A Cinderella Story

Cinderella’s stepmother fancied herself a scepter                                                                           She never loved poor Cinderella or strove to protect her                                                              Instead she chided, spurnéd, and decided to reject her.

So Cinderella scrubbed the hearth and laved the kitchen floor                                                       Her jovial stepsisters’ antics made her wish for more                                                                     Until one day she said, “Enough! This living is a bore.”

Indeed this was a verity; fairy godmother said,                                                                                   “I augur life will change anon.  Now Cindy, go to bed.”                                                                   But Cindy, with malevolence, formed other plans instead.

Alas, no handsome prince arrived to woo her as his bride                                                               So Cinderella, all alone, was disposed to decide                                                                         She’d improve life by ending one- resort to parricide!

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Finding a Friend in a Buggy-Bug World: Insect Olfaction

All living things sense the world they live in, and we are familiar with a set of senses specific to humans.  However, the senses humans use are neither the only senses nor the best; rather they simply differ from other species’ sensory systems both in mechanism and range based on differing needs and abilities.  Insects have highly developed olfaction or sense of smell, which they use for various activities including predator and food detection, sex, aggregation, spacing, trail forming, and alarm.  Often, insects place emphasis on olfaction, which is atypical of most other clades of organisms, many of which rely heavily on vision and audition.  Why do insects utilize olfaction to such a great extent? I argue that it is the combination of both the specificity and the lingering nature of olfactory cues that makes olfaction so highly valuable to insects as a clade.

Humans can sense chemical cues through smell conveying messages varying in nature from sexual to warning – we can sense each other’s hormones and emotions through pheromones (de Groot et al. 2012).  Insects emit and detect similar signals through olfaction, but are much more sensitive to these cues than humans, and are often able to detect a single molecule of a sex hormone (Zhou et al. 2012).  Insect chemoreception begins with signal detection on smell-gathering organs called sensilla that are located on the insect’s antennae, mouthparts, and sometimes genitalia.  Chemical signals are then transduced into electrical signals that travel through the insect’s nervous system to the brain, at which point insect has perceived the signal (Gullan & Cranston 2010).

Because chemical signals consist of matter (molecules) rather than energy, they persist in a particular location over a longer period of time than waves of energy in the form of light or sound.  For the many insects that are small, travel long distances during the day foraging for food, and live solitarily or widely separated spatially relative to their size, communication is hindered by behavioral and morphological limitations.  An insect more easily traces a physical substance because it can almost literally pick up a trail of breadcrumbs in the form of chemicals left hanging in the air if it is following a trail for food, its nest, or a potential mate.

If an insect is searching for a mate, what will matter to that insect?  First and foremost, knowing that the signal it detects is actually a member of its own species!  In such a “buggy-bug world” as ours, with millions of insect species that are difficult to distinguish even for humans, how can a poor-sighted insect pick one of its own species out of a crowd from miles away?  Chemical signals permeate the air in droves (Hansson & Stensmyr 2011), and tracing a path of breadcrumbs through a forest made of breadcrumbs would be impossible if the breadcrumbs weren’t highly distinguishable – and they are, to insects.  Chemical signals emitted by females are often species-specific with male counterparts possessing receptors specific to the female’s signals (Vieira et al. 2012).  Otherwise, insects would all be trying to mate with each other regardless of special boundaries and get nowhere – and even with highly specialized systems this can sometimes occur.

Social insects are sometimes able to bypass these hurdles.  For example, honeybees have evolved highly complex system to visually communicate navigation to food sources through “dances.”  Also, the bees live in close quarters with each other and can therefore hardly fail to notice that the other animals in their hive are their own species.  However, only certain types of honeybees are fertile, therefore the bees still use pheromones to attract and detect mates.

Speaking of honeybees, alarm signals are very important to these and other insects.  The nest of social insects like honeybees provides protection and harbors food and juveniles, making it a vulnerability if it is threatened.  Under duress, a bee releases a pheromone that attracts others of its own species over a limited distance.  However, if the bee is in close proximity to the hive, others immediately come to its rescue and attack the intruder in order to protect the hive and its resources (Breed et al. 2004).  Unlike other forms of communication, chemosignaling can be performed relatively passively and persistently (in contrast to vision in which the insect must be looking at something to see it or audition in which the insect actively works to create sound), which means that the insect can convey messages to many other insects at the same time without using much energy.

