With all the bristlenose colour morphs floating about, it’s worth a look at how they get that way. New contributor Alice Bignell takes a deep dive into catfish genes.
ALICE BIGNELL Alice is owner of In The Bag! Tropical Fish UK, and the creator of the Pleco Pops range of catfish food.
It’s probably one of the most asked questions in the pleco community. Amidst the hundreds of identification and food related queries, the concept of creating a different coloured fish as the result of selective pairing is an exciting prospect not just for beginners but also for seasoned breeders.
It’s not a very straightforward question to answer though—responses will vary from individual anecdotes, photographs of batches of fry, those who are avidly against crossing different colours, and those who believe it takes years to do.
Armed with not much more than a plethora of responses to such questions, I set out one afternoon, just for fun, to come up with some hypothetical explanation for it all.
Dominant and recessive
If you’ve heard of Mendelian Genetics before, proposed by George Mendel in the 1860’s, the concept is that there are both ‘dominant’ and ‘recessive’ genes which interact with each other in pairs. Many of us will be familiar with the concept of Punnet Squares from our school biology lessons—different eye colours and different colours of sheep are used to represent how different genes are expressed when the parent sheep are crossed.
Some readers might even remember the big browser-based online Pet Sim craze of the ‘90s and ‘00s and perhaps have a sound grasp of things like horse genetics. A more recent popularity boom in different ‘morphs’ of pet snakes also works in a similar way—royal (or ball) pythons come in a huge array of colours and there are dozens of known genes that can combine to create different looking animals.
Now, bristlenose catfish are a lot more simple than royal pythons, thankfully. When I first began, I was under the impression that there were just seven bristlenose colours: brown, albino, blue eye lemon, red, calico, and the newer colours, white and green. However, it became apparent that there are three or possibly four different kinds of albino, all with varying spots and various genes that get them there.
Mendel himself did warn that his theory may have some limitations, and some traits may be what’s known as Non-Mendelian. The pairs of ‘genes’ I’m referring to are actually called alleles, and this all assumes that bristlenose genetics are based on two alleles; the gene is made up of t
