Did you know that several creatures in the animal kingdom can change or manipulate their sex for various reasons, a major one being survival of their species? There are indeed certain organisms in nature, who change their reproductive identities or adapt the behaviour of the opposite sex based on a time-specific need. Some animals even have working male and female reproductive organs. Crazy right? Not really!
These animals or creatures are called hermaphrodites. Remember the Disney movie Finding Nemo? When Nemo, a young clownfish, is unexpectedly carried far from home, his father and Dory, a blue tang, embark on a journey to find Nemo. Well, a clownfish is a hermaphrodite and while we knew Nemo was a boy, he could very well have been a girl the whole time!
According to a universally accepted definition found in Science books, a hermaphrodite is an organism with both male and female reproductive organs. In reproductive biology, a hermaphrodite is an organism that can produce both gametes (they are an organism’s reproductive cells, also referred to as sex cells. Female gametes are called ova or egg cells, and male gametes are called sperm) associated with male and female sexes. Hermaphrodites tend to be solitary animals, although there are exceptions.
Among various types of organisms, a hermaphrodite may arise because of variations in the genetic code. For instance, in human beings, hermaphrodites are caused by a variety of genetic conditions. In one form, as per research over the years, a hermaphrodite or an intersex person is created when two fertilised eggs fuse together, giving the zygote two X chromosomes and one Y chromosome. Several other cases of hermaphrodites can be caused by the SRY gene, the gene responsible for testosterone and male organs, being transferred to the X chromosome during meiosis (the process where a single cell divides twice to produce four cells containing half the original amount of genetic information), resulting in both male and female reproductive organs.
Now, if you take a good look around, you might find hermaphrodites in nature. Let’s look at a few of them and how they seem to manipulate their gender.
Clownfish are all born male, but that doesn’t mean they simply remain so for their entire lives. Rather, some — the most dominant males — turn into females (a process known as sequential hermaphroditism).
What is sequential hermaphroditism?
Sequential hermaphroditism is a type of hermaphroditism that occurs in fish, gastropods, and plants. It occurs when the creature changes its sex at some point in its lifetime. In particular, a sequential hermaphrodite produces eggs and sperm at different stages in life.
Given their importance in breeding, female clownfish play an integral part in the species’ survival. This importance is clearly observed in the school’s physical makeup. The female clownfish, generally the largest fish in the school, surrounds herself with a gang of males exclusively for the purpose of breeding. If she dies during the process, the dominant male — second in command — will change his gender to replace her, ensuring the school’s survival.
Earthworms can be found in your own backyard. Earthworms spend their days deep beneath the soil, burrowing in random directions and aerating the soil. While two earthworms could be only a short distance apart they might never come into contact. Because of this isolated lifestyle, it is important for the worms to be able to reproduce successfully when they meet. Earthworms are hermaphrodites as they have both male and female reproductive organs. When they copulate, both organisms give a gamete and receive a gamete. An advantage of being a hermaphrodite is that if a worm never finds a mate, it can fertilise its own eggs and reproduce.
They grow between six and eight inches long, the banana slug is one of the largest slug species. But that’s not the only thing that makes this creature unique. Banana slugs are born with both male and female organs, making them hermaphrodites. In matters of reproduction, the slugs simply have to look for a mate of similar size. When they do so, the creatures can then impregnate each other. On rare occasions, the banana slug has also been known to impregnate itself.
The whiptail lizard’s entire population happens to be female and they are found in New Mexico. Given the evident impossibility of exchanging genetic material, researchers have stated that these lizards are at a “major disadvantage” when it comes to adapting to a changing environment. After all, unless these creatures can recombine their DNA, they will produce offspring with an identical set of chromosomes. If these are weak or mutated, they have no chance of being overridden by another mate.
How do they survive then? According to researchers from the Stowers Institute for Medical Research, the whiptail lizards do so by altering their genetic code. It includes pairing their ‘sister’ chromosomes — as opposed to their homologous chromosomes, as sexually-reproductive species do. By this the lizards maintain the ‘heterozygosity’ (the possession of two different alleles of a particular gene or genes by an individual) needed to survive.
Well, can you find more hermaphrodites around you, in nature? Then let us know in the comments below.
If you wish to read more such exciting stories, check out the Learning Tree blog.
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