Authors: Cassandra Nelson, Braden Richards, Grace Van Buren, Fernando Gonzalez, Ian Kirkpatrick, Paul Dunn
Mentors: Paul Dunn
Insitution: Utah Valley University
Many organisms experience a life history pattern called ontogenescence, a high but declining mortality risk during early life. Ontogenescence can have a large effect on a population’s growth by limiting the number of new recruits to the population. Clearly, and yet paradoxically, death before reproductive maturity should be selected against, yet ontogenescence persists across many otherwise dissimilar organisms. Some intriguing hypotheses to explain this pattern have been proposed but have not been thoroughly tested. One of these hypotheses, acquisition of robustness as a function of age, is perhaps the most intuitive. The goal of our current research is to examine the validity of this hypothesis by using brine shrimp (Artemia franciscana) as a model organism.
Tracking life-history traits like ontogenescence often requires the researcher to be able to follow an individual throughout its lifespan. In aquatic invertebrates, this means culturing animals individually, which can be quite difficult. Here we report on
progress we are making with these culturing methods by testing how food availability and variety affect the early life mortality and development rate of brine shrimp in small-volume culture. Our null hypotheses are that neither of these variables will affect mortality or age to maturity in the animals. Our alternative hypotheses are that increased food availability and variety should lower mortality risk and age to maturity. To test our hypotheses, we hatched brine shrimp cysts in artificial seawater and placed individual artemia into wells of 6-well cell-culture plates filled with artificial seawater. We fed the shrimp one of several food treatments to see how diet affects development and mortality. In our first round of trials, we provided our animals with two different food concentrations (high food vs. low food) of the three food types we evaluated: a unicellular alga (Nannochloropsis), a cyanobacterium (Spirulina), and brewer’s yeast (Saccharomyces cerevisiae). In our second set of trials, we provided the shrimp with less variety in their diet (only two of the three food types). As the artemia developed, we conducted regular water changes and monitored development and mortality. We tracked the fate of the artemia until all individuals had either died during development or reached adulthood. Our food availability trials resulted in no significant difference in either mortality risk during development or age at maturity based on food concentrations. Trials examining the effects of limiting the variety of food types are ongoing.