@Doodledibob My guess is that the low population density (individuals per square mile) & solitary nature coupled with the timeless, featureless nature of their environment are what drove this.
If a species has high population density or is fairly social, then when a female is ready to reproduce there are likely a few males around that can fertilize her. And if the species is low population and solitary they can they can use the changing seasons or time of day to coordinate their mating periods or scent mark landmarks to let others know they are the are and are fertile.
So what likely happened is that the males that stayed near the female, reproduced more than the males that were nomadic & relied on chance encounters because they were more likely to be near a female when she was ready to reproduce. So that right there would force pair bonding.
Next comes the shrinking of the males. Sperm is cheap and eggs are expensive in terms of calories. So every calorie that is utilized by the female in the pair bond results in more offspring for the couple than if it went to male. So males that are smaller have more offspring. Eventually the males probably got so small they probably started to live off the female's dead scales, scraps, parasites, and waste.
Then one day a male bit a little too deep when cleaning his female and started living off her blood. From there the diminishing of organs kicks in. Remember the golden rule for him, the more calories that he let's the female have, the more offspring he has. The less digestion the male does to the blood, the more calories and oxygen it provides to him. So there goes the digestive system and gills. And the blood was already the perfect medium to support him, so out goes the liver and several glands. He is no longer having to find his own food, so out goes the brain, bones, muscles and most of the skin. When all is done he is has deferred all of the calories he can to the female except for those necessary for him to reproduce.
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@Doodledibob My guess is that the low population density (individuals per square mile) & solitary nature coupled with the timeless, featureless nature of their environment are what drove this.
If a species has high population density or is fairly social, then when a female is ready to reproduce there are likely a few males around that can fertilize her. And if the species is low population and solitary they can they can use the changing seasons or time of day to coordinate their mating periods or scent mark landmarks to let others know they are the are and are fertile.
So what likely happened is that the males that stayed near the female, reproduced more than the males that were nomadic & relied on chance encounters because they were more likely to be near a female when she was ready to reproduce. So that right there would force pair bonding.
Next comes the shrinking of the males. Sperm is cheap and eggs are expensive in terms of calories. So every calorie that is utilized by the female in the pair bond results in more offspring for the couple than if it went to male. So males that are smaller have more offspring. Eventually the males probably got so small they probably started to live off the female's dead scales, scraps, parasites, and waste.
Then one day a male bit a little too deep when cleaning his female and started living off her blood. From there the diminishing of organs kicks in. Remember the golden rule for him, the more calories that he let's the female have, the more offspring he has. The less digestion the male does to the blood, the more calories and oxygen it provides to him. So there goes the digestive system and gills. And the blood was already the perfect medium to support him, so out goes the liver and several glands. He is no longer having to find his own food, so out goes the brain, bones, muscles and most of the skin. When all is done he is has deferred all of the calories he can to the female except for those necessary for him to reproduce.