|This article relies on references to primary sources. (January 2008)|
||This Star Trek-related article describes a work or element of fiction in a primarily in-universe style. (July 2008)|
|Base of operations||Fluidic space|
Species 8472 is a fictional extraterrestrial race in the science fiction television series Star Trek: Voyager. They inhabit another dimension called fluidic space. These beings are rendered by animation from Foundation Imaging, Inc. The multiplayer game Star Trek Online gives their proper name as Undine.
Cellular characteristics 
A designation given by the Borg (the species' name referred to by Star Trek Online as the Undine, though the Hirogen refer to them as 'Fluidians'), Species 8472 has a dense genetic structure, with each cell containing more than a hundred times the genetic material of a human cell because of their triple-helix DNA structure. On the cellular level, Species 8472's own somatic cells can become extremely virulent when in a foreign blood-stream, duplicating themselves rapidly. When a member of Species 8472 attacks a victim with its claws, some of the former's cells are left in the wound. These stray cells multiply, spreading through the victim's entire body, consuming it from the inside out while the victim remains conscious. Since the attacking cells employ the same advanced immune response as when inside the creature, they are able to resist conventional treatment methods. This system also makes them entirely immune to Borg assimilation.
Species 8472's anatomy is unique in that they possess three five-jointed, even-toed ungulate feet or hooves. They have cross-shaped pupils, and communicate exclusively through telepathy. They have tall, thin, skeletal bodies possessing very little soft tissue, and appendages appear to be supported by sinuous strands of muscle. Their outward appearance is marked mainly by bony crests located on their chest and disproportionately large heads, giving them a generally gangly appearance. They have as many as five genders, each of which apparently occupies a different region of fluidic space. Species 8472 can also survive the unprotected rigors of normal space, and appears to not need to breathe an atmosphere, or even the organic fluid present in its own realm. Members of Species 8472 emit a biogenic field around their bodies which interferes with normal transporters and renders them partially invisible to sensors. It is one of the most evolutionarily advanced corporeal species encountered in the Star Trek universe. However, while species like the Borg have reached the pinnacle of technological achievement through assimilation, Species 8472 has established dominance based on its biological superiority. Their powerful biology renders them immune to most Federation scanning technology and has prevented their assimilation by the Borg.
Species 8472 possess incredible strength and stamina as demonstrated in the episode "Prey", when a single member of Species 8472 is attacked by a Hirogen hunting party with heavy weapons. Thinking it dead, they take it back to their ship, only to discover otherwise after the alien injures the Alpha Hirogen and decapitates his subordinate. When the alien makes its way across Voyager's hull, it tears a bulkhead to gain access to the ship. Though the alien is badly injured, it eventually heals itself, regenerating wounded flesh, and appears capable of surviving and recovering from significant injury. Members of Species 8472 exclusively attack with their claws and raw strength; they never use a hand-held weapon, instead allowing their superior immune system to be used in an offensive role.
Native environment 
Species 8472 live in "fluidic space", a different dimension (probably meant to be outside our universe although it is stated that it is only definitely outside our galaxy). Fluidic space is a continuum filled with an organic fluid. Fluidic space has no stars, planets or nebulae. However, in Star Trek: Armada II, fluidic space has several nebulae referred to as fluidic nebulae, and are identical in nature to those produced by the massive Behemoth-class bioship.
Species 8472 uses a type of organic spacecraft known only as a bioship composed of the same organic material as their pilots and typically controlled by a single pilot. Despite Species 8472's use of telepathic communication, it is not clear whether the Bioships themselves are controlled telepathically as Species 8472 has been witnessed to operate a console in order to pilot a bioship. A bioship explored by members of the Voyager crew contained an atmosphere breathable by humanoids; however as it was in atmospheric contact with the inside of a Borg cube at the time, it is possible the original atmosphere of the bioship had been displaced by the internal atmosphere of the Borg vessel.
Each bioship possesses an electrodynamic fluid circulatory system presumably for the distribution of power, a neurological computer core, an incredibly powerful biogenic energy weapon system, and warp capability. The hull can change shape to attach to other ships, melting through the hull, and can rapidly heal damage. The vessel can function effectively in both normal space and fluidic space. The bioship's main weapon is powerful enough to destroy a Borg cube in only a few shots. Likewise, when a Borg cube rammed a bioship to destroy it, both vessels were annihilated despite the comparatively smaller mass of the bioship. The weapons of eight bioships (referred to in Star Trek: Armada II as "Species 8472 battleships") can be linked with that of a larger ninth bioship of modified design (referred to in Armada II as a "Species 8472 bio-frigate"); the collective weapon thus formed can destroy an entire planet in seconds.
Relevant episodes of Star Trek: Voyager in which Species 8472 appear include season 3 episode 26 (season finale) "Scorpion: Part 1" and season 4 episode 1 (season premiere) "Scorpion: Part 2", season 4 episode 16 "Prey", and season 5 episode 4 "In the Flesh".
Species 8472 are discovered by the Borg in 2373 when the Borg invade fluidic space (as revealed in the episode Scorpion, Part II) by opening a rift in space using a deflector dish. The Borg discover Species 8472 in the Delta Quadrant and try to assimilate its biotechnology which is more advanced than anything the Borg have seen. The Borg quickly realize that 8472 is immune to assimilation, and that contemporary Borg technology is no match for it. In fact, 8472 is one of the few species so advanced that its ships are able to destroy Borg cubes in seconds. Species 8472 then invades the Delta Quadrant in retaliation to Borg aggression and begins a systematic extermination of the Borg and innocent species as well. Over the course of five months, tens of billions of drones are lost, as well as several hundred planets. When the crew of Voyager realizes that it has no choice but to go through Borg space in order to continue home in any kind of timely manner, Captain Janeway hatches a plan to construct a weapon to kill Species 8472 and use it as a bargaining chip with the Borg in exchange for safe passage through Borg space. The Borg accept. In conjunction with Janeway, the Borg develop a high-yield warhead armed with modified nanoprobes, developed by the Doctor, the ship's Emergency Medical Hologram (EMH), from the Borg's own technology, that is extremely effective at killing 8472 and forces it to retreat to fluidic space. In return for Janeway's help, the Borg allow Voyager safe passage through their space for the duration of their cooperative efforts. However, upon Species 8472's retreat from normal space, the Borg terminate the alliance in favor of (unsuccessfully) assimilating Voyager.
A member of Species 8472 is left in the Delta Quadrant during the retreat and is relentlessly hunted by a group of Hirogen for several months.
Concerned about the threat posed by humanity, Species 8472 builds 13 "terraspheres" in the Delta Quadrant and recreates Starfleet Academy within as a staging ground for an intelligence gathering mission on Earth. The plan is uncovered by Voyager and peace talks commence. Voyager convinces 8472, led by an individual posing as Boothby, that the Federation has no quarrel with them – it had in fact long been known that the Borg themselves started the war between the two species by invading fluidic space to assimilate the superior technology of Species 8472.
Video games 
Species 8472 appear as villains in the video games Star Trek: Voyager – Elite Force and Star Trek: Armada II. They also make an appearance in Star Trek Online, in which they are referred to as the Undine.
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