?

Log in

No account? Create an account

Previous Entry | Next Entry

Over the last couple of days, I keep thinking about justifications for various kinds of experiments, and the impact of those experiments. It's necessary to consider justifications and impact, especially when one studies organisms that might be dismissed or ignored.

The circadian metabolism project, to me, is inherently cool and interesting because of the uniqueness of the system we work with. The vast majority of research on hormonal differences focuses on huge differences between males and females, but those differences are very extensive and far-reaching. The other major alternative is to work with a well-developed model system where individual genes can be manipulated, but most such systems lack clear connections to natural settings. The closest related work occurs in honey bees, which are still domesticated insects. We don't want this line of work to be pigeonholed as something that applies only to crickets. So we continually have to ask ourselves about the broader implications.

The circadian metabolism project is moving forward nicely. From my initial round of hemolymph collections, we've learned that there are constitutive differences in the total hemolymph volume between the long-winged and short-winged crickets; the long-winged crickets have a lower hemolymph volume across the day. Hemolymph volume also changes in both morphs over the course of the day, increasing towards nightfall. Right now an intrepid undergraduate is working to measure lipids, carbohydrates, and protein in the same samples, so we'll have a good and detailed picture of how these nutrient levels fluctuate across the day, too.

The feeding experiments...progress. I'm just starting the next round this week. The first round was informative but left some large questions unanswered. At first, I was concerned that it looked like the adult crickets might just be feeding randomly when given a choice between two diets because their intake was pretty evenly divided between the dishes. However, the last-instar crickets definitely made a different selection, preferring carbohydrate-biased food over protein-biased food. Perhaps it is unsurprising that juvenile crickets have different nutritional requirements than adult crickets, but if you were to have askd me before this experiment, I would have predicted that the juveniles would want more protein than the adults, not the other way around.

There have been two major confounding factors, however: out of the 34 juvenile crickets I set up, 14 died, and only 2 crickets (both male) developed into long-winged adults. In contrast, the stock colonies tend towards 50-50 production of long-winged and short-winged adults, and only one of the 54 adult crickets died. Supposedly morph fate is locked in by the time crickets reach the last instar, so this could simply reflect the luck of the draw, especially if the short-winged crickets are slower to develop than their long-winged counterparts. Or it could be that something about the diet was inadequate for the long-winged juveniles; the stock diet is more nutrient-rich in protein and carbohydrate, and contains more fat as well.

I've also been interested in determining how group size affects feeding, so for the next round, we're also setting up groups of four crickets.

There are a lot of large unknowns when it comes to how nutritional needs vary across life stages in different kinds of organisms, and about how flexibly organisms can respond in terms of nutrient allocation when confined to suboptimal foods. And we don't know a tremendous amount about how crickets manage nutrient intake in the wild. All of this would be useful to study from a comparative standpoint, because the vast majority of related work has been confined to vertebrates. To what degree are vertebrates weird and special, vs. sharing things in common with smaller-lived, more ubiquitous organisms? There have been heated debates about this recently in the ageing and lifespan literature.

Latest Month

November 2017
S M T W T F S
   1234
567891011
12131415161718
19202122232425
2627282930  

Tags

Powered by LiveJournal.com
Designed by Naoto Kishi