Friday, 11 July 2008

Sex on the move – a blunt approach.

As in most birds, the males in dragonflies appear more colourful and are dressed to impress. On the other hand, their females are differently-coloured. Take for example the Scarlet Basker Urothemis signata signata that I photographed at my local wetland. This is the male, which is rather gaudy.

The female, shown below, is less showy, but has a better 'dress sense' in my opinion. As their name implies, Scarlet Baskers love to bask in the hot sun. When they do it, during the warmest times of the day, they are often quite approachable for photography (you need a bit of technique, of course).

Scientists assume that wing patterns, body size and colour all help the male dragonflies to recognize the females of their own species. Females of some species may closely resemble females of another species, and if the two species share the same habitat, males may grab any female they can. At times males will even grab other males only to realize their mistake later on. Just like this male found out.

This is hardly surprising as some dragonfly males are almost identical to the females in their looks. Take a look at this post to see how similar the two sexes of the Sri Lanka Forktail are.

As I explained here, to initiate sex, a male dragonfly grabs a female by the head—often in mid-air, using special appendages at the end of their abdomen. This vital part of male anatomy will only fit to perfection with females of the same species. If the fit isn’t quite right, the female will not be impressed and will not cooperate in connecting her genital openings with the male’s copulatory organ, which is at the second segment in case of the dragonflies. When that happens, the male will soon let go to hook up with another—in all good sense of the phrase.

A Marsh Skimmer in tandem at Sinharaja 'World Heritage' rain forest - 8 July, 2008
So, although dragonfly sex appears forceful especially with their submissive aerial manoeuvres, the female dragonfly has the final say in “choosing” her mate by this act of non-cooperation.
Most dragonfly males remain focused on mate-guarding at pre-copulatory, and post-copulatory stages, and will chase away any intruders.

You may ask why mate-guard at post-copulatory stages? That is because girls can misbehave. And due to sperm competition. That is intruding males can ‘remove’ sperm packets delivered by the males that have mated previously, which in the case of the intruding male is a way of ensuring that his genes are passed on to the progeny. For this end, dragonfly males are endowed with multi-purpose intromittent penises fashioned with brushes, and hooks that function to physically remove rival sperm from the female reproductive tract.

A Marsh Skimmer female at Sinharaja 'World Heritage' rain forest - 8 July, 2008
In some dragonflies, their multi-purpose penises also can provide sensory stimulation during copulation for the females to induce ejection of any previous sperm received before delivering his load. Furthermore, they can also ‘reposition’ the rival sperm to an area in the reproductive tract of the female that is less likely to cause fertilization. Another method is 'sperm flushing' by displacing any previously stored sperm in the female reproductive tract by the new deliveries.

A Marsh Skimmer male at Sinharaja 'World Heritage' rain forest - 8 July, 2008 So, doesn’t the female have any choice of “choosing” the sperm she wants just as any self-respecting female would do? The answer is, yes. Just as males have evolved sperm-displacement mechanisms using their fancy gear, females too have presumably evolved means to avoid sperm displacement. For this end, females have sperm storage spaces that allow them to manipulate the sperm they've received—to avoid sperm displacement, re-distributing sperm masses, favouring sperm located in certain sites and ejecting sperm after copulation.
So, as it is the case with most animals, in dragonflies mating first will not ensure that you will farther a child. This explains why some male dragonflies appear to be paranoid with mate-guarding at post-copulatory level, by holding up to the back of the female’s head, and remaining in tandem until the female deposits her eggs.


Anonymous said...

I never thought I'd read so much about Dragon flies!

Anonymous said...

I guess the female dragonflies don't have to worry abt being taken advantage or worse being raped..:)

Amila Suwa said...
This comment has been removed by the author.
Amila Suwa said...

Hi Kalusussa,
There is more to dragonflies than their beautiful colours and graceful flights. They are complex and interesting creatures to study. There's a lot that can be done in that area over here with our massive tally of 117 species.

Hi Chaarmax,
Yes, female dragonflies can avoid being an 'unwilling sperm recipient' - as the good old George Carlin feared that a rape victim would be called one day. Good observation.

Amila Suwa said...

Oops Kalusudda! Sorry mate, I have called you Kalusussa..although I think that too is not a bad name..rhyming with gallicissa!

oldcrow61 said...

This is fascinating information about dragonflies. Not having known much about them, now I can spout off some intelligent information to friends, lol. Love the way you wrote it. The pictures are just beautiful.

Amila Suwa said...
This comment has been removed by the author.
Amila Suwa said...

Hi OC,
Thanks! Glad you found it useful.I am happy you liked my way of writing. Your recent dragon pics are just as beautiful I must comment. You are lucky to have a home garden rich in life just as I do, so that there's a lot to see & photograph without going too far!

p.s. I photographed a goodie today in mine!

Sandpiper (Lin) said...

Such an interesting post and, as always, your pictures are fantastic. I enjoyed your previous posts, too. Hope all is well with you!

Amila Suwa said...

Hi Lin,
Thanks as always! I am glad you enjoyed this & the one before. I am back from a terrific 2-day trip to Sinharaja rain forest with loads of goodies. No plan to blog about it soon as I am busy with some other work!

Mel said...

Great post!
I never knew so many facts about dragonflies. Thank you for the lesson :)
It was a fun and educational post, thanks!

Amila Suwa said...

Thanks Mel!
Glad you found it useful.
I am looking forward to seeing some dragonfly pics from La Laguna soon!

Margerie said...

LOL now I know why my husband said I looked "different" the first time he saw me without makeup. Hmm... I wonder if the lady dragonflies remember every little comment even years later.....

Fabulous photos and information. The dragonfly and the art of reproduction!

Amila Suwa said...

Hi Margerie,
hehe...husbands over here are not as subtle when it comes to expressing such sentiments! And am not surpised you still remember that remark!

I am glad you liked this post. Thanks for dropping by!

Related Posts with Thumbnails