Ok I think I understand. Is it obvious if they have cross bred or not? Or if I see any fry just assume they cross bred even if they may not have. I will obey this fish hobby rule of not introducing any cross bred ones but I am curious as to why that is a rule if you don't mind explaining. Also is there a rule like that with cross breeding other types of fish?
Albino Cories
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Externally, you can usually tell a cross by the pattern; it will be different from the parents because it is a mix or combination. In my tank, one cross has been Corydoras axelrodi with I think C. metae; the reason I assume this cross is that the fry, of which there are now three nearly adult, have markings close to C. axelrodi but this fish is a female that has been on its own (no other of this species) for five years now, and it could not possibly produce fertile eggs if a male of another species was not involved in spawning with her. And the C. metae seems the most likely, given the dorsal lateral line on the fry, plus I have spotted the male C.metae (I only have one of these, a male) pursuing her in true spawning interaction, so there is little doubt.
That is how most of us would see a cross. A biologist of course could examine the fish and from the DNA determine the parentage.
Cories are fairly prolific spawners, when they are "happy" in their environment. Most of the eggs get eaten by them or more usually upper fish; if an egg happens to be placed where it goes unnoticed, it may hatch, and the fry can often find food (infusoria and various micro critters among thick plants, wood, etc) to survive and then one day you see the fry. I have also retrieved several over the years from the canister filter whenever I clean it; it is interesting how they can survive in their for weeks, finding food among the thick detritus, and without any light or air.
It is not so much a rule (there is no governing body for this hobby, perhaps unfortunately) as a respect for life on this planet. The issue is not relevant when it comes to livebearers and other hobby species, but when one is dealing with wild fish (as all but a small handful of species of cory will be) the scientific community does not support or encourage cross-breeding. This destroys the pure gene pool of the species if the hybrids should get loose. The day may well come, indeed for some species already has, when the species fry resulting from aquarist spawnings are/will be used to supplement an endangered or replace an extinct species.
This is a scientific hobby, and every responsible aquarist must understand and accept that this is the case. We should have learned by now what happens when humans think they know better and start fiddling with this or that, causing extinctions and loss of habitat. We are dealing with living creatures, part of the huge web of life to which all living things including ourselves belong, and this carries very serious ramifications.
aaah ok that makes sense but I still have one more question.
So guppies are "hobby species" and almost all Cories are "wild fish" what does that mean? Like domesticated vs. not? So guppies from pet store couldn't survive in wild but Cories from pet store could? (hence why we must keep the Cories genes pure so that a crossbreed doesn't get out in the wild and become an invasive alien species?)
So guppies are "hobby species" and almost all Cories are "wild fish" what does that mean? Like domesticated vs. not? So guppies from pet store couldn't survive in wild but Cories from pet store could? (hence why we must keep the Cories genes pure so that a crossbreed doesn't get out in the wild and become an invasive alien species?)
No fish is "domesticated" in the sense of dogs and cats. The species are still natural species (some may be man-bred varieties of the natural species). Wild caught means the fish were collected in their native habitat and exported. Commercially raised means the fish were raised either in tanks or outdoor ponds so they are not wild caught. However, even commercially raised fish that are still the true species and not some human variety could theoretically be released into the habitat to replenish the species in nature. But this is not as easy as it sounds, and I don't need or want to get into all the pitfalls of disease, etc. Most commercially raised fish have been so weakened they can no longer fight off their normal natural disease/pathogens.
Guppies from a pet store might or might not survive in the wild; most likely not. The generations of inbreeding has seriously impacted these fish.
Cross-breeding destroys the gene pool so the species is no longer the true species. Introducing such a species might have dire consequences for the wild fish in the same watercourse, but it also carries the risk of not surviving in any event because it is no longer the same species, biologically.
Viewed from above, females will be broader or plumper than the slender males. This is obvious in mature fish, less so in juveniles. Most species of cory have no external gender differences, but I believe there is one but can't remember which. No matter, the girth is the only guide, and provided the fish are healthy it should be reliable.
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