Why you need to be a guppy mechanic

Micariff

Recently someone who had read my last blog about the MC1R gene asked me why they should care. Not an easy question to answer in an email.

The MC1R gene plays a role in the manufacture of black pigment in guppies and most other animals. So understanding the role of the MC1R gene involves understanding how guppy black color is produced. It is a complex process, like the manufacture of a modern car, with many parts and many interlinked processes. Does knowing how a car is put together make you a better driver? Obviously not, if that is all you do with a car. But if you own a car it helps to understand how it is put together when something goes wrong. Truth is everything in the biological process of color formation in the domesticated guppy has gone wrong. It has multiple mutations affecting the manufacture and distribution of color pigments. If you don't have a clue about how pigments are manufactured you don't have a clue about what makes guppies special and different from most other fish.

The only people who don't have to think about color pathways in the guppy are those who have them as pets or use them to adorn a planted community tank. Even guppy collectors or people competing in guppy competitions benefit from knowing how color is put together in the guppy. That is why there is a lot of lore about how to breed and maintain well known strains like the American guppies or the European show guppies. But this knowledge has come largely from trial and error. For example the lore in the hobby is that the Micariff came from a cross between a half-black red and a snakeskin.

I have been trying to find out if this guppy tale has any basis in fact by attempting the cross. I have young F1s from the cross and so far there is no sign of the Micariff phenotype. The first generation males are what Asians call "dragons," guppies with half-black bodies and snakeskin influenced spotted fins and front of body patterns. I will have to wait until the second generation to see if any Micariff phenotypes emerge. If the Micariff phenotype does not emerge in the F2, I will not have definitively proven the theory wrong. But doubt will be cast on the theory of its origins.

This is the problem with such hobbyist information. Isolated and unrelated observations abound. There is no connecting thread. However if the Micariff phenotype was related to the melanocortin signalling pathway and its MC1R gene, the mysterious origin of the Micariff has the potential to be solved by examining seemingly totally unrelated strains for congruences. The analogy is to a car. If the car does not start, it does not immediately mean the starter is dysfunctional. It could be out of gas. Or the battery may be dead. Somebody who never climbed into a car before would not have a clue.

My own knowledge of what is under the hood in cars is entirely the result of what mechanics have told me when something went wrong. Long ago, this came back to bite me when my Volkswagen beetle broke down outside a small BC town. I had it towed into a local garage and told the mechanic that I had a problem with my timing chain. This diagnosis was meant to warn the mechanic that I knew a thing or two about cars. It was said out of fear I would be taken advantage of. He looked at me and laughed. "They don't have a timing chain," he told me. From that moment on I was at his mercy. I think I still had my shirt on when I left town in my repaired car and damaged ego.

I don't know the genetics of the Micariff, except that the snakeskin gene or genes does play a role. In the past I outcrossed a Micariff to a non-snakeskin and got snakeskins in the F1. I am guessing that the half-black gene has something to do with the full metallic body. It turns out the full metal color of the Micariff shares something common with the Asian Full Platinum. The Asian Full Platinum is a half-black guppy. How can a half-body black pattern be responsible for a full body metal pattern? It turns out that the half-black pattern is actually a full body black pattern. There is a protein that suppresses the expression of black color in the front of the body. And it turns out that black color cells and metal color cells (iridophores) can have an inverse relationship. One is expressed in the place of the other. I also know that the snakeskin phenotype can be converted into a full metal guppy with the appropriate metal gene, like the magenta gene. A magenta snakeskin is a full body blue metal guppy. Given that the snakeskin is composed of islands of black color cells in a sea of metal color cells (iridophores) that would be a good place to look. Find a gene that causes the snakeskin pattern to break down to a full metal pattern.

I am putting my neck out here. My knowledge of guppy color pathways is not complete, and my prediction could be wrong. I risk a damaged ego :) But my studies of the guppy's and other fishes color pathways is liable to serve me well here. Unlike my knowledge of cars which is partial, sporadic and unconnected, my knowledge of guppy genetics and color biology is more thorough. So like a mechanic trying to figure out why the car won't start, I know where to look and what the symptoms of the problem mean. The construction and operation of cars is well known and documented in the owner's manual. So far guppy color and pattern does not come with an owner's manual. But some day it will That is what the article on the MC1R makes possible.  And that is why it is important to study and understand the MC1R gene. That is why it is important to "get under the hood" of the guppy, with the manual in one hand and a Punnet Square in the other.