Tetra

A tetra is one of several species of small freshwater fish from Africa, Central America and South America belonging to the biological family Characidae and to its former subfamilies Alestidae (the "African tetras") and Lebiasinidae. The Characidae are distinguished from other fish by the presence of a small adipose fin between the dorsal and caudal fins. Many of these, such as the neon tetra (Paracheirodon innesi), are brightly colored and easy to keep in captivity. Consequently, they are extremely popular for home aquaria.

Tetra is no longer a taxonomic, phylogenetic term. It is short for Tetragonopterus, a genus name formerly applied to many of these fish, which is Greek for "square-finned" (literally, four-sided-wing).

Because of the popularity of tetras in the fishkeeping hobby, many unrelated fish are commonly known as tetras, including species from different families. Even vastly different fish may be called tetras. For example, payara (Hydrolycus scomberoides) is occasionally known as the "sabretooth tetra" or "vampire tetra".

Princess Zelda

Princess Zelda (Japanese: ゼルダ姫, Hepburn: Zeruda-Hime) is the name of a fictional character in Nintendo's The Legend of Zelda video game series, who was introduced in its original entry in 1986. The name has applied to many female members of Hyrule's royal family, which includes several distinct characters in Hyrule legend.

Though she is the eponymous character, her story role is often that of donor or damsel in distress. The player instead controls Link, the series' central protagonist, and usually focuses on defeating Ganon (or Ganondorf), the series' main antagonist. Many Zelda games adopt the classic princess-and-dragon premise of chivalric literature: Zelda is usually kidnapped or imprisoned by Ganon, prompting Link to come to her rescue. Some games in the series have also emphasized Zelda's magical abilities and importance to the functioning of Hyrule, demonstrating that she is more than capable of taking care of herself. In several games, she is one of the Sages, whose work is essential to defeating Ganon; in others, she adopts alternative personae in order to take a more active role in her kingdom; and in some, she is a self-sacrificing princess regnant. Zelda's alter egos include the ninja Sheik in Ocarina of Time and the pirate Tetra in The Wind Waker and Phantom Hourglass.

Tetra (disambiguation)

Tetra is any of several species of freshwater fish in the family Characidae from Africa, Central America and South America.

Tetra may also refer to:

See also

Human swimming

Human swimming is the self-propulsion of a person through water or another liquid, usually for recreation, sport, exercise, or survival. Locomotion is achieved through coordinated movement of the limbs, the body, or both. Humans can hold their breath underwater and undertake rudimentary locomotive swimming within weeks of birth, as an evolutionary response.

Swimming is consistently among top public recreational activities, and in some countries, swimming lessons are a compulsory part of the educational curriculum. As a formalized sport, swimming features in a range of local, national, and international competitions, including every modern summer Olympics, which takes place every four years.

Science

Swimming relies on the natural buoyancy of the human body. On average, the body has a relative density of 0.98 compared to water, which causes the body to float. However, buoyancy varies on the basis of both body composition and the salinity of the water. Higher levels of body fat and saltier water both lower the relative density of the body and increase its buoyancy.