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The article looks at a research which evaluates the impact of quorum sensing on the virulence of Vibrio anguillarum towards gnotobiotic sea bass larvae. It mentions wide and frequent use of antibiotics in aquaculture in order to control bacterial diseases has resulted in resistance development in aquaculture pathogens and virulence factors have been identified, including haemolysin, lipase, and protease production. It also mentions monitoring of expression of activity of virulence factors.

Abstract: In the present study, the hypothesis that the difference in axenic conditions in the incubation and rearing environment of European seabass larvae induces size and shape effects on the specimens is tested. This difference is studied between xenic and axenic seabass larvae of DAH (day after hatching) 0, 5, 11 and 15. The axenic rearing protocol involves an egg disinfection with glutaraldehyde after the primary one with iodine in the hatchery, and the hypothesis that this secondary disinfection induces size and shape effects is also tested. In order to accomplish this, three egg and larvae treatments are included: “DA” (disinfected axenic), “DX” (disinfected xenic) and “NX” (nondisinfected xenic). Regarding the effect of antibiotic‐induced axenity, DA larvae exhibited larger bodies than both DX and NX on DAH 5 and 11. They also had a smaller yolk sac than DX at hatching, but consumed it slower. Towards the end of the experiment, DA larvae were thicker, but slightly more curved than DX and NX, which may be an abnormal shape, or a slightly more advanced ontogenetic stage. As far as egg disinfection, it had significant but very moderate shape effects on DAH 5 and 11, and disinfected larvae consumed their yolk sac faster. To the best of our knowledge, this study is one of the first to illustrate the subtle but significant size and shape effects caused by antibiotic‐induced axenity and secondary egg disinfection in the early larval stages, which suggest the existence of bacterial mechanisms that play a phenotypic role. [ABSTRACT FROM AUTHOR]

Abstract: Bacterioplankton is an important component of marine as well as fresh waters and accounts for a large fraction of the production of particulate matter in those ecosystems. The concept of bacteria as providers of essential nutrients in aquatic food webs has been raised most recently in relation to the utilization of bacteria as a food source in aquaculture food chains. This article represents a comprehensive review on the potential role of bacteria as a direct food source for aquaculture organisms. After studying shortly the analytical tools that can be applied to determine the uptake and assimilation of bacteria by higher trophic levels, it describes the bacterial loads that are found in closed and open aquaculture systems and elaborates on the composition of bacteria from a nutritional point of view. Next this study elaborates in more detail on the role of bacteria as food for the zooplankton groups used as live food in aquaculture hatcheries and for various groups of aquaculture target organisms, such as fish, crustaceans and especially bivalves. This includes an assessment of the specific uptake mechanisms of the different taxonomic groups of interest in relation to their efficiency to ingest bacteria. Finally, future research lines are suggested to elucidate the nutritional impact of the bacterial community in aquaculture systems and how to steer this in order to optimize the production. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the present study was to quantify the effects of antibiotic‐induced differences in bacterial load on the size and shape of fish larvae, using Dicentrarchus labrax of day after hatching (DAH) 3 as a case study. They were split in two treatment groups and reared in 50 ml vials until DAH 14, with the control treatment (“NA”) including larvae reared in filtered autoclaved seawater without antibiotics, while the second (“A”) included larvae reared in filtered autoclaved seawater with rifampicin, ampicillin, kanamycin, trimethoprim and gentamicin, with a concentration of 10 mg/L each. They were sampled for bacterial presence on DAH 4, 7 and 14, and had their mortalities recorded, their total lengths, gut lengths, anal body depths, eye diameters, head depths, yolk sac lengths and yolk sac depths measured, and their outlines analysed on DAH 7 and 14. Treatment NA exhibited the highest mortalities on DAH 14. The antibiotics had a significant size effect, yielding larvae with larger total length on DAH 7 and 14, larger bodies on DAH 7, and on DAH 14 larger anal body depth and greater variance in body size. Their effect on outline shape was also significant in both age classes, with increasing differences from DAH 7 to DAH 14. On DAH 7, “A” specimens were more uniform in their dorso‐ventral development, and on DAH 14 “NA” had more slender shapes. The beneficial total length and size effects and the witnessed shape effects might be associated with the low bacterial presence. [ABSTRACT FROM AUTHOR]

In aquaculture hatcheries, egg disinfection is commonly employed as a mortality mitigation and disease management tool. In addition, disinfection protocols are utilized in research facilities, as a means to create axenic and gnotobiotic larval models. For the latter, a complete sterilization of the eggs is warranted. Multiple research groups have tested various disinfectants in fish eggs adopting different protocols and a range of parameters to evaluate their efficacy and safety. However, there is a clear lack of a critical review listing these different studies and stressing the advantages and shortcomings of the protocols and adopted disinfectants. This review provides a commented survey of the findings/experiments on the most frequently used and upcoming disinfecting products, the protocols in which they are included and their purposes with emphasis on decreasing bacterial and/or fungal load, underscoring the benefits and the limitations of each product. Supplemented with a critical note, this review assists both aquaculturists and researchers in making an informed choice. Moreover, it will help stakeholders to identify the gaps in knowledge where future research on egg disinfection is needed. [ABSTRACT FROM AUTHOR]