Early transition to microdiets improves growth, reproductive performance and reduces skeletal anomalies in Zebrafish (Danio rerio)

Zebrafish is a model species with a high variability of feeding regimes among fish facilities. The use of live feeds for early life stages is a common practice, and few studies have focused early weaning into microdiets. The lack of standardized feeding protocols among research facilities promotes discrepancies in biological performances, and few studies relate dietary regimes to zebrafish development. The objective of this work was to assess the effect of an early transition into microdiets in zebrafish development by evaluating growth, survival, reproductive performance, and skeletal anomalies. These parameters were assessed in one group exclusively fed on Artemia nauplii and two groups fed on microdiets (commercial and experimental). Results showed that an early weaning with the two microdiets significantly improved zebrafish growth and reproductive performance, while a decrease in incidence of vertebral column anomalies was observed. A high survival was also maintained in fish fed microdiets at an early developmental stage when comparing to exclusive Artemia nauplii feeding. In conclusion, early weaning with high quality microdiets is beneficial for zebrafish growth, reproductive performance, and skeletal development, contributing to the standardization of zebrafish husbandry practices.FEDER through PO Algarve 21 in the framework of QREN - 3000-ZEBRAFEEDS. Portuguese Foundation for Science and Technology -SFRH/BD/974662013.info:eu-repo/semantics/publishedVersio

Mercury toxicity in livers of northern pike (Esox lucius) from Isle Royale, USA

Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology 147 (2008): 331-338, doi:10.1016/j.cbpc.2007.12.003.Many laboratory studies have documented that mercury can be toxic to fish, but it is largely unknown if mercury is toxic to fish in their natural environments. The objective of our study was to investigate the toxic effects of mercury on northern pike (Esox lucius) at Isle Royale, Michigan. In 124 northern pike from eight inland lakes, concentrations of total mercury in skin-on fillets ranged from 0.069 to 0.622 µg/g wet wt. Concentrations of total mercury in livers increased exponentially compared with concentrations in fillets, to a maximum of 3.1 µg/g wet wt. Methylmercury constituted a majority of the mercury in livers with total mercury concentrations <0.5 µg/g wet wt, but declined to 28-51% of the mercury in livers with total mercury concentrations >0.5 µg/g wet wt. Liver color (absorbance at 400 nm) varied among northern pike and was positively related to liver total mercury concentration. The pigment causing variation in liver color was identified as lipofuscin, which results from lipid peroxidation of membranous organelles. An analysis of covariance revealed lipofuscin accumulation was primarily associated with mercury exposure, and this association obscured any normal accumulation from aging. We also documented decreased lipid reserves in livers and poor condition factors of northern pike with high liver total mercury concentrations. Our results suggest (i) northern pike at Isle Royale are experiencing toxicity at concentrations of total mercury common for northern pike and other piscivorous fish elsewhere in North America and (ii) liver color may be useful for indicating mercury exposure and effects in northern pike at Isle Royale and possibly other aquatic ecosystems and other fish species.Financial support was provided by the U.S. Environmental Protection Agency STAR Graduate Fellowship Program to P.E.D

Effect of water hardness on peracetic acid toxicity to zebrafish, Danio rerio, embryos

The use of peracetic acid (PAA) in aquaculture has been suggested as an alternative therapeutic agent. Few data are available concerning fish toxicity by PAA or factors that modify this toxicity. The aim of this study was to investigate the influence of water hardness on the acute toxicity of PAA products to embryos of zebrafish (Danio rerio). Embryos were exposed to PAA ranging from 0 to 9 mg/L in low-hardness (1. 4 °dH or 25 mg/L hardness as CaCO3), medium-hardness (14 °dH or 250 mg/L hardness as CaCO3) and high-hardness (140 °dH or 2,500 mg/L hardness as CaCO3) waters. The lowest LC50 value was 2. 24 mg/L PAA in the low-hardness water, and the highest LC50 value was 7. 14 mg/L PAA in the high-hardness water. Toxicity of PAA to embryos was found to be negatively correlated with water hardness. The pH decreased with increasing concentrations of PAA, and the test waters were observed to become more acidic in low hardness. In conclusion, aquaculturists using PAA should pay attention to water hardness to avoid acidosis. © 2012 Springer Science+Business Media Dordrecht