pH and evolutionary tolerance

[duanes]

I’ve been doing a little casual research (albeit less than text book) on how long it might take for a species of fish (and the bacteria species it has evolved resistance to, (or not)) looking at history to make adjustments to naturally, and to drastic changes in pH when circumstances force them over time to evolve.
Many aquarists claim, a few years of aquarium breeding may be sufficient to acclimate even some of the most sensitive species to do so.

I’m a little skeptical of those claims, especially because some successful and serious breeders, cater to natural water parameters, where the cichlids they breed, originate.
Living in Panama is a good place to contemplate this natural adjustment, because some of the same species that live in the mineral rich, high pH water here, live in totally opposite water parameters, just across the border in Colombia.
Panama and Colombia are only separated by the Serrania del Darien, Sapo, and Pirre mountain ranges which isolate the two countries and their species at an altitude of 1800 meters, well above where low land species such as tropical cichlids usually traverse.

And the Panamanian mountain range(s) according to geologic theories, only arose from the sea, about 2.5 to 3 million years ago separating the similar species variants from each other.
On the Panamanian side, much the water is mineral rich, with pH at times, above 8, when ancient coral reefs were pushed up from below the sea.
On the Colombian side, pH can drop to as low as 4, and hardly reaches much above 7. And in the much older Andes, rains have long since eroded those coral skeletons away.
Yet similar species are found across both their countries borders.

Andinoacara coeruleopunctus (the smitten image of Andinoacara pulcher) inhabits the high pH, mineral rich waters of Costa Rica, and Panama, and is the only representative of the Andinoacara genus found this far north.
Yet the S American species, Andinoacar pulcher, rivulatus, stalsbergi, biseratus, latifrons, sapyensus, and blombergi are all found west of the Andes far south of the Darien Gap, in drastically different and neutral, water parameters of S America.


Very similarly, only one Geophagine, G crassilabrus is common in Panama, while a few other Geophagines of the red hump clade (G pelligrini, and G steindachneri) are found west and north of the Andes, in neutral parameter conditions, and a host of other Geophagines reside on the east side of the Andes, in markedly soft, low pH water parameters


But not only cichlids.


Whip tail Armored Catfish such as Sturisoma panamense are found in higher pH waters of Panama, while many others of the genus are only common in low pH waters of northern South America.



Other armored catfish of the genus Chaetostoma, are mainly found in South America, yet only species fischeri from that genus is a common rubber lip pleco in areas of Panama bordering the Darien.



That mountain range appeared between 2.5 and 3 million years ago, separating fish on either side of the geological divide, allowing millions of years and many generation of survival of the fittest to adapt, selectively breed and weed out the best or worst suited individuals for each countries water parameter conditions.

 

[duanes]

A more recent species transfer occurred in the 1960s when 6 Cichla species escaped their pond into lake Gatun.
In only less than 60 years they have come to dominate the predatory cichlid species of lake Gatun, and migrated to other lakes like Bayano, and Arenosa, and its tributaries to the point where endemic cichlids are becoming hard to find in the main lake bodies. Many smaller species are being edged out into smaller rivers by invasive species such as the Cichla, introduced African Tilapines and aquarium releases (?) of South American Oscars.



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[Toby_H]

This is very interesting. And of course there are far more factors at play than we could ever list or understand.

With your explaination, "rains have long since eroded those coral skeletons away." I would assume the Colombian side also got those corals, also saw that spike in mineral rich water, forcing local species to adapt or die out, then the corals depleted and the local waters reverted back. If that is accurate the flip-flop adds to the curiosity.

We're also at a disadvantage, as we are considering the impact of 2.5-3 million years of evolution with only being able to witness species from a single time frame. Who knows what species existed in the middle. I'd wonder if the flip-flop I described actually happened, if the Colombian specimen streamlined like they did on the Panamanian side, then became diverse after the water softened again.

I think the suspicion that, "a few years of aquarium breeding may be sufficient to acclimate even some of the most sensitive species to do so." is closer to the example your second post outlined. A few specimen being thrust into differing water parameters and either learning (evolving) to thrive, or suffering.

