Distinguishing Larvae

[Sean Brady]

I saw some salamander larvae in some small ponds in the southern Adirondacks today. Most of them looked like spotted salmander larvae except for their heads which already looked how they should look full grown. Some of the larvae I saw actually looked like how spotted salamander larvae should look and then I also saw a couple of larvae that looked plain yellow orange. They were definitely mole salamander larvae.
Why did some of the larvae's heads look like a full grown spotted salamander head and some look as they do in the picture below?
http://i.pbase.com/o4/94/339594/1/64377497.UVZYDYrz.IMG_9020.JPG
And what might the other yellow-orange larvae have been?
Also, in all the pictures of these spotted salamander larvae I see such as the one in the link above, none of them have as little gills as the ones I saw. Why is this? Were the ones I saw almost ready to come out of the water. I am guessing they are 4 months old, but I could be wrong.
Thanks.

 

[Slimy2]

I think some of them could have been neotenic which means they will keep their gills into adulthood. They will stay aquatic, gilled adults the rest of their life. However, I'm unsure about the rest of them.

 

[Otterwoman]

I can't access your pictures.

 

[Nathan050793]

I can't see the picture either, but it sounds to me like you saw larvae of varying ages/ stages of development. While some were getting some adult coloration prior to metamorphosis, others weren't at that stage yet.