Fish Fertility: Fish Switching Genders

Fish, unlike most human beings, can naturally switch their gender in some instances. Clownfish and wrasse are known to change sex. Clownfish have a hierarchy with a female fish at the top; and when she dies, get this, the most dominant male fish changes sex and takes her place. It all sounds suspiciously like our political system at the moment. With wrasses, the gender change is from female to male, and involves the largest female in the harem switching sexes and changing into a male. Life is obviously very interesting when you are a fish; playmates abound. Life in the goldfish bowl may not be as boring as we all thought. Parrotfish can also live for some time as either male or female, then different hormones takeover and cause the parrotfish to change. In the case of parrotfish this only occurs in their immature stage before their organs have developed as either a male or female.

More recently, fish have been turning from male to female caused by birth control pills for humans entering natural river systems. Chemical components of birth control pills excreted in urine and flushed down toilets have made their way into waterways. In a recent study by the US Geological Survey, it found that fish that were exposed to synthetic hormones call 17a- ethinylestradiol, or EE2, produced offspring which struggled to fertilize eggs. This affects them on an intergenerational level, with the grandchildren of the originally exposed fish suffering a 30% decrease in fertilization rates.

Fish Fertility: Fish Switching Genders

According to The Washington Post newspaper, male smallmouth and largemouth bass throughout the United States have switched sex; growing ovaries where their testes should be. Oral contraceptives for women are widely considered to be the cause of this sex change in fish, in this instance. The number of intersex fish keeps increasing and spreading. Scientists have been looking into the chemicals used by miners as possible cause for the sex changes as well. Synthetic estrogen, such as EE2, is more persistent than natural steroids and is usually present in higher concentrations in treated wastewater.

Even chickens, can on occasion undergo natural sex changes.  In the case of the female chicken, she usually only has one functional ovary on her left side. If Mrs Chicken has a problem with her ovary, in that it does not develop properly, her right side may begin to grow a male organ; and the hen changes completely into a rooster. No wonder so many people are worried about hormones in their chicken dinners.