While escaping predators, similar advantages to chemical signaling hold true.  Visual detection of a predator may help if the insect can fly away, as you can see when a fly detects your fly swatter’s movement and escapes, but for slower, more vulnerable insects this simply isn’t an option.  It would be more advantageous if the insect could detect predators from a distance through chemical signals, allowing for time to prepare defenses or flee.  If the insect were communicating to the predator, unless it is flashy like some butterflies (Olofsson et al. 2013), it would be unable to communicate its disgusting taste quickly without pheromones like those that the stinkbug employs.

Other social insects like ants, which have no way of visually communicating food location, lead other ants to food and nest through pheromones.  Ants actually combine a sun compass, visual cues, and a path integrator (counting its steps) with chemical signals, but research indicates that ants choose to follow chemical signals over others – in fact, ants have four to five times more odor receptors than most other insects (Zhou et al. 2012).  In one study in which odors normally associated with a nest were moved away from the nest, ants repeatedly moved toward the odors rather than the nest, meaning that the combination of non-chemical signals was not adequate to overpower the importance of the chemical signals in nest location (Steck et al. 2010).  This makes intuitive sense – if an ant can use a passively detected chemical signal to find its way, it can free up other senses like audition and vision for detecting danger, both physical (environmental) and biological (predators).

Clearly, there is a tradeoff whether insects are social or solitary.  However, both types of insects use pheromones to counterbalance the disadvantages of these tradeoffs.  While a combination of senses is necessary to survival, insects rely more heavily on olfactory cues because of their specificity, substantial and persistent nature, and potential for long-distance emission.

Works Cited

Breed, M. D., E. Guzman-Novoa and G. J. Hunt. 2004.  Defensive behavior of honey bees: organization, genetics, and comparisons with other bees.  Annual Review of Entomology 49: 271-298.

Gullan, P.J. and P.S. Cranston.  The Insects.  Ed. 4.  Wiley-Blackwell: UK, 2010.

Hanson, Bill S. & Marcus C. Stensmyr.  2011.  Evolution of Insect Olfaction.  Neuron 72(5): 698-711.  DOI 10.1016/j.neuron.2011.11.003.

J. H. B. de Groot, M. A. M. Smeets, A. Kaldewaij, M. J. A. Duijndam, G. R. Semin. 2012. Chemosignals Communicate Human EmotionsPsychological Science, DOI:10.1177/0956797612445317.

Olofsson, M, H. Lovlie, J. Tiblin, S. Jakobsson & C. Wiklund. 2013.  Eyespot display in the peacock butterfly triggers antipredator behaviors in naïve adult fowl.  Behavioral Ecology 24: 305-310.

Steck et al.  2010.  Do desert ants smell the scenery in stereo?  2010.  Animal Behaviour, DOI:10.1016/j.anbehav.2010.01.011.

Vieira et al. Unique Features of Odorant-Binding Proteins of the Parasitoid Wasp Nasonia vitripennis Revealed by Genome Annotation and Comparative Analyses.  2012.  PLoS ONE 7(8): 43034.  DOI:10.1371/journal.pone.0043034.

Zhou et al.  Phylogenetic and Transcriptomic Analysis of Chemosensory Receptors in a Pair of Divergent Ant Species Reveals Sex-Specific Signatures of Odor Coding.  2012.  PLoS ONE. DOI: 10.1371/journal.pgen.1002930.

A Sizeable Advantage: Why Insects Are So Small

Insects are a highly successful clade of organisms, as evidenced by the myriad forms one can daily observe.  This success is due to the layering and interaction of many different advantageous evolutionary and ecological factors over the eons, allowing for such massive speciation.  One such advantage may be that of size.  Insects are reasonably small in comparison with the wide variation of scales other clades of living organisms have achieved.  Why?  The correct answer is a combination of several hypotheses, but what combination?

Among the most prevalent hypotheses are those pointing the finger of size-limitation blame towards tracheal respiratory system limitations, an unfavorable surface area to volume ratio causing biomechanical exoskeleton non-scalability, and the evolution of more potent flying life forms such as birds and bats posing potential biotic size-limiting factors including predation and competition.  At the opposite end of the scale, evidence shows that insect miniaturization is limited more simply by egg size large enough to produce viable larvae (for females), brain size, and the inability to fly, a highly advantageous evolved behavior (Grebennikov 2008, Niven & Farris 2012, Polilov 2012).

