Shellos have two different appearances: West Sea (pink and white) and East Sea (blue and green), found on the respective sides of Sinnoh's mountain range.
Shellos is a sea slug-like Pokémon whose appearance changes drastically depending on the sea it is found in. However, both forms have amorphous, slug-like bodies. Like real sea slugs, they have mantles covering the top halves of their bodies. Unlike real sea slugs, they have bulbous heads and four small feet rather than one large foot. Both forms also have black oval-shaped eyes, tiny noses, wide yellow lips, and yellow outlines around their eyes and mantles.
In the West Sea form, the underside is white and the mantle is pink. The mantle has several small spike-like protrusions on it. On its head is a ring of pink fleshy knobs resembling the gills of a nudibranch. West Sea Shellos's appearance is theorized to have been influenced by warm ocean waters.
In the East Sea form, the underside is green and the mantle is blue. The shell has two flap-like protrusions, resembling cerata. These protrusions are lined with yellow. On its head are two white-tipped tentacles resembling rhinophores that extend away from its face. East Sea Shellos's appearance is theorized to have been influenced by cold ocean waters.
Shellos lives along seashores; its color becomes more vibrant the better the waters it lives in is. It can travel onto land, although its skin dries out if it stays on land for too long. If Shellos is pushed or squeezed, a mysterious purple fluid similar to greasy sweat will ooze out of its body. This fluid is its defense mechanism against enemies; although it is harmless, it is very sticky and hard to wash off. Shellos has a friendly disposition, and is said to have great regenerative capabilities. In the anime, West Sea Shellos can extend their necks to incredible lengths. It is unknown if the East Sea form can do this as well.
This species once had a shell on its back a long time ago, and as such it is considered a close relative to Shellder. The Nurse Joy featured in Gateway to Ruin! revealed Mount Coronet's formation led to an allopatric speciation event, in which the original population of Shellos was separated into two. As a result, Shellos's color and other physical differences began to vary due to environmental differences and population isolation over time. It is also believed that Shellos's diet, which consists of plankton, also influences its form, but this has yet to be proven. The two forms are still able to interbreed; the child takes the mother's form or the father's if bred with a Ditto. Recently, East Sea Shellos's populations have been declining, while West Sea Shellos has become more abundant than before.
Shellos, the Sea Slug Pokémon. Shellos's shape and color varies depending on where it lives. Two different varieties have been confirmed in the Sinnoh region.
Shellos, the Sea Slug Pokémon. A mysterious purple fluid oozes out of its soft body when Shellos is strongly squeezed. Two kinds of Shellos, pink and blue, have been confirmed.
Shellos's most notable appearance is that of a companion of Mr. Fuego's. He typically keeps his East Sea Shellos on his shoulder, continuing to do so even after he accidentally imprisoned himself to avoid Team Galactic. It first appeared in Maddening Magby.
Found in abundance on seashores bordering warm waters. Shellos are unexpectedly friendly and will crawl toward any person they see. Take care not to get coated in mucus!
Found in abundance on seashores bordering cold waters. When pressed upon, the Pokémon will secrete from its body's surface a purple fluid that will stain one's clothes.
Both Shellos and Gastrodon have early back sprites that can be found in the game data for Pokémon Diamond and Pearl; however, there are no front sprites for these forms.
In Diamond and Pearl, no in-game Trainer uses East Sea Shellos in battle, even on the east side of Mount Coronet.
Shellos and its evolution were accidentally released in Pokémon GO on April 29, 2019, but were removed shortly after. On May 17, 2019, they made their official debut along with various other Pokémon from Generation IV.
Shellos is the only Pokémon with Sand Force that benefits from its sandstorm immunity, since every other Pokémon with the Ability are naturally immune to sandstorm damage due to their typing.
The Pokémon Scarlet and Violet Pokédex entries mentioning an increase in West Sea Shellos and a decrease in East Sea Shellos may be in reference to changes in the populations of real life sea slug species due to climate change — with species that better survive in warmer waters becoming more common.[2]
Origin
Shellos is based on a sea slug.[1] It resembles various species of nudibranchs, and its ability to secrete purple fluid may be based on sea hares, most of which secrete a purplish ink for self-defense.
Name origin
Shellos may be a combination of shell and loss or lost (referring to its lack of a shell), or the German suffix -los (-less).
Karanakushi may be a combination of 殻 kara (shell), 無くした nakushita (to have lost), and 海牛 umiushi (sea slug; nudibranch).