Day Length?

[alan]

Every year for the last three years my Mesotriton alpestris apanus have started laying eggs during the first week of April. They are kept in a location where the temperature varies and they receive no artificial light. So how do they know what date it is? Over the years, the temperature has varied, with this year being the warmest on record, but they're still right on time. This suggests day length rather than temperature is the most important trigger for laying.
Any thoughts?

 

[john]

That's a pretty interesting correlation. You should probably test it later in the year by placing them in dark room and slowly ramping up the number to lit hours.

 

[jennifer]

Yes, interesting. I'm trying to recall when my apuanus were laying. They produced some eggs in the fall, then stopped, then started again in Feb. It's possible that their production was correlated to day length, though in my case they have artificial lighting on a timer that I vary by season.

 

[alan]

Then Jenn is best placed to make the experiment! There's a paper in that!