RSS button

the latest news

We’ve moved to OEB / CBS

I’m happy to say we’ve finished most of the move from the Rowland Institute to our new home in the Northwest building on the main campus!

The crates are now unpacked and we’ve resumed collecting data.

Our summer intern Sandra has been collecting Y-maze handedness data on flies reared under standard culture conditions, and flies reared in visually and spatially enriched environments. Our hypothesis: that environmental enrichment during development and early adulthood will increase the extent of inter-individual behavioral variability. What’s great about this hypothesis is that whether it, or its opposite, is true, we’ll have an interesting result. Both alternatives are plausible and have theoretical support:

  • Given circuit plasticity, and the possibility (in enriched environments) that each fly can find its own particular microenvironment, environmental complexity may increase behavioral variability.
  • But, environmental enrichment has been shown in numerous protocols, to increase the “robustness” of development, i.e. how closely to the standard blueprint each animal ends up. If behavioral variability is a symptom of developmental decanalization (a lack of robustness to environmental perturbation) then enrichment may diminish variability.
  • The results so far? Well, they’re complicated, but it looks like enrichment may increase the inter-individual variation in some traits, and have no effect whatsoever on others. It seems that there is substantial variation behavior-to-behavior in the extent to which environment can alter inter-individual variability. For some behaviors, the amount of inter-individual variability may be (paradoxically) hard-wired in the genome.

    The data is flowing in and it will be great to see this story emerge.

    The last view of the lab (in crates) at the Rowland Institute. Thanks Rowland, you were a wonderful incubator for my brain.

    July 24, 2013 on 12:51 am    ~    No Comments

    A manuscript’s Companion Data Page

    screenshot of Accompanying Data Page
    Last fall we pre-published a manuscript on This work describes a new method to track the position of all six fly legs in a live fly behaving spontaneously on a floating ball. We image leg position using infrared dyes invisible to the fly, and an optical path running through the very ball the fly is running upon.

    This manuscript is progressing through the formal publication process, and in anticipation of its completion, we are posting the raw data from this paper, as well as as all the LabVIEW and MATLAB scripts involved in data acquisition and analysis. The image at right is a screenshot of that data and script page, which we think of as a sister document to the publication itself.

    Please take a look at the Companion Data Page.

    If you feel like commenting on it (here would be best): do you approve? is the level of annotation and code-commenting appropriate and helpful? is the formatting clear and satisfactory?

    Is this what you would hope to find on such a page?

    February 21, 2013 on 12:51 am    ~    2 Comments

    Phototactic personality in fruit flies

    first page of the fly phototactic personality paper
    Download the PDF

    a group of flies moving toward a light source, with a single fly moving in the opposite direction

    Do animals as simple as flies have personalities?

    Definitions of personality vary substantially across fields, and are often left implied. The heart of the phenomenon seems to be that individual organisms display idiosyncratic behavioral patterns that persist for a substantial amounts of time. By this definition, flies have abundant personality. The culmination of a couple years of work by Jamey Kain in our lab, our paper on fly personality was just published at PNAS.

    The detection of such personality requires a method to statistically distinguish variability within the behavior of an individual from variability between individuals. If there is more variability between individuals than within (i.e. the observed behavioral distribution is over-dispersed compared to what would be expected from sampling error alone) – and the particular behavioral tendencies of individuals persist on subsequent re-evaluation then you have uncovered personality. There is mounting evidence in organisms ranging from pea aphids to trout exhibit personality in a wide variety of behaviors. We suspect that personality may be universal.

    We came to work on this project while trying to map genetic differences between lab strains of Drosophila simulans that exhibit different light preferences. One runs toward light, while the other runs away from light, when startled. These strains are essentially isogenic, harboring no genetic diversity between individuals, and yet we found that the distribution of behavioral scores within each strain was broader than we’d expect based on sampling error alone (we gave each fly a choice to go toward or away from light 20 times, and thus had a fairly precise estimate of its preference).

    This heterogeneity meant that mapping the genetic underpinnings of the difference in strain mean preference was going to require bigger sample sizes, and consequently be very labor intensive. That’s when we decided to build FlyVac, a platform for the autonomous manipulation of flies to measure phototaxis. That’s also when we realized that fly phototactic idiosyncrasy was an interesting phenomenon on its own.

    So, after a couple years’ work, what have we learned about fly phototactic idiosyncrasy? A number of things:

      • All fly strains seem to have it. Only when we put blind flies into the device, or gave them symmetrical light stimuli did we observe behavioral distributions matching what we’d expect based on sampling error alone. In fact, the phenomenon is not limited to flies. The white clover weevil Ischnopterapion virens performed very similarly.
      • It is persistent. Flies recovered from FlyVac and tested up to 28 days later show significantly correlated phototactic preferences
      • Genetic differences between animals cannot explain their behavioral differences. There isn’t much genetic diversity to begin with in most of the lines we examined, but additionally we inbred them for 10 generations, mating daughters back to fathers or grandfathers (sorry flies). This did not reduce the magnitude of personality; if anything, it amplified it.
      • Personalities cannot be inherited (even by non-genetic means, such as epigenetics). Mating two flies with strong positive (or negative) light preferences had no effect on the behavioral distribution of their progeny. In all cases the progeny had behaviors identically distributed as the parents.
      • The gene white, and the neurotransmitter serotonin (whose synthesis may depend on white) act in wild type flies to suppress personality, driving behavior toward homogeneity.

    Please see our paper for all the gory details:
    Image of the title and authors of the FlyVac Paper

    Why does non-heritable personality exist?

    This will be the focus of forthcoming paper from our lab (hopefully soon). But there are two basic ideas. Personality could be essentially noise, i.e. non-adaptive, but tolerated for some other greater good. Possible greater goods include rapid development, or avoiding the metabolic costs of additional signaling pathways or neurons that would suppress the developmental stochasticity that generates the variability.

    Alternatively, it might be inherently advantageous. Retaining a population with high diversity might mean that when a transient selective pressure arises that favors a subset of animals, they will successfully produce a subsequent generation. If that selective pressure goes away, then the non-heritability of the behaviors means that the subsequent generation will revert to the original (well adapted for typical conditions) distribution of behaviors immediately. Another consideration is that if behaviors are entirely predictable, they can be exploited. If flies always run toward the light, predators will learn this, and any fly that runs away from the light will have an advantage. This is an example of frequency-dependent selection, in which the fitness of a particular phenotype depends on the number of other individuals exhibiting it. Such dynamics often equilibrate to what economists and game-theorists call mixed strategies, when the optimal strategy entails acting randomly from instance to instance.

    Jamey and I have a Q and A conversation about this work in the following video/podcast. If you stick around to the end of the video, we’ll take you on a walking tour of the lab, and show you FlyVac in operation:

    Still frame from movie about FlyVac with Jamey gesturing

    November 15, 2012 on 3:16 am    ~    3 Comments

    Next Page »