Shellder is a black pearl-like Pokémon, encased within a spiky, two-piece, purplish-blue shell. It has two round white eyes with tiny black pupils. It has an enormously long red tongue that it keeps extended out at all times. It uses its tongue to burrow itself into river and seabeds, and to lure and capture prey. It swims by rapidly opening and closing the two halves of its shell while it faces backward. Its black pearl-like body is known to be soft and tender; however, its shell is said to be harder than diamond. Despite its hard shell, clamping on to an opponent will reveal its vulnerable parts. It is due to this that it will only clamp itself to a foe as a last resort.
It has a parasitic, albeit symbiotic relationship with Slowpoke. After attaching itself to the Dopey Pokémon's tail, the two undergo a metamorphosis and together evolve into Slowbro. If it attaches to the head of a Slowpoke in possession of a King's Rock, the two will instead evolve into Slowking. These relationships allows it to travel onto land and obtain a new stage in its life-cycle.
As part of Slowbro, its shell transforms into a spiny, spiraled cone with four tiers. It also develops a jaw and sharp teeth to bite down, and securely anchor itself onto the host Slowbro's tail. In this state it feeds off both the sweet tasting secretions of Slowbro's tail, as well as any leftovers from Hermit Crab Pokémon. Should the two become separated, Slowbro will revert back into a Slowpoke.
As part of Slowking, its shell also transforms in a similar drastic fashion. However, its shell becomes one-piece with three tiers, a red jewel on its underside and it sprouts to large horn like protrusions on either of its side. It does not appear to have a jaw, but does have very sharp teeth that it uses to keep a firm grip onto the host Slowking's head. It releases venom whenever Slowking yawns, causing Slowking to become more intelligent. Should it fall off of Slowking's head, the Royal Pokémon will forget everything it has learned since evolving. It likely feeds off any food or scraps offered to it by its host.
When not attached to a member of the Slowpoke line, it primarily lives on the sea floor. It may also be found in rivers and streams, especially those with an inlet to the sea. Its is native to the Kanto and Johto, but is occasionally found within the Sinnoh and Unova regions as well.
In the anime
For a list of Shellder's appearances in the anime as part of Slowbro or Slowking, see the anime sections of Slowbro and Slowking.
Pokémon Pinball: Three Shellder appear on the Red Table and give the player points when hit. When Catch'em Mode is activated, they also reveal the silhouette of the Pokémon attempting to be captured upon being hit.
Pokédex entries
This Pokémon was unavailable prior to Generation I.
At night, this Pokémon uses its broad tongue to burrow a hole in the seafloor sand and then sleep in it. While it is sleeping, Shellder closes its shell, but leaves its tongue hanging out.
At night, it burrows a hole in the seafloor with its broad tongue to make a place to sleep. While asleep, it closes its shell, but leaves its tongue hanging out.
In the anime, Shellder is required to evolve Slowpoke into Slowbro or Slowking. Shellder clamps onto a Slowpoke's tail to evolve into Slowbro, or onto its head while wearing the King's Rock to evolve into a Slowking. Even though Shellder changes form drastically when it bonds with Slowpoke to evolve (see above), it is not considered an evolution in and of itself.
Shellder and Cloyster share the same species name with Clamperl. They are all known as the Bivalve Pokémon.
Shellder are one of the few Pokémon to show their entire body in a backsprite before Generation V, which it does in Generation II.
Shellder were shown to be capable of floating through the air in Pokémon Snap, a trait that has been seen in no other media.
In the episode The Evolution Solution, it's revealed that Shellder is still capable of speech as the shell of a Slowbro.
Origin
Shellder is similar to bivalves, more specifically the clam, with its tongue representing a clam's "foot".
Its parasitic relationship to Slowpoke may be inspired by leeches. Interesting enough, Slowbro is known as the Hermit Crab Pokémon and many real-world parasites, including leeches, often target crabs.
Name origin
Shellder is derived from shell. It also may be a pun on shelter, referring to the fact that it lives in a shell.