Cyprinodontiformes vivíparos e ovovivíparos
Biologia > Temperatura
Biology > Temperature
Water temperature it is one of the mainly and most important impacts on fish physiology.
Science describes all known freshwater fish species as poikilothermic.
This means that body temperature follows closely that of their environment.
Biochemical reaction rates are largely in function of temperature and, at this point, we can set a large difference between animnals like fish and homiotherm animals like man…
Actually, many “ cold-blooded “ animals, and fishes in particular, thermoregulate behaviorally and not physiologically.
In addition, water temperature can also represent a prevailing influence on biological as well on physical performance of fishes.
To see how it works, take for instance the oxygen solubility in water.
It has an inverse relationship with water thermal progress but, in contrast, metabolic process intensity increases with warmer temperatures. In very specific situations, when this take place, adequate dissolved oxygen can than fall below essential levels for most fishes respiration.
As behavioral thermoregulation is forced by the temperatures available in the environment, a fish’s temperature can be assumed to be generally around 1ºC or 2ºC different to the adjacent water.
All natural subsistence processes are regulated and strongly dependent from temperature, so any little variation can produce an instant effect.
Physiologic functions, growth speed, nourishment level, breathing rate, metabolic process and even homeostasis are directly dependent on water temperature.
Once near or within most favourable values range, fish’s metabolism increases operational rate as well as continued existence process efficiency.
On next image we can realise water temperature effect on some physiologic and metabolic progression in Gambusia holbrooki.
Every species can survive only in a thermal array stuck between two limits, maximum critical temperature ( CTmax ) and minimum critical temperature ( CTmin ). These two critical limits are casually expressed only as survival limits on this website.
They represent temperatures that species can tolerate only for minutes to less than one hour long.
Above this without returning back to more favourable environment there aren’t any chances of recovery and death is almost certain.
The best decrease or increases some fish can perform are some hours or at least minutes of endurance extend if properly acclimated to this extremes.
The range where species can overcome more than minutes or hours is positioned flanked by minimum sub lethal temperature or incipient lower lethal temperatures ( ILLT ) and maximum sub lethal temperatures or upper incipient lethal temperatures ( UILT ).
Above UILT or below ILLT, although death can overcome to some individuals, as near as fishes are from sub lethal temperatures, higher are their probabilities of lower mortality levels or acclimatising capacity for continued existence during longer period under those unfavourable conditions.
Below the UILT and above ILLT just to the ideal ( optimum ) temperatures narrow range limits, fishes can live with more or less complications.
Their physiologic processes can suffer from some level of reliability shoddier but in effect, as a rule, there is no trouble to stay alive.
Ideal or optimal temperatures are roughly in the middle of incipient lethal temperatures array.
Inside this range, physiologic mechanisms accomplish an most favourable routine. It is expected that species arrive at a highest physical and biological performance, achieve a high metabolic efficiency. Under these circumstances breeding can take place and immunity get to uppermost effectiveness.
As we can see, any deviation from ideal temperatures upper and lower limits can impose fish some kind of effect on subsistence.
Very well acclimated, almost all species can adjust a little above superior or under lower limits.
This margin however doesn’t go further than a few ºC.
There are restrictions to this ability that depend upon species potential to withstand this challenge as well as some populations or individual resistance.
The capacity to overcome usual temperature limitations in upper and lower edges can depend much on natural habitat location.
Species with vast geographical distribution, in particular when some populations are more capable to stand on adverse temperatures due to history evolution, are more elective to show enhanced resistance individuals, above all if they are indigenous from those marginal regions.
Due to habitat sort of climate we can find stenothermal species ( can olny survive in a narrow thermal range ) and eurythermal species ( are adapted to a wide thermal range ) species–specific array.
To ensure proper living conditions, in any case of the above mentioned classes, species must be held under specific suitable global thermal range.
It is not acceptable maintain fish only submitted to a narrow part inside optimal temperatures array all year round. Depending on the seasons, to more or less all the species it is even crucial than occasionally they can stand under slightly below or above ideal temperatures.
Never forget than many livebearer tooth carps are native from water bodies where daily thermal amplitude is significant.
