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rebeccmeisterI'm sometimes hesitant to write about intellectual projects while they are midstream to avoid somehow scooping myself. But I think I might be on reasonable ground at the moment, just given the specifics of the system I'm working with and the effort that would be involved in duplicating my work. So.
At the moment, the main topic on my to-do list involves learning more about life-history evolution, nutrition, and respiration. This came from a coauthor's recommendation to explore more of the Drosophila literature on the topic. He and one of his collaborators have written a couple of excellent, insightful book chapters in a pair of the previously mentioned books on evolution. Both chapters review the literature on life-history evolution in two main study organisms, the humble fruit fly Drosophila melanogaster and in wing-dimorphic crickets, my current study organism. For some of my work to date, I've been able to skip over a bunch of the Drosophila literature, but now it's becoming more relevant. Here's an attempt to explain why.
For the next "current manuscript," I have measured cricket respiration rates. Respiration, the consumption of oxygen and production of carbon dioxide, is often studied as a gestalt, whole-animal phenomenon. It has been measured in a tremendously wide range of organisms, and is generally used as a proxy for whole-animal metabolic rate (if one wanted a direct measure, one would need to put one's study subject in a bomb calorimeter and measure heat production; this gets logistically finicky). From my standpoint, there are then two ways to look at the data. One way is to ask, "Why does whole-animal metabolic rate vary between individuals?" I've spent a considerable amount of time trying to dig through the literature that examines this question, but kept feeling like I was coming up short when it came time to talking about the specifics of the system I'm working with, and how to talk about the results from our experiment.
Instead, in the evolutionary literature, the question tends to be something more like, "How are different life-history traits related to each other, in an evolutionary sense?" For Drosophila, this involves conducting selection experiments, where thousands of fruit flies are subjected to some specific environmental perturbation over a series of generations. Then, characteristics of the descendant flies are measured. For instance, a carton of 500 adult flies might be put into a container that lacks a moisture source, and then after about half of the flies perish, the remaining flies get to reproduce and the children get subjected to the same regime. When the grand-flies reach adulthood, different characteristics might then get measured and compared to a control population - for instance, resting metabolism, fat stores, activity levels, molecular underpinnings, et cetera.
Back to the crickets. I am not working with ordinary crickets. I'm actually working with selected populations of crickets. They haven't been selected in the same fashion as my fly example - instead, when these crickets reach adulthood, in one box, all of the adult crickets with long wings get to reproduce. In another box, all of the adult crickets with short wings get to reproduce. Over time, this has resulted in nearly pure-breeding populations of long-winged or short-winged adults. Our coauthor's research program has consisted of looking at the correlated characteristics that differ between these two selected populations, to determine the underlying physiological mechanisms that have generated a trade-off between flight and reproduction that occurs in these crickets.
Flight is a metabolically expensive activity. That's a fancy way of saying it takes energy to fly. On the standard lab diet, the long-wing crickets store up more fat as flight fuel, compared to the short-winged crickets. Their flight muscles are also way more metabolically active. However, the two cricket lines have similar whole-animal metabolic rates - and this pattern is consistent across a range of diet contexts. So I'm tasked with putting this finding in a meaningful context.
I think I'm finding what I'm looking for in the Drosophila literature, but boy has it been a labor-intensive project to reach this point. That's the difference, however, between an adequate manuscript and a good manuscript.
And with that, I've got to run off, but hopefully I've left myself enough breadcrumbs to be able to pick up with this work soon.
At the moment, the main topic on my to-do list involves learning more about life-history evolution, nutrition, and respiration. This came from a coauthor's recommendation to explore more of the Drosophila literature on the topic. He and one of his collaborators have written a couple of excellent, insightful book chapters in a pair of the previously mentioned books on evolution. Both chapters review the literature on life-history evolution in two main study organisms, the humble fruit fly Drosophila melanogaster and in wing-dimorphic crickets, my current study organism. For some of my work to date, I've been able to skip over a bunch of the Drosophila literature, but now it's becoming more relevant. Here's an attempt to explain why.
For the next "current manuscript," I have measured cricket respiration rates. Respiration, the consumption of oxygen and production of carbon dioxide, is often studied as a gestalt, whole-animal phenomenon. It has been measured in a tremendously wide range of organisms, and is generally used as a proxy for whole-animal metabolic rate (if one wanted a direct measure, one would need to put one's study subject in a bomb calorimeter and measure heat production; this gets logistically finicky). From my standpoint, there are then two ways to look at the data. One way is to ask, "Why does whole-animal metabolic rate vary between individuals?" I've spent a considerable amount of time trying to dig through the literature that examines this question, but kept feeling like I was coming up short when it came time to talking about the specifics of the system I'm working with, and how to talk about the results from our experiment.
Instead, in the evolutionary literature, the question tends to be something more like, "How are different life-history traits related to each other, in an evolutionary sense?" For Drosophila, this involves conducting selection experiments, where thousands of fruit flies are subjected to some specific environmental perturbation over a series of generations. Then, characteristics of the descendant flies are measured. For instance, a carton of 500 adult flies might be put into a container that lacks a moisture source, and then after about half of the flies perish, the remaining flies get to reproduce and the children get subjected to the same regime. When the grand-flies reach adulthood, different characteristics might then get measured and compared to a control population - for instance, resting metabolism, fat stores, activity levels, molecular underpinnings, et cetera.