Insects’ breathing system consists of pairs of holes called spiracles along their bodies connecting to tubes called tracheae which transport oxygen to cells and remove carbon dioxide.  As insects increase in size, tracheae take up a proportionally greater amount of space in their bodies because they need to increase in length and width to deliver oxygen as a larger body size increases oxygen needs.  This inhibits growth because at a certain point the tracheae become impractical and crowd other organs (Kirkton 2007).

Unlike an endoskeleton, which allows continuous growth, an exoskeleton limits an organism to discrete or incremental growth through molting.  During molting, an organism is highly vulnerable to predation and the forces of gravity.  A very large insect would take too long to molt, put too much energy into the production of a new exoskeleton, and collapse under its own weight.  Also, an exoskeleton must be scaled to the dimensions of the organism to prevent it from collapsing.  For example, if an ant’s exoskeleton must become thicker as body size increases (strength is proportional to length squared whereas mass is proportional to length cubed), at a certain point this thickness would cause the ant’s legs to crumple under the strain of holding up its own body weight.

One hypothesis points to biotic factors constraining size.  If flying insects were large, they would be easier to prey upon because they would be more conspicuous and less acrobatically maneuverable.  Also, insects would be outcompeted by other flying animals like birds and bats.  This hypothesis is outlined and explored further below.

One way to logically determine the possible evolutionary pressures limiting insect size is to trace the different evolutionary paths a primitive insect may have taken on its journey of terrestrial invasion and ultimate colossal diversification.  Imagine a primitive insectoid form crawling out of the ocean.  It pioneered the terrestrial space for its slimy kin.  This creature does fairly well for a while, but then its squishy body becomes a hindrance to its fitness to reproduce-it is too physically vulnerable and too costly in terms of moisture conservation.  Therefore, the organism evolves an exoskeleton to help conserve moisture and protect itself from predators.  However, this primitive exoskeleton reduces the insect’s diffusion, and it must evolve a respiratory system-either tracheal or some intermediary.  If the insect possesses an exoskeleton upon colonization, but has a diffusive respiratory system causing it to lose too much moisture, it may also evolve a tracheal system.

In either scenario, the primitive land-bound insect is limited by size because of its exoskeleton and tracheal system.  If for some reason the insect first has no reason to evolve an exoskeleton-perhaps it is small enough or evasive enough to avoid prying predators – then it would be limited by its tracheal system.  The opposite is true if the insect has a different respiratory system than a tracheal one – it would be limited by its exoskeleton.  Interestingly enough, a lack of exoskeleton could also have limited the pioneering insect’s size.  If it got too large but remained squishy and vulnerable, it would have been much easier to see and capture as well as to rip apart and ingest.  Fast forward to the Carboniferous period.  During this time period, oxygen levels were higher, meaning insects needed smaller quantities of air to meet their oxygen demands and could thus grow much larger (Clapham & Karr 2012).  In fact, one study suggests insects may have needed to grow larger to avoid hyperoxia.  Aquatic larvae which respire through diffusion are more sensitive to oxygen fluctuations and primitive forms which may have been unable to regulate their oxygen intake could solve this issue by growing bigger (Verberk & Bilton 2011).  Only those organisms unconstrained by the exoskeleton could have grown large during the Carboniferous period, such as odonates, which overcome the surface area to volume problem by changing their shape.  Bloated boxy beetles would have been size-limited, but organisms with long skinny body parts could overcome this obstacle.

When insect size did decrease, this event coincided first with the evolution of birds, and then again with that of bats.  With predatory birds in the air, the need for maneuverability and evasiveness trumped the evolutionary drive to be big, and insects decreased in size.  Additionally, large insects were outcompeted by birds and bats for air space.  At this point in time, biotic interactions superseded oxygen as the most important constraint on insect maximum body size (Clapham & Karr 2012).

The scenarios outlined above and their various implications on insect size-limitation are simple and consider few variables.  In reality, the issue is much more complex, including many different factors (genetic, environmental, abiotic, biotic, etc.) that complicate the issue of picking apart the importance of various factors on insect size limitation and evolution in general.  Currently, insects are limited by all of the above.  In order of priority, basic math-related issues (exoskeleton and tracheae) are the most crucially size limiting because without any other constraints they would still limit body size.  As outlined earlier, competition and predation with birds and bats supersedes oxygen availability constraints.  Perhaps one could make the claim that insects are ultimately constrained by gravity – in a low-gravity world exoskeleton and body weight would be irrelevant and they could just swim through the air gulping down oxygen like fish rather than bothering with tracheae!  Only by further experimentation and research can scientists piece together the highly complex puzzle depicting the size limitations on and evolutionary path of insect forms.

