Growth and survivorship of larval zebrafish Danio rerio on processed diets

Within the past decade the zebrafish or zebra danio Danio rerio has become a major vertebrate model for the study of developmental biology, neurobiology, and molecular genetics. Most research universities now include large zebrafish colonies where considerable resources are expended for their feeding and maintenance. Larvae are particularly labor intensive because they are commonly fed a live diet such as paramecia Paramecium sp. and brine shrimp Artemia sp. We evaluated 10 processed (i.e., nonliving) diets as alternatives to a live diet using the criteria of survivorship and growth during the 2-3 weeks following hatching. The test diets included commercial diets, two experimental diets, and freeze-dried brine shrimp. The control diet consisted of live paramecia and brine shrimp. Four experiments that varied in water exchange rate, aeration, and in the timing and method of diet delivery were conducted. No processed diet performed as well as the live-diet control when both larval survivorship and growth rate were considered. Furthermore, differences in water exchange rate and method of diet delivery were equally important in determining survivorship and growth as were differences among individual test diets. Under conditions when larval growth rate was similar to the live-diet control (high water exchange rate), survivorship was approximately 50% of the control value. Under conditions where larval survivorship was high (low water exchange rate), growth rate was 14-37% of the control value. Although no single test diet performed appreciably better than the others, the following general diet characteristics appeared to increase performance; resistance to breakdown, 200-400- mu m particle size, and a high residence time in the water column. Overall results suggest that processed diets for zebrafish larvae can be substituted for a live diet only if a decrease in either growth rate or survivorship is acceptable.