Speculative creature design that displays sexual dimorphism.
This species displays a high degree of sexual dimorphism. The male retains its larval form and develops an elastic, balloon-like airsac that is inflated with the gases that are the byproduct of the floating microbes in the atmosphere. Females grow to a colossal size and are much rarer, appearing in a ratio of one female to a million males. They spend most of their life as a deep sea predator, and when they become sexually mature, they rise to the surface to mate. They have a display of red and green feathery appendages which exhibit bioluminescent receptacles that attract males. The bioluminescence of the receptacles is produced through the same methane and hydrogen byproducts that keep the males afloat. The males mate with the receptacles and sperm is transported through the appendages to the female's ovaries.