Science Sunday: Field Research vs. Lab Research

backswimmer

Backswimmer

I really enjoy field work.  Having grown up in an outdoorsy family, I spent a lot of time outside as a kid.  When it came time to choose a senior thesis topic in college, I headed straight for the local wetlands, plopped myself down on a boardwalk, and watched damselflies flying around for several weeks.  I swore to myself that I was going to do all of my graduate research outdoors because that’s what I loved to do.

My regular readers know that plan didn’t quite pan out (click here for examples).  But there’s a reason for that!   There are times when it’s easier do work in the lab and there are questions that are nigh impossible to answer in the field.  So, today I’d like to do something a little different for Science Sunday.  Instead of discussing an article about research, I’m going to discuss a few (very few) of the pros and cons of working in the field versus the lab.  For the scientists out there: you probably know all this already, so thanks for stopping by.  But for those of you who aren’t scientists, this might give you some insight into how scientists plan their experiments and the research decisions they make.

Let’s start with a hypothetical question, something that you might find me doing: do the behaviors of backswimmers (pictured above) allow them to use the air bubble they carry on the underside of their abdomens as physical gills so they can extract oxygen from the water?  Now, there are several different ways I can approach this question, so let’s consider some pros and cons of doing this sort of study in the field.

Field Work

PRO: You are able to observe the bugs in their natural surroundings.

When you’re dealing with behavioral questions, you can often make the best observations in the field.  In our hypothetical scenario, the bugs are going to be much happier, and therefore much more apt to behave as they do normally, if you observe them in the field.  As an observer, you will cause a certain level of distraction that might interfere with their normal behaviors to some extent, but it’s certainly going to be far less than what you’re going to get by scooping the bugs out, driving them back to the lab, and dumping them into containers.  When possible, it’s great to do behavioral studies in the field for this reason.  However, that’s not always possible because…

Con: You have no control over the conditions

To be able to say that X causes Y, you need to do a carefully controlled experiment where all the variables are accounted for.  It’s possible to do experiments in the field, but there are a lot more variables that you have to take into account.  For example, let’s say you’re doing a field experiment with the backswimmers.  However, it turns out that one set of treatments was applied to bugs in the middle of the stream and another to bugs closer to the shore.  If you compare the treatments and observe differences, you can’t ever be completely sure that you know why they’re different.  Your treatments likely had an effect, but what about the differences in flow between the two areas (faster in the middle, slower closer to shore)?  The increased energy demands of swimming in the middle of the stream relative to the areas closer to shore?  The different oxygen levels in the two areas?  Taking your experiment into the lab ensures that the only difference between the two treatments is the treatment itself so you can say that your treatment caused the observed outcome.  You probably also want some field observations when possible so that you provide evidence that your lab experiments didn’t affect the behaviors (e.g. did you know that female mantids don’t normally eat their mates and only do that in the lab?), but this isn’t always possible.

LabLab Work

Working in the lab has benefits, but it’s not always the ideal place to work.  Apart from being able to precisely control your experiments at the cost of removing things from their natural environment, the pros and cons of lab work include:

Pro: Greater access to a wider variety of Research tools and equipment

There are some things that are difficult or impossible to do in the field.  For example, let’s say you want to measure the oxygen in the air bubble that the backswimmer carries with it in the water.  That involves using some expensive precision equipment with specific power and space requirements that are hard to replicate in the field.  You might want to use a microelectrode to measure the oxygen level of the bubble.  Microelectrodes break very easily, so dropping one into the stream or on the ground would be a terrible thing – $5000 down the drain!  You wouldn’t be able to use the stands or the micromanipulators in the field that make using the electrodes easy in the lab.  It’s certainly not ideal to take the computers and analyzers you need to record the data out to the field.  Microelectrode oxygen readings also change depending on the temperature, which is impossible to control in the field.  If you need any sort of fancy equipment, it’s often better to do your experiments in the lab.

Con: Space can be an issue

Working with insects is great because you rarely need a lot space to do your experiments.  For the hypothetical backswimmer scenario, a small lab (heck – a table!) has ample space to do a behavioral study.  But what if you’re working with deer or leopards or bald eagles?  You’re certainly going to have a much harder time bringing them into the lab, nor could you expect their behavior to be normal indoors.  In fact, you’ll probably have to sedate them to get them into the lab in the first place and then house them in small cages while they’re there to do anything with them.  If you’re planning to measure hormones in blood or are interested in body measurements, then this sort of thing is ideal.  If you want to study behavior…  Not so much!  You’ll get better results in the great wide outdoors than you ever will in a lab.

