Dartons

Dartons include the decedents of the hexdarter and the hexdigger, and are indigenous to Mason. They fill a wide variety of niches, from detrivores, to apex predators, and even parasites.

Anatomy
The common trait that defines dartons from other decedents of the mason hexspourous is their quadrilateral symmetry. Two sets of hardened teeth-analogues line the mouth, which, along with the secondary oral appendages, help break down food for the dartons. Four breathing tubes are set around the body, which not only help to exchange gases but also with movement.

Breathing and Blood
Four breathing tubes help exchange gases, lining the exterior of the body in even intervals. Decedents of the hexdarter force oxygenated water through these, while decedents of the hexdigger the tubes are closed off, and oxygen is absorbed through microscopic holes in them. Like all decedents of the mason hexspourous, their blood is copper based, and therefore blue.

Diet & Energy
All dartons are heterotrophic, although methods vary greatly from lineage to lineage.

Evolution
Both hexdarter and hexdigger evolved from a sub-population of mason hexspourous that expressed quadrilateral symmetry through a rare mutation.

Locomotion
Both branches use their breathing tubes to move; decedents of the hexdarter force water through their breathing tubes, while hexdigger decedents rotate slowly, allowing their twisted breathing tubes to propel them through dirt or flesh.

Reproduction
Dartons are asexual, and either inject eggs into a carcass, or simply let them gestate inside themselves, letting them eat their way out of the parent.

Senses
Dartons have two primary senses, smell and touch. Hexdarter decedents generally have a well developed touch sense, allowing them to form a mental map of their surroundings by detecting vibrations in the water.

Size
The size of dartons varies widely, from just a few millimeters to the some of the largest marine species.

Types of Dartons
Two types of dartons exist, those descended from the hexdarter, and those descended from the hexdigger.