Sticklebacks reveal dangerous oestro gen substances

It is possible to «see» oestrogen-like pollution before it does physical harm, says Aasa Espmark Wibe. She is checking the behaviour of sticklebacks which have been exposed to hormones.

«Fish would probably not have survived a similar exposure to impregnating substances in the wild», says NTNU-scholar Aasa Espmark Wibe.

Wibe is also examining the effect of oestrogen on the natural environment, and she is writing her PhD in this field.

«We can even find these oestrogen-like compounds in certain soaps and cosmetics», says the scholar.

She wants to develop a method that can «see» this pollution at an early stage, by examining the behaviour of fish before and after they have been exposed to oestrogen.

Wibe is also exposing sticklebacks to female hormones. She has carried out two large research projects with this little freshwater fish at the university research centre in Trondheim. In one of these she made use of pure oestrogen, in the other a substance that reduces oestrogen.

Behavioural changes

The effect of the substances was immediate, and it was obvious that the stickleback was suffering a hormonal shock. The exposed fish became nervous and wary, while the control group showed no visible changes.

Previously the hormones had been mixed in with the water for the test group, but Wibe is now injecting the oestrogen into each individual fish so that she knows exactly what dosage they get.

«We used small syringes for injecting under the abdominal cavity. This went well, but it is obvious that these fish are somewhat on the small side, says the 28-year old scholar, referring to a type of fish which is very commonly used for research.

The committee for research animals has approved the use of this fish for experimentation. The stickleback was caught in fish traps in the spring, possibly a bit too late according to its yearly cycle, because even though the hormone shock was very obvious, the tests were not as successful as those which Wibe had conducted before.

Boat impregnation

«I tested whether the fish would lose its ability to avoid those predatory fish and birds which eat small fish. The effect was clear even in small concentrations. The stickleback reacted so slowly to danger that it was doubtful whether it could have avoided hunters in the wild. The control group remained easy to frighten, says Wibe, who used the beak from a heron to threaten the fish.

In the early 1990s no one talked much about the influence oestrogen-like substances have on, for example, human reproduction. Aasa Wibe only found out afterwards that this impreg-nation solution works in the same way as does oestrogen.

«I would probably also have found changes in the reproduction pattern if I had examined that, says Wibe. Moreover the stickleback is too tiny for us to look for deformed sexual organs.

No «blacklisting»

According to Wibe, however, it is no longer a secret which substances produce such effects. The problem is that most people do not know the different chemical substances, and the list is growing steadily.

Oestrogen-like substances represent an increasing problem. New substances are added to the list every day, mainly in the form of heavy metals and chloride-organic compounds, in addition to other polluting elements in nature. It is within this area that Wibe wants to contribute the most.

«It is, by the way, easier to measure changes in behaviour than to test if organs have been physically damaged. The challenge lies in enumerating this behaviour and in generating statistics from the material, she says.

Wibe uses the stickleback's nesting habits as one of her criteria, because this is a fish that makes nests for its offspring.

It is the male fish which builds the nest and rears the young. But this time no nests were built, either by the fish that had been given oestrogen or in the control group.

This coming winter she is going to expose the guppy ­ a little aquarium fish ­ to oestrogen. She will make use of the sticklebacks again next spring, but next time less close up to the breeding season and using smaller doses of oestrogen. Far too many fish simply died the previous summer.