Sunlight Backhugger
The Sunlight Backhugger split from its ancestor and ascended, continuing to parasitize Gills but specifically in the Sunlight Zone. They retain their nomadic habit, automatically detaching if their host moves somewhere too hot, too cold, or too deep. They notably have a preference for one specific host—the Prickle Gill. More specifically, the mating types which have venomous spines. This is because venomous Prickle Gills are less likely to be attacked by predators. Once a Sunlight Backhugger has found a Prickle Gill host it may be unwilling to detach unless forced to by temperature changes, so it will often be bloated on blood by the time it changes hosts. It has fewer isomers per individual than its ancestor, therefore allowing it to have proportionally bigger paddles for swimming.
The Sunlight Backhugger is otherwise much like its ancestor. It can swim between hosts using paddles along its body, and it mates by touching chins and wrapping its tentacles around the head of its mate. Eggs are laid on a host and fertilized externally. Hatchlings feed on the host they hatched on initially, but despite their host preferences they still eventually move to a new host to avoid overcrowding or accidentally killing their host.