Monday, April 23, 2012

Wood frogs still calling

Wood frog adults and eggs appear to have survived the freezing temperatures last week. This frog species is well adapted to cold (it is the only amphibian in Alaska) and has started calling again after a break during the cold weather over the last week or so.

On Friday afternoon last week there were many frogs calling in Duluth parks and backyards. In a pond in Hartley Park, the wood frogs were making a huge racket (along with one spring peeper).
Wood Frog eggs in Hartley Park (about 2 weeks old)

Some wood frogs laid eggs 2 weeks ago, and many of these eggs are developing well. The small black embryos are elongated with visible heads and tails. In some locations they have started to emerge from the gelatinous envelopes of the eggs, but are not yet free-swimming. In the egg masses that I have been following, there are also many that are not developing due to the cold temperatures or other causes.
Developing wood frog embryos (black) in egg masses turned green from symbiotic algae (notice the dead eggs, which have almost entirely white centers)  

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