Friday, October 03, 2008

Sex is No Fun !

The sexual mating of dragonflies is probably one of the most misleading sights ever. Their mating position causes them to form a heart shape thus when seeing from a slight distance people perceive the scene as 'beautiful lovemaking' but that is surely far from the truth. What actually happens is that the male grasps a female and holds her in a particular position with the claspers at the tip of his abdomen that fit perfectly into a plate of her thorax or the plate behind her eyes. Once she settles into the position, she curls up to bring her vagina in touch with his penis, which is at the base of his abdomen (at this point they form a heart shape). Yes, nothing seems wrong with what I've just described but it all goes downhill when most males use spiny claspers to hold their females in place and these claspers cause severe damage. The claspers cause deep puncture marks, holes in their heads, and there has even been cases where the claspers "gouged the female's eyes, punctured and split her exoskeleton, and pierced her head." The question is how do males really benefit from treating the females in this manner.


In order to understand this odd sexual behavior specific experiments were done by Jonathan Waage of Brown University, and the results of one experiment seemed to somewhat justify the cruel behavior of the male dragonflies. The experiment specifically looked into the female's sperm storage organ only to discover that after a couple of matings (with different males) the amount of sperm didn't increase, the amount of sperm remained the same regardless of how many times she mated. This shocking result caused Waage to also look into the male's sexual organs and that's when he figured out that the male penis was not only used to transfer sperm to the female, but the penis was also responsible for taking out any sperm left in her storage from former matings (which explains why even after a couple of matings, the amount of sperm in the storage area didn't increase). Thus it explains that the male feels the need to use force and harass the females in order to win against the others competing with him and become the victorious one by actually fertilizing the female's eggs. After the males remove the sperm of the previous mating and spread their own sperm around, they try to convince the female to lay their eggs immediately so that the females don't get a chance to mate with any others. If the female doesn't lay her eggs right after, the males usually hold onto the females with their claspers until they do so.

Update:
The article doesn't say anything about the female dragonflies dying, it is just said that they suffer from severe injuries through having sex with the males. All in all, the females do try very very hard to escape from the males, "[they]attempt to escape this boorish behavior by flipping, zigzagging, spiraling upward or downward, submerging in water, fleeing at high speed, or fighting back, sometimes murderously." Also what is really interesting is that in some of the dragonfly species, the females are now being seen in two different colors. For instance, in a particular species known as the 'bluets', the females are now being seen in colors of green and blue. Usually the females are green and only the males are blue, but now some of the females are blue in color also. It is believed that the female has evolved its colors because males are less likely to mate with a female that closely resembles them. An experiment was conducted to see if the males are less likely to mate with the blue female dragonflies, and as expected the results proved that the blue females were harassed less than the usual green female dragonflies because the males just weren't that interested in them.



Posted by Tazneena Ishaque
(3)

10 Comments:

At 12:21 PM, Anonymous Anonymous said...

This seems very odd, it makes sense that the males would want to be sure that the females layed the egss soon after breeding. It seems odd that they dont mind harming the female inteh process. I would think that this would only work in species where parental care is minimal so i wonder how many other species have hurtful mating rituals.

Erica Damon

 
At 2:48 PM, Anonymous Anonymous said...

Wow, this was very interesting. I had no idea that the males sperm could be removed from the female. I feel bad for the female species! Does this mating behavior decrease reproduction. In other words it would seem to me that the females wouldnt want to mate if they have a huge risk of injury. Do females only mate once? Whats the average life span of a dragonfly?

Mia DiFabbio

 
At 5:49 PM, Blogger PWH said...

poor females! but i guess thats how these species have evolved, if the females didnt like it they wouldnt have several partners. does the article mention how the male takes the previous set of sperms out?

Hessom Minaei

 
At 5:26 PM, Anonymous Allison Cornell said...

I found this article very interesting, as I had never heard of males removing the sperm of other males from the female. I'm not an expert with how dragonflies fertilize their eggs. Do they fertilize them as they lay them? Otherwise, wouldn't the previous male's sperm have already fertilized some of the eggs? How long can a female store sperm? How soon after one mating does another male try to mate with the same female? Do the males fight? How much damage do the females incur? Do they usually survive?

Allison Cornell (3)

 
At 9:06 PM, Anonymous Anonymous said...

Wow abuse. Do many females die from these attacks? If so, does this cause a low dragon fly birth rate?
-Sasha Rogers

 
At 10:18 PM, Blogger PWH said...

This seems very interesting, but I'm a little skeptical about the study. If the violence is so necessary, then why don't the females have a developed action pattern that naturally releases the eggs? Instead of taking the beating from the males. This seems very counter-intuitive. Also, do male dragonflies tend to be larger than females? Thank you for your post. I will definitely be looking into this study further.

Amanda Sceusa

 
At 10:22 PM, Anonymous Anonymous said...

I never knew that male dragonflies were that aggressive. You would think that because the female is the one carrying the offspring they wouldn't harm them but that's obviously not the case. I was wondering how do that go about transferring out the sperm of the previous mate of the female?


- Debbie Theodat

 
At 11:11 PM, Anonymous Anonymous said...

How long goes it take for the dragonflies to lay their eggs meaning how long does the male dragonflies hold on to female in that painful manner. Wow it seen like too much pressure to give birth. Do the females ever die from the claspers penetrating too deep. Defiantly not fun.

Tenzing Y. Dundutsang

 
At 11:37 PM, Anonymous Anonymous said...

This is sooooo harsh and cruel!!! I didn't know that males were such bullies!! My main question is that if the female sustains too much damage can they die before they lie their eggs? Or does it not really matter to the male as long as the female can give birth to his offspring? Also, how long does a female live after breeding and what happens to the other male's sperm when the mating male succions it out?

Ada Marie Flores

 
At 11:49 PM, Anonymous Anonymous said...

I'm not sure how the experiments were done. The article said that the males usually hang onto the female to ensure that she lays his eggs and another male doesn't have the chance to remove his sperm. In the experiments they mentioned looking at the females sperm storage bank after she mated with a couple of males. Does this mean that researchers separated the males somehow to allow other males to mate with the female? Although it does sound painful, I guess if you're going to be flying around while you mate then you're going to need a way to hold on tight. It was mentioned that the female has a special plate on her thorax for the claspers to fit into, so I wonder if most of the time the female dragonfly is unharmed and it only happens on accident that the male puts his claspers through her eyes or some other tender spot.

Rachel Carboni

 

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