Many amphibian species morph faster in shrinking pond, etc. What causes this?

[Bill B]

The subject header says it all, pretty much. I've done a little searching, and I have access to a LOT of electronic resources of journals, but I don't quite know where to start.

Bill

 

[SludgeMunkey]

Primarily it is generally accepted that the change is triggered by a combination of things- age, photoperiod, water temperature, population density, and food availability. It is different for each species, though significant similarities exist.

This is a tough topic to research from scratch, but I would suggest starting with keywords like metamorphosis trigger, larval development, developmental embryology and the like in caudates or urodeles. I suspect though one would be hard pressed to find a specific paper on just this subject. Not too many folks work with caudates these days it seems.

I'll have to do some digging here, I have a few that discuss various ambystomids, a common developmental model, somewhere.

 

[mikebenard]

The work coming out of Bob Denver's lab at University of Michigan is a good place:

Denver Lab at the University of Michigan

 

[Neotenic_Jaymes]

What causes shrinking ponds? Current weather conditions affect ponds especially ponds not surrounded by woods or trees. Dry hot weather dries up unprotected ponds easily. Amount of spring rains make a big difference also. I visited a couple ponds this year that usually don't dry up but were completely dry when I saw them. Michigan summer was intense this year.

What causes amphibian larvae in ponds to morph faster? Amphibian larvae are affected by temperature especially. There are many factors that come into play when a pond is shrinking. Density becomes a major factor and I'm assuming the water chemistry changes. Try keeping lots tadpoles in a tank with a heater. You'll have tons of tadpoles with a moving metabolism and they'll morph real fast. Do the opposite and keep 1 tadpole in a tank kept at cool temps and you could have tadpole for 2 years.

This is just my shallow response, didn't want to make a long response.

 

[caleb]

'metamorphic plasticity' would be another good term to search for.

This has been quite well studied in natterjack toads, and temperature and density seem to be the most important factors in that species.

 

[Bill B]

'metamorphic plasticity' would be another good term to search for.

This has been quite well studied in natterjack toads, and temperature and density seem to be the most important factors in that species.

What about the density seems to be the factors? Seeing other larvae, which causes stress?

 

[Neotenic_Jaymes]

What about the density seems to be the factors? Seeing other larvae, which causes stress?

Being crowded. Being in close quarters with other larvae is stressful. I've been to ponds where it was very crowded and dense due to the pond drying up. Everything from tadpoles to newt larvae to salamander larvae had nipped tails. With water levels low the ambient temperature was a lot higher, metabolisms were up. Not to mention the constant use of energy used to evade and dodge every other second because there's a lack of hiding spots in high density.

 

[Bill B]

Ponds which have Wood Frogs especially have nipped tails in them. I visited pond a couple summers ago, and it was crowded with Gray Treefrog and Wood Frog tadpoles. The Wood Frog tads had apparently nipped off tads of Grays and fellow Woods.

 

[Azhael]

In some cases it´s known that the concentration of specific chemicals that are released by the animals cause physiological responses that cascade into hormonal shifts. I suppose the mere sight of conspecifics could also be a factor, but i don´t know that this has been confirmed in amphibians.

All the factors that have been mentioned, like temperature, photoperiod, food availability, etc, ultimately cause direct physiological responses.

 

[caleb]

In some cases it´s known that the concentration of specific chemicals that are released by the animals cause physiological responses

Microbes can be involved as well- tadpole growth has been shown to be affected by increased amounts of particular yeasts, for example. I don't know if this is known to affect metamorphosis, though.

 

[curtpw]

As has been mentioned previously on the thread, there are all kinds of factors which have been empirically proven to contribute (temperature, oxygen, population density, etc). But that isn't nearly as interesting as what might be happening at a physiological level. There is plenty in the lit that will measure hormone levels etc under various environmental conditions, especially growth hormone, thyroid hormones, prolactin etc. What really needs to happen is research into the epigenetics of caudate metamorphosis. If anyone knows of anything interesting and wants to share links please feel free, definately something I'd like to learn more about. Impact of environmental factors on caudate metamorphosis has epigenetics written all over it.