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The cardinal tetra is a very popular aquarium fish, but is less widespread than the neon tetra because until recently, it was difficult to breed in captivity. However, many breeders are now producing the fish; in most cases, one can determine if the cardinal tetra is bred or wild-caught due to damaged fins on wild-caught specimens.
The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.
In fact, several species, including cardinal tetras, show the adaptive trait of iridescence which may provide lower visibility in a blackwater environment. [ 4 ] Project Piaba started with an ecological baseline study of the region which was conducted in 1989 by a group of researchers and students from the Universidade do Amazonas (UA) and the ...
Paracheirodon tetras reach maximum overall lengths of 2.5 to 5 cm (0.98 to 1.97 in) depending on the species, and are of elongated, tetra shapes. All share a distinctive iridescent blue lateral line, but differ slightly in their other colorations.
The green neon tetra (P. simulans) and black neon tetra (Hyphessobrycon herbertaxelrodi) are distinct species—the latter belongs to a different genus—and not color varieties. The cardinal tetra (P. axelrodi) is also a similar species, but its greater extent of red coloring distinguishes it from the neon tetra. [28]
The rummy-nose tetra (Petitella rhodostoma) is a species of tropical freshwater characin fish originating in South America, popular among fishkeepers as a tropical aquarium fish. [2] One of many small tetras belonging to the same genus, it is on average 5 cm (2 in) long when fully grown. [ 3 ]
The flame tetra (H. flammeus) is bred in large numbers in captivity and common in the aquarium trade, but rare in the wild. [5] </ref> [6]Most of the species in the genus have not been rated by the IUCN Red List as Threatened, but many species have small distributions and at least three, H. flammeus, [5] H. coelestinus and H. duragenys are classified as endangered. [7]
Cynodontidae are elongated in shape with a silvery or grey colour and an upturned mouth. Some species have a hunchbacked appearance. The family names (both scientific and common) derive from the long and well-developed canines which are used to spear their prey, mainly other fish.