These are the sorts of things all biologists wrestle with when they decide how to answer their research questions.  You have to carefully weigh the pros and cons of any particular experimental design and choose the one that’s most likely to produce reliable results.  Sometimes it’s better to do your work entirely in the field or entirely in the lab, but other studies (like mine!) lend themselves well to doing both.  And thank goodness for that!  I wouldn’t want to spend all my time indoors.  :)

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

Science Sunday: Adult Dragonflies and Damselflies as Indicators of Water Quality

dragonfly

Aquatic insects and other invertebrates have been used as indicators of water quality for about 40 years.  Insects can be found in a huge variety of freshwater habitats year round and can tell scientists and water resource managers a great deal about the conditions within a body of water.  By simply scooping some insects out of a stream and identifying them (that is the hard part), you can assess the conditions of the stream’s water relatively cheaply, easily, and reliably.  I suspect that their use in water quality assessments drives most current research on aquatic insects – they’re that valuable.

However, using aquatic insects as indicators of water quality only works if you’re able to identify the insects that you pull out of a body of water and know something about the sorts of habitats the species you find typically inhabit.  What happens if you want to do water quality assessments in an area where aquatic insect habitats aren’t all that well-known, or a place where many species haven’t even been identified?  Such areas are at a disadvantage because they are unable to rely on a valuable insect tool for determining their water quality.  Unfortunately, the areas that would typically benefit most from a cheap, easy, and reliable insect-based assessment of water quality are also areas where the freshwater insects aren’t known well enough to make it work.

This is exactly the sort of situation that you find in Mexico and several South American countries.  One of the big problems is that no one’s really bothered to describe the aquatic insects.  If an insect lives on land, there’s at least a chance that someone somewhere has gone through the trouble of describing it, but in the water…  That’s a whole different matter.  What ends up happening is that certain groups of aquatic insects that are terrestrial as adults have been incompletely described and the immatures remain obscure.  In many common damselfly and dragonfly species, for example, people have no idea what the nymphs look like!  And, if you can’t identify the aquatic insect species in a region, you can’t use them to assess water quality, making things like odonates useless as indicators.

damselfly

This is the situation that researchers Daniel de paiva Silva, Paulo De Marco, and Daniela Chaves Resende faced in Brazil.  They were interested in using aquatic insects as indicators of water quality, but they are incompletely described in their area, especially the odonates.  So, they wondered: since odonates lay eggs in water, females choose males based on characteristics of their territories that are conducive to the survival of their offspring, and nymphs typically grow in the same areas where adult males patrol, is it possible to use the adults as a measure of water quality instead of the nymphs?  With all the habitat assessments odonates apparently do on their on as they choose where to lay their eggs, it just might work!

The team tested their idea along the Turvo Sujo River in southeastern Brazil.  The river is impacted by humans along a large part of its length, especially near the urban area of Viçosa.  Upstream of the city the banks of the river have been converted from the natural forest lands into pastures.  Donwstream of the city the river is surrounded by pastures as well, but is influenced by the city too, especially by sewage.  By comparing the odonate species and water quality at six sites upstream of the city and six downstream, the researchers hoped to determine whether it was possible to use odonate adults in place of nymphs to assess the quality of water.  They assumed that the downstream sites would be more polluted and would have fewer adult dragonflies relative to upstream.  If there was greater abundance and species diversity of odonates at the upstream sites, they could argue that they were useful as indicators of water quality.

Pachydiplax longipennis female

Their efforts were, unfortunately, largely unsuccessful due to one major issue in their design: both the upstream and the downstream sites were so impaired by land use, pollution, and other factors that there was less of a difference between the two areas than they expected and there was no real control.  They found that because the forest had been replaced by pasture, many perching species of odonates that would normally be found in the area were conspicuously absent both up and downstream.  The team measured several water quality parameters in the two areas and found that they were nearly identical apart from a slightly lower dissolved oxygen level downstream of the city.  The diversity of odonates was a little higher at the upstream region, but only in the wet season, and  a few species of damselflies dominated both areas in abundance.  All in all, the upstream and downstream areas were very similar.

So, the researchers didn’t get the answers they sought and were unable to determine whether adults odonates could be used instead of nymphs in water quality studies.  Instead, they learned that when humans, with their sophisticated water measuring tools, can barely tell the difference between the water quality of two areas, the odonates can’t seem to tell the difference either.  They also learned that because the riparian vegetation along the river had been destroyed, the rest of the water quality parameters no longer seemed to matter.  And, they found that most of the odonates along the river were exactly the sorts of species you expected to find in rivers that are highly impacted by humans. The river had been so completely altered that several pond species were even found mixed in with the river species, a clear sign of river impairment at both ends of the city.

