Re: Insects at K/T boundary

[James Mahaffy <mahaffy@xxxxxxxxx>]

Neale said:

[snip]
> Conclusion - just because some Late Cretaceous animals might have been able
> to hibernate during the (relatively brief and mild?) winters, doesn't mean
> they were likely to fare any better than non-hibernating ones.
> 
> In fact, the reverse might be true - reptile, amphibians and fish respond
> directly to cold temperatures by slowing down and ultimately becoming
> torpid. A rapidly cooled fish or lizard will become lethargic, and
> certainly over days or weeks become prone to disease, predation etc. Ask
> anyone who has kept a tropical fish in a coldwater tank. Do the same to a
> mammal or bird which is not in "winter mode" already and its metabolism
> will bring about rapid use of energy reserves and eventually death if food
> cannot be replaced. For a small mammal or bird, we're talking hours or days
> at most. A fish or lizard can go without food for weeks or months.

Ditto for insects.  They would be able to withstand some cooling
perhaps better than "warm blooded" chaps that normally operate at a
higher temperature.  Like Neale, I doubt if a lot of insect adults would
go into hibernation, but 10 degrees C I lot of them would slow down and
survive.  Even in the case of adults (like lady bird beetles) that can
"hibernate" as adults you can't drop the temperature too low.  I had two
students doing a small project on freezing lady bird beetles this past
semester in Zoology.  The temperature of our freezer in the fridge was
too cold. If memory serves me right it was -16 C and even with cold
pretreatment all the ladybird beetles died.  But when we put them in a
growth chamber at I think (working form memory) -4 they did fine.  Of
course like ladybirds around here they could still withstand colder air
temperature by crawling under leaf litter close to the ground that stays
warmer than the air. 

The critical question is how long is the cold spell and how cold is it
thought to have gotten.  I don't know the K/T literature well enough to
know if there is an answer to that question - but without at least a
general idea, it is hard to predict how insects would be affected. 


-- 
James F. Mahaffy                   e-mail: mahaffy@dordt.edu
Biology Department                 phone: 712 722-6279
Dordt College                      FAX 712 722-1198
Sioux Center, Iowa 51250