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Aldeadávila de la Ribera, Spain

Bjork S.J.,Oregon State University | Zhang Y.-A.,CAS Wuhan Institute of Hydrobiology | Zhang Y.-A.,University of Pennsylvania | Hurst C.N.,Oregon State University | And 4 more authors.
Fish and Shellfish Immunology

We investigated intra-specific variation in the response of salmon to infection with the myxozoan Ceratomyxa shasta by comparing the progress of parasite infection and measures of host immune response in susceptible and resistant Chinook salmon Oncorhynchus tshawytscha at days 12, 25 and 90 post exposure. There were no differences in invasion of the gills indicating that resistance does not occur at the site of entry. In the intestine on day 12, infection intensity and Ig+ cell numbers were higher in susceptible than resistant fish, but histological examination at that timepoint showed more severe inflammation in resistant fish. This suggests a role for the immune response in resistant fish that eliminates some parasites prior to or soon after reaching the intestine. Susceptible fish had a higher IFNγ, IL-6 and IL-10 response at day 12, but all died of fatal enteronecrosis by day 25. The greatest fold change in IFNγ expression was detected at day 25 in resistant Chinook. In addition, the number of Ig+ cells in resistant Chinook also increased by day 25. By day 90, resistant Chinook had resolved the inflammation, cytokine expression had decreased and Ig+ cell numbers were similar to uninfected controls. Thus, it appears that the susceptible strain was incapable of containing or eliminating C.shasta but resistant fish: 1) reduced infection intensity during early intestinal infection, 2) elicited an effective inflammatory response in the intestine that eliminated C.shasta, 3) resolved the inflammation and recovered from infection. © 2014 Elsevier Ltd. Source

Escobar S.,Institute Acuicultura Torre Of La Sal Iats | Escobar S.,University of Chile | Felip A.,Institute Acuicultura Torre Of La Sal Iats | Zanuy S.,Institute Acuicultura Torre Of La Sal Iats | Carrillo M.,Institute Acuicultura Torre Of La Sal Iats
Comparative Biochemistry and Physiology -Part A : Molecular and Integrative Physiology

Previous works on European sea bass have determined that long-term exposure to restrictive feeding diets alters the rhythms of some reproductive/metabolic hormones, delaying maturation and increasing apoptosis during gametogenesis. However, exactly how these diets affect key genes and hormones on the brain-pituitary-gonad (BPG) axis to trigger puberty is still largely unknown. We may hypothesize that all these signals could be integrated, at least in part, by the kisspeptin system. In order to capture a glimpse of these regulatory mechanisms, kiss1 and kiss2 mRNA expression levels and those of their kiss receptors (kiss1r, kiss2r) were analyzed in different areas of the brain and in the pituitary of pubertal male sea bass during gametogenesis. Furthermore, other reproductive hormones and factors as well as the percentage of males showing full spermiation were also analyzed. Treated fish fed maintenance diets provided evidence of overexpression of the kisspeptin system in the main hypophysiotropic regions of the brain throughout the entire sexual cycle. Conversely, Gnrh1 and gonadotropin pituitary content and plasma sexual steroid levels were downregulated, except for Fsh levels, which were shown to increase during spermiation. Treated fish exhibited lower rates of spermiation as compared to control group and a delay in its accomplishment. These results demonstrate how the kisspeptin system and plasma Fsh levels are differentially affected by maintenance diets, causing a retardation, but not a full blockage of the reproductive process in the teleost fish European sea bass. This suggests that a hormonal adaptive strategy may be operating in order to preserve reproductive function in this species. © 2016 Elsevier Inc. Source

Escobar S.,Institute Acuicultura Torre Of La Sal Iats | Felip A.,Institute Acuicultura Torre Of La Sal Iats | Salah M.,Institute Acuicultura Torre Of La Sal Iats | Zanuy S.,Institute Acuicultura Torre Of La Sal Iats | Carrillo M.,Institute Acuicultura Torre Of La Sal Iats

In sea bass (Dicentrarchus labrax), the onset of puberty under intensive farming conditions is likely related to the availability of food. Therefore, a close connection between feed intake, lipid storage and onset of reproduction can be established. This study reports the effects of long-term feed restriction on the reproductive performance of male sea bass entering their first breeding season. A control group (C) was fed to apparent satiety, while experimental groups were restricted to 1/4 (1/4 C) or 1/8 (1/8 C) of the ration administered to the control group. It was determined that restricted feed regimes influenced the weight, length, growth rate and gonadosomatic index (GSI) of the fish. Specifically, the 1/8 C group showed lower GSI values than the control animals. In the experimental animals, the histological analysis revealed a moderate delay in testes development and a larger number of apoptotic bodies at onset of gametogenesis. The plasma level profiles of 11-ketotestosterone (11-KT) were comparable among the groups. Additionally, certain sperm parameters, including sperm count, motility and expressible milt volume, were evaluated throughout the reproductive season, and long-term fasting was found to affect sperm volume and counts, curvilinear velocity (VCL), average path velocity (VAP) and percentage of static and medium motility sperm of sea bass sperm. However, puberty was not suppressed; at most, gonadal development was reduced and progression of gonadal stages delayed as well as the duration of the production of sperm. Unexpectedly, some characteristics of their motility experienced a significant increase. © 2014 Elsevier B.V. Source

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