The cytoplasmic pseudo-parasite was a sentient cytoplasmic insectoid species native to the Delta Quadrant, circa 50,000 light-years from Earth. By the 2370s, the pseudo-parasites were warp-capable and travelled through space with organic-looking starships. (VOY episode: "Nothing Human")
The cytoplasmic pseudo-parasite was an insectoid arthropod. A notable feature were its several nerve clusters located in the mid-section, and possibly elsewhere in the body. This species was normally independent but could invade other creatures systemically to sustain itself, thus making it an occasional parasite. (VOY episode: "Nothing Human")
The pseudo-parasite was less than two meters long. It was flat and divided into a head, middle and tail section. There were four three-pronged limbs. The head included a pair of eyes and a thin, long snout. The parasite's underside, face and limbs were pink, it's top green. The dorsal skin consisted of soft tissue with larger blisters or bubbles. (VOY episode: "Nothing Human")
Cytoplasmic pseudo-parasites communicated through high-pitched screeches of varying frequencies. In 2375, Starfleet's universal translator failed to decipher the language. They controlled their ships using biochemical secretions that they produced. (VOY episode: "Nothing Human")
In 2375, Federation starship USS Voyager responded to a distress call that emanated from a pseudo-parasite vessel in form of a high-warp shockwave. The wave's ion trail led Voyager to the compromised vessel. Its sole occupant was injured and transported to Voyager's sickbay. The pilot jumped from the biobed, effortlessly crossing a force field and attaching itself to Lieutenant B'Elanna Torres.
Voyager's chief medical officer, the Doctor created a holographic program based on exobiologist Crell Moset to save both Torres and the pilot's lives. They were successful in stabilizing both patients until another pseudo-parasite starship arrived, summoned by a distress call transmitted by Voyager. Voyager beamed the pilot to that vessel. In the aftermath, the Moset hologram suggested penning a scientific paper with the Doctor about the pseudo-parasite's systemic invasion of the half-Klingon Torres. (VOY episode: "Nothing Human")
In 2381, Voyager encountered another cytoplasmic species that was part of the Indign cooperative, which Seven of Nine identified as the Greech and compared to the pseudo-parasite. (VOY novel: Unworthy)