Even though this particular study didn’t support using adult odonates in place of nymphs for water quality analyses, I think the authors have a really great idea that should be pursued by other researchers.  Their argument is sound: odonates are assessing water quality to ensure the survival of their offspring, so using adult odonates in place of immatures to make those cheap, easy, and reliable studies of water qualities might be possible.  And if it turns out that it works, well that would be an amazing thing!  Adult odonates are big, beautiful, showy insects that people pay attention to.  The adults are well described in many areas where the aquatic insects remain largely ignored.  If you could use well-described adults in place of undescribed nymphs, many more regions would be able to use aquatic insects as indicators of water quality.  I, for one, think that’s a very good thing.

Literature Cited:

Silva, D., De Marco, P., & Resende, D. (2010). Adult odonate abundance and community assemblage measures as indicators of stream ecological integrity: A case study Ecological Indicators, 10 (3), 744-752 DOI: 10.1016/j.ecolind.2009.12.004

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

Science Sunday: Experimenting with Respiratory Behaviors of a Giant Water Bug

Abedus herberti

Abedus herberti in its standard underwater pose.

Last week I covered some of my research with giant water bugs and described how one species, Abedus herberti, breathes.  Respiration in this species is a fairly simple matter of going to the surface to collect a bubble of air that the bugs carry with them underwater, then using that air store as a source of oxygen while submerged.  By adding two simple behaviors, gaping and dynamic gaping, the bugs can dramatically increase the length of time they can remain submerged.  If you observe these behaviors and know a little something about aquatic insect respiration, it seems clear that these behaviors have some respiratory function.  However, that’s not good enough for science!  You have to provide evidence that a behavior does what you say it does.  So, today I’m going to finish the A. herberti respiration story.  First I’ll share the condition in which the bugs exhibit gaping and dynamic gaping and I’ll finish up by sharing how I know that these are indeed respiratory behaviors.

When you observe A. herberti in ideal conditions in the field, you notice that they prefer to stay within a few inches of the surface, usually holding onto the rocks along the banks of streams.  They simply climb up the rocks and stick their air straps out to collect air, then crawl back down.  This way they remain out of sight of predators, but still have easy access to the surface.  However, not all bugs are in this sort of ideal environment.  Some bugs need to dive further into the water to find a suitable perch, and they fight against the air bubble they carry the whole way down.  With these observations in mind, you could imagine that bugs that can reach the surface easily might never use gaping and dynamic gaping.  Bugs in deeper water, however, might want to stay underwater as long as possible because surfacing is hard work.  If gaping and dynamic gaping are respiratory behaviors, you might expect bugs in deeper water to exhibit them more often than bugs in shallow water.

shallow treatment

Shallow treatment

To test this idea, I did an experiment where I placed bugs in observation tanks filled with water to three different depths.  In the shallow treatment, the bugs could reach the surface easily without letting go of the substrate.  In the mid-depth treatment, the surface was just out of reach of the bugs as they did their surfacing behavior and they were forced to float to the surface.  The deep treatment tanks contained water deep enough that the bugs were well out of reach of the surface.  I placed bugs in the tanks one at a time and observed the behaviors of several bugs in each depth before comparing the treatments.

I learned that bugs forced to release their hold on the bottom are much more likely to use gaping and dynamic gaping than bugs that can reach the surface without letting go.  A few bugs in the shallow treatment gaped and one dynamically gaped, but the behaviors were rare.  Nearly every bug in the deep water gaped and dynamically gaped though, as did most of the mid-depth bugs.  Thus, bugs forced to float to the surface and then swim back to the bottom are more likely to express both gaping and dynamic gaping than bugs that can reach the surface easily.  Most likely, gaping and dynamic gaping require less energy than surfacing, so they do these behaviors to cut down on the number of trips to the surface they must make in deep water.

Exposing the air store

Exposing the air store during the gaping behavior

Once I established that water depth played a role in gaping and dynamic gaping, I set out to collect evidence that these behaviors were respiratory behaviors.  I did two tests.  In the first, I divided several bugs into two groups.  I taped the wings to the abdomen using waterproof tape in the first group, preventing them from dynamically gaping or gaping.  In the second group, I added the same amount of tape, but cut the strips in half so that they could do both behaviors.  I then tested both groups to see how long they could stay underwater by forcing them to stay submerged until they showed signs of stress.  I measured the length of time the bugs remained underwater before becoming stressed and the time spent gaping and dynamically gaping.  The next day, I did it all again, except I reversed the treatments.