Back to the crickets. I am not working with ordinary crickets. I'm actually working with selected populations of crickets. They haven't been selected in the same fashion as my fly example - instead, when these crickets reach adulthood, in one box, all of the adult crickets with long wings get to reproduce. In another box, all of the adult crickets with short wings get to reproduce. Over time, this has resulted in nearly pure-breeding populations of long-winged or short-winged adults. Our coauthor's research program has consisted of looking at the correlated characteristics that differ between these two selected populations, to determine the underlying physiological mechanisms that have generated a trade-off between flight and reproduction that occurs in these crickets.
Flight is a metabolically expensive activity. That's a fancy way of saying it takes energy to fly. On the standard lab diet, the long-wing crickets store up more fat as flight fuel, compared to the short-winged crickets. Their flight muscles are also way more metabolically active. However, the two cricket lines have similar whole-animal metabolic rates - and this pattern is consistent across a range of diet contexts. So I'm tasked with putting this finding in a meaningful context.
I think I'm finding what I'm looking for in the Drosophila literature, but boy has it been a labor-intensive project to reach this point. That's the difference, however, between an adequate manuscript and a good manuscript.
And with that, I've got to run off, but hopefully I've left myself enough breadcrumbs to be able to pick up with this work soon.
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überkrikketen!
Date: 2014-08-30 06:32 pm (UTC)We actually don't know all that much about the "why," for crickets. However, the species characteristic of wing polymorphism, where some individuals are flight-capable and others are not, is a fairly widespread characteristic among insects. The hypotheses for why are fairly straightforward (largely, dispersal to reach patchy resources), but they can be supremely difficult to test - think hours and weeks of marking individuals that are primarily night-active, then trying to hunt them down. There are a handful of short-range radio telemetry experiments that have been conducted, but I think most of those have been in somewhat different contexts (day-active species that are not polymorphic).
The thing that's especially interesting is that wing polymorphism appears to be an evolutionarily stable condition, so populations maintain certain ratios of polymorphism. But then, even that has only been sketchily studied for particular species.
Our collaborator and I would LOVE to be able to get back out to the field to test a number of things in a real-world setting, but it has been difficult if not impossible to convince funding agencies that this is an invaluable aspect of this scientific work.
Re: überkrikketen!
Date: 2014-08-30 07:05 pm (UTC)Huh! I would have said it goes hand in hand. I mean, the long-winged ones must have other metabolic differences to maintain the peak power requirements for climbing flight... beyond fat storage, I mean.
The hypotheses for why are fairly straightforward (largely, dispersal to reach patchy resources), but they can be supremely difficult to test.
Yeah, that's more or less what I meant by "range expansion": they can cover more ground per unit time, maybe even per unit energy, given how dense vegetation is on their scale.
The testing part's gotten easier, I think. I've read that folks studying bees have gotten pretty good results with tiny radio transponders on the bees (I think RFID gear) and big fixed-base transcievers to generate and collect the signals from them.
Our collaborator and I would LOVE to be able to get back out to the field to test a number of things in a real-world setting, but it has been difficult if not impossible to convince funding agencies that this is an invaluable aspect of this scientific work.
Sure. So find a practical example -- there are plenty of (distantly) related species that are agricultural pests -- and hit up USDA or industry. Industry spends on R&D on scales matched only by NIH, DOD, and NASA, in that order, I think.
(Industry does publish some, and they give a little unrestricted funding for basic academic work.)
Re: überkrikketen!
Date: 2014-08-30 07:53 pm (UTC)My understanding of what people are doing with RFID is that there are still some technological limitations in terms of scanning capabilities, so most applications have involved setting up scanners at nest entrances. But I haven't been keeping super-careful tabs on these things, partly because I got really tired of people making suggestions about how to automate my behavioral observations of leafcutter ants without understanding how much troubleshooting has to go into fine-tuning such systems for a particular biological system (e.g. hard to video tape ants that travel underneath the fungus garden).
The funding situation is not quite so simple as that, because a person also has to have a specific institutional status to obtain funding (either at a university, nonprofit, or in industry). I could see the utility of transferring to a system that could be studied in the context of both basic and applied research, but there is often a LOT of legwork involved in making that kind of switch between organisms if one wishes to do it correctly (fine-tuning rearing conditions, figuring out what's known about natural history, figuring out breeding possibilities, etc.). At the moment, most of the type of work that I'm doing has been done only in fruit flies and crickets.
Re: überkrikketen!
Date: 2014-08-30 10:46 pm (UTC)And, um, don't get me wrong: I'm not saying either that there's just pots of gold lying around for the taking or that switching to other organisms is easy. Having worked on mumble, mumble and mumble, mrph, mumble as an academic, I'm really clear why we have model systems and why we stick to them. Even in industry-land, there are models used for a lot of things, because reality doesn't actually want to be studied. It doesn't object, of course, but it's not like it's gonna help us either. :)