By Philip Shaddock
Originally published on the Guppy Designer website
Pictured is an image of a guppy embryo I captured with my new digital microscope. The microscope has such a shallow depth of field at 400X magnification that I had to capture several images at different focusing distances and combine them in Photoshop to present the entire embryo in focus. The mother was a wild type guppy.
The yellow globules at the center are the embryos food, since guppy fry cannot take sustenance from their mother.
What’s really interesting is the location and size of the black color cells. You can see them on the embryo’s head and back. They originate in an area of the guppy body called the neural crest, which is roughly where the spine will develop later in development. They migrate from the neural crest to the rest of the guppy body.
Recently I “surveyed” my colorless guppies (the See-Thru) and wild type guppies I sourced from Brazil. By “survey” I mean I have been shooting specific areas of the guppy’s body at the three main magnification levels of my microscope, and storing the images in a structured document with annotations. I plan to survey all the main guppy mutants, from Moscows to Full Reds, cataloging the color cells I find and eventually analyzing them. This will form the basis for the third and final book in what has become a trilogy of books on guppies.
It is indeed like a geological survey of the kind done in North America in the 18th and 19th century. Although there have been a few scientific papers on guppy color cells, they have all been on wild type guppies, with the exception of a paper on some black mutant color cells. So I am exploring virgin territory.
I am sure you might wander what, if anything, I will find. My mission is to create a book of facts about guppy color. These facts will provide a much better basis for developing theories of color inheritance. Imagine being able to discuss a guppy mutant in terms of the actual color cells. Without a microscope, you must describe what you see with vague terms like “green color.” But seen under a microscope there is no green color, but rather a mixture of blue iridophores and yellow xanthophores. There is no green gene.
In my work I have long talked about white iridophores, but I have not actually directly observed them. I assumed that white metallic color is due to white iridophores, but like the color green, the factual basis for the observation was not completely solid. As a result of a recent study that is no longer the case. Here is a picture of a white iridophore, found in the caudal fin of my See-thru guppies.
Iridophores in the caudal fin of a male See-Thru guppy. 400X
Looking at this photo, my friend Oscar Inostroza remarked on the colored dots seen in the iridophore seen just below the yellow color cell in the picture. In fact a white iridophore reflects all the colors, but because of the lumpy, chaotic structure of the iridophore, the light is scattered and mixes again to appear white to your eyes.
This is what I will be doing across all the guppy strains that I study with the microscope. Removing conjecture and second hand information from my work and replacing it with first hand factual observation.
The colors we see in the guppy come from color cells. But there are not simply red, yellow, black, blue, silver or white color cells. The yellow dot you see in the picture above is a yellow color cell. But it is a yellow color cell of one of many types. Finding the specific color cells associated with certain mutations is going to help base descriptions of mutations on a more solid basis of facts.
Another example is the magenta mutation. I have done some preliminary studies of the magenta color cells and found a peculiar type of red color cell in them.
Red, yellow and black color cells in the caudal fin of a magenta Moscow.
I call them peculiar because the wild type of red color cell is very diffuse, with a very hazy outline.
Red color cells in a red spot on a wild type guppy.
In thinking and speculating about the magenta mutation, the microscope studies will help me reason on a much more solid basis of facts then I would have using only my eyes or a camera image.
I am going to keep an open mind as I go through my survey. I am not looking for evidence to support a theory. I am building a library of facts I can come back to when a theory arises elsewhere.
It is a well known truism that you need to get your facts straight before you theorize about what you see. That’s what the microscope studies are going to do for me.