A few species are even native from regions where the four seasons are very distinctive and need to fluctuate seasonally as in temperate and subtropical original locations with large annual temperature ranges.
It is strongly advisable to study very well any potential fish derivation typical weather.
A good temperature management can avoid numerous health problems to aquarium kept fishes.
One unfortunately very widespread mistake is when you keep your fishes constantly at the same optimal temperature. Aquarium fishes are this way hold for extensively wide-ranging periods, ( that can go as long as a year ), at same constant temperature.
Deviation can even reach some values flanked by lower and upper optimal limits and UILT or ILLT boundaries for some time.
Captivity Guppy strains ( Poecilia reticulata ) show better performance and achieve the highest fry production rates between 25ºC and 27ºC.
Above 30ºC adult giving birth females and young fry mortality increase as well as degeneration of ovaries and reduced brood size are more and more frequent.
In contrast, as long the permanence below incipient lower lethal temperatures larger and substantial will be the suffered damages.
Recovery is very slow as well as recuperation or convalescence can go as several times longer.
For each day submitted to adverse temperatures means that several days are needed beneath optimal conditions to restore fish form and recover.
As next to critical temperatures they have been live in, more indispensable and extended will be a recovery period under optimal limits.
Another temperature close relation is host–parasite dynamics.
Parasite transmission depends on host condition, but also very much of a proper environment, ( water with accurate quality ), and… basically an correct temperature.
Without adverse seasonally fluctuation, a limiting factor on the standing stock of fish’s parasites, they can propagate continuously.
This way natural dormancy cycles are over and this may cause increased parasite loads due to greater than before transmission opportunity.
Some can even develop medicine and fish’s natural defenses resistance, as they have the chance to produce constantly new generations with improved genetic quality to face these threats.
Invariable thermal management will also affect fish susceptibility as parasite abundances and infectivity can not change with temperature.
This can become in deed an excellent environment for some piscine pathogenesis.
In some occasions a simple short period temperature change in aquarium is enough to reduce the impact of certain pathogenic agents as well their embarrassment without chemicals use.
Individual immunity although can drop in face of overcrowding and osmotic stress is also affected by intense cold or heat.
Another interesting factor is the effect of temperature on toxicity.
Studies that examine the toxicity of certain pollutants, like organophosphates and heavy metals, to fish have generally found that toxic effects increase with hotness.
Scientific studies have shown a correlation between temperature and pollutant uptake with predictable accumulation.
It is not difficult to predict why, because this increased uptake is thought to result from increased metabolic rates at warmer temperatures.
Nevertheless, for the reason, in the presence of clean waters, pollutant decrease can also take place at higher rates under higher temperatures.
Growth is also much correlated with temperature, as we can appreciate on the graphic.
It can be uninterrupted or irregular, depending on the sort of climate and extent of seasonal warm weather.
If fish development depends a great deal on proper temperature range, by contrast, excessive heat can also have the opposite effect.
In the vicinity of upper incipient lethal temperatures, growth decrease. Further on, near critical upper limit it nearly stops, similar to when fish carry on in intense cold on the opposite extreme.
Similar to enlargement, nourishment consumption it is also significantly underneath a thermal regime straight association.
Warming generates an instantly metabolic acceleration and, as consequence a power demand that can only be compensated by sustenance.
When food abundance and nutritive diet can be within fish’s resources, this process will be complete on the whole. Otherwise, unsatisfied power demand can live fish to death in result of usual metabolic and physiologic course burning up.
Besides climate issues that you can read on the convenient section of this website, some other specific situations regarding a particular region indigenous species must be considered here.
To a better understanding of temperature demands related to these species you should consider paying a visit to the Livebearer Cyprinodontiformes approximated ancient geographical distribution map.
The geographical allocation results very often from thermal considerations and not imposed by substantial geologic barriers. In consequence, some Livebearer Cyprinodontiformes are restricted by type of weather as well as average temperature and height above sea level, both in native range as well as at introduction resultant numerous new territories.
Cold is a survival restraint however annual growth season can also be put in cause. In extreme examples, lack of warm can delay proper sexual maturity accomplished in a useful period of time to provide next generation with enough breeders on subsequently procreation season.