 It's been about 60 years since George Streisinger started to use zebrafish in research. A child's move from pet chop aquaria to lab has grown to zebrafish been kept in over 1200 laboratories around the world. Now much more recently, scientists have been looking at wild zebrafish to learn lessons about how to make the life of lab zebrafish less stressful. These are zebrafish in the wild. They're found in the shallow margins of rivers and streams in North India where they live in shoals darting in and around river plants. They mainly feed on insects and crustacea and in turn are prey for larger fish, prey for snakes and birds. Wild zebrafish are quite tolerant of different environmental conditions. Perhaps one of the reasons they've made such a successful aquarium animal they've been found to live in a range of temperatures from 24 to 30 degrees C. The water they're found in has a pH anywhere between 7.1 and 7.7 and oxygen levels can change as well. They've been measured between 3.9 and 8.9 milligrams per litre. One factor that's very different between the lab and the natural environment is the amount of noise. Zebrafish listen to their surroundings in their natural home but in the lab where tanks can be loud up to 146 decibels sound levels can be loud enough to damage zebrafish hearing. So the ambient noise in fish facilities is likely to be stressful to the fish and potentially can found research work. In the lab zebrafish are used in an astonishing variety of research. Zebrafish can regenerate heart muscle so they're used in heart research. They can catch diseases like TB and they're transparent when they're young so they're ideal for following the movement of cells and tissues during early development. But whatever the field of research it's important the fish are healthy and behaving normally so that any results are not an artifact of laboratory living. In the wild zebrafish shawl in groups that can grow to several hundred but are usually smaller. In captivity zebrafish are almost always kept in groups except when individuals are removed for breeding or other work. Wild zebrafish are usually found in clear running water but they can occur in more murky, turbid conditions. In the lab tanks are always supplied with clean running filtered water. While wild fish have to find their own food zebrafish in the lab are fed daily and tend to be heavier than their wild relatives. In the wild the riverbed can vary from mud to pebbles. The laboratory fish are now sometimes housed in tanks put over sheets decorated with a pebble pattern representing a riverbed. And when given the choice zebrafish prefer to swim above a pebble pattern compared to being in a playing tank. Sometimes fish are provided with floating plastic plants and occasionally live plants but here the fish preference is less clear. Although floating plants whether they're artificial or real do give the opportunity for fish to hide from aggression from other fish. Recently zebrafish have been shown in the wild to seek out warmer water when they have an infection. Apparently this induces a fever like reaction that helps to reduce the infection. In the future laboratory tanks might be modified to give more of a gradient of conditions such as heat and light and oxygen concentration but for now the priority in the majority of labs is to maintain all these environmental factors within very tight limits. Zebrafish in the wild have to contend with a complex environment and the ever present threat of predation. Zebrafish in captivity are in a far simpler world. By presenting zebrafish with choices we can learn how to make their laboratory world a little more to their liking perhaps removing some of the stresses of living in tanks. Stresses were only just becoming aware of.