Zooplankton mothers make bigger offspring, but it’s not enough to protect them against harmful blue-green algal blooms

Jessica E. Beyer and K. David Hambright

One of the goals of all organisms is to ensure that as many offspring as possible will survive to adulthood. To accomplish this, organisms use many different strategies, including changing features of the offspring, such as their size. However, to supply offspring with the right set of tools for their survival, a mother must anticipate the future environmental conditions that the offspring might encounter. The maternal match hypothesis suggests that mothers use current environmental conditions as a clue to conditions their offspring will encounter.

In our research, we were interested in whether rotifers, microscopic freshwater herbivores, change characteristics of their offspring in response to different types of food available in their environment. Freshwater herbivores like rotifers often experience rapid declines in the quality of food (algae) available to them, particularly during harmful algal blooms, when, for example, toxic algal species become very abundant. By changing the type of offspring she produces, a mother may be able to produce longer-lived offspring better suited to the current environment. Based on the maternal match hypothesis, if mothers feed on a toxic diet, they may produce offspring better able to survive and reproduce on that same toxic diet.

To test this hypothesis, we raised rotifers on either good food (green algae) or bad food (toxic blue-green algae), after having raised their mothers on either the same or opposite food. We then measured how long these rotifers lived, as well as how many offspring (the original mothers’ grandchildren) they produced in each of these conditions. We found that offspring from mothers fed the toxic algae died sooner and had fewer offspring themselves, whether they ate good or toxic food. Mothers fed toxic algae did not create offspring who did better under these adverse conditions – rather, these offspring did worse than offspring produced by mothers fed the good algae. Our evidence suggests that rotifer mothers do not compensate for a toxic diet by producing offspring who are more resistant to that same diet. Thus, in a world with increasing harmful algal blooms and changing environmental conditions, rotifers may face cumulative problems across multiple generations.

Read the article in full here.
Image caption: Photo provided by authors.

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