Abedus herberti at the surface

Abedus herberti at the surface

With this experiment I learned that when denied access to the surface, nearly all bugs exhibited both gaping and dynamic gaping when free to do so.  The bugs were also able to remain underwater over three times as long when they could perform gaping and dynamic gaping than when they could not.  This suggested that there was a respiratory purpose to the behavior, that bugs were able to absorb oxygen into the air store from the water when exposed and extend the length of time they could remain submerged.  That is, they were using the air store as a physical gill.

To strengthen the evidence for a respiratory role for the behaviors even more, I did one final experiment.  I once again forced the bugs to remain submerged until they showed stress, but allowed all bugs to perform gaping and dynamic gaping freely.  I then altered the oxygen content of the water by bubbling air (adds oxygen) or nitrogen (removes oxygen) through a tank for 15 minutes before adding a bug.  I divided the bugs and put half in the oxygen treatment and half in the nitrogen treatment the first day one at a time, then reversed the treatments the following day.  Then I compared the time submerged, gaping, and dynamically between treatments.

Abedus breathing

Abedus herberti gaping

The results were clear: bugs in high oxygen water can remain submerged 10 times longer than bugs in low oxygen water.  Bugs that could freely gape and dynamically gape could only remain submerged a few minutes in the low oxygen, nitrogen treated water while bugs in the high oxygen, air treated water were able to remain submerged nearly an hour.  Clearly, the air store is acting as a physical gill.  Bugs in low oxygen water weren’t able to remain submerged longer than bugs that were prevented from gaping and dynamically gaping entirely.  In both cases, the air store was unable to absorb oxygen from the water.  Bugs in the high oxygen water, however, were able to remain underwater much longer, strong evidence that the air store does act as a physical gill and absorbs oxygen from the environment when it is exposed to water.

So, the giant water bug Abedus herberti depends on oxygen at the surface, but it can extend the length of time the air store provides oxygen underwater by using two simple behaviors: gaping and dynamic gaping.  I think it’s amazing that two seemingly insignificant behaviors, these tiny little movements, are capable of doing so much for these bugs.  This sort of thing is why I love being a biologist!  Isn’t nature marvelous?

Literature Cited:

Goforth, C. L. and Smith, R. L.  2012.  Subsurface behaviours facilitate respiration by a physical gill in an adult giant water bug, Abedus herberti.  Animal Behaviour: doi:10.1016/j.anbehav.2011.12.02.  (Published online only currently – will replace this with the print citation when the issue is released)

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

Science Sunday: How Giant Water Bugs Breathe

It’s the start of a new week and you know what that means: Science Sunday!  I thought I’d mix things up a little today by talking about some of my own research.  The subject of today’s post is this bug, a bug that should be quite familiar to my long-time regular (awesome!) readers:

giant water bug

Giant water bug, Family Belostomatidae, Abedus herberti

This is Abedus herberti, a giant water bug in the family Belostomatidae within the order Hemiptera (true bugs).  It’s a large, aquatic insect native to Arizona and northern Mexico that you’ll find in streams, often in the mountains.  It’s an interesting bug for many reasons, but it is especially well-known because the male bugs care for the eggs until they hatch (see my post about giant water bug parents for more details!) and they are wickedly efficient predators.  These traits make these bugs fascinating for entomologists like me, but they’re not what got me interested in giant water bugs originally.  I got excited about giant water bugs because of this:

Abedus herberti at surface

Abedus herberti at surface, collecting air

Respiration!  I never thought I would ever work with either insect respiration or aquatic insects (except dragonflies), but this project opened up a whole new world of possibilities to me and completely changed the direction of my research.  So, today I’m going to tell you  about the project.  It’s too long for one post, so this week I’ll give you an overview of the respiratory behaviors of Abedus herberti and next Sunday I’ll talk about the experiments I did to show that this is a respiratory behavior.

Giant water bugs are aquatic insects and, as such, have several adaptations that allow them to live in water.  I’ve talked about aquatic insect respiration before, so I’m not going to go over the respiratory adaptations again here, but note that giant water bugs depend on air to breathe.  Water bugs in the genus Lethocerus have a long respiratory tube (called a respiratory siphon) that they stick out of the water that works a lot like a human using a snorkel.  They also have a small space under their wings that holds a small amount of air so they can breathe underwater for a short time.  (Imagine using a SCUBA tank – same deal!)  Abedus herberti does things a bit differently.  First, the respiratory siphon has been reduced to short air straps:

air straps

Abedus herberti. Arrow points to the air straps.

