Characterizing the epigenetic mechanisms underlying maternal age effects in Brachionus rotifers

A maternal effect is a phenomenon in which the physiological state of a mother influences the phenotype of her offspring, without a change in genotype. The age at which a female produces offspring can be an important driver of maternal effects. However, little is known about intraspecific variability in the magnitude and direction of maternal age effects, or whether maternal age effects persist or accumulate across multiple generations. As a Postdoctoral Scientist in the Gribble Lab at the Marine Biological Laboratory (MBL), I am using Brachionus rotifers as a study system to explore the molecular mechanisms that drive maternal age effects.

The rotifer Brachionus manjavacas. Photo credit: M. Shribak, E. Ivashkin & K.E. Gribble

Using multigenerational life table experiments, I have found that maternal age affects the life history of offspring in distinct ways among closely-related strains of Brachionus. I am conducting experiments to understand how maternal age interacts with environmental factors, such as changing food quality, to affect offspring fitness. Using old- and young-mother lines, I am characterizing whether maternal effects remain consistent across generations (e.g., investigating the role of grand and great grandmaternal ages), and whether they can be reversed within a generation of shifting maternal age. I am using RNA-seq to quantify differences in gene expression among rotifers with different grandmaternal and maternal ages, and sampling throughout the lifespan. This project will inform future research to test whether histone protein post-translational modifications and changes in chromatin accessibility are key components of plastic responses to environmental change across generations.

Multigenerational responses to pH in the copepod Tigriopus californicus 

The copepod Tigriopus californicus.

Tigriopus californicus is a model copepod that is well-studied in terms of its ecology and stress tolerance but surprisingly, few studies have investigated its responses to pH. In its high intertidal habitat, where pools are like small isolated mesocosms, pH can be extreme and variable (as low as 6 to above 9 pH units). Respiration, photosynthesis, and many other factors drive the pH dynamics that these animals experience.

Water samples during spectrophotometric pH analysis- from the top down: pH of ~ 7, 7.5, and 8.

I am investigating how different pH treatments affect the life history and morphology of T. californicus across multiple generations, and whether previous pH exposure influences performance in current conditions. Since populations of these copepods are often highly genetically differentiated, even at small geographic scales, I am comparing responses among four populations to test the generality of responses to pH in T. californicus.

I have completed long-term experiments in the Ocean Acidification Environmental Laboratory at Friday Harbor Laboratories, where I maintained target seawater pH treatments by adjusting quantities of dissolved carbon dioxide gas, mimicking how pH changes in Tigriopus pools in the field.

Check out my findings here.

Testing for local adaptation to salinity and temperature variability

I am exploring the potential for local adaptation to microhabitats with different amplitudes of abiotic variability in T. californicus. Understanding the evolution of plasticity to such variation will be critical for predicting the population dynamics of Tigriopus and other coastal organisms that can experience environmental variability, which will likely become more extreme with continued climate change.

Measuring salinity in a Tigriopus pool.

In previous research, I found that T. californicus populations on San Juan Island in Washington have distinct morphology, stress responses, and life history characteristics. I am working to determine if these differences are due to genetic differentiation and local adaptation, and testing whether populations have evolved different capacities for coping with the combined stressors of high salinity and temperature variability. I am characterizing population performance under a range of abiotic conditions in common garden laboratory experiments, and monitoring environmental conditions (potential selective pressures) in the field at each population site.

Read more about this work here.

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Study sites on San Juan Island, WA.

Population genomics of Tigriopus californicus on San Juan Island, WA

As part of a NSF GRIP internship at the NOAA Northwest Fisheries Science Center with Dr. Krista Nichols, I used RAD-seq and Pool-seq methods to characterize genomic differentiation among the T. californicus study populations from my dissertation research.