The electric eels are a genus, Electrophorus, of tropical freshwater fish from South America in the family Gymnotidae. They are electric fish, and can stun their prey by delivering shocks at up to 860 volts. Their electrical capabilities were first studied in 1775, contributing to the invention in 1800 of the electric battery. Despite their name, they are not closely related to the true eels (order Anguilliformes) but are electroreceptive knifefish (order Gymnotiformes), more closely related to catfish. Previously, the genus was believed to be monotypic, containing only Electrophorus electricus. In 2019 it was discovered that there were three species. They are nocturnal, air-breathing animals, with poor vision complemented by electrolocation; they mainly eat fish. Males are larger than females. Electric eels grow for as long as they live, adding more vertebrae to their spinal column. Some captive specimens have lived for more than 20 years. (Full article...)
Ninety-three nations received medals at the 2020 Summer Olympics, and 65 of them won at least one gold medal, both records. The 2020 Summer Olympics was an international multi-sport event held in Tokyo, Japan, from 23 July to 8 August 2021. The games were postponed by one year as part of the impact of the COVID-19 pandemic on sports. Athletes from the United States won the most medals overall, with 113, and the most gold medals, with 39. Host nation Japan won 27 gold medals surpassing its gold medal tally of 16 at both the 1964 and 2004 summer ions. American swimmer Caeleb Dressel won the most gold medals at the games with five. Meanwhile, Australian swimmer Emma McKeon won the greatest number of medals overall, with seven in total. As a result, she tied Soviet gymnast Maria Gorokhovskaya's seven medals at the 1952 summer ion for most medals won at a single games by a female athlete. Bermuda, Qatar, and the Philippines won their nation's first Olympic gold medals. (Full list...)
Siege of Khartoum currency was an emergency issue of paper money created by the British major-general Charles George Gordon, the governor-general of the Sudan, during the siege of Khartoum by Mahdist forces between 1884 and 1885. Denominated in piastres (and 50 Egyptian pounds), the first banknotes were dated 25 April 1884 and they were issued as late as November 1884. This set of ten banknotes, some of which were hand-signed by Gordon, is part of the National Numismatic Collection at the Smithsonian Institution.