. Such an approach has been tested in sea bass for gonadotropin delivery in vivo. The hormones produced by the injected genes were functional and have allowed for different studies on gonadotropin action in spermatogenesis. All together, the use of gene therapy for hormone replacement in fish is a real alternative to the production of recombinant gonadotropins for in vivo use, due to the low cost of production and the high persistence of the injected DNA, and has a broad range of potential applications such as its use in out-of-season breeding programs or reproductive dysfunctions in fish species.Supported by MINECO (AGL2011-28890) and GV (ACOMP/2013/085).Peer Reviewe

Characterization of the European Sea Bass (Dicentrarchus labrax) Gonadal Transcriptome During Sexual Development

The European sea bass is one of the most important cultured fish in Europe and has a marked sexual growth dimorphism in favor of females. It is a gonochoristic species with polygenic sex determination, where a combination between still undifferentiated genetic factors and environmental temperature determines sex ratios. The molecular mechanisms responsible for gonadal sex differentiation are still unknown. Here, we sampled fish during the gonadal developmental period (110 to 350 days post fertilization, dpf), and performed a comprehensive transcriptomic study by using a species-specific microarray. This analysis uncovered sex-specific gonadal transcriptomic profiles at each stage of development, identifying larger number of differentially expressed genes in ovaries when compared to testis. The expression patterns of 54 reproduction-related genes were analyzed. We found that hsd17β10 is a reliable marker of early ovarian differentiation. Further, three genes, pdgfb, snx1, and nfy, not previously related to fish sex differentiation, were tightly associated with testis development in the sea bass. Regarding signaling pathways, lysine degradation, bladder cancer, and NOD-like receptor signaling were enriched for ovarian development while eight pathways including basal transcription factors and steroid biosynthesis were enriched for testis development. Analysis of the transcription factor abundance showed an earlier increase in females than in males. Our results show that, although many players in the sex differentiation pathways are conserved among species, there are peculiarities in gene expression worth exploring. The genes identified in this study illustrate the diversity of players involved in fish sex differentiation and can become potential biomarkers for the management of sex ratios in the European sea bass and perhaps other cultured species

Pesquisa de mercado para abertura de um segmento de distribuição de medicamentos veterinários

O presente estudo tem o objetivo de analisar a oportunidade de mercado para abertura de um segmento de distribuição de medicamentos veterinários na empresa Ciamed Distribuidora de Medicamentos LTDA. e faz parte de um trabalho de conclusão de curso em Administração de Empresas. Este trabalho busca atender aos seguintes objetivos específicos: identificar as principais empresas que atuam no ramo de distribuição de medicamentos veterinários no estado do Rio Grande do Sul, indicar os medicamentos que possuem maior demanda no mercado veterinário, verificar as principais necessidades dos clientes e identificar os possíveis clientes no ramo de medicamentos veterinários a serem atendidos. No desenvolvimento da fundamentação teórica foram abordados conceitos de autores das áreas de marketing e estratégias de mercado, juntamente com um embasamento teórico de macroambiente e microambiente na visão de Philp Kotler e Garry Armstrong. O método utilizado foi exploratório e a análise das informações e dados coletados de forma qualitativa. Espera-se que os resultados deste estudo auxiliem a empresa a tomar a decisão no momento de escolher iniciar ou não as atividades no segmento de distribuição de medicamentos veterinários

Photoperiodic Modulation of Circadian Clock and Reproductive Axis Gene Expression in the Pre-Pubertal European Sea Bass Brain

The acquisition of reproductive competence requires the activation of the brain-pituitary-gonad (BPG) axis, which in most vertebrates, including fishes, is initiated by changes in photoperiod. In the European sea bass long-term exposure to continuous light (LL) alters the rhythm of reproductive hormones, delays spermatogenesis and reduces the incidence of precocious males. In contrast, an early shift from long to short photoperiod (AP) accelerates spermatogenesis. However, how photoperiod affects key genes in the brain to trigger the onset of puberty is still largely unknown. Here, we investigated if the integration of the light stimulus by clock proteins is sufficient to activate key genes that trigger the BPG axis in the European sea bass. We found that the clock genes clock, npas2, bmal1 and the BPG genes gnrh, kiss and kissr share conserved transcription factor frameworks in their promoters, suggesting co-regulation. Other gene promoters of the BGP axis were also predicted to be co-regulated by the same frameworks. Co-regulation was confirmed through gene expression analysis of brains from males exposed to LL or AP photoperiod compared to natural conditions: LL fish had suppressed gnrh1, kiss2, galr1b and esr1, while AP fish had stimulated npas2, gnrh1, gnrh2, kiss2, kiss1rb and galr1b compared to NP. It is concluded that fish exposed to different photoperiods present significant expression differences in some clock and reproductive axis related genes well before the first detectable endocrine and morphological responses of the BPG axis.European Community [222719 - LIFECYCLE]; Foundation for Science and Technology of Portugal (FCT) [SFRH/BPD/66742/2009, PEst-C/MAR/LA0015/2011]; Valencian Regional Goverment [Prometeo II/2014/051]; Spanish Ministry of Science and Innovation (MICINN) [CSD 2007-0002]info:eu-repo/semantics/publishedVersio