The urge to mate is a trait that all animals share. The inherent need to perpetuate our own genetic line could be argued as the driving force behind life and the fight to ensure that our offspring are the best they can be has led to some seriously interesting, and often quite ingenious, mechanisms. Females have developed numerous ways to block undesirable mating and often even have some level of control over which suitor’s sperm is successful while the males of the species are constantly developing new ways to overcome these obstacles. There are a number of defences found in the animal kingdom that females use to protect future offspring from being born of inferior parentage. The potential mothers use everything from simply demanding open displays of a male’s superiority to implementing natural internal defences such as plugs or environments inhabitable to sperm. After displays of affection have been mutually accepted and coupling has occurred you would think that we have reached the end of the story but this is really just the beginning, just because the male has managed to convince the female to allow him to mate with her doesn’t necessarily mean that any offspring she produces will actually be his, especially considering that most creatures will not limit their options to only one mating. That tiny sperm’s journey is only just beginning and its biggest challenge is definitely still ahead of it! The odds really are against those little guys so the males of different species have developed a variety of ways to give them the best chance possible.
This constant fight to ‘one up’ each other means that some animals copulate in manners that could only ever be described as bizarre. The bedbug (Cimex lectularius) is a great example of this. Although once only found in bat caves and mammalian dens, bedbugs are now better known for being found in the crevices of mattresses you would rather not frequent and are famous for crawling out in the dead of night to feast on their unsuspecting victims, sucking their blood and leaving angry red spots in their wake. Bearing this in mind, I really ought to have very little time for them but actually I have quite a lot of begrudging respect for these little insects. You see, the males go to extreme lengths to ensure a females offspring is theirs, namely by using a method called ‘traumatic insemination’. The name doesn’t fill you with confidence does it! Despite the fact that female bedbugs have fully functioning genitalia and are totally capable of mating in a ‘traditional’ manner, the male bedbugs have developed a method to completely cut out the middle man, avoiding all of the female’s nifty defences. They simply inject their sperm straight through the abdomen of the female and straight into the haemocoel, a blood filled cavity, using genitalia that resembles a hypodermic needle. Suddenly the term ‘traumatic insemination’ makes sense!
Despite its obvious efficiency this method isn’t 100% fool proof as some of the sperm will become victims of the female’s immune defences, but some of the sperm will fare better and make it to a special gland, the seminal conceptacle, in the females system where it will be stored for later use. In response to this undoubtedly traumatic mating mechanism the females of the species have evolved the organ of Berlese, a special type of tissue that helps the female heal as quickly and efficiently as possible following each mating event. The organ of Berlese has also been shown to reduce the chance of infection from the various fungi and bacteria that can be found in the male’s penis therefore protecting from infection on top of promoting healing.
And so it continues – The Battle of the Sexes!