K.S.Parthasarathy
Date:01/11/2007 URL: http://www.thehindu.com/thehindu/seta/2007/11/01/
stories/2007110151122300.htm Sci Tech
Will cockroaches emerge as survivors of a nuclear war?
Everyone expects cockroaches to survive a nuclear war. If cockroaches are close to the ‘epicentre,’ they will be incinerated because of the intense heat. The legend is built on the notion that cockroaches are radiation resistant.
Safe testing
Recently, ‘myth-busters’ of the Discovery Channel decided to settle the issue once and for all. Kari Byron, the TV hostess, revealed that the radiation resistance of cockroaches was in their list of myths from day one.
The TV team had to convince the Discovery Channel that they can do the testing safely (Tri-city Herald, October 19, 2007). Kari Byron noted that people are just scared when they hear radiation. She attributes this to the availability of “too many zombie movies”.
Routine use
It appears that the Channel does not know that industry routinely uses hundreds of irradiators all over the world safely to expose thousands of samples of food, medicine and surgical products to precisely known radiation doses. Irradiating a few hundred roaches is no big deal! Byron’s team will expose 200 ‘farm fresh’ cockroaches, bought from a scientific supply company.
Different doses
The staff of Pacific Northwest National Laboratory will assist the TV team to expose the cockroaches to different doses of gamma radiation using an irradiator located in the basement of a building at Hanford.
A group of 50 cockroaches, left unexposed will serve as control. The second group of 50 will receive 1000 rads. The third and fourth groups of 50 will have to suffer doses of 10,000 rads and 100,000 rads respectively. (Rad is a unit of radiation dose; a dose of 450 rads may kill 50 per cent of the persons exposed).
To add insult to injury, the experimenters will confine the beasts to small boxes to ensure uniform doses to each group! They plan to expose flour beetles and fruit-flies to similar doses.
The team faces some logistic problems. The exposed insects must reach San Francisco for close observation.
They cannot fly them as airlines will not let them in the passenger cabin; they cannot be placed in the baggage hold without wrecking the experiment (PhySorg.com, 2007).
Final destination
Grant Imahara, electronics and radio-control specialist of the TV Channel revealed that they have to maintain reasonable temperature and humidity so that the cockroaches will not go into shock. A ‘mythbusters’ employee will drive them to the final destination in San Francisco.
Tri-city Herald quoted Michelle Johnson, a technical group manager of the national lab as saying that the show presents good examples of scientific method and encourages developing a questioning attitude.
Gamma irradiation
“I have been told that cockroaches are more resistant to radiation and in a world nuclear war, only the cockroaches would survive. But I have not seen any publication that discusses it with any credibility… I have irradiated cockroaches and constructed killing curves for them using gamma irradiation… my opinion is that insects in general would be relatively resistant to radiation compared to non-insects…” Joseph G. Kunkel, Professor of Biology, at the University of Massachusetts at Amherst, who maintains a cockroach home page, asserted.
The lives of insects revolve around their molting (periodical shedding and renewal of the outer skin) cycles. “During a molting cycle the cells of the insect divide usually only once.
“This is encoded in Dyar’s Rule, i.e. insects double their weight at each molt and thus their cells need to divide only once per molting cycle”, he wrote.
“Cells are most sensitive to radiation when they are dividing. Now if a typical cockroach molts at most once a week, its cells usually divide within a 48-hour period within that week...about 3/4 of the cockroaches would not have cells that are particularly radiation sensitive at any one time.
“If a killing radiation is endured by a cockroach and human population, then 3/4 of the cockroaches might survive while none of the humans might survive since our blood stem-cells and immune stem-cells are dividing all the time”, he clarified.
Four months from now, we may get an answer when Discovery Channel airs its show!
K.S. PARTHASARATHY
Former Secretary, AERB
ksparth@yahoo.co.uk
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