Second, it has a much bigger space under the wings.  That means it can carry more air with it underwater and can remain submerged a lot longer.

So how does Abedus herberti breathe?  Let’s trace the behavior from the moment the bug sticks its air straps out of the water, fills the space under its wings with air, and dives into the water to settle near the bottom.  The bug then follows one of three behavioral pathways.  The simplest is this: the bug absorbs oxygen from the air bubble into the body.  When it has used up most of the oxygen, it goes to the surface to replace the bubble.  If the bug’s close enough to the surface, it simply raises its abdomen and sticks the air straps out.  If it’s in deeper water, it stretches as far as it can to try to reach the surface without letting go by raising the abdomen up, releasing the hind and middle legs, and holding on with only the front claws.  If that’s not enough, it will let go completely, float to the surface, and quickly replenish the air store before diving to the bottom again.  You can see the behavior in this rather blurry video:

That’s one behavioral pattern.  In the second pattern, the bugs add one more step: gaping.  The bugs surface, dive, and sit at the bottom, using the oxygen in the air bubble as before.  However, after about 5 minutes they expose the air bubble to the water.  To do this, they lower the abdomen, creating a space between the abdomen and the wings:

Abedus herberti

The giant water bug Abedus herberti gaping, exposing its air store to the water. The silvery part is the air bubble.

Gaping is a tiny behavior, one very small movement, but it does so much for the bug.  By exposing the air bubble to the water, the bug transforms the air bubble from a simple oxygen store into a physical gill capable of absorbing oxygen directly from the water, tripling the length of time it can remain underwater!  The bugs may gape for 20 minutes, then close the gap before returning to the surface.

The third behavioral pattern adds one important step: dynamic gaping.  This pattern starts with the bug surfacing, diving, sitting on the bottom, and gaping.  After gaping for 5 or more minutes, the bug starts doing this:

They do this motion over and over and over for up to three hours.  Gaping allows the air store to become a physical gill, but dynamic gaping makes the physical gill function as efficiently as possible by stirring the water around the bubble.  This pushes oxygen-depleted water away from the bubble and draws in oxygenated water.  The physical gill is much less efficient at absorbing oxygen from the water when the bug gapes, but does not dynamically gape.  Dynamic gaping is thus a form of ventilation that allows the bugs to remain underwater ten times longer than they can without gaping or dynamically gaping!  But even a dynamically gaping bug must eventually return to the surface (see my post on better breathing underwater to learn why), so it closes the gap between the abdomen and wings and surfaces.

The advantages of this behavior are clear: gaping allows the bugs to remain underwater 3 times longer and dynamic gaping ten times longer than they can when they do not expose the air store to the water.  But why is it important to stay underwater?  This is one reason:

egret

Egrets and other wading birds like to eat water bugs!

Many things love eating large, protein filled insects, so staying hidden underwater as long as possible likely helps A. herberti avoid predators.  However, the bugs carry a lot of air with them, which makes them very buoyant. If they let go of the bottom, they float immediately to the top.  Diving is probably very hard too because they have to fight against their tendency to float to the surface.  So, if the bugs benefit from remaining underwater, but it’s hard to stay underwater, then it’s a good idea to stay underwater as long as possible.  Gaping and dynamic gaping to the rescue!  These two simple, easy behaviors greatly extend the length of time the bugs can remain submerged, but the behaviors probably also require far less energy than diving from the surface.  If so, then gaping and dynamic gaping help the bugs avoid predators, save energy by avoiding trips to the surface, and maximize the time the bugs can spend trying to capture food.

So that’s gaping and dynamic gaping!  Next week, I’ll discuss how I know that these are actually respiratory behaviors.  I hope you’ll check back for part two!

Literature Cited:

Goforth, C. L. and Smith, R. L.  2012.  Subsurface behaviours facilitate respiration by a physical gill in an adult giant water bug, Abedus herberti.  Animal Behaviour: doi:10.1016/j.anbehav.2011.12.02.  (Published online only currently – will replace this with the print citation when the issue is released)

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Unless otherwise stated, all text, images, and video are copyright © TheDragonflyWoman.com

Science Sunday: Impediments to Invertebrate Conservation

Hadrurus arizonensis giant hairy scorpion

Giant hairy scorpion (Hadrurus arizonensis)

Back in October, the New York Times Green Blog featured a post about a paper that had been recently released covering seven major reasons why invertebrate conservation isn’t garnering as much attention as it should nor being acknowledged as an important use of conservation resources.  I liked the blog post, so I recently read the paper that it was based on.  I think the paper makes some great points, so I’d like to take you through it here.

