Animal Lab News - November/December 2015

16 NOVEMBER/DECEMBER 2015 ALNmag.com In July 2012, a group of accomplished scientists across the spectrum of bio- logical disciplines met to discuss the neurobiological substrates of conscious experience in human and non-human animals. They concluded that human and nonhuman animals are sentient—but never mentioned fish. This may have been because fish are cold-blooded, because they don't appear to have facial expression or emotion, or because they shine with a splendid palette … or it may have been because of just about anything else. But, fish simply didn't come up.

Of course, the exclusion made plain the case: how could fish not experience the vagaries of existence—changes as they occur in such as weather and temperature and pain, yes; but, even more to the point, utter departure from the natural habitat.

Looking back, this was a remarkable omission and portentous. It allowed for widespread recruitment of zebrafish into studies across the biomedical spectrum despite an absence of knowledge about zebrafish behavior in the wild. Only anecdotal tidbits about their behavior in the lab existed, and virtually no attention to welfare or enrichment was given.

Little by little, scientists are gathering facts and creating a rich picture of zebrafish life and of the zebrafish as a living system. With any luck, we'll soon have a compendium on zebrafish natural behavior that will inform welfare and enrichment. Frankly, we believe the field is long overdue for a gap analysis: that is, what we know about zebrafish basic needs and how we organize and manage their living conditions in the lab. With such a gap analysis at hand, scientists could routinely provide for zebrafish ease just as they now do for laboratory rodents, rabbits, primates—and lately, birds.

At last some scientists say that zebrafish feel pain. And as a result, scientists are taking steps to determine which end of life practice is euthanasia—a painless death. Specifically, the chemicals that cause the fish distress are replaced in some EU countries (but not the UK) with clove oil or rapid chilling of water to between 2 and 4°C. This is the first major step in developing welfare and enrichment standards and practices for zebrafish.

That is a good start but not nearly enough. In this article, we summarize highlights of what's known about zebrafish behavior—principally behavior observed in the lab—that may inform welfare and enrichment plans in the future.

Noam Miller, Assistant Professor, Department of Psychology at Wilfrid Laurier University in Ontario, Toronto, shared his experiences with us, and exclusive text from Noam can be found online. And we spoke with Carole Wilson, Head of the Fish Facility at University College London, about how more knowledge about zebrafish behavior in the wild would help her create a welfare and enrichment program for her many charges. Both contributed generously to our understanding, and their knowledge informs the text.

A SKETCH OF THE FISH ITSELF

A zebrafish measures about three centimeters in the wild, four to six centimeters in captivity. The male has predominant blue and lesser gold stripes; the female is blue and silver. Both exhibit nuptial coloring.

All are highly predated from above and below, but not such easy prey, being dark on the top and very light on the bottom.

There are many strains and each shows
a unique behavior profile. All strains live
for about three years in the lab; it is not
known how long they live in the wild.

The zebrafish, Danio Rerio, is a minnow. Danio is a Bengali word that means of the rice paddies, and the fish is aptly named. The natural habitat is small shallow Himalayan pools that tend to measure 1/2 to 2 meters wide and 50 cm deep—quite small and typically inhabited by a few dozen fish.

Residential pools tend to be near river banks and rice paddies, but these cyprinids are adaptable. As farmers flood the paddies and weather changes the nature of tide pools, the fish stay steady in the shallower areas. They can thrive as the seasons change the level and composition of the water. They can easily survive in ditches, canals, and stagnant pools. There are no rocks and little sunlight. Puberty is affected by fat content of the diet, by the individual's size, and by sunlight. Zebrafish eat mostly insects that fall on the surface of the water, and they spawn in the early hours of dawn.

BEHAVIOR

Zebrafish are highly social creatures and welcome additions to any group. They have individual personalities and there are distinct behavioral differences across strains. By and large, they are not jealous creatures since they don't pair bond.

In general, Danio Rerio are calm in a group of 20 to 30, become uneasy with fewer than eight, and distressed when alone. They are rarely territorial, and they are family oriented, showing a strong preference for swimming and shoaling with those they know. In fact, when they consistently swim with familiars, they grow 15% larger than those who have no choice but to swim in non-kin groups,