03 March 2009

A matter of patience

This graph shows one of the biggest obstacles facing researchers who want to work with Marmorkrebs and, to a lesser degree, a lot of other crustaceans. It’s a graph comparing generation time of common research animals. How long does it take for an organism to grow and reproduce? Clearly, most modern model organisms have been selected in part for short generation times. Live fast, die young.

While I don't pretend that this graph is exhaustive, the only datum on this graph longer than Marmorkrebs deserves comment. Xenopus laevis has been used for research for a long time, but even it is competing with a related species, Xenopus tropicalis, which has a much shorter generation time.

Most decapod crustacean researchers have dealt with this problem in a straightforward way: they only study adults, and they don’t rear animals in the lab. Instead, crayfish, lobsters, and crabs are collected from wild populations or from commercial suppliers. But this seems rather too limiting on research that can be done.

There may be a silver lining for Marmorkrebs, however. Generation time may be long, but there are two mitigating factors. First, crayfish lifespan is relatively long. Second, once a Marmorkrebs hits reproductive age, it can generate new batches of eggs in a couple of months. I'm not sure how many times fruit flies or C. elegans can generate offspring in their brief lives, but the number of reproductive opportunities per animal may be lower for some of the fast-living animals.

Furthermore, short life span has traditionally been a major advantage for genetic research, where breeding used to be necessary to examine the traits of interest. You had to have animals reproduce to see the patterns of inheritance Now that there are many more genetic tools available, straight ahead breeding experiments may be a little less common, less of a staple experiment, than they used to be. Instead of trying to breed a mouse with certain characteristics, you can use directed genetic tools to affect the relevant genes.

Given that Marmorkrebs reproduce asexually, those directed tools might be able to take the place of the traditional breeding experiments. Thus, it might not matter that Marmorkrebs live slow and die old.

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