This type of lifeform is not given a name on screen. However, it was referred to as a "'techno-larva'" in the final draft script of "The Shipment".
The idea of something organic living inside a Xindi rifle originally came from the producers of Star Trek: Enterprise. Junior illustrator Berndt Heidemann, who thereafter designed the weapon, later remarked, "They wanted to add that part of the Xindi, as if they utilized some organics in their technology." (Star Trek: Communicator issue 149, p. 54)
In the final draft script of "The Shipment", the techno-larvae were described as "organic-looking components that resemble larvae", "larvae-like technology", "odd components", and "worm-like organism"s. Although the final version of that episode shows at least one techno-larva inside a destroyed Seeker, no mention of it was made in the script of "The Shipment".