Etenus Hominidae is an upright mammalian species adept at swimming and breathing underwater from Malisk II. The species stems from a strong and hardy group of primitive fishlike primates known as the Helduns. Species in this group are all carnivorous or omnivorous, and their land-inhabiting relatives are similar in this regard. While Eteno on average have the same muscle mass as other species of greater stature, they are exceptionally muscular for their small height.
The Eteno are short, humanoid, dark yellow-skinned creatures with smooth, hairless skin. Their dark yellow flesh pigmentation is a result of the yellow flora that covered Malisk II's landmasses for much of its history. The uniquely colored skin lends itself well to camoflauge. Eteno possess two hands with five individual digits each, as well as two feet with five webbed toes for faster swimming.
Their two forward-facing eyes allow for greater depth perception, and have a second set of transparent eyelids under their first set of opaque skin eyelids. This film protects the eyes when underwater, where early Eteno spent much of their time. To make up for a below-average sense of hearing, Eteno are capable of seeing in the infrared, a trait developed due to the great infrared emission of their planet's star, Sius. This infrared vision capability is mixed with regular color vision to create a unique heat glow effect on top of full color perception. This improved sense of sight proves very useful in combat or when hunting for food, as it enables Eteno to better pick out camoflauged prey or enemies even at great distance. As omnivores, they possess sharp incisors with a rear set of grinding molars for breaking apart plant matter.
Only just above half of Eteno males are able to grow hair on their heads, and those that do have very short and relatively sparse folicles. Almost all females can grow hair, but it also grows very slowly and sparse. Most females' hair only goes halfway down their heads.
Eteno also possess a set of gills on their neck that can be used to breathe on land and underwater. These gills allow an Eteno to stay underwater indefinitely, but as Eteno are incapable of eating or drinking underwater, they must surface at some point. These gills are also uniquely used as a method of physically showing emotion. Eteno gills hug the neck and close when an individual is stressed or angry, and flare when an individual is happy, or amused. Numerous kinds of subtle gill movements signify other specific emotions, such as embarrassment or nervousness.
Vocal chords on Eteno produce deep sounds, and are incapable of producing sounds greater than 580 Hz or under 30 Hz. Males produce the deepest sounds but rarely go past 300 Hz, while females can make sounds between 210 and 580 Hz.
An Eteno male can grow to be as tall as six feet in rare cases, but most males only reach five feet and four inches in height, while females rarely breach five feet. Both genders on average only live to be seventy years of age.
Eteno are humanoid creatures similar in many ways to other humanoid species in terms of overall internal and external physiology. A pair of arms are at most comfortable rest when the forearms are held out 45 degrees vertically, which allows for the arms to quickly snap to a position advantageous for swimming stroke.
As a result of the constant rains of their world and their evolutionary proximity to coast almost constantly, Eteno skin is waterproof. Rainwater will bead up and quickly drip off of their flesh while skin partially or fully submerged in an actual body of water will be unaffected.
To allow for a more aerodynamic figure as well as a sense of hearing, Eteno have cavities in the sides of their heads that serve as ears. Hearing range of Eteno is limited, and sounds above 740 Hz are impossible for them to pick up.
Respiration is achieved through the intake of oxygen and release of carbon dioxide through the mouth, nasal cavities, and gills. Air taken in by Eteno goes into a pair of lungs evolved to dispose of helium on account of the high helium content of Malisk II's atmosphere. This helium is exhaled along with carbon dioxide and other waste products.
Befitting their evolutionary development as strong and constant swimmers, the metabolisms of Eteno are extremely high. They consume large quantities of food very quickly, and have evolved to digest food just as rapidly. Eteno possess a symbiotic relationship with a particularly widespread and ravenous Maliskian bacteria which helps fulfill the need for expedited digestion. As a result of their fast metabolism, members of the Eteno race speak much quicker than most other creatures capable of vocalization, a trait which comes across as annoying to some sentients.
This symbiosis is one of many between Eteno and micro-organisms of Malisk II. While this means that there are fewer lethal diseases for Eteno to contract on their homeworld, the prospect of visiting other life-sustaining worlds is made much more dangerous, as their immune system is significantly weaker. This has been offset by medical nanotechnology, aggressive vaccination, and aggressive quarantining of afflicted colonies, groups, and individuals.
While particularly debilitating for ancient Eteno societies reliant on hunting for fish underwater, Gillclog ceased to be more than an annoyance before medical advances made it extinct. Gillclog afflicts the gills of an Eteno by filling them with liquid, preventing dissolved oxygen from filtering in. Eteno unaware of their affliction could easily drown when swimming underwater, but when the need to do so was eliminated through societal and technological advancement, those who contracted Gillclog saw it as a mere inconvenience.
A particularly gruesome affliction that once pervaded the now-extinct swamps of Malisk II's islands, Fleshmelt is a fast-acting disease that rapidly consumes the flesh of an afflicted individual from the inside out. Death is painful and occurs within several days. Before medical technology rendered it extinct, Fleshmelt had a 100% fatality rate.