A Simple Method for Inducing Masculinization of Zebrafish Stocks Using 17α-Methyltestosterone.

Severely skewed sex ratios in zebrafish stocks can pose significant hurdles for line propagation and sperm cryopreservation. To overcome female-biased sex ratios in stocks derived from imported sperm samples, the Zebrafish International Resource Center has implemented routine supplementation of larval food with 17α-methyltestosterone to skew gonadal sex differentiation toward masculinization. Resulting stocks averaged 80% males.

Zebrafish breeding in the laboratory environment.

The zebrafish, Danio rerio, has become a major model organism used in biomedical studies. The widespread use of Danio rerio in research laboratories requires a comprehensive understanding of the husbandry of this species to ensure efficient propagation and maintenance of healthy and genetically diverse colonies. Breeding is a key element in zebrafish husbandry. It is a complex process influenced by a number of factors. Mate choice and mating behavior depend, for example, on olfactory cues, visual stimuli, and social interactions. Spawning is affected by the age and size of fish, interval at which fish are used for egg production, light cycle, diet, and fish health status. A number of breeding strategies, based on either single-pair matings or group crosses, are commonly employed in the laboratory to propagate lines and to identify carriers of specific mutations and/or transgenes. Propagation of zebrafish lines, in particular wild-type-derived strains, is closely monitored to ensure that genetic diversity and vigor are maintained. A robust zebrafish line typically carries a large number of polymorphic variations, which may interfere with reproducibility of experiments. To get a better insight into these variations, a wild-type hybrid Sanger AB Tübingen line has been generated from sequenced homozygous founders.

Transmission, diagnosis, and recommendations for control of Pseudoloma neurophilia infections in laboratory zebrafish (Danio rerio) facilities.

The microsporidium Pseudoloma neurophilia represents a considerable challenge for laboratory zebrafish (Danio rerio) facilities. In 2010, P. neurophilia infections were diagnosed in zebrafish from 74% of the facilities that submitted fish to the Zebrafish International Resource Center (ZIRC) pathology service, and this organism remains the most commonly diagnosed pathogen in submitted fish. Accordingly, many of the ZIRC pathology service consultations deal with control and prevention of microsporidiosis. Here we describe observations and experiments performed at the ZIRC elucidating aspects of P. neurophilia transmission in zebrafish colonies. We then review current knowledge about P. neurophilia transmission and diagnosis. Considering this information, we present recommendations for control of P. neurophilia in zebrafish facilities.