Crystalsucker
The crystalsucker evolved from the carpotesta lucermundare as a result of a series of adaptations developing in the organism. It first developed a more complex digestive system that allowed it to consume and digest more microorganisms. This was followed by a change in behavior in which specimens began to melt and consume the chitinous shells and later the fungal cores of the binucleus crystal shrub. This feeding behavior was then improved with the selection for a leech-like sucker that developed around the mouth as well as the addition of chitinase to their cocktail of digestive enzymes. This ultimately culminated in a liquivorous diet of the binucleus crystal shrub: a species that so far had no predators due to its sheer size and thick armor. Crystalsuckers will feed by latching onto the side of the binucleus crystal shrub with its sucker, sealing the edges and allowing it to force its enzymes directly into the chitinous shell of the binucleus crystal shrub. It will continue to eat through the crystal until it creates a cavity too large for it to successfully fill with enzymes and/or consume the soup of digested matter. They generally are sluggish creatures due to the sparse deep-sea populations of binucleus crystal shrubs. This allows them to conserve energy and travel long distances in search of new crystals to feed on. They are equally as sluggish when feeding and will remain firmly attached to the side of its host until it can no longer feed.
This sluggishness is only broken if it is attacked by its only predator: the carpotesta devoratori. Its has firstly developed simple eyes that allow it to detect the distinctive light pattern of its predator. It has four eyes, with one pair on the top of the head, and another pair at the bottom, effectively giving it a 180 degree field of view from the front. This allows it to better detect incoming attacks. If it detects the light pattern of a carpotesta devoratori, it will use its rearranged muscular structure and improved respiratory system to attempt to outswim it. The crystalsucker has developed gills; water enters through the mouth and passes through them, either forcefully by swimming or passively by turning to face the ocean current. This allows them to strain more oxygen from the oxygen-poor waters of the deep ocean, allowing them to better power their new method of swimming. Their muscular structure mostly involves a series of cartilaginous rods that serve as attachment points in the fins and dorsal side. These are in turn, connected to the crystalsucker's newly developed notochord. From there, the muscles are affixed to the bones and form muscle blocks. This allows them to swim in a sub-carangiaform manner, as opposed to its ancestor's method of swimming which involved it beating its fins. This allows for faster movement and a chance to outswim the carpotesta devoratori. However, this often fails as the carpotesta devoratori will usually outpace the crystalsucker. Therefore, spikes derived from a swollen extension of the cartilaginous elements have developed on the dorsal and ventral fins. This makes them significantly less palatable to its predator, as like the knightworm, they can cause tears in the carpotesta devoratori's stomach. Their bioluminescent pattern has diminished and is concentrated around the fins. This makes it look like a swarm of smaller creatures and increases the chance of the carpotesta devoratori impaling itself on its spikes, as it will focus on the fin due to the small light.
Because it may take incredibly long spans of time for crystalsuckers to find other individuals to mate with, crystalsuckers have become hermaphrodites. They will attempt to mate whenever they come across another member of their species, as such an occasion is typically rare. An even more rare phenomenon is a mating swarm, which occurs around large clusters of binucleus crystal shrubs, which will provide enough food for the crystalsuckers to maintain a dense population for a few months until it ultimately dies off from being ravaged by the ever-growing mating swarm. Crystalsuckers will mate by releasing their games into the open ocean within close proximity to each other, allowing for a higher chance of fertilization.