26-02-2024, 10:48 AM
Cryptofertility in Endler livebearers is absolutely fascinating. There was a project in Germany where the researchers put a trio or two in a pond and left them to get on with life undisturbed for two years before checking their genetics. They expected a lot of inbreeding, but found none. From there they went on to discover the females could select sperm packets from specific males to fertilse their eggs, by tagging the packets in a way that allowed the female to give preference to the males they chose over the many opportunistic partners they were forced to encounter. And often, it was not the flamboyant dominant male they chose - the researchers postulating that those males used more energy, and had shorter lives by way of being more attractive to both predation and environmental threats.
I chose Endlers this time round because they are unusual in several ways. They are a fairly recent addition to the international market, being discovered in the 30s and then forgotten until the 70s, and they are a family still being studied in various institutions outside of Venezuela. They are tiny fish, smaller than other guppy species, and different in other ways too, and as you say because they interbreed so readily with other poecilia their types are easily muddied and lost, and new lines created once the breeding stabilises. The tigers I have are probably one of those newer forms, but one of the other interesting things about them is they can throw back to the wild type on rare occasions, something I really hope happens in my tank. A wild form is exactly what I would really like to have, but my search indicates they are present in some South Island aquariums, but not so common in the north.
The gender change thing is fascinating, and some tropical fish definitely have that ability, an evolutionary adaptation to environments where populations can be trapped perhaps, by seasonal rainfall changes. Like the ability to breathe air, or to leap out of one puddle as it dries up, to find another, or to slow metabolism to such a point a fish can survive in the mud layer of a dried up pond, till water returns. But it is a major physical transformation, akin to a caterpillar becoming a butterfly, so I suspect hermaphroditism is more likely. Especially in guppies, which are often inbred in home aquaria, and the results are not always positive. The varieties of form among guppies are truly wondrous, I can see why they are one of the most popular fish.
But oh I so want a wild type Endler! Just one would do! I would give him his own tank and a harem of nubile brides...
I chose Endlers this time round because they are unusual in several ways. They are a fairly recent addition to the international market, being discovered in the 30s and then forgotten until the 70s, and they are a family still being studied in various institutions outside of Venezuela. They are tiny fish, smaller than other guppy species, and different in other ways too, and as you say because they interbreed so readily with other poecilia their types are easily muddied and lost, and new lines created once the breeding stabilises. The tigers I have are probably one of those newer forms, but one of the other interesting things about them is they can throw back to the wild type on rare occasions, something I really hope happens in my tank. A wild form is exactly what I would really like to have, but my search indicates they are present in some South Island aquariums, but not so common in the north.
The gender change thing is fascinating, and some tropical fish definitely have that ability, an evolutionary adaptation to environments where populations can be trapped perhaps, by seasonal rainfall changes. Like the ability to breathe air, or to leap out of one puddle as it dries up, to find another, or to slow metabolism to such a point a fish can survive in the mud layer of a dried up pond, till water returns. But it is a major physical transformation, akin to a caterpillar becoming a butterfly, so I suspect hermaphroditism is more likely. Especially in guppies, which are often inbred in home aquaria, and the results are not always positive. The varieties of form among guppies are truly wondrous, I can see why they are one of the most popular fish.
But oh I so want a wild type Endler! Just one would do! I would give him his own tank and a harem of nubile brides...