Photo: A large male Green Sailfin Molly from four years ago and one of our breeders used in our attempt to create a giant molly.
For about eight years, I’ve been working to develop a very large Green Sailfin Molly, which I creatively named Giant Green Sailfin Mollies (“GGSM” for short for the rest of this blog). Catchy, right? I have a real knack for naming fish.
While Hurricane Harvey and its aftermath set back most of our molly breeding programs, four of our experimental GGSM breeding colonies survived. They suffered losses, but nothing like our Poecilia species sailfin mollies (those of you who subscribe to our newsletter got a discussion of our molly losses in the June 2019 edition). Unlike the wild Poecilia species, the GGSMs survived in larger numbers and continued to reproduce. They are hybrids and maybe heterosis (hybrid vigor) explains why they did better than the pure species.
For some background, here is a blog about Blue Mollies with an aside about Giant Green Sailfin Mollies.
This last week, we processed one of the four GGSM colonies. This colony originated from a swarm of sailfin hybrids of Poecilia velifera (Bobby Ellermann’s strain), P. petenensis, and P. latipinna. For good measure and to introduce some additional genetic variation, P. mexicana was added to the mix.
The colony’s reproduction was good despite them being polycultured Fossochromis rostratus, a large cichlid from Lake Malawi, Africa.
Some of our breeder females have reached impressive sizes as this photo shows.
For sizing, the grid behind her has one-inch squares. She is not only five inches long, but look at the depth of her body. The new breeding colony consists of a couple of dozen females just like her.
One young male also caught my eye. He looks like he’ll be a hunk. He’s only about three months old and already has a massive build.
The male behind him is a run-of-the-mill fish from the colony who was culled. The breeder males placed back in the breeding colony are about an inch longer. See the male at the top of the blog for comparison. He was added to a different breeding colony (see discussion below) about four years ago and is no longer with us, but his genes survive. Some of our present breeding males look a lot like him. The pictured young male, who is only beginning to show gonopodium development, has a very deep body. I’ll be watching him and will probably move him into the breeding colony next breeding cycle (about December of this year).
I’m working with four breeding colonies to increase the odds of producing a GGSM. Why have four different colonies? I’ll explain. Each of the four colonies started from a different mix of fish:
- I’ve discussed the breeding colony we just processed; it was developed from a deliberate hybridization program.
- Another of the colonies was selected out of a set of matings I was making trying to develop a Blue Sailfin (see blog above). During that process, I found some larger than normal mollies. They were set aside as one breeding colony.
- Yet another arose whenever I found a large molly from any large fish from any of our breeding colonies.
- The fourth one came from some large Marble Sailfin Mollies I found in that breeding colony. Marble Sailfins occasionally throw some Green Sailfins. I picked the largest of these for this colony.
Rather than combining these fish into a single breeding colony, I decided to see if a very large molly could be produced simply by selection within each line. By selecting in each generation only the largest fish in each line, I hoped to concentrate genes for size. Much like humans, mollies have about 30,000 genes. Many of those must be involved in size. I plan to continue this until a line ceases to produce any gain in size, meaning there is no more variation and the potential for this line has been reached.
Once the lines aren’t showing any progress to larger sizes, I’ll begin crossing the lines on the theory that each line likely has a unique set of genes contributing to its large size. By crossing, I hope to combine these gene sets. It could be that there could be a synergistic impact on size by such combinations. We’ll see what happens assuming no more setbacks from hurricanes.
You might see this as the typical process of inbreeding to concentrate beneficial characteristics, in this case large size, and then outcrossing to increase genetic variation. The outcrossing to be followed by another round of inbreeding. This might be a good place to mention the benefits of inbreeding. Inbreeding allows for the removal of deleterious genes and the concentration of good genes. Inbreeding is your friend.
I look forward to processing the three remaining GGSM breeding colonies to see how they are doing. I’ll keep you posted.