Fungus commonly known as sac fungi or ascomycetes, constitute the largest taxonomic group within the Eumycota. These fungi form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus. This phylum includes morels, a few mushrooms and truffles, unicellular yeasts (e.g., of the genera "Saccharomyces", "Kluyveromyces", "Pichia", and "Candida"), and many filamentous fungi living as saprotrophs, parasites, and mutualistic symbionts (e.g. lichens). Prominent and important genera of filamentous ascomycetes include "Aspergillus", "Penicillium", "Fusarium", and "Claviceps". Many ascomycete species have only been observed undergoing asexual reproduction (called anamorphic species), but analysis of molecular data has often been
Parasites in fiction subservient puppets, able to crawl but unable to act independently; or the barnacle-like crustaceans that castrate their crab hosts, or grow into their brains, altering their behaviour to care for the young barnacles. All the same, a 2013 poll of scientists and engineers by "Popular Mechanics" magazine revealed that the parasite-based science fiction films "The War of the Worlds" (Byron Haskin, 1953) and "Alien" were among their top ten favourites. Several types of parasite, corresponding more or less accurately to some of those known in biology, are found in literature. These include haematophagic parasites (fictional vampires), parasitoids, behaviour-altering parasites, brood