Water factors in morphing/neoteny

[eljorgo]

Hey All. I just crossed a contradictory line when regarding to water issues on delay of metamorphosis.

I am having a problem with some of my larvae witch are incredibly morphing at super small sized animals Thing is that the info I have is:

Factors that promote metamorphosis:
-->Shallow waters
--> T > ~20ºC
--> [O2] < 1,24 x10^-3 mol^ L-1

Factors that delay metamorphosis OR promote neoteny:
--> Deep waters
--> T< ~20ºC
--> [O2] > 1,24 x10^-3 mol^ L-1

Thing is that this all is serious interrelated:
Oxygen concentration is bigger in shallow waters;
Oxygen solubility in water is as big as lower the temperature is.

So if we have a shallow, hot water pond vs a deep cool pond, witch one will promote neoteny/ delay on metamorphosis?! Remember that the deeper the pond the lower the [O2]. And in shallow waters, despite bigger temps, [O2] is bigger too, witch is a complete mess. I am starting to get really confused. As far as i can see in the end the real factor that triggers both morphing or neoteny is [O2] in water...? No matter the other factors?
:errr:

thanks,
Jorge

 

[JM29]

Nothing contradicory, in fact.
Even if the water is shallow, with hig temperatures, the maximum O2 concentration is lower than with low temperatures.

Température °C
O2 saturation en mg/l
5
12,8
10
11,3
15
10,1
20
9,1
25
8,3
30
7,6

Example for an atmospheric pression of 1013 hPa (hectopascal)

At a given temperature, you will never obtain O2 concentration higher than those indicated.

 

[Azhael]

I would suspect oxygen concentration to be the less important of the factors mentioned, if only because caudates can very easily adapt the gill surface to the existing conditions.

There is also the very important factor of genetics. Although many of the populations that contain neotenic individuals are in deep, cold water, it´s not always the case.

If what you want is to get them to be bigger at metamorphosis i would suggest a big volume of water, lots of plants (if at all possible, use a cycled, well stablished tank) and most importantly, LOTS of food.

This year i´ve had some very small C.pyrrhogaster morphs, very very small....it is indeed not the ideal situation, but it´s not the end of the world either.

 

[eljorgo]

THANK you for both valuable opinions. JM29 I knew [O2] was bigger when the water is cold but the shallow is also a great factor.
Azhael, genetics do not influence in nothing I guess because the parents that breed for me this year were the same that breed for me last year when their larvae morphed around 7cm and now only with 2-3cm.
That might be valiable in neoteny not in delay or quickness of metamorphosis.
Thanks on the advice.

If what you want is to get them to be bigger at metamorphosis i would suggest a big volume of water, lots of plants (if at all possible, use a cycled, well stablished tank) and most importantly, LOTS of food.

Nice to know I did what was right. Now I will wait and pray for them to not morph..

but it´s not the end of the world either.

For me it is, same as death.

Thanks all,

 

[JM29]

To be honest, I'm not sure that water depth is per se a factor.
In shallow water, gas exchanges are surely easier, but light also penetrates the upper layers of the water.
So, shallow water in a permanent shade (or a cave, why not) may not trigger metamorphosis.

There are other factors cited in the litterature, like soluble organic matter, food availability, nitrates or overcrowding.

 

[eljorgo]

Wow! Thank you so much for that info! Never acesses that.

what you said is correct. shallow water 20cm or less with cold temperatures (springs) in caves are the best examples to avoid metamorphosis. One example of caudata doing that is Chioglossa lusitanica. And yeah their larvae stay for centuries in water environment.