All articles starting with O
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Ophidiophobia
Ophidiophobia, also called ophiophobia, is the specific phobia of snakes, an anxiety disorder affecting 2–3% of people; treated mainly with exposure therapy and studied through preparedness and snake detection theories.
Ophiocomina nigra
Ophiocomina nigra, the black brittle star (ophiure noire), an ophiocomid brittle star from Norway to the Mediterranean; disc to 25 mm, arms 5x disc, dense beds with Ophiothrix fragilis, genetically homogeneous populations.
Ophiocordyceps sinensis
Ophiocordyceps sinensis (syn. Cordyceps sinensis; 冬虫夏草, Yartsa Gunbu), the caterpillar fungus, an entomopathogenic Himalayan fungus parasitizing Thitarodes moth larvae at 3000–5000 m; prized in Tibetan and Chinese medicine, critically endangered, and one of the world's most valuable biological commodities.
Ophiocordyceps unilateralis
Ophiocordyceps unilateralis, the zombie-ant fungus (basionym Torrubia unilateralis), is an entomopathogenic ascomycete in Ophiocordycipitaceae that infects carpenter ants, manipulates them into a death grip, and represents a large host-specific species complex; it never infects mammals.
Ophioglossaceae
Ophioglossaceae, the adder's tongue fern family (Martinov, 1820), are eusporangiate ferns with trophophore and sporophore frond segments, subterranean mycorrhizal gametophytes, and record chromosome counts up to 1440 in Ophioglossum reticulatum.
Ophioglossum
Ophioglossum, the adder's-tongue ferns (adder's-tongue), a cosmopolitan genus of about 50-64 simple-leaved ferns in Ophioglossaceae, known for the highest chromosome counts of any organism, 2n up to 1,260.
Ophiolite
An ophiolite is a fragment of oceanic crust and underlying upper mantle thrust, or obducted, onto continental crust, occurring in all Phanerozoic mountain systems as fossil oceanic lithosphere.
Ophiophagus
Ophiophagus, the king cobra genus, is a genus of large Asian elapid venomous snakes; long monotypic with Ophiophagus hannah, split in 2024 into four species: hannah, bungarus, kaalinga, and salvatana.
Ophiostoma
Ophiostoma, genus of ascomycete fungi in the Ophiostomatales with long-necked perithecia and insect-dispersed spores; type species O. piliferum; includes Dutch elm disease pathogens O. ulmi and O. novo-ulmi; distinct from Ceratocystis (Microascales).
Ophiothrix fragilis
Ophiothrix fragilis, also known as the common brittle star, is a brittle star that forms dense beds, sometimes over 2000 individuals per square meter, in the eastern Atlantic and Mediterranean.
Ophir
Ophir (Hebrew Ophir) is a biblical land or port, source of Solomon's gold, almug wood, apes, and peacocks, sailed to from Ezion-geber; its location, proposed in Arabia, East Africa, India, or Southeast Asia, remains unconfirmed.
Ophir Catenae
Ophir Catenae is an IAU-approved 577-km system of pit crater chains on Mars at 9.49S, 300.60E, south of Ophir Chasma near Valles Marineris, named in 2006 from a classical albedo feature and linked to groundwater-fed outflow channels.
Ophir Chasma
Ophir Chasma, a 317-km canyon in north central Valles Marineris, Mars, holding Ophir Mensa, sulfate-rich interior layered deposits, gray hematite, and large Amazonian landslides.
Ophir Klein
Ophir D. Klein is a developmental and stem cell biologist, pediatrician, and clinical geneticist who studies organ formation and regeneration, known for his 2018 Nature study on intestinal repair.
Ophir Labes
Ophir Labes is an IAU-approved landslide (labes) feature on Mars in Valles Marineris near Melas and Coprates Chasmata, about 92.53 km across, named in 1985 from a classical albedo feature.
Ophir Mensa
Ophir Mensa is a 103 km wide mesa of layered sulfate-rich sedimentary deposits in Ophir Chasma, Valles Marineris, Mars, IAU named 2013, containing kieserite, polyhydrated sulfates, jarosite, and hematite.
Ophir Planum
Ophir Planum, a 642-km-wide plateau (planum) on Mars near Valles Marineris, IAU-approved 1973 as a classical albedo feature name; Hesperian volcanic ridged plains with outflow channels.
Ophisaurus
Ophisaurus (glass lizards), genus of legless anguid lizards named from Greek ophis + sauros. Eyelids and ear openings distinguish them from snakes; tails autotomize and regenerate without vertebrae.
Ophiuchus (astrology)
Ophiuchus, the Serpent Bearer, is an equatorial constellation the Sun passes in front of from about November 30 to December 17, often called a "thirteenth zodiac sign."
Ophiuchus (Ὀφιοῦχος)
Ophiuchus (Ὀφιοῦχος), the serpent bearer, is one of the 88 IAU constellations, an equatorial constellation between Scorpius and Sagittarius representing Asclepius; the Sun crosses it each November, though it was never a classical zodiac sign.
Ophiuchus Supercluster
The Ophiuchus Supercluster is a large concentration of galaxies behind the Galactic Bulge, centered on the Ophiuchus galaxy cluster about 390 million light-years away, known for the most powerful AGN outburst recorded in any cluster.
Ophiura ophiura
Ophiura ophiura (common sand-star, ophiure commune) is a northeast Atlantic and Mediterranean brittlestar with a disc up to 35 mm, five thick arms rooting inside the disc, living buried on soft sediments to about 300 m, distinguished from Ophiura albida by pores between ventral arm plates.
Ophiurida
Ophiurida (Müller and Troschel, 1840) is the larger order of brittle stars within class Ophiuroidea, with 13 families, 223 genera, and 1883 species, placed in Euryophiurida sister to Euryalida, moving by arm rowing rather than tube feet.
Ophrys
Ophrys (bee orchids) is a Mediterranean-centered orchid genus pollinated by sexual deception: flowers mimic female insects' looks and sex pheromones, inducing pseudocopulation by males; species counts range from nine to 400+.
Ophrys (bee orchid) pollination by sexual mimicry
Ophrys orchids reproduce by sexual mimicry, or pseudocopulation: flowers copy the sex pheromones of female bees or wasps, so males mate with the labellum and carry away pollinia.
Ophrys apifera
Ophrys apifera, known as the bee orchid, is a European orchid whose flower mimics a female bee; unlike most of its genus, it pollinates itself by wind.
Ophthalmic Administration
Ophthalmic administration: delivering drugs to the eye via topical, intravitreal, periocular, systemic, intracameral, and suprachoroidal routes, shaped by ocular barriers and low topical bioavailability.
Ophthalmic artery
Ophthalmic artery: first branch of the internal carotid artery, supplying the eye and orbit via the central retinal and ciliary arteries; variant origins in 2–3%, occlusion is a sight-threatening emergency.
Ophthalmic zoster
Ophthalmic zoster, also called herpes zoster ophthalmicus (HZO), is shingles of the eye caused by reactivation of varicella-zoster virus in the ophthalmic branch of the trigeminal nerve.
Ophthalmodynamometry
Ophthalmodynamometry (ODM) measures retinal vessel blood pressure by pressing on the eye while observing the central retinal vessels; developed by Bailliart (1923), used for carotid disease, later displaced by Doppler sonography.