Mermaid

Description
A mermaid is, quite simply, a fish youkai. Or, more specifically, a female fish youkai. Merfolk can be either female or male, and are called either mermaids or mermen, depending. Merfolk come about in a variety of manners--either by living for a very long time, growing very large or being very ferocious and becoming feared or revered among humans, or by being born of a mermaid. Most mermaids come about from the first and third methods, as it is very rare for very large or ferocious ocean fish to be seen by humans without being killed, either by being drawn up in a fishing net, harpooned, or killed by the large fishing vessels that crisscross the oceans nowadays. Merfolk are well-known for being able to reproduce either through laying eggs for a male to fertilize, or, if there is no male around (or desired, as the case may be), through parthenogenesis. Merfolk are unique in the fact that they do not reproduce until they find a permanent partner, and even after this, they normally do not have many children because of their long lifespans. Most marine merfolk can reach ten thousand years of age before dying. Whether freshwater merfolk can reach this age as well is unknown, due to the fact that most freshwater merfolk die prematurely due to humans either polluting their lakes and rivers or catching and cramming them into tiny tanks in sideshows and circuses. It isn't uncommon for mermaids--either freshwater or ocean-dwelling--to commit suicide by effectively drowning themselves in their tanks if they are caught and imprisoned by humans.

Though most merfolk--well over ninety-five percent--live in the oceans and other large bodies of salt water, there are some merfolk that have come about in smaller bodies of fresh water. Ocean-dwelling merfolk can come in many shapes and sizes, and can come from many different marine life, including (but not limited to) fish, eels, and certain types of cephalopods. Most marine merfolk, especially those that live in warmer, tropical waters, are well-known for their vivid coloration and brilliant, flowing fins compared to plainer, simpler freshwater merfolk. However, most marine merfolk are unable to breathe if they are fully out of water, as during the course of their existence, their lungs have evolved to be smaller and much less useful in favor of constantly using gills. On the other hand, freshwater merfolk have much stronger lungs, allowing them to easily breathe both above and below water if need be.

There are many defining traits that merfolk possess, the most obvious of these being a long fish tail from the waist down. This tail, instead of housing the mermaid's internal organs, is mostly comprised of fat and muscle, along with some of the mermaid's intestines and reproductive organs. Along with this unique tail, merfolk also possess other traits including:


 * Gills as well as lungs
 * Fins on their human half
 * Webbed hands
 * Transparent third eyelids to allow them to see underwater

While all merfolk, regardless of origin, have all of these traits, it's easy to tell the difference between the two based on these traits. For example:


 * Ocean-dwelling merfolk have their gills on their hips, while freshwater merfolk have their gills on their necks.
 * Ocean-dwelling merfolk have vertically-aligned tail fins, while freshwater merfolk have horizontally-aligned fins (very much like marine mammals like dolphins and whales)
 * Ocean-dwelling merfolk have pronounced dorsal fins on their backs, normally between the shoulder blades. They also possess fins on their arms and on their head. Freshwater merfolk only have the fins on their heads.
 * Ocean-dwelling merfolk normally have slightly-modified skeletons to allow them to survive the increased pressure under deep water, whereas a freshwater mermaid's skeleton (at least, from the waist up) is normally very similar to a human's.

Origin
The true origins of mermaids are cloaked in mystery. Some claim that the species came to be millions of years ago when most living creatures were still living in the vast seas, while others claim that the species is only a few thousand years old, having come about with the rise of civilizations. The truth is, mermaids have been around as long as youkai have--several million years. In fact, mermaids are arguably some of the oldest known species of youkai. Some merfolk civilizations located in the sea have reportedly existed for close to a million years, with some of the oldest inhabitants of these civilizations pushing ten thousand years old.

((More will be added here eventually!))

Characters of this Species

 * Wakasagihime

Related

 * Animal Youkai