Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

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Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by bekateen » Mon Nov 27, 2017 10:52 pm

Zabarburú, C.A.C., Koo, F.W.C., Castillo, W.G., del Aguila Panduro, E., Tamani, F.V., & Rios, J.F. (2017). Maximum lethal temperature evaluation for Hypostomus hemicochliodon and Pterygoplichthys pardalis (Loricariidae). Revista Científica UNTRM: Ciencias Naturales e Ingeniería, 2(1), 22-25.

DOI: http://dx.doi.org/10.25127/ucni.v2i1.221

Zabarburú, C.A.C., Koo, F.W.C., Castillo, W.G., del Aguila Panduro, E., Tamani, F.V., & Rios, J.F. (2017). Evaluación de la temperatura letal máxima para Hypostomus hemicochliodon y Pterygoplichthys pardalis (Loricariidae). Revista Científica UNTRM: Ciencias Naturales e Ingeniería, 2(1), 22-25.
Castillo et al. wrote:ABSTRACT
Temperature is a relevant factor in the distribution of fish within their environment, influencing their biology and physiology. The objective of this investigation was to evaluate the maximum lethal temperature (TLM) and three sublethal temperatures (TSL) for brown carachama (Hypostomus hemicochliodon) and black carachama (Pterygoplichthys pardalis). Fry were captured and acclimated to four different temperatures (room temperature, 30, 31 and 32ºC). Four limit temperatures or endpoints (three sublethal and one lethal) were determined for each treatment. The maximum lethal temperatures (TLM) found were for H. hemicochliodon 40,82ºC and for P. pardalis, 41,44ºC both at 32ºC of acclimatization. In addition, there is a direct relationship between the acclimation temperature and the TLM for both species. The size of the fish had no significant influence on thermal tolerance.
*I can't gain access to the full journal article, or to its original abstract as published, so I'm assuming the 82ºC is a typographical error which should more likely read 42ºC.
Castillo et al. wrote:RESUMEN
La temperatura es un factor relevante en la distribución de los peces dentro de su ambiente, influyendo en su biología y fisiología. El objetivo de esta investigación fue evaluar la temperatura letal máxima (TLM) y tres temperaturas subletales (TSL) para carachama parda (Hypostomus hemicochliodon) y carachama negra (Pterygoplichthys pardalis) . Se capturaron alevines y se aclimataron a cuatro diferentes temperaturas (temperatura ambiente, 30, 31y32ºC). Se determinó cuatro temperaturas límite o endpoints (tres subletales y una letal) para cada tratamiento. Las temperaturas letales máximas (TLM) encontradas fueron para H. hemicochliodon 40,82ºC y para P. pardalis, 41,44ºC ambas a 32ºC de aclimatación. Además, existe una relación directa entre la temperatura de aclimatación y la TLM para ambas especies. La talla de los peces no tuvo influencia significativa en la tolerancia térmica.

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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by Bas Pels » Tue Nov 28, 2017 7:48 am

While both does refer to two measurements, I would guess that this both refers to both the group of pardalis and the group of hemicochliodon which had the highest lethal temperature for the 32 C adaptation group.

That is, the lethal temperatures are 40.82 and 41.44 degrees. In Europe we write 4,5 where in English this would be 4.5.

The only thing with this explanation is that I wonder how one can determinde lethallity on a one hunderdth of a degree. Perhaps mathematically, without any concern for the margin of error.

40.82 plus or min 0,56 degree is, to me, 40.2 to 41.5
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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by TwoTankAmin » Wed Nov 29, 2017 8:49 pm

I am not even certain that one tenth degree increments would be all that accurate. I would think a range of perhaps a half degree or so might be a better representation? The other thing I wonder about is the time factor. I would bet that all the fish in a group did not all rollover dead at the exact same moment. Some had to die at slighter lower temperatures while others must have survived even at a bit higher temperature. I am assuming the fatal temperatures are chosen because 50% of the subjects are dead when that temperature is reached.
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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by Bas Pels » Thu Nov 30, 2017 8:09 am

I´ve done toxicity tests when a student, and lethal dosis tests are fairly easy to perform.

You start with, say, 10 tanks, each with the same amount of fish, and at T=0 you add the toxin. Each tank its own concentration. 1 tank without, the very important control group

Then you wait for the fish to die. You either note when one dies, or return each 12 hours to count the corpses and remove them.

The results, as a percentage are put in a diagram, a line is fitted and where the line crosses the 50 % level, that is the LC50 value. LC stands for lethal concentration. Normally, 50 is put in subscript.

It is better to speak of LC5024 or LC5048 - the concentration which kills 50 % in 24 hrs or 48 hrs.

If a fish dies in the control group, something went wrong, and the testing has to start all over again.

Obviously, the hard thing is when to declare a fish to be dead - when it does no longer react to a stimulus, when it does no longer move the operculums or whatever.

in most cases, LD50 tests are very crude, and mesningless. After all, why would we want to know what a certain compound does? I think in order to know how much we can savely eat of it, or spill into the environment.

It is therefore better to determine a no measurable effect level. Those tests are much more complicated, unfortunately.
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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by Lycosid » Fri Dec 01, 2017 2:10 am

Bas Pels wrote:
Thu Nov 30, 2017 8:09 am
in most cases, LD50 tests are very crude, and mesningless. After all, why would we want to know what a certain compound does? I think in order to know how much we can savely eat of it, or spill into the environment.
In my end of the world where LC50's are often measured for venoms or defensive toxins LC50's are fairly reasonable (although straight up LD50's are equally common). If a catfish, say the infamous Plotosus lineatus, injected a LD50 worth of venom into a target in a defensive action then this defensive action will have a high probability of, minimally, crippling the attacker. Similarly, a temperature LD50 seems useful: don't go swimming in water at your LD50 temperature, odds are as good as not that you'll die. (Obviously exposure time matters, too.)

