A Big Breakthrough in Guppy Research?

There has been a lot of new and exciting things happening in my fish room and under my microscope in the last week.

I did an extensive study of some magenta guppies at two different ages. Three months ago a young magenta's caudal fin were revealed under the microscope to be quite bizarre.

Caudal fin of a three month old magenta at 100x.

I did not know what to make of the cells. They are abnormal because they are small and round, with no dendritic extensions. The wild type red and yellow color cells are normally quite diffuse, with an indistinct edge. Also wild yellow and red color cells are quite different in size and shape. On top of that the red color cells in this magenta looked quite orange.

When I examined them again four months later, I got a big surprise. The yellow color cells had disappeared. I thought this might be peculiar to my strain but my observation received independent confirmation when my friend Junichi Ito told me that a member of his forum was a veternarian (Mr. Matsukura) with a microscope and had made the exact same observation using his lab microscope.

That was huge! I wondered why I had not noticed that there are no yellow magentas. Why had nobody else noticed? It took two guys working independently of each other to come to that observation through the tunnel of a microscope...unless I am mistaken and it was noticed by somebody else somewhere else.

Obviously magenta is a mutation that affects all classes of color cells. It causes yellow color cells to become red color cells when the guppy matures, demonstrating a principle I have often stated in my publications that you have to pay attention to how color cells develop over time. The pigment color cells seem arrested in development, not getting beyond the small punctate shape. The iridophores proliferate.

There is something very interesting about the missing yellow in magentas. It causes snakeskins with the magenta gene (at least lace snakeskins) to become metallic guppies, losing their snakeskin pattern. It's well known effect in the Moscow is to produce the Flamenco Dancer phenotype, again a guppy with an overabundance of iridophores and a proliferation of red in the fins. The color blue goes to purple. 

I think this adds evidence to a theory about yellow color cells that is accepted in Zebrafish research, but has never been established in guppy research. Yellow color cells are necessary for stripe formation in Zebrafish...and they apparently are  necessary for snakeskin patterns in guppies. I am about to publish another microscope study of a Kaden Lace Snakeskin on the books site, where I see yellow color cells more or less evenly distributed in the skin...and also having the rounded punctate shape. I suspect that the yellow color cells are necessary to the formation of the  lace pattern, although I plan to do some studies of coarse cobra snakeskins in the next few days for comparison.

There is another very interesting finding that emerged from my correspondence with Junichi Ito. In the discussion photos album of the Guppy Designer facebook page I posted a picture of a Tangerine guppy kindly provided to me by Jun. It is an Endler with the magenta gene. The guppy is a distinct orange tangerine color. But the same gene incorporated into a guppy instead of an Endler produces a magenta guppy. I have long thought there was something peculiar about Endler color, and this study by Junichi nails one aspect to a gene. This magenta gene has turned out to be a valuable tool in the hobbyist geneticist tool kit now that its effect on  color cell development is better understood.

There is another case where the patterns on the guppy break down and the other guppy color cells fail to develop properly. That's the homozygous blau. The homozygous blau is missing yellow color cells. The heterozygous blau, which keeps its stripes, has yellow color cells but no red color cells.

I have always wondered why wild type guppies (and most if not all domestic guppies) are born with yellow color cells. Perhaps they need them for proper development and deployment of all classes of color cells. Or more especially, maybe there is a protein involved in the development of yellow color cells that is shared by other color cells, or performs a role in their development.

If all of this holds true through further studies, then this is a big breakthrough in our understanding of guppy genetics.

My microscope studies published on the books site are like field notes to a new exploration of guppy color. The value of the microscope as an observation tool has already proven itself after only a handful of entries. I am feeling very optimistic that in the next year major progress is going to be made in the understanding of how many common guppy mutations affect the development and expression of the color cells. (It makes the base body system of classifying guppies fairly useless to the guppy geneticist.) At the end of the studies, when they have been properly analyzed, a powerful set of genetics tools will emerge to make further substantial progress for guppy genetics possible. Imagine being able to precisely target what types  of color cells to genetically remove from a guppy.

I was going to blog about some other discoveries I have made (particularly on the Galaxy), but this blog is long enough.

You can discuss this blog on the Guppy Designer facebook discussion page.

Philip