Arthrofin

The arthrofin split from its ancestor the mud centiworm. It lives much like its ancestor did, staying at the river and scavenging for food as well as eating other rotten organic materials. A mutation has occurred to reactivate the fin genes its ancestor the centifin use to have. This gives it an advantage when swimming, but not enough to displace its ancestor.

Like its ancestors its blue blood filled gill are located behind its head. It uses its 4 mandibles to scoop up food from the bottom. Its three primitive eyes are only used when it can see through the muddy water. Otherwise it relies on touch to navigate through murky waters.

During the rainy season the arthrofin gather in mass at the junction of Nuke and Terra rivers to breed. It takes three sexes to complete the reproduction process: one sperm, one egg and one hormone cell. They release the eggs into the mud, which then hatch within a few days before the rainy season is over.