Insects and other invertebrates make up the majority of the described species on the planet Earth.  About 80% of all described species (this includes everything – plants, mammals, bacteria, fungi, insects…) are invertebrates.  Beetles alone make up 25% of described species and outnumber vertebrate species ten to one.  Clearly, invertebrates are an important part of the world.  They also perform an enormous array of environmental functions, from decomposing organisms and fixing nitrogen in soils to controlling pest species and processing leaf materials in streams to begin the nutrient cycling that drives freshwater ecosystems.  The services invertebrates provide are important for a wide range of other organisms.  Thus, it is important that we consider invertebrates and their role in biological and chemical processes when making plans for the conservation of organisms.

Water scorpion, Ranatra quadridentata

Water scorpion, Ranatra quadridentata

However, that’s not what’s happening.  Invertebrates are widely ignored by conservationists in favor of the showier organisms, the warm and fuzzy creatures that make people say, “Awwww…” before reaching into their pockets to fund research.  Far fewer people who say, “Awwww…” and shell out a few bucks to protect a parasitic wasp, a spider, or an aquatic beetle.  In fact, many people would probably rather let an insect species go extinct than pay to protect it.

This sort of attitude is also reflected in the endangered species lists, such as the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species.  These lists rarely include insects and other invertebrates so that the representation of invertebrates does not reflect their abundance and diversity in the natural world.  This is a problem, especially when you start to really think about the necessary services that invertebrates provide, the medical and research advances we’ve made based on invertebrate models (think fruit flies and C. elegans), and their the utility of invertebrates as indicators of ecological health.

Katydid

Katydid (I think this is the common short winged katydid, Dichopetala brevihastata)

Scientists recognize the value of invertebrates in the environment and are aware of the fact that invertebrates are often neglected when it comes time to conserve species.  Why, then, are there still so underrepresented?  Pedro Cardoso, Terry Erwin, Paulo Borges, and Tim New discussed seven reasons why these problems exist and recommend actions to solve them in their important paper.  Let’s go through each of them!

Problem #1: Invertebrates and the services they provide are not widely known among the public.  It’s hard to convince people that they should allocate funds (or at least support allocation of those funds) for invertebrate conservation when they’re not aware of the diversity of invertebrates or the valuable things they do to keep the world running smoothly.  Even worse, most people come to believe that most invertebrates are either pests or dangerous (neither is true) and fail to understand why anyone would want to prevent their extinction.  Solution: Cardoso et al recommend increasing awareness of invertebrates through media and outreach, a sort of invertebrate PR campaign if you will.  Even simply using common names when communicating with the public might be a step in the right direction.

Banded argiope, Argiope trifasciata

Banded argiope (Argiope trifasciata)

Problem #2: Politicians are largely unaware of the issues surrounding invertebrate conservation.  When our policymakers, the people who will ultimately determine the fate of research finding, are mostly unaware of invertebrate conservation issues, it’s hard to them to justify why invertebrates are important enough to deserve funding.  Solution: Educate the policymakers!  Working toward  better representation of invertebrates on the IUCN Red List and similar lists will also allow people to lobby on behalf of invertebrates to ensure that their conservation becomes a priority.

Problem #3: Basic taxonomic, ecological, and behavioral research is becoming increasingly understudied and underfunded.  It’s hard to determine which species demand our attention for conservation when we don’t even know what their role in the environment actually is.  Basic research helps answer these questions, but is becoming increasingly unpopular and funding for such work continues to decline.  Solution: Citizen science to the rescue!  Amateurs come across new species more often than you’d think and are able to provide useful data on distribution and abundance.  There are more non-scientists than scientists, so why not make use of hundreds of extra eyes and ears to cheaply answer some of the basic questions that are becoming hard to procure funding for?

Blue eyed darner, Rhionaeschna multicolor, flying

Blue eyed darner (Rhionaeschna multicolor)

Problem #4: Most species remain undescribed.  Estimates of the total number of invertebrate species in the world vary widely, but one thing is certain: we have probably only scratched the surface of invertebrate diversity.  According to Cardoso et al, a new invertebrate species is described every 35 minutes, but at that rate it’s going to take another hundred years or more to describe every species.  Just think of how many species might go extinct in that time!  Solution: Careful use of indicator species or surrogate species might be useful in applying conservation efforts to undescribed species.  Increased support for both taxonomic research and the speed of publication of new species descriptions will also help.

