Backhugger
The backhugger split from its ancestor when some jockey charnlit larvae settled on the backs of twilight gills. While some developed normally, others retained their organ systems into adulthood. Then, more mutation accumulated, ultimately giving rise to the backhugger.
The backhugger has changed dramatically from its ancestor. It lies flat against the back of its host and holds on using suckers on its tentacles and frond. Four of its holdfast tentacles have atrophied away, while the other four are used for sensory and grabbing onto the host. Muscles similar to that of the lituslug are found in the backhugger’s isomers, and are used for locomotion. The last isomer on its body has been modified into a lobed ‘tail’ that buds off to form a larva.
The backhugger’s internal organs have changed to an even greater degree than its exterior. The nutrient ducts from the larvae now branch throughout the body, with the largest ducts running in between the isomers. From there, smaller capillaries branch off into the isomers themselves. There, they supply nutrients to the muscles and interface with the digestive surface. It is at this conjunction between the digestive surface and the nutrient ducts where nutrients are transferred into the body and wastes are expelled. The nutrient ducts also run through the cephalon, supplying oxygen and nutrients to the brain, tentacle muscles, and sensory organs. The nervous system runs along the sides of the nutrient ducts, and is centered around a brain in the cephalon. The backhugger has also developed nephridia in each of its isomers.
The backhugger has developed gonads on the bottom of its head. Backhuggers mate by pressing the bottoms of their heads together while wrapping their tentacles around the other mate’s head. This amplexus-like behavior keeps the gonads in contact and ensures that the gametes fuse. The eggs are then adhered to the host.
The larvae have changed little from their ancestors. They remain solitary and simple. In order to conserve energy while they search for a host, they will move sluggishly unless disturbed. Once the larvae detects a nearby twilight gill, it will swim over to it and attempt to land on its back, where it will metamorphose into an adult. These larvae can be produced sexually from eggs, or asexually from budding.