Bunnie1978 wrote:Just another thought about hybrid fish...
We call all these different fish, that have been named by whomever it is that does so, different "species" without really understanding what that means. Most definitions of "species" include a population of individuals which can breed to produce viable offspring.
This is not entirely true. It is indeed one definition of species, but for various reasons it is not a viable concept in science, even if it was true for all "species" that we know of [and it is not - there are plenty of species of animals that are scientifically described as a species, where it can and will cross and form viable (and fertile!) offspring with another described species]. The other way around is true - if two individuals (that are otherwise healthy and fertile) can NOT breed and form viable, fertile offspring, they are indeed NOT the same species. And it is still the definition given in most start/medium level biology books - you need to get fairly high into the education of biology before the detailed distinction between this definition and a more upto-date and more accurate definition gets meaningful for the general public.
The main problem with this principle, besides the conclusion that all Hypancistrus are one species - which I think nearly all serious fish-scientists will agree they are NOT, is that it's very difficult to prove in science. Some animals are VERY difficult to breed under ideal "laboratory" circumstances, e.g. a salmon that travels several thousand miles on it's journey from feeding to breeding grounds - so you take two supposedly different species and reproduce this travel effect. And if they breed, you then have to reverse the travel, then do the same thing again, and maybe 3-4 years later we could have viable offspring. And I'm sure that's not even the worse scenario. Large animals like whales would be nigh on impossible, likewise animals with large territory and aggressive behaviour. And we have plenty of plecos (and other fish) that have never been bred in captivity - if we as hobbyists can't breed them, the scientists that have little experience in keeping fish outside of alcohol and formaldehyde, it seems unlikely that they will have more luck... How would you describe a single fish - it's clearly different from everything we've found, but they live at 4000m under sea-level, and they only got a single one, because food is so scarce that they can't get another one [and it was dead when it got to the surface, due to the pressure loss in being dragged up to surface!]
Further, if you try to scientifically describe, using the above principle, say, Hypancistrus zebra, how many different species would you have to "try" before you can determine for sure that it's not going to breed with it's similar species? How long do you keep the male or female H. zebra with each opposite sex other species?
I don't believe it's even possible to have a (relatively simple) single species concept that covers fungi, plants, bacteria and animals. I've got some reading material that I've received from a scientist on this particular subject (which is part of a 500 page book, but I've only got "the best bits"). It's not particularly easy to digest, so I've only read about a quarter of it so far, and it would be very unfair to try to describe what my understanding is until I've at least completed ONE of the two articles I'm trying to read.
Our catagorizing fish with very small differences in their appearence or genetics or perhaps based solely on their location of origin is not the "natural" way of defining species as most of the fish from certain families CAN and WILL interbreed, producing viable offspring that can pass their new combination of traits on to the next generation, in a sense outcrossing, like breeders of highly domesticated fish do to strengthen the genetic lines. I think it's more appropriate to think of the L-numbers classification (within family) as a sort of racial profile. I am white, so I might have a different L-number than my hispanic friend. Make sense?
L-numbers do make a difference based on location. Scientists do use this to HELP define a species, but if there is no difference other than location, in science, that is the same species. If there is tiny differences between one population and another (e.g. the spots are slightly more yellow in one population and more white in another), then that would PERHAPS mean that it's a different species. It would depend on the scientist examining the fish - it becomes a judgment as to how much of a difference makes a different species, and what isn't.
I don't think we can really compare humans with wild-caught fish, as the general difference between humans is their (historical) location and adaption to that (lighter skin further north, to allow Vitamin D production, darker skin further south [assuming northern hemisphere] to avoid skin cancer). But in an L-number concept, then yes, humans that originate from different parts of the world would definitely be classified as different L-numbers [no matter where they are NOW, just like L129 is L129 whether you live in the US or live in England - it is L129 because it was caught in a particular river in Venezuela, not based on where it was, for example, purchased or bred].
Understand, I am not advocating crossbreeding. I believe that responsible fish breeders should make every attempt to preserve the beauty of fish created by God in nature without our influence. But really, is there such a thing? Are there any bodies of water not affected by humans? Is it reasonable to conclude that there are any places humans have seen that we have not affected the natural order of things, including breeding behavior of native fish?
I do agree that humans have in various forms meddled with nature for a long time, and there are very few places in the world that isn't AT ALL touched by humans. However, that is different from the subject of this discussion, which involves the INTENDED breeding of species [loosely defined] that are distinctly different in shape and/or pattern and/or location. I don't suggest that humans should unnecessarily interfere in nature, but it's certainly not the same thing that the native population in South America catches fish in the river, and us trying to breed "prettier" versions of wild fish...
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Mats
There are several strains of so-called L173 in captivity, and that can be because around Belo Monte you can find very similar looking L173 that may actually carry quite different genes. This will show itself when they are bred further in captivity. But the breeders will sell all their offspring as L173 even though only a few of the fish look like their nice parents - because they see no other way to get rid of them.
). A huge number of Ukraine breed Sturisoma are these hybrids.
