And now for some Sea dweller talk.
So isozyme made this post, and it was flawless and totally made the genetics work, and also explained oxygen affinities, which I posted a bit before. And then I had a brainwave, cause it also explains a hell of a lot about how seadwellers can breathe both in and out of water.
Seadwellers have basically got the same respiratory system as fish, with gills allowing countercurrent circulation. When a seadweller opens their mouth, the lid over the gills close, and water floods into the mouth as though they had just taken a very deep breath. When their mouth then closes, the lid then opens, allowing the water to flood in. The gills have a bunch of blood vessels in the filaments, and the water flows in one way over the top of them. The blood is flowing the other way. This means that deoxygenated blood is constantly meeting oxygen rich water, and gas transfer can take place. This would be into the red colour pigmented molecules, as there is so much oxygen for the seadwellers. Water has way way more oxygen than air.
The problem however comes when the seadwellers come out onto land. The reason that fish suffocate while on land is that the gill filaments are thin, and will collapse without the pressure of the water on them. However, like the walking catfish, the seadweller has an organ called the suprabranchial arborescent organ. This supports the gill filaments, and prevents them from collapsing on land. It also facilitates the uptake of oxygen from the air and into the bloodstream, kind of like a giant fish lung. However, it won’t allow for much air to be taken in. It’s a good thing those seadwellers have those blue pigmented molecules. These molecules have a much higher oxygen affinity than the red ones, and are capable of removing much more oxygen from the air. This means that the seadwellers can take in relatively little air compared to their land counterparts with their land based systems, and still remove enough oxygen to support themselves!