Not exactly on topic but close enough. Maybe we need a "Fish Science" section for us fish nerds .

A team of scientists led by Richard Broughton, associate professor of biology at the University of Oklahoma, published two studies that dramatically increase understanding of fish evolution and their relationships. They integrated extensive genetic and physical information about specimens to create a new "Tree of Life" for fishes.

April 18th, 2013
The Tree of Life and a New Classification of Bony Fishes
Abstract
The tree of life of fishes is in a state of flux because we still lack a comprehensive phylogeny that includes all major groups. The situation is most critical for a large clade of spiny-finned fishes, traditionally referred to as percomorphs, whose uncertain relationships have plagued ichthyologists for over a century. Most of what we know about the higher-level relationships among fish lineages has been based on morphology, but rapid influx of molecular studies is changing many established systematic concepts. We report a comprehensive molecular phylogeny for bony fishes that includes representatives of all major lineages. DNA sequence data for 21 molecular markers (one mitochondrial and 20 nuclear genes) were collected for 1410 bony fish taxa, plus four tetrapod species and two chondrichthyan outgroups (total 1416 terminals). Bony fish diversity is represented by 1093 genera, 369 families, and all traditionally recognized orders. The maximum likelihood tree provides unprecedented resolution and high bootstrap support for most backbone nodes, defining for the first time a global phylogeny of fishes. The general structure of the tree is in agreement with expectations from previous morphological and molecular studies, but significant new clades arise. Most interestingly, the high degree of uncertainty among percomorphs is now resolved into nine well-supported supraordinal groups. The order Perciformes, considered by many a polyphyletic taxonomic waste basket, is defined for the first time as a monophyletic group in the global phylogeny. A new classification that reflects our phylogenetic hypothesis is proposed to facilitate communication about the newly found structure of the tree of life of fishes. Finally, the molecular phylogeny is calibrated using 60 fossil constraints to produce a comprehensive time tree. The new time-calibrated phylogeny will provide the basis for and stimulate new comparative studies to better understand the evolution of the amazing diversity of fishes.

A totally agree that breeding practices and husbandry can improve any line, including size. What I was saying is when a Platy ends up several times the size it would naturally reach, it's probably made possible by Swordtail genes, since Swordtails can naturally reach a much larger size. Every species maxes out in size at some point, no matter how well they're cared for.

For example, you can selectively breed a Neon Tetra for size but at some point they just won't get any larger... although it would be cool to see a Neon Tetra the size of a salmon...LOL. The same goes for the Platy, but mix in a little of the larger X. helleri and their size potential is drastically increased. It's just one factor that may explain the GIANT Platy specimens.


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Nice shots! Thanks for sharing them with us.

I suspect significant size differences are largely due to Swordtail genes, since the vast majority of fancy strains are hybrids to one degree or another. We can breed for size and end up with larger specimens than would be found in the wild, but I'm betting the giants actually get their size from a Swordtail in their ancestry.

Welcome to the ALA community, Gail. It sounds like the fish bug has bitten you in a big way!

That's a good point. Hopefully outcrossing them with the wilds will do just that.

The food shouldn't have caused it, they can handle pretty much anything. Either there's a deformity/injury or he's had an infection twice and it's a coincidence. Parasites can cause it but you should have noticed other symptoms by now. Let us know how he does.

Thanks for the information & photo of your pretty Guppies, Doug. What I've read agrees with you, it's just elongated Geissen fins that can show up anywhere and doesn't necessarily mean she's a swallow tail, etc. I will have to be patient but waiting isn't my strong suit...LOL. I'm not surprised that they are often weaker fish, as I've found that with many fancy strains.

Platies aren't particularly prone to constipation, which may mean there is an internal defect or damage. What are you feeding?

I'm sure it's distressing to see your fish like that and I hope he feels better soon.

That could certainly be the case with mine. They look like Variatus but they're a bit more... compact, for lack of a better word.