Been fiddling with the genetics of Inland Karraguls' 3 sex system on and off, figured I'd actually share some of it. Note that the chromosome letters are placeholders because I found myself getting too confused if I used other letters. Needed to Earthify it. The sex names are also placeholders.
Originally, I was playing with ploidy levels, with some individuals being triploid and some diploid. Unfortunately, the issue of making triploid individuals practically sterile messed with things. I wanted one of the sexes to not directly be involved in intercourse but still contribute gametes, but have now realised that was unnecessarily convoluted for what was just a cool image in my head. Hopefully the new system is still unnecessarily convoluted, but in a way that's more realistic to actual biology :)
Anyway, ancestral Karraguls had two sexes: "X0" and "XX", with sex determination based on the number of "X" chromosomes. They'd be somewhat equivalent to male and hermaphrodite in terrestrial animals. Coastal Karraguls still have these two sexes, but Inland Karraguls may be headed towards another speciation event, with "Y" diverging abruptly from "X" due to an inverted supergene. Although it is normal for up to 50% of eggs to be inviable, over that amount is seen as very undesirable, so "guardians" and "divergents" don't usually mate with intent to reproduce.
"G" meanwhile, further back in evolutionary history, was originally part of another chromosome that fragmented. Its genetic information is still necessary for development, so if there are no copies, the embryo is inviable. However, without the original surrounding genes as a buffer, two copies are also lethal. It's a bit of a shit show. The "G" breakage became established in the genome during a dry era that limited resources because, well, it's easier to feed your children when half of them come out dead. Free food and fewer mouths.