Problem #5: We don’t know the distribution of most species.  Describing a species is a start, but to protect it you need to know the extent of its distribution – where it actually lives.  Many species descriptions are based on 3-4 insects from a single location, so we don’t know the range of most species.  Solution: It is important that survey projects such as the Planetary Biodiversity Inventory continue to catalog and document life on Earth so that we know where species are actually located.  Online databases of distribution data such as the Global Biodiversity Information Facility will also help decrease the amount of time a researcher or conservationist must search for distribution information.

Problem #6: Changes in abundance over time and space are unknown for most species.  To conserve a species, it’s essential to know where that species is located, when, and how abundant it is.  We don’t, however,  have abundance data for most species.  Solution: By developing standardized sampling protocols, an effective biological inventory of an area can be undertaken by nearly any researcher for whatever purpose, yet provide information that is valuable to conservation efforts and other researchers.  Long term ecological and monitoring projects will also provide valuable information for conservation efforts.

crane fly side view

Crane fly (Tipula sp.)

Problem #7: Life histories and sensitivity to changes in the environment remain unknown for most species.  If we don’t know which ecological services a species requires or provides, it’s hard to develop invertebrate conservation strategies that will actually work.  Solution: Indicator taxa in an area might alert researchers and conservationists to problem within an environment (protect the environment, protect the species within it).  Determining which species make good indicators within an environment is a good way to start conservation efforts in an area.

Cardoso and colleagues identified seven impediments to invertebrate conservation, but they admitted that, in the end, it all boils down to one overarching issue: public perception of invertebrates.  We aren’t going to be able to solve any of Cardoso et al’s list of problems without the support of the public – support for invertebrates, support for science and research, support for conservation.  It is thus vitally important to get the public on board if we’re going to save invertebrate species from extinction.  And why should we save invertebrates?  I think Cardoso and his colleagues sum it up best: “Only by preserving all species and guaranteeing interactions and ecosystem services may we reach the goal of overall biodiversity conservation.”  And, ultimately, what’s best for invertebrates is best for us too.

Literature Cited:

Cardoso, P., Erwin, T., Borges, P., & New, T. (2011). The seven impediments in invertebrate conservation and how to overcome them Biological Conservation, 144 (11), 2647-2655 DOI: 10.1016/j.biocon.2011.07.024

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From the Literature: The Cost of Breathing

I have a subscription to the science journal Science, but I rarely do more than shuffle through the contents every 6-8 issues.  While it’s considered one of the premier science journals, there are a lot of articles that are not applicable to what I do, so I usually choose to focus my attention on journals more closely aligned with my research.  However, I happened to look at the October 14, 2011 issue of Science and I’m happy I did!  I came across a great paper by Nick Lane that proposes a possible link between respiration and fitness, fertility, and life span within eukaryotes and explains how this might work.  I’ll talk about Lane’s hypothesis today, but I want to go a step further too.  The examples in the article are all vertebrates and the hypothesis fits well to these organisms.  But how well does it fit with insects?  I’ll discuss that at the end.

Note: if you don’t remember what the respiratory chain of cellular respiration is, you’re likely to get a little lost as you read through this.  I created a handy-dandy respiration refresher yesterday though, so you might want to take a look at that before you go any further.

Lane begins his paper by describing how respiration depends on two different sets of genes within cells, the mitochondrial genome (the genes found in the mitochondria) and the nuclear genome (the genes found in the cell nucleus).  The mitochondrial genome is passed directly from a mother to her offspring while the nuclear genome results from the combination of genes contributed by the mother and the father.  These two genomes must work together to create a functional respiratory chain, the important last step in cellular respiration.  If the mitochondrial and nuclear genomes are perfectly compatible, the respiratory chain will work nearly flawlessly and produce ATP and water as it should.  If there is a mismatch between genomes such that the respiratory chain develops incorrectly, electrons can escape the respiratory chain and react with oxygen to form free radicals, specifically reactive oxygen species (ROS).  Leaks in the respiratory chain can result in excessive ROS production, which can in turn cause damage and even programmed cell death.  It is thus essential that the mitonuclear compatibility be sufficient to form a functional respiratory chain capable of supporting an organism’s energy requirements.  In fact, offspring with severe mitonuclear mismatches will likely die during development or shortly after birth, leaving only those individuals with functional cellular respiration alive to reproduce.

hummingbird

A hummingbird has a very high metabolic rate.

