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iLabs: Rotifer Questions

August 23, 2012

We’ve had a couple of new questions come from visitors about our rotifers. So without further delay, here’s the questions, and what I’ve found for answers:

How long do rotifers live? 

From the Environmental Leverage website and the Microscopy UK website: Females live 6-45 days whereas males, if there are any in a species, live a day or so. They are only for reproduction and don’t even have a digestive tract.

How often do they reproduce?

The short answer is: it depends.

From a research project I came across:

The Effect of Temperature on Reproductive Characteristics of an Asexually Reproducing Rotifer (Class Bdelloidea), Kurt E. Galbreath ’97, Illinois Wesleyan University

From The Breeder’s Net: The Rotifer and Rotifer Home Culture

Essentially when environmental conditions are good, female rotifers produce up to 7 eggs simultaneously, without any genetic help from a male rotifer. These eggs are genetically identical, and will hatch to form new “daughter” rotifers with in 12-hrs. (Fig. 2c). By 18-hrs post hatching, the daughter rotifers begin to reproduce themselves, and egg production is maintained for up to a week or so. It is this rapid increase in rotifers that we as fish breeders find so useful for our home cultures. Nevertheless, you may have noted the statement “when conditions are good,” which implies that conditions can be bad, and in fact when conditions are not favorable or stressful rotifers convert to producing haplo-identical eggs, meaning only half the genetic material is placed into an egg. These halpo- identical offspring hatch as smaller nonfeeding male rotifers, which then fertilize the other haplo-identical eggs. These fully fertilized eggs develop a thick outer coating and are called cysts. Rotifer cysts can survive adverse conditions and remain dormant for years if required, and it’s these cysts (resting rotifers or rotifer cysts) that allow rotifers to be reestablished at a later time when conditions are favorable again.

And from Scientific American, an article that explores the variations in reproductive frequency when food quality is varied:

One set of populations had a consistent exposure to only high-quality food, a second set only to low-quality food. Other populations were alternated each week between high- and low-quality food environments.

After 15 weeks (with about one new generation per day), the researchers found that rotifers in the homogeneous environments were better adapted to their respective food environments (than they were to the alternative environment), and about seven percent of these rotifers’ eggs were created via sexual reproduction. The rotifers that had been transferred between the two food-quality environments, however, were reproducing sexually at more than double the rate (some 15 percent). The results “indicate that sex evolves differently in heterogeneous versus homogeneous environments,” noted the researchers in their paper.”

So essentially, the final answer is, “It depends.”

Do they eat Vorticella?

This one is MY question. I had a couple of very nicely thriving Vorticella cultures only to see them disappear, replaced by large numbers of rotifers. Given this quote from an 1882 microscopy book, I suspect the rotifers ARE the problem:

book quote on rotifers eating Vorticella

From the 1882 book: Microscopical news and northern microscopist, Volume 2, By George Edward Davis, Rotifers apparently “love” Vorticella

And I came across this very blunt assessment of rotifer eating habits, from the Fairfax County, Virginia, Public Schools Website:

“To eat, Collotheca extends its body fully from its tube and waits for small swimming organisms to get close. Once an organism touches the rotifer’s cilia, it gets sucked into its mouth. Common foods of rotifers include: algae, protozoa (such as amoeba and paramecium), small crustaceans (such as water fleas and copepods), and small bits of plant or animal matter floating in the current. They’ll pretty much eat anything that fits into their mouths.”

So I think I need to get some more Vorticella and somehow keep the rotifers out!! 🙂

One Comment leave one →
  1. August 24, 2012 5:20 am

    Thanks for your grateful informations Students Portal

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