From the Literature: Nice Guys Get the Girls!

I love aquatic insects!  They do some amazing things and are incredibly interesting animals.  That said, I feel like most people know very little about aquatic insects and the role they play in our world.  Heck – some people don’t know that aquatic insects even exist!  So, for my first From the Literature post, I thought I’d discuss a recent paper dealing with aquatic insects.

In biology, it is thought that males benefit from mating with as many females as possible.  Because males usually do not care for their offspring and invest little in producing sperm, it is best for them to mate with as many females as they can, thereby contributing their genes to as many offspring as possible.  There are, of course, exceptions to this general rule (the giant water bugs I study are an excellent example!), but it holds true for many species.  Because females usually make a greater investment in their children – if nothing else, eggs are much more nutritionally expensive to produce than sperm – they often cannot mate as often as males.  As they contribute their genes to fewer offspring, it is to their benefit to choose the best mates, the ones that will likely produce strong and robust children that have a high chance of surviving to adulthood.  In essence, there is a battle of the sexes going on: males want to mate all the time with every female they can find while females want to mate with only the best males.  It pays for a male to be aggressive and secure as many mates as possible while it pays for a female to be choosy.  In essence, there is a trade-off between what males want and what females want: when one sex succeeds, the other suffers.

water strider interactions during mating

In this image by Omar Eldakar, a hyper-aggressive male (on the right) attempts to break up a mating pair of water striders. The colored dots were used by the researchers to keep track of individuals.

This idea sets the stage for a recent paper by Dr. Omar Eldakar (currently a postdoctoral fellow at the University of Arizona) and his colleagues published in the November 6, 2009 issue of Science.  Eldakar and his team studied a type of aquatic insect called water striders (order: Hemiptera, family: Gerridae).  Water striders (also known as Jesus bugs, water spiders, and pond skaters) are long, skinny insects that live and hunt on the surface of water.  Water striders are typically found in groups of several individuals called aggregations in calm areas of streams and ponds.

The species Eldakar studied is Aquarius remigis and it is well-known for its battle of the sexes.  Many male A. remigis individuals are highly aggressive when pursuing females, lunging at and jumping on their potential mates.  While the females often resist  mating with these hyper-aggressive males, the behavior has been known to improve mating success.  Aggressive males are usually more successful at securing mates than non-aggressive males.  This leads to a question: if aggressive males mate with more females than non-aggressive males, why aren’t ALL males aggressive?  Eldakar and his colleagues wondered if the fact that most studies of sexual conflict in water striders do not allow individuals to migrate between aggregations might explain why hyper-aggressive males are reportedly so successful.  If females are forced to remain in an area with hyper-aggressive males, the males might have a higher mating success than if the females could be choosier about who they mated with.

Eldakar and his colleagues set up an ingenious experiment to test this idea.  First, they placed water striders in an artificial pond and observed male aggression, movement of females, and mating attempts/successes.  Water striders were able to form their own aggregations and move freely between them.  The researchers then divided the pond into several sections, placing males of various aggression levels with females in each section.  The same observations were made, though this time individuals were not able to move between groups.  Finally, the group compared their observations of the open treatments to the closed treatment to see how movement contributed to the mating success of aggressive and non-aggressive males.  They discovered some interesting things.

As had been reported in other water strider studies, hyper-aggressive males had more successful mating attempts than the non-aggressive males in the closed system.  If females were not able to move to another aggregation (i.e. their choices in mates were restricted), they mated more frequently with the aggressive males than the non-aggressive males.  However, when the striders were able to move between groups, Eldakar observed that females moved to other aggregations when harassed by aggressive males.  Aggressive males repelled the females they wanted to mate with!  The females would, however, readily mate with the less aggressive males in their new areas.  This meant that less aggressive males were able to secure many more mates in open systems than in closed systems.  In other words, the females avoided the aggressive jerks and the nice guys were getting the girls!