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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by Bas Pels » Fri Dec 01, 2017 10:55 am

You´re right that for venoms which can be injected into a human body such as from catfish the LD50 or LC50 is rather relevant. But that is, mainly, because our body will destroy the venom in case we don´t die from it, and after any exposure, we get back to healthy again.

For snakebites, where muscles degrade, such an approach is less significant
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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by Lycosid » Fri Dec 01, 2017 10:39 pm

So, this wanders off topic a bit, but in the case of temperature where fish recover from heatstroke wouldn't the LT50 be a decent measure?

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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by Bas Pels » Sat Dec 02, 2017 8:22 am

I think the temperature where the fish recover will be somewhat lower than the temperature which kills half the fish in 48 or 96 hours.
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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by Lycosid » Sun Dec 03, 2017 2:09 pm

Bas Pels wrote:
Sat Dec 02, 2017 8:22 am
I think the temperature where the fish recover will be somewhat lower than the temperature which kills half the fish in 48 or 96 hours.
Presumably. I meant that they can recover from approaching the lethal temperature, as long as they don't die.

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Re: Maximal lethal temperatures of Hypostomus hemicochliodon & Pterygoplichthys pardalis

Post by bekateen » Tue Dec 05, 2017 5:08 pm

TwoTankAmin wrote:
Wed Nov 29, 2017 8:49 pm
The other thing I wonder about is the time factor. I would bet that all the fish in a group did not all rollover dead at the exact same moment. Some had to die at slighter lower temperatures while others must have survived even at a bit higher temperature. I am assuming the fatal temperatures are chosen because 50% of the subjects are dead when that temperature is reached.
Bas Pels wrote:
Thu Nov 30, 2017 8:09 am
You start with, say, 10 tanks, each with the same amount of fish, and at T=0 you add the toxin... Then you wait for the fish to die. You either note when one dies, or return each 12 hours to count the corpses and remove them... The results, as a percentage are put in a diagram, a line is fitted and where the line crosses the 50 % level, that is the LC50 value. LC stands for lethal concentration. Normally, 50 is put in subscript... It is better to speak of LC5024 or LC5048 - the concentration which kills 50 % in 24 hrs or 48 hrs.
TTA, Your first comment is more correct, but not universal. Yes, some research protocols progressively raise the temperature on an animal to wait for impairment; other protocols require you dump the animal straight into the temperature of interest (see my comments below on Thermal Shock).

I think most temperature tolerance tests are done by immersing groups of animals straight into a set temperature and waiting: When LT50 tests are done (and assuming they're done properly), scientists usually do not base their results on "when the temperature is reached;" I'm not saying the tests have never been done that way, but rather, usually there is a defined time period of exposure (i.e., how many fish died at XXX degrees after XX minutes of exposure). This is often a very brief period, but does not have to be instantaneous (as @Bas Pels mentioned above for LC50, although often temperature tests are conducted on the order of minutes or only a couple of hours, not over days for upper lethal temperatures).

Also, physiologists refer to both "lethal temperatures" and "incipient lethal temperatures:" Lethal temperatures kill the animals within a very short time period; incipient lethal temperatures do not kill the animal quickly but will ultimately lead to the animal's death if left there long enough (hours or days - this latter type of lethality can be thought of as a type of chronic stress).
Bas Pels wrote:
Thu Nov 30, 2017 8:09 am
Obviously, the hard thing is when to declare a fish to be dead - when it does no longer react to a stimulus, when it does no longer move the operculums or whatever.
And there is also a difference between an animal being dead vs. an animal that stops moving: sub-lethal temperatures may not kill an animal immediately, but if the temperature is sufficiently high to impair nerve or muscle function, then that animal may be "as good as dead" from an ecological perspective in a real-world situation... If it cannot move, it is unable to escape predation or aggression and it might be killed by other organisms rather than by the heat itself.

This becomes particularly important when we are examining animals that do and do not have time to acclimatize to the temperature changes - without time to acclimatize, animals can experience momentary "thermal shock" - impaired vitality due to sudden extreme temperature changes. But after a few moments, the animal may recover and start moving. I must shamefully admit that I did this to my fish once (on the cold end, not the warm end of the temperature spectrum) when I did a mid-winter water change using tap water. The tank was full of corys and Apistogramma agassizii, plus other species. I did an 80% water change and I didn't pay attention to the tap water temperature, which was below 50F going into a 78F aquarium. Almost immediately I noticed my fish twitching and some were floating and listless; I thought for sure that I killed them all. Then about 5 minutes later they started swimming. The next day the corys had the most explosive spawn I'd ever seen. (Note- I am not advocating THERMAL SHOCK to trigger spawning).

Much of this discussion ties back to an earlier conversation on physiological "tolerance polygons." You can read about them here: Re: temperature range for Oxydoras Niger.

One last thing. Here (Lethal Temperatures) is a link to a government publication on thermal limits of aquatic organisms. Although not strictly about fish, it goes into much detail about the types of issues involved. Enjoy. ;-)
Cheers, Eric

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