Male-like mothers: The male perchlorate waste of fish species

Widely known as a component of rocket fuel, perchlorate is a common waste in soil and water. In many studies, it disrupts the concentration of thyroid hormones, affecting the development of height and nervous system. However, recent studies have shown that perchlorate can also interfere with sex formation.

Some of the observed changes surprised scientists because there were initial differences in the sex of the fish: they were female instead of male. Some females are male-like and produce sperm.

Richard R. Bernhardt of the University of Alaska at Anchorage and his colleagues focused on the study of the species of thorns (threespine sticklebacks), a small marine creature. In three weeks, scientists have raised adult animals caught in the wild in clean or domestic water environments that have been added 30, 60 or 100 ppm perchlorate. During this period adults have laid eggs.

The juveniles obtained from each group are then reared to maturity in their respective water environments. To the reproductive age, in each group reared in an extra perchlorate environment 10 bulls obviously show their instincts. Once a day, the males receive a 10-minute "visit" from each female carrying eggs in the same group.

AI READY?The bright skin of a male stickleback caught from nature (left photo) shows that they are ready to fertilize. Poisoned child perchlorate (right photo) only has grayish brown skin and is not interested in binding. (C. Furin and Bernhardt of the University of Alaska)

The first sign of this difference is : Among the fish infected with perchlorate, many male breeds lack the blue and red pigments, a sign of readiness to be fertilized. Most of these fish do not exhibit normal sexual behaviors, such as building nests, and many are ignoring children. Meanwhile, 80% of males have fertilized eggs in the group fed in clean water. When perchlorate content increased from 30 to 100 ppm (parts per million), successful fertilization rate decreased from 50% to 0%.

Finally, the belly of these males becomes bulging with the eggs. This proves that these are bisexual fish, with the ability to produce eggs and sperm.

Perchlorate contamination has caused males to develop abnormally through long-term experiments.

Last month, the Environmental Protection Agency stated that the limited concentration of perchlorate in aquatic organisms is 24.5 ppb (parts per billion). While the concentrations used in this study were at least 1,000 times greater than that limit.

However, these doses are only naturally generated doses, which is the objection of the toxicology researcher in the water environment Bernhardt and his colleagues in the Institute of Chemistry and August poison. They suggested that the concentrations in the experiments were similar to or close to the concentrations measured in some contaminated areas in the United States.

The ' big surprise ' is that perchlorate has the ability to produce bisexual individuals in many experiments, according to EPA's Mid-Continent Ecology Division researcher Gerald T. Ankley. Duluth, Minn. Obviously, that 'is not something you can predict according to previous thoughts about how perchlorate works,' he added.

All observed changes show that perchlorate ' acts as a male hormone' or male sex hormone , Ann Cheek fish physiology researcher at the Texas Health Science Center in Houston, commented. To confirm this, it is necessary to conduct analysis of the cells and thyroid tissue of experimental fish.

Scientist Christopher W. Theodorakis of the University of Southern Illinois in Edwardsville argues that this ' interesting ' maleization may open a new perspective on thyroid hormones - hormones that play a role in maintaining the race.

'This article tells us more about perchlorate - and their effects on the thyroid gland - compared to what we already know,' said R. Thomas Zoeller, a thyroid endocrinologist at the University. Massachusetts in Amherst - agree. That 'could be an interesting issue to think about , ' he said.

Le Pham Thanh
Email: lpthanh_blackrose84@yahoo.co.uk
(Translation from Science News, August 12, 2006, Vol. 170, No. 7, p. 99)