Hermaphroditic Fish Can be Two Sexes at One Time
Fish Can Change Gender to Increase Their Reproductive Potential
Apr 8, 2009
It is not always easy for a fish to reproduce. The ocean is a big place and many fish do not wander far from their homes. It can be hard for a fish to find that special somebody. Luckily, nature has provided many fish with a partial solution. Many fish can change sex, thus factoring out gender as a mate qualifier.
Types of Fish Gender Change
Not all fish can change sex, but many can. In fact, the majority of reef fish will change gender at some point in their lives. These fish are considered hermaphroditic and such fish have a few options. Some fish are simultaneous hermaphrodites meaning they are both genders at the same time and could potentially mate with any other individual in their species. Other fish are sequential hermaphrodites and these fish change sex at some point in their lives. Protandry is when a male becomes a female and protogyny is when a female becomes a male. Some fish can change their gender more than once, going back and forth between genders.
Why Do Fish Change Sex?
Fish will change their gender in order to maximize their fertility. Maximizing reproductive success is influenced by the amount of resources around, the current male to female ratio in the fish population, and the size of the current males and females. Some fish species will start off all female and a large aggressive male will form a harem, using aggression to keep the smaller fish female. If he dies off the largest female fish can change sex and use her size to maintain dominance over the harem. In other species the juveniles are all males waiting for their chance to mate with the large female. This is useful to fertility because larger females can produce more eggs. When the female dies the largest male fish will change gender.
How Do Fish Change Sex?
The endocrine system is almost certainly involved in the gender switch. The endocrine system is in charge of releasing hormones into the body and includes the gonads. However, while progress is being made the exact mechanisms are still not known. Scientists are still researching which hormones, genes, and chromosomes are involved.
Examples of Fish Gender Switches
There are many examples of hermaphroditic fish. One of the most well-known is the clownfish or anemone fish. Clownfish exhibit protandry, with juvenile males waiting to one day become the large female. Since there is only one female clownfish mate in pairs. Parrotfishes on the other hand exhibit protogyny with one dominant male lording over a harem. Salmon are not reef fishes, but they do exhibit simultaneous hermaphroditism. Certain types of goby can change their sex serially, going back and forth between genders.
Gender identity may not easy for a fish, but evolution has certainly found an interesting way for fish to become successfully reproductive. Different species of fish can change sex in different ways, showing interesting adaptations to life's challenges.