And in this later example, I think each species may or may not thrive each parameter change.
There may also be impacts we could never perceive. For example, if the fish mostly thrived in the new parameters, but a single organ suffered, we wouldn't recognize this. And if it caused a fish with the potential to live 12 years die in 8 years, most of us would think 8 years was a good long life.

Considerations like this are very interesting to ponder... but at the end of the day I have to accept I simply don't have enough data to draw a conclusion, nor do I have the formulas to properly consider all the data.

 

[jjohnwm]

Interesting indeed. I'm sure that the degree of adaptability will vary significantly from species to species. Another aspect of it is species whose natural range is large enough that it encompasses a wide range of differing chemical parameters and/or temperature differentials.

I've been thinking about this a bit lately, toying with the idea of experimenting with a couple of species that I find appealing. I let my basement aquariums sit at ambient temperatures, which drops as low as 50-55F during the winter and then naturally increases to near 70F in summer. This works great for goldfish, many gymnos, some other cichlids, many livebearers, Garras, catfish, etc.

Three species that I find particularly appealing are Black Ghost Knifefish (Apteronotus albifrons), Pterodoras granulosus catfish, and South American Lungfish (Lepidosiren paradoxus). They all have fairly wide ranges that extend to the equator or close to it, but also reach southwards into the cool waters near Uruguay. Soft acidic water in the north end of their range, but harder and more alkaline at the southern extreme. The specimens that are available in the trade always seem to come from the warmer end of this range, but I'm curious as to how adaptable these specimens would be to a slow and gradual alteration to the opposite extreme.

At the moment I have only one, a small SA Lungfish "rescued" from a lad whose mother was on the verge of flushing it away! I had one of these for years back in Ontario, kept at the standard recommendation of around 78F; this new one has spent the past few months at 68F and is active, appears healthy and shows good appetite and decent growth. He originated from the northern end of his natural range, but was already living well in the hard (250ppm) and somewhat alkaline (7.5pH) tap water of his previous owner's home. My well water, which I do not treat in any way, is more like 325pm and 7.5pH, so even further from the water he originally came from.

I will likely drop the temperature very gradually at the end of summer and observe the reaction. And a LFS has a couple of small granulosus cats in stock; hmmm.....

In the example of the Cichla in Lake Gatun, it seems likely that only a certain percentage of the escapees survived and bred, with each successive generation being naturally selected for its adaptability to the unnatural (for them) conditions.

In my case, I realize that I am not about to see actual evolution taking place in one specimen of Lungfish. Just curious to see how adaptable the fish are as individuals rather than as a species.

 

[duanes]

The uplift of the Andes mountain range was 30 to 40 million years ago, making the more recent rise up lifting bridge of Panama and Costa Rica only 3 million years ago between the Americas quite recent, in geologic time, and may acount for the lack of erosion of ancient carbonates still hardening water parameters in here , in rivers where collect cichlids in Panama. (compared to soft low pH waters in S America.)

Very similar to the American great lakes water parameters , those lakes were formed only 14,000 years ago.
Lake Michigan pH is still high, and water quite hard, averaging 8.4 pH and over 250 mg/L hardness, where I collected daily samples working as a chemist at a water purification plant on the lake.

 

[tiger15]

Until the rise of the Panama bridge about 3 million years ago, the South American continent was separated from the North America continent for eons. CA was part of the NA continent. There were no Cichlid in CA until the land bridge was formed, but the evolution of cichlid in CA into many species was very fast. On the other end, Africa was connected to SA for eons until split up of the Gonguana land about 70 millions years ago. This is why Africa and SA share more common fishes such cichlid and characin than in NA.

Adult fish can adapt to different pH and water chemistry much easier than spawning as having the wrong pH or chemistry can impede egg hatching. Many saltwater fish are found in the Panama canal but not established because they cannot spawn successfully. pH adaptation is a slow evolution process and given enough time, all fish can adapt to different environment by natural selection of the survivors.

Not all SA waters are acidic. Water on the Pacific slope of the Andes are neutral to alkaline. Water in southern Brazil and Argentina, and white water in the Amazon and Orinoco basins tend to be neutral.

Cichla ocellaris was introduced to South Florida in the 80s as game fish. Now you can catch peacock bass in S. Florida canals regularly, out numbering other exotic species.