Microinjection system for manipulation of yolk and lipids in developing fish embryos

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Most species of fish produce many eggs (r-selected). For example, a female winter flounder (Pseudopleuronectes americanus) can produce up to 3 million eggs per year and is reproductive for an average of 7 years. However, very few embryos survive to reproduction. Mortality rates for these r-selected species, both in field and aquaculture setting, are extremely high during the first year of life.  This life-history strategy is of fundamental importance to our understanding of fish population dynamics and a significant challenge to aquaculture development. The quality of the yolk and lipid reserves provided by the mother is extremely important for survival during these early life history stages. Recently, we developed the first successful microinjection approach to control yolk and lipid quality and quantity in developing fish embryos. This advance is important because by controlling yolk and lipid size within a female's batch we can examine the effect of egg quality on survival. Specifically, we will examine the importance of larval size (controlled by yolk size), size at age (developmental stage or experience), family and stock origin on performance traits and survival in both natural and aquaculture contexts.  Using our new microinjection system that we have designed and proposed here, we will take two approaches to determine the effect of yolk quality on larval growth and survival. First, we will inject specific macronutrients to determine their importance. For example, DHA is an important fatty acid for larval fish development. We will examine its importance by directly injecting various amounts of DHA into the yolk of developing embryos and then examining their growth, survival and performance.  Second, we will modify our microinjection technique to allow us to manipulate almost all of the yolk; swapping the yolk within developing embryos with a "designed" or "standard" yolk will provide greater control of non-genetic maternal effects on performance. These approaches will allow us to address the effect of yolk and lipid quality on survival and growth in both ecological and aquaculture settings. The equipment requested here will allow us to maintain a leadership role in this newly developed area of research.