Works Cited

Beutel, R.G., H. Pohl and F. Hünefeld. 2005. Strepsipteran brains and effects of miniaturization (Insecta). Arthropod Structure & Development 34:301-313.

Clapham, M.E. & J.A. Karr. 2012. Environmental and biotic controls on the evolutionary history of insect body size. Proceedings of the National Academy of Science USA 109:10927-10930.

Grebennikov, V.V. 2008. How small you can go: factors limiting body miniaturization in winged insects with a review of the pantropical genus Discheramocephalus and description of six new species of the smallest beetles (Pterygota: Ptiliidae). European Journal of entomology 105:313-328.

Kirkton, S.D. 2007. Effects of insect body size on tracheal structure and function. Hypoxia and the Circulation 618:221-228.

Niven, J.E. & S.M. Farris. 2012. Miniaturization of nervous systems and neurons. Current Biology 22:R322-R329.

Polilov, A.A. 2012. The smallest insects evolve anucleate neurons. Arthropod Structure and Development 41:29-34.

Verberk W.C.E.P. & Bilton D.T.  2011. Can oxygen set thermal limits in an insect and drive gigantism? PLoS ONE 6(7): e22610. doi:10.1371/journal.pone.0022610.

We’re looking in the wrong place for evidence of life on Mars! — new research from Brown

Ridges on Mars have been identified as fossilized cracks formed from flowing water depositing minerals, making life on Mars a distinct possibility.

Researchers at Brown analyzed 4,000 ridges on Mars and used high-resolution images to determine how the ridges were formed.  John Mustard, geology professor at Brown, explains cracks on Mars’ surface “filled with minerals” when water flowed through the cracks.  Then, when the rock around these cracks eroded over the millennia, the minerals were left in place as “fossilized cracks.”

To the average citizen, this might mean absolutely nothing.  But to Mustard, whose eyes light up at very thought, these fossilized ridges represent “microbial coffins” and a place where humans will find the first remains of Martian life.

“If we look at the tree of life,” Mustard says, “the most primitive organisms… are called Archaea… that live in hot springs.”  When the cracks existed, they were ready-made “microbial condominiums” because they had the ideal environment and nutrient source for Archaea-like life forms.

Mustard thinks of the ridges as “microbial coffins.”  To him, the area where he found the ridges “represents the largest, most long-lived habitable environment on the planet” and is thus the place to go when looking for life on Mars.

The rover currently on Mars is not headed for the ridges, so for the time being, Mustard hopes he can communicate to the world the importance of the ridges as habitats harboring denizens of the Martian subsurface; ready-made “microbial coffins” for humans to rob and see what treasures lie within.

Cacti explosion!

I’ve posted a lot of “creativity” lately, but not much on the matter of curiosities 😉 here’s something I wrote up after interviewing a researcher at Brown, the school I attend as an undergrad majoring in biology.  Enjoy!

Research Into Succulent Plants Yields New Insight Into Formation of New Species Millions of Years Ago

Brown University biologists and colleagues have uncovered new evidence suggesting that cacti evolution accelerated with the origin of many new species 5 to 10 million years ago and coincided with global diversification of succulent plants.  Interestingly, this time period, the late Miocene, was marked by arid conditions and a precipitous drop in carbon dioxide as well as the evolution of a new form of photosynthesis (C4) that maximizes moisture conservation.

Researchers emphasize that learning more about the coincidence of these three events can help scientists obtain insight into what drives plant evolution and why.

The team began research with the intent of determining the origin of cacti.  Erika Edwards, an assistant professor in the Department of Ecology and Evolutionary Biology at Brown, explained that by sequencing the DNA of different plants, the scientists were able to compare across species and reconstruct branches of the evolutionary tree or phylogeny for succulent plants and flowering plants in general.

Although the scientists were able to deduce that cacti first originated about 35 million years ago, they were more surprised that cacti greatly diversified only 5 to 10 million years ago.  Curiously, a new type of photosynthesis (C4) adapted to arid conditions as well as all succulent plants chose this time to diversify as well.

If succulent plants were around 35 million years ago, why did they wait so long until diversifying into the myriad succulent life forms we see today?

The answer to this question lies in the global environment of the time period, known as the late Mioscene in geological time.  The researchers knew that the evolution of all three life forms at the same time could not be mere coincidence, and did some digging into environmental conditions to find an explanation.

Succulent plants, which have evolved the ability to hold water and include such familiar species as cacti, aloe, and ice plants, seemed to have evolved these adaptations during the late Mioscene because of the arid conditions and low carbon dioxide levels accompanying the period.  “The landscape was fundamentally changing” on a global scale, Erika Edwards explains.

Similarly, C4 plants are much better equipped to handle lowered carbon dioxide conditions, so they also took their chance to diversify during the same time period.

As to how plants will respond to the rapid increase in carbon dioxide at present, Edwards simply stated, “we don’t know!”  She emphasized that further research into plant physiology, anatomy, and evolution can help scientists obtain insight into the upper limits to plants’ physical abilities to handle temperature and drought and predict how plants will fare in the perilous, rapidly approaching future of global climate.

Ode to a love-hairte relationship

Oh! What futile workers
Who toil to no avail
They hack-­‐cut-­‐shear the enemy                                                                                                 But sadly they will fail

A more persistent army you never saw                                                                                     Armed with many a sharp tool
But any but time that fights such a foe                                                                                           Will inexorably be made a fool

But halt! What turn of fate-­‐
Do I accept what I descry?
Such mortal enemies I’ve never found                                                                                            Yet this surmisal new evidence belies

For behold,
How the worker caresses
Grooms
Nurtures the very pestilence she strives to eradicate

Like an epiphyte, it grows, takes over its host’s anterior                                                                 Yet the worker simply chops a little away
Never attacking in one fell swoop

In the one instance in which this was the case,                                                                             The host became interminably angry
As if the worker was ridding her of a major organ                                                                       Rather than sloughing off a ghastly growth

Alas! I shall revise
My predictions; they are flawed
The Dresser and the Hair                                                                                                           Must-­‐clearly-­‐have symbiotically coevolved.

Elza

T’was cruel to betoken the men she ne’er loved;                                                                           Their requests she dismissed as prate,
Because the all-knowing God from up above                                                                             Would assay, then descry, her ill fate.

For Elza thought naught of the men who beseeched
So desperately for her embrace;
All hoping perchance that their aims would be reached;                                                               That she would comply in good grace

E’er relentless men attempt her heart’s myst’ry to solve,                                                             Alas, to no meager avail;
‘Till after long torment congeals their resolve:
Her love is not worth the travail.

Each man who came to the threshold of her heart                                                                       Was met with promise, then disdain.
Fearing feelings for him she’d force them apart;                                                                         Ne’er once did she ponder their pain

Fair Elza deemed love to be fleeting and rare;                                                                             Meant only to importune her,
Thus, when a man would lay his tender soul bare,                                                                       She’d go all lengths to avoid hurt.

In evading the pain that was so sure to come,                                                                                 She deemed all men’s hearts imperv’yus.
The lonely men wallowed in languish and rum;                                                                               Their friends and their kin all quite fyur’yus.

And while crumbling asunder were their spirits,                                                                                A sad madrigal their souls played;
Singing several soft sadistic lyrics,
When Elza’s luck slowly decayed.

With men’s severed souls splayed ‘round her path,                                                                     Elza’s fate for her sins was found.
No longer would she escape God’s mighty wrath;                                                                         She felt the pain of those around.

Among those around her the suff’ring was worse,                                                                         And as it may be predicted;
In avoiding her pain she was caught in a curse;                                                                             One entirely self-inflicted.

Fickle fiera

Fiera, the fairy of fickle mettle,                                                                                                       With hair flaxen as wheat,                                                                                                                   Is mischief’s minion.

She brings the chalice of malice                                                                                                         To the lips of fine folk;
Her wicked merriment.

Fiera, the fairy of games folly,                                                                                                         Believes that surcease of others                                                                                                         Is her divine power.

In hopes of devil’s exaltation,
Fiera curses ladies’ pendent trinkets;                                                                                             Trouble and sin brood.

Fiera, the missive of death,                                                                                                                 Unveiling her cruel plot                                                                                                