But, Lane wondered, how good does this mitonuclear match really need to be for an organism to survive?  Consider an animal with a high metabolic rate such as a hummingbird or a bat.  These animals must have high mitonuclear compatibility to produce a respiratory chain capable of supporting the high energy demands of flight.  In these animals, any individual with even a minor mitochondrial mismatch should die because it cannot produce the necessary energy to survive.  However, more sedentary animals, such as rats and other rodents, can likely tolerate a higher ROS leak because their energy demands are lower.  It’s not as crucial that every electron make it to the end of the respiratory chain in these species.  If so, then offspring with mitonuclear mismatch (up to a point, the ROS threshold) may survive long enough to pass their genes on.

Let’s consider what this hypothesis, if correct, means with regard to reproductive success (i.e. fitness), fertility, and life span.  Think about the hummingbird and the rat for a moment.  If the hummingbird requires low ROS leakage, many of its offspring are likely to die during development because the ROS leakage threshold is low.  In contrast, a rat has a higher ROS leakage threshold and more of its offspring will survive relative to the hummingbird.  This means that fertility should be low in hummingbirds and high in rats, which is indeed the case.  Fitness could also be affected by ROS leakage thresholds.  Hummingbirds have fewer offspring relative to rats, but their offspring are also less likely to survive to reproduce themselves if their ROS threshold is very low. But there’s a trade-off too (there’s almost always a trade-off in biology!): a higher ROS leakage threshold means that more ROS are being formed.  Excessive free radicals can lead to cellular damage and death.  Rats, with their higher ROS leakage threshold, will have a higher ROS production as well as higher cell damage.  High free radical production is known to decrease life span, so the rat, with its high ROS production relative to the hummingbird, will have a shorter life than the hummingbird.

gerbil

A typical rodent has a low metabolic rate.

So Lane’s hypothesis fits the data for terrestrial vertebrates very well and he has generated a testable idea that people will be able to experimentally support or refute.  That’s good!  I think this idea, that a cellular process helps determine fitness, fertility, and life span, is very interesting and I’m eager to see the research that results from this paper.  However, at the end of the paper Lane suggests that the ROS leak hypothesis should apply across species, presumably across eukaryotic species such as fungi, plants, and invertebrates.  He might be right, but let’s consider insects for a moment.  There’s nearly always an exception among insects, and I think this is a case where there might be a big exception.

Let’s think about flies for a moment.  Many flies have high metabolic rates, which, according to Lane’s hypothesis, should mean that their ROS leak threshold is low with a corresponding low fertility and long life.  This isn’t necessarily the case.  Some flies produce few offspring, but many of them produce a lot of offspring!  Many flies also have very short lifespans of only a few weeks from egg to dead adult.  Let’s then contrast this to the flightless giant water bug I work with (not an altogether fair comparison as they are larger than most flies and that needs to be taken into account, but this is just a thought experiment).  The water bug spends most of its life sitting in one place, a highly sedentary insect with a low metabolic rate.  If Lane’s hypothesis applies to all eukaryotes, this giant water bug should have a short life and high fitness.   Giant water bugs have huge eggs, so they don’t produce as many offspring as some species, but 1000 or more offspring in a mating season is nothing to sneeze at and they seem to fit Lane’s hypothesis.  However, these bugs tend to have comparatively long life spans, sometimes a year and a half as adults!  Last, think about social insect queens.  These are sedentary insects that sometimes have very long lifespans (sometimes decades long!).  According to Lane’s hypothesis, these insects should have short lifespans, which isn’t always the case.

I don’t want to sound like I think Lane’s hypothesis is worthless because I think it can potentially explain several patterns of metabolism, fitness, and life span that we see in nature and I honestly hope it pans out.  However, I have two predictions, one or both of which I suspect will hold true as researchers begin exploring the limits of the hypothesis:

Prediction 1.  The ROS hypothesis will not apply to all eukaryotes and instead apply mainly to warm-blooded, terrestrial vertebrates.

Prediction 2. If the hypothesis holds up to experimentation, I suspect researchers will find other forces at play in insects and other invertebrates that overshadow or alter the impact of ROS leaks on life span and fitness so that they do not follow the same patterns that we see in warm-blooded, terrestrial vertebrates.

Ultimately, I don’t think the hypothesis in its current state is going to be as widely applicable to eukaryotes as Lane suggests, but I hope it will lead to some interesting new research dealing with the link between cellular processes and the life histories of organisms.  If it does that, even if it proves to be incorrect, I think this hypothesis can contribute something very meaningful to science.  And even if it doesn’t pan out, at least it was an exciting idea that got people thinking.  I consider that a success!

Literature Cited:

Lane, N. (2011). The Costs of Breathing Science, 334 (6053), 184-185 DOI: 10.1126/science.1214012

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