The infants are transported in large numbers by the Space Pirates in Metroid Cocoons and used as portable energy sources. Although they lack the ability to drain life energy, they still exhibit highly aggressive behavior by continuously ramming their opponents.
If an Infant detects Phazon nearby, it will be unable to resist its emanating energy and fly towards it. Mere contact with the substance will cause them to rapidly mature into Tallon Metroids, making them more powerful and far more dangerous.
Infant Tallon Metroids are genetically engineered by Space Pirates, likely the result of experiments performed on mature Tallon Metroids. They differ immensely from SR388's naturally-born Infant Metroids; while the latter already possess most of the features seen in the next stage of their life cycle, such as their four nuclei enclosed in a green-colored membrane and four hardened fangs, Infant Tallon Metroids instead appear highly underdeveloped. They carry only a single nucleus within a blue translucent membrane that has yet to convert into the color seen in mature Tallon Metroids, and their fangs are transparent as well, seemingly still made up of the same tissue as the membrane.
An Infant Tallon Metroid possesses many shortcomings, such as its tolerance to damage in which a relatively low amount of weapon fire is sufficient to kill it. Metroid Fusion demonstrated that an Infant Metroid born in SR388's environment is invulnerable to all weapons except those that are cold-based; in fact, a single shot from a Freeze Gun in Metroid: Other M is enough to kill it outright. Interestingly, an Infant Tallon Metroid can be frozen numerous times before dying. Yet another inferior trait to the Infant Tallon strain is its inability to grip onto prey and siphon its life energy, possibly a result of its fangs having yet to harden. To make up for this, it will exhibit highly aggressive behavior through repeated use of a weak ram attack. This is nearly the complete opposite of a natural infant: while the latter is indeed capable of using its fangs to their full extent and kill in the same fashion as Metroid larvae, the organism is often playful and curious, causing it to rarely do this and leaving it exposed to many potential attacks.
The only true advantage the artificial infants have over their natural counterparts is the steps required to reach the next stage of their life cycle. Coming into physical contact with the mutagen known as Phazon is sufficient to trigger a dramatic transformation of their bodies in which they rapidly mature into the highly dangerous Tallon Metroids in mere seconds. SR388 Infants require an unspecified amount of sustenance and time in order to attain the larval form. Metroid Prime 2 never clarifies if Infant Tallon Metroids are capable of reaching the next stage without relying on Phazon, though if they cannot, this extreme dependence would prove to be highly detrimental, as the complete absence of the mutagen would leave them indefinitely trapped in this immature form.
Metroid Prime 3: Corruption introduces the Phazon Metroid and its juvenile form, the Miniroid, the latter which is similar in appearance and size to an Infant Tallon Metroid. Contrary to its mature form however, the Miniroid is completely harmless and makes no attempt to attack foes. Its body is also extremely frail, dying to a single shot of any weapon and on contact with any armored entity.
Infant Tallon Metroid
Morphology: Infant Tallon Metroid
Genetically engineered energy parasite.
Ramming attack will do minor damage. Exposure to Phazon will mutate them into a deadly version.
The Space Pirates use Infant Tallon Metroids as a portable energy source. Small in size, they are easy to transport in large quantities. They are docile efficient organic batteries... until they are exposed to Phazon. At that point, they grow rapidly and acquire their full array of powers.