I think this is a great paper.  The experiment was very simple, but it ended up revealing a lot of information.  Many scientists call this sort of experiment “elegant” and I think this research certainly qualifies as an elegant experiment.  Eldakar was able to refute the findings of several previous papers with an experiment that should be very easy for others to duplicate, one of the conditions for good science.  He also clearly reminded biologists of one of the perils of doing behavioral research in the lab: unnatural conditions sometimes lead to unnatural behaviors.  As a behavioral researcher myself, I think this isn’t reinforced enough.  By modifying what had been done in the past, by allowing aggregations of water striders to form naturally rather than forcing them into pre-determined groups, Eldakar learned that aggressive males are not always the most successful in nature.  This corrected what we already knew and gave us some great information that will be useful for many future studies.  Thanks, Dr. Eldakar!

Literature Cited:

Eldakar OT, Dlugos MJ, Pepper JW, & Wilson DS (2009). Population structure mediates sexual conflict in water striders. Science (New York, N.Y.), 326 (5954) PMID: 19892974

_______________

Text copyright © 2009 DragonflyWoman.wordpress.com.

This post was chosen as an Editor's Selection for ResearchBlogging.org This blog post was an Editor’s Choice selection at ResearchBlogging.org!

Advertisements

New Feature: From the Literature

I thought I should start writing occasional reviews of recently published scientific papers featuring aquatic and other insects, so I am starting a new feature called From the Literature.  We scientists collectively call all scientific papers ever published “the scientific literature,” so “from the literature” refers to papers that have been published in a scientific journal. I’ll try to do one review every couple of weeks, but first let me tell you why I think this is important.

One of the major downsides to science is that we use what is effectively our own language, the language of science.  Our language is full of big words derived from Latin and Greek and is full of jargon.  These words allow us to describe what we’ve done in very precise terms within our personal fields of study, but they are often difficult for someone who is not familiar with the literature to understand.  Furthermore, each different science has the equivalent of it’s own dialect.  The words I use in my entomology papers might be totally different from those written by scientists in other fields.  I frequently have a hard time reading papers pertaining to other sciences, such as physics or chemistry, because I do not understand their jargon.  They use a different “dialect” of science than I do.

I believe that the use of scientific language generally causes problems when you want to communicate your research to other people.  However, I think the language barrier is especially problematic because it creates an enormous disconnect between scientists and the rest of the population.  If it’s hard for me to understand a physics paper, even though I am a scientist myself, how can the author expect non-scientists to understand?  I at least have some of the jargon down, but many people have never come across some of the words used.  Some words are so specialized and used by so few people that it is even hard to look them up!  The use of scientific language in scientific papers means that it can be very difficult for non-scientists to delve into the literature and learn more about what scientists are actually doing.  This is a problem.

Another problem in science relates to the availability of scientific papers.  If you’re a non-scientist and you want to read a scientific paper (you’re willing to break down that language barrier and dive in!), where do you go?  You can’t simply run down to Barnes & Noble and pick up the latest copy of Freshwater Biology.  If you happen to be lucky enough to live in a city with a big research university, you can access scientific papers in the university library.  You can always subscribe to a scientific journal, but many of these cost hundreds or thousands of dollars if you are not a member of the scientific society that publishes it.  Most non-scientists aren’t willing to shell out the cash to pay for a full-priced journal subscription.  Neither are most scientists!  If you want to look at one specific article from one specific journal, you can often download that one article from the publisher’s website, but it will cost you to do so.  Essentially, most science is not open access – not all people are able to access scientific information.  If you are not a scientist yourself, it can be incredibly difficult and/or expensive to find things in the scientific literature, and this is a problem.

Now let’s get back to my original goal in starting this feature.  I think it is awful that most people can’t read science.   It causes all sorts of problems, from general scientific illiteracy to faulty policy making decisions to issues with funding for scientific research.  There is also a lot of really fascinating information available in the world that most people can’t even look up!  I hope to make a tiny dent in this problem by reviewing papers, effectively translating them into plain English, so that non-scientists can learn about some of the fascinating discoveries made by entomologists.  I want to get some of this information out to the general public.  We entomologists do some very interesting things and the world should know about it!

Next time, I’ll review a great new paper that was published a few weeks ago in the prestigious scientific journal Science.  I hope you’ll enjoy my new feature!

_______________

Text copyright © 2009 DragonflyWoman.wordpress.com

A strange fall visitor

While I hear stories of blizzards and frigid weather in other parts of the country, here in southern Arizona it’s still quite warm.  Unseasonably warm actually.  I had to wear a jacket for a few days a couple of weeks ago, but then it got hot (as in almost 100 degrees!) again.  Luckily for me, this means that there are still a lot of bugs out.  A few days ago, my coworker and I tried to catch some painted lady butterflies when we got back to the office after our field work.  The bird of paradise plants and the other things planted with them are still in bloom, so there are still tons of painted ladies and sulphur butterflies flitting around.  Yesterday, I was on my way out to run errands when I saw this on the wall of my carport:

Mantid

Mantid

As I always do when I find mantids outside, I ran back into the house and grabbed my camera, snapping some quick pictures of it before I did my errands.  It was still in the carport when I returned, so I scooped him up and brought him in the house to take some better photos indoors where the light was better.  The image above is one of those.

I love mantids.  I think they are amazing and beautiful animals.  Unfortunately, I don’t see them all that often.  It’s hard to find them most of the time.  They are masters of camouflage, or blending in with their environment, so I just don’t notice them.  Mantids are known to mimic all kinds of plants and flowers (to see some amazing mantid flower mimics, see this great blog post from Asia), tree bark, sticks, and other insects, so they are very hard to see if you’re not actively looking for them.  But that’s the point!  If you want to avoid being eaten, one great way to do it is to blend in with the background so effectively the predator doesn’t even notice you’re there.  If you’re an ambush predator (more about this in a moment), it also helps if the things you want to eat can’t see you very well.  I put the mantid pictured above into the bush in front of my house when I was finished photographing it.  It wasn’t the kind of plant this mantid would normally be found in, but it was still a little hard to see:

camo mantid

Mantid camouflage - can you find it?

This particular mantid was bright green against the deep rust color of my carport when I found it, so it really stood out.  It didn’t take much skill to find this one before I put it in the bush!  I have an idea of why this might be, but I’ll get to that later.

Mantids have some very interesting behaviors.  Their amazing abilities to mimic the plants they live on don’t end at their coloration and body shape.  They are also well-known for mimicking leaves and plants blowing in the breeze.  They use their hind and middle pairs of legs to sway back and forth gently every now and again.  If they are living on plants and want to blend in, it’s to their benefit to mimic the plant as much as possible.  This includes moving the way the plant does – the swaying behavior helps them look more like the plant than their coloration and body shape alone.  Whether they use this behavior specifically to avoid detection is debatable, but it helps them blend into their environment regardless of its primary purpose.  The mantid I found yesterday started swaying when I went to grab it in what may have been a rather desperate attempt to avoid detection and capture, so I got to see this behavior in action.  If you’d like to see it too, check out this YouTube video (which I did not take):

Isn’t that fun?  Just picture this mantid swaying on a stick being gently blown in the wind.  I love watching these little mantid “dances!”

Many mantids are ambush predators, which means that they sit and wait for food to come near before darting out to capture their prey.  Because they blend in with their environment so well, many prey animals won’t notice a mantid sitting on a plant or on a flower and walk right by it.  The mantid then uses it’s forelegs to reach out and grab the prey with amazing speed.  Like the giant water bugs I study and have written about in earlier posts, mantids have what are called raptorial forelegs.   These are legs that are specifically designed for capturing prey.  They’re big and bulky and full of muscles, so they’re both very fast and very strong.  They can often fold back on themselves to allow them to grasp things.  People have long thought that mantids have the appearance of praying when they hold their legs ready to grab prey, hence the common name praying mantis.  Mantids also frequently have spikes or other structures that help them keep hold of things they grab.  Check out the raptorial forelegs on the mantid from yesterday:

Mantid raptorial foreleg

Mantid raptorial foreleg

This one has bulky forearms and some pretty formidable spikes!  Those spikes help them subdue prey so they can eat them.  And mantids can eat some pretty impressive things including other insects, small snakes, lizards, frogs, small rodents, and even the occasional bird!  If they can grab it and keep a hold of it, they’ll likely try to eat it.  I think this is part of why I like mantids so much – they remind me of my water bugs in their ability to capture, subdue, and consume their prey, and they just look so darned cool doing it!

So back to why I think this bug was in a strange and very conspicuous spot.  If you have a weak stomach, this is where you should stop reading.  I went out to the bush where I had released the mantid this morning to see if it was still there and was sad to see that it had died overnight.  Because I’m an entomologist, my first thought was, “Wow!  It’s sad the mantid died, but it would make a great addition to my collection!”  So, I brought it inside and started pinning it.  Much to my horror, as soon as my pin hit the abdomen, I disturbed the mass of maggots that were growing inside the mantid and feasting on its living flesh.  They burst out of the mantid and spewed onto my counter.  Now I’m not a very squeamish person, but maggots spewing out of anything is enough to make me queasy.  I ended up preserving the maggots in alcohol (why collect one type of insect when you can add two to your collection?) and will figure out what they are later, though I know they are a type of parasitic fly.  An adult fly likely deposited its eggs inside the mantid a month or two ago and the maggots slowly consumed the living mantid as they developed.  Parasites are known to alter the behavior of many insects they infest so that they are better able to infest other organisms.  It’s quite possible that the maggots altered the behavior of this mantid when it was near death so that it made itself conspicuous enough to come into contact with another animal that the maggots could use as food.  Alternatively, it could simply have become delirious as its body was hollowed out and mistakenly crawled up a surface it would normally avoid.  Whatever the reason, it didn’t matter that it was in a conspicuous place – it was dying anyway.  And I’m happy I got to see it before it did.  A mantid will always brighten up my day.

_______________

Text and images copyright © 2009 DragonflyWoman.wordpress.com

Field Stories: Attack of the Giant Water Bug!

Today I’m going to share a story about an experience I had at my field site a few years ago.  It’s about a young scientist trying to do field work for her Ph.D. and a determined father giant water bug who took great offense at her attempt to remove his eggs from the pond for study in her lab.  This particular story has the makings of an excellent bad, B-grade horror movie, so I hope you will enjoy it!

For those of you who don’t know, Arizona is an area of high traffic for illegal immigrants.  We get all kinds of people wandering into our country from other locations, stumbling through the desert looking for a better life in America.  Unfortunately, it means we also get some hefty drug trafficking.  The area where I do my field work is a high-traffic area, so I always make sure I have someone with me when I do field work.  I also like to have another person with me in case I get stuck in the mud in bottom of the pond and need to be pulled out (see my post about my field site if you don’t know why this is important!).  On the day in question, I had a friend with me, another environmental physiologist who works on insect eggs.  I’ll call her K for the sake of this story.

me in Papago in wadersK and I made the 45 mile drive out to the pond.  We chatted about work and our lives on the way there and were in a generally good mood by the time we arrived.  I put on my very stylish chest waders (see image at right), and wandered out into the pond.

When I pull sticks out of the pond, it is common to find the father clinging to the bottom of the stick.  They frequently sit still for only a few seconds before dropping back into the pond.  Occasionally, one will hold on a bit longer and I’ll have to shake the stick a bit to get him off.  The emergent brooders are well-known for protecting the eggs they have fathered.  If you tap a stick with eggs on it, you can frequently get the water bug to rush out of the water and up the stick in an attempt to protect his eggs from predators.   They can actually be rather ferocious.

On this particular day, I pulled a stick out that had a male attached to it.  He didn’t come loose with my usual shaking method, so I wasn’t sure what to do.  I had a handful of sticks with eggs in the other hand, so I couldn’t just push him off the stick.  I poked him with one of the sticks in my other hand, certain that he would be startled and fall into the water.

Instead, he crawled up the other stick.  Fast.  Right toward my hand.  Doing that “How dare you mess with my kids!” behavior.  I started shaking the stick really hard, trying to knock him off, but he still kept coming for me.  Not wanting to be bitten (and not wanting him to screw up the eggs I’d harvested when he crawled over them), I whacked him gently with another stick and he fell into the water with a satisfying “plunk.”  I waded back out of the water with my sticks, and knelt on the bank to trim them down.

If you thought the story was over at this point, think again!  A few minutes into trimming sticks, I felt something scrabbling around my neck area, scrambling over the straps of my waders toward my head.  Something big and strong.  Something that felt suspiciously like a certain angry giant water bug that had already tried to attack me…  I asked K, “Whoa!  What’s on my neck?” as I reached up and flicked whatever was on my neck off.  I was horrified to see that what fell to the ground WAS the giant water bug!  He’d climbed all the way up my waders and had ended up inches from my jugular!  He was clearly out for my blood.  :)  I may have let out a little shriek of horror and K laughed.  She knew full well that she would have done exactly the same thing if it had come after her.

Site of this adventure!

Site of this adventure!

So I grabbed the persistent little guy and tossed him back into the pond, thinking that was that.  I went back to stick trimming and egg counting, but a few moments later, I heard K laughing.  “He’s coming back!” she said.  I didn’t believe her, but I turned around anyway, ready to be a sucker since she’d already made fun of me that morning.  Sure enough, there was the darned water bug, climbing out of the pond, onto the shore, and headed right for me.  Again.  Now this is where I think the B-grade horror movie would come in.  If the water bug was a couple of feet long, it would have been perfect – me sitting on the ground, helplessly scrambling to get up, while the giant water bug bore down on me!  You’d see him crawl onto me and a few scenes later, some random hiker would find my dead body, sucked completely dry, as ominous music played in the background.

In reality, I picked the bug back up and chucked him back into the pond.  AGAIN.  Surely he was finished trying to exact his revenge for stealing his eggs from him.  Hadn’t I clearly demonstrated that I was the bigger, stronger opponent in this confrontation?

Apparently not.  A few minutes later, the bug came for me again.  He crawled out of the pond once more and headed straight for me.  This time, I was finished with my sticks and was watching the shore.  I saw him emerge and let him get a couple feet out of the water, marveling at his tenacity, before I picked him back up, yet again, and tossed him back into the water,  yet again.  If there was an award for the most protective giant water bug father, this would clearly be the winner.  He was quite determined.

K and I packed our stuff up and went back to the car.  Who knows.  The bug may have crawled out again and started looking for me one more time, but we weren’t there to see it.  We joked all the way home about the incident.  We kept imagining the bug clinging to the back of the seat, ready to reach his raptorial forelegs around the headrest as he grappled with me, his sworn enemy, as I drove home.  That was one persistent little bug!

In the horror movie version of this incident, the giant bug would have indeed clung to the back of the seat, then slipped out of the car and into the house while I unpacked my gear.  He would waited until dark, after I’d fallen asleep, then attacked.  Neighbors would notice that they hadn’t seen me for a few days and call the police.  An officer would calmly open the door and jerk back in horror as a gigantic beast rushed past him, eager to find new victims as he wandered the streets of Tucson…

_______________

Text and images copyright © 2009 DragonflyWoman.wordpress.com