Page 132 - AWSAR 2.0

108 || AWSAR Awarded Popular Science Stories - 2019
from that they are exposed to naturally varying time-cues such as light temperature, humidity, etc., hence semi-natural. In contrast, the fly populations in the lab are maintained in a schedule of 12-h of light and 12-h of darkness at a constant temperature of 25°C.”
She interrupted,” First, tell me, why do youusefruitfliesforyourstudyinsteadofsay rats, mice, or humans? Oh, wait. It must be so convenient to store thousands of them in a small space, right?”
“Yes, also fruit flies reproduce quickly, so I can hope to see them evolve during my lifetime, which would be certainly impossible using humans,” I added.
“It does make sense,” she added,” What kind of rhythms do flies have?”
“They have rhythms in locomotor activity, sleep, the emergence of adult flies from pupae, feeding, mating, egg-laying, etc., driven by the circadian clock. Additionally, one can test for RNA or protein concentrations
of a handful of clock genes
at different times of the day
to observe the molecular
oscillation.”, I added.
She had more to ask, “So do you think that in semi-natural conditions, the rhythms of these flies would’ve changed in any manner?”
“Well, I have found some
changes already,” I replied.
“The fly populations reared
in semi-natural conditions
have evolved to have a more
precise activity–rest rhythm,
meaning there is less day to
day variation in the starting of
their activity compared with
the lab-reared fly populations. Also, at a low temperature, more of the flies reared in semi- natural conditions have rhythms persisting, while the lab-reared ones lose their rhythm.
This suggests that in semi-natural conditions their circadian clock may have evolved to become more robust.”, I said.
She looked perplexed, “Aren’t flies ectotherms? So, their circadian rhythm should get slowed down at lower temperatures and quickened at higher temperatures like all biochemical reactions. Right?”
I nodded my head, saying, “It would have been so if circadian clocks were not compensated for temperature changes. There are by-standing mechanisms in the molecular oscillation due to which the biological clock timing remains relatively uninfluenced by temperature fluctuations. Imagine how unreliable circadian clocks would be without that!”
“They wouldn’t have been useful at all because temperature fluctuations are so frequent in nature. Also, I have observed that
like temperature change across seasons, our daily behavior also changes with seasons, for example, most people would like to take a nap instead of working in the hot summer afternoons. Do you think the behavior of your flies reared in natural conditions would also vary with seasons?” she asked expectantly.
“Yes, it does. For the emergence rhythm, the time at which the emergence of adults from the pupae starts occurring varies in the semi-naturally reared flies compared to the lab-reared flies according to the season. In fact, in relatively
harsher seasons, the semi-naturally reared flies start emerging earlier from pupae compared with the lab flies, whereas in a relatively moderate season, there is little or
My objective is to see how circadian rhythms evolve in natural–like environments compared to laboratory ones. To do this, I am looking at rhythms of populations of Drosophila melanogaster, also called fruit flies, reared in standard lab conditions and comparing them with populations reared in an outdoor enclosure, under semi- natural conditions.