Pond Boss Forums INTRO Questions & Observations Documentary of a Texas Georgia Giant

Bob Lusk's comments quoted above got me thinking about the combinations and probabilities in multiple-species hybrids. Counting chromosomes didn't get me back to sleep this morning so I decided to post it.

Let's set up a fictional fish Genus - the Spielekarten group. There are four species, each with 13 pairs of chromosomes, that can interbreed: S. diamante (diamonds), S. assaultus (clubs), S. excavator (spades), and S. cardiac (hearts).

Make two completely disimilar F1 hybrids - clubsXspades and heartsXdiamonds (black F1 and red F1). These two crosses each have 13 chromosomes from both parent species, that is, chromosomes 1 (Ace) through 13 (King) of two separate full suits. Their genetic content is pretty predictable (50% from each parent species) and I would expect the appearance of large numbers of black hybrids to be similar; the same for red hybrids.

Now let's cross the red F1 with the black F1. The red parent's (let's make it the female) chromosome contribution will vary from all hearts to all diamonds. The number of possible combinations of red chromosomes in the red egg is a 13 digit binary number - there are 2 to the 13th (which is 8192) different possible red chromosome combos. Similarly, the black F1 male can contribute 8192 different possible chromosome combinations in his milt, from all spades to all clubs. This means there are 8192 times 8192 (which is 67,108,864) different possible chromosome combinations for the redXblack [(heartsXdiamonds)X(spadesXclubs)] hybrid (I'm not sure "F2" is exactly the correct term but I am going to use it to represent this four-species second generation hybrid).

That's a really large number of variations. And I'd expect to see some intereresting differences in the F2s, because the genetics controlling each trait (stripes, spots, fin size & shape, mouth size, aggressiveness, coloration, etc.) can be either spadesXhearts, spadesXdiamonds, clubsXhearts, or clubsXdiamonds. And with > 67 million different combos, that's gotta be some amazing differences just in the visible traits.

IF GGs are a hybrid of four Lepomis species (a big IF - multiple species seems assured but how many? I don't want Deb to violate her NDA because then she'd have to kill us ) each with 24 chromosomes (IIRC), then each F1 parent can contribute 2 to the 24th or 16,777,216 different chromosomes combos to their eggs/sperm, for a total of 281,474,976,710,656 (that's 281 trillion and some change) different possible combinations of chromosomes and hence traits in my supposed "4-species" GG.

Some of these combinations may well be fatal before hatching or at the fry or small fingerling stage, but if 99.99% of the F2 fertilized eggs and offspring died, that still leaves over 28 billion different combinations of traits for the GG to exhibit. And given the number of offspring that can be produced in a sunfish pond, I'd expect to observe quite a number of them.

So ML, you'd better take a lot of pictures.