Tetra is the common name of many small freshwater characiform fishes. Tetras come 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.
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".
Tetras generally have compressed (sometimes deep), fusiform bodies and are typically identifiable by their fins. They ordinarily possess a homocercal caudal fin (a twin-lobed, or forked, tail fin whose upper and lower lobes are of equal size) and a tall dorsal fin characterized by a short connection to the fish's body.[2] Additionally, tetras possess a long anal fin stretching from a position just posterior of the dorsal fin and ending on the ventral caudal peduncle, and a small, fleshy adipose fin located dorsally between the dorsal and caudal fins. This adipose fin represents the fourth unpaired fin on the fish (the four unpaired fins are the caudal fin, dorsal fin, anal fin, and adipose fin), lending to the name tetra, which is Greek for four.[2] While this adipose fin is generally considered the distinguishing feature, some tetras (such as the emperor tetras, Nematobrycon palmeri) lack this appendage. Ichthyologists debate the function of the adipose fin, doubting its role in swimming due to its small size and lack of stiffening rays or spines.[3]
Although the list below is sorted by common name, in a number of cases, the common name is applied to different species. Since the aquarium trade may use a different name for the same species, advanced aquarists tend to use scientific names for the less-common tetras. The list below is incomplete.
I don't usually like metal puzzles much, but the Tetra Puzzle is way cool! A tetrahedron is a fascinating shape and the way the four congruent interlocking pieces come together is very satisfying. This puzzle is very fun to manipulate and looks great on display too. It's cool to the touch and to the eye and has a nice heft to it as well. I highly recommend the Tetra Puzzle from Craighill!
This syndrome can also cause severe malformations of other parts of the body, including the nervous system, face, head, heart, skeleton, gastrointestinal system, urinary tract, and genitalia. The lungs are underdeveloped in many cases, which makes breathing difficult or impossible. Because children with tetra-amelia syndrome have such serious medical problems, most are stillborn or die shortly after birth.
Variants (also called mutations) in two genes have been found to cause tetra-amelia syndrome. Variants in the WNT3 gene cause tetra-amelia syndrome type 1 and variants in the RSPO2 gene cause tetra-amelia syndrome type 2.
The variants in the WNT3 or RSPO2 gene that cause tetra-amelia syndrome likely prevent cells from producing any functional protein. As a result, Wnt signaling is impaired and normal limb formation is disrupted, which leads to the serious birth defects associated with tetra-amelia syndrome types 1 and 2.
In some affected individuals, the cause of tetra-amelia syndrome has not been determined. Researchers believe that unidentified mutations in WNT3, RSPO2, or other genes involved in limb development are probably responsible for the disorder in these cases.
Tetra-amelia syndrome appears to have an autosomal recessive pattern of inheritance. Autosomal recessive inheritance means both copies of the gene in each cell have mutations. The parents of an individual with tetra-amelia syndrome each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.
Methods: This was a randomized, double-blind, trial with treatment arms for cannabidiol (CBD), tetra-hydro-cannabinol (THC), CBD and THC combination (CBD/THC), and placebo in a 1:1:1:1 ratio and flexible drug doses (CBD 5-50 mg, THC 2.5-25 mg, and CBD/THC 5 mg/2.5 mg-50 mg/25 mg). Treatment periods of 8-week duration were proceeded by 1 week for baseline observations. Patients with painful polyneuropathy, post-herpetic neuralgia and peripheral nerve injury (traumatic or surgical) failing at least one previous evidence-based pharmacological treatment were eligible for inclusion. The primary outcome was the change in weekly average of daily pain measured with a numeric rating scale (NRS). Trail Making Test (TMT) was used as one of the tests of mental functioning.
35fe9a5643