holoparasitism

Holoparasitism is a type of parasitic relationship in which the parasite is completely dependent on its host for all of its needs, including nutrition, reproduction, and even survival. In this symbiotic interaction, the parasite does not contribute to the host's survival or reproduction, and often, it may even harm the host. Holoparasites are typically smaller than their hosts and often have a specialized structure or organ, such as a haustorium, that allows them to extract nutrients directly from the host's tissues.

Holoparasitism is common in various organisms, including plants, animals, and fungi. In plants, holoparasites such as dodder (Cuscuta spp.) and mistletoe (Viscum spp.) rely entirely on their host for water, nutrients, and sometimes even structural support. In animals, holoparasites like tapeworms (Cestoda) and flukes (Trematoda) live entirely within the host's body, deriving all their nutrients from the host's digestive system. In fungi, holoparasites such as rusts (Pucciniales) and smuts (Ustilaginales) infect plants and derive their nutrients from the host's tissues.

Holoparasitism is often considered a form of exploitation, as the parasite benefits at the expense of the host. However, in some cases, holoparasitism can have beneficial effects for the host, such as facilitating the spread of the parasite's spores or providing nutrients to the host. Despite its negative connotations, holoparasitism plays a significant role in the ecology and evolution of various organisms.