**Unsupplemented** *Artemia* **Diet Results in Reduced Growth and Jaw Dysmorphogenesis in Zebrafish**

Michael P. Craig, Mitul B. Desai, Kate E. Olukalns, Scott E. Afton, Joseph A. Caruso and Jay R. Hove *University of Cincinnati USA* 

#### **1. Introduction**

34 Aquaculture

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growth performance, feed utilization and digestive enzyme of juvenile ivory shell, *Babylonia areolate*. *Aquaculture*, Vol. 272, No. 1-4 (November 2007), pp. 535-540, ISSN The number of laboratories using zebrafish as an experimental animal model has risen tremendously over the past two decades (Craig et al., 2006). As a result, the number of zebrafish facilities around the world has dramatically increased to meet the elevated demand for proper animal care and maintenance. In order to meet this demand, aquaculture facilities must employ husbandry protocols designed to produce a constant supply of healthy, viable eggs. Surprisingly, many husbandry strategies, particularly feeding protocols, are frequently passed down from members of one lab to another in a colloquial fashion without rigorous experimental validation. An ideal diet should consist of a minimal variety of foodstuffs designed to be nutritionally complete, simple to prepare, non-fouling, and cost-effective. Previous studies aimed at streamlining adult zebrafish feeding strategies in large aquaculture facilities have emphasized cost-effective, single-food models, but such diets lead to diminished survivorship and reproductive capacity (Goolish et al., 1999; Meinelt et al., 1999; Barnard & Bagatto, 2002), suggesting that these diets are lacking in some key nutritional component(s). Restricting adult fish diets to single foodstuffs, while desirable from a time and cost perspective, may not provide the trace mineral balance needed for adequate hormone and enzyme production, proper skeletal formation, and other biochemical or physiological needs. Nonetheless, given the intense breeding schedules many facilities are forced to adopt to meet research needs, a single component, high protein diet for enhanced egg production is frequently adopted.

Processed flake food diets are generally rich in proteins and essential trace elements required for normal physiological function. Despite their critical role in modulating somatic growth and basal metabolic rate in homeotherms (Eales & Brown, 1993), recent studies aimed at identifying alternative diets for improving the growth and reproductive capacity of zebrafish have paid little attention to minimum dietary iodine requirements. This may be due, at least in part, to the fact that zebrafish maintain a large reserve of T4 in the follicular colloid effectively allowing the animal to accommodate transient iodine deprivation (Brown et al., 2004). Additionally, iodized salts in system water and iodine-fortified processed foodstuffs are commonly used to avoid iodine-deficiency pathologies such as hyperthyroidism and goiter. Nevertheless, environmental conditions such as poor water quality or malnutrition can lead to marked proliferation of thyroid tissue in some fishes (Hoover, 1984) indicating that care must be taken to maintain a minimum iodine level in artificial environments including zebrafish aquaculture facilities. Dietary supplements have been shown to prevent thyroid hyperplasia in the saltwater cyprinodont *Fundulus* (Pickford, 1954) and goiters in the Chinook salmon (Woodall & La Roche, 1964), but no study to date has effectively assessed the minimum iodine level for maintaining normal development and thyroid health in zebrafish.

While experimenting with varied diets in our facility, we observed that conditions of reduced iodine result in less robust somatic growth and an elevated incidence of jaw dysmorphogenesis. This prompted us to evaluate the developmental consequences of rearing zebrafish on a single live food or a mixed food diet with varying levels of iodine. Herein we demonstrate that a strict single-food *Artemia* diet, although high in the protein necessary for robust egg production, may also result in a morphological alteration of the zebrafish jaw architecture formed in response to swelling and hypervascularization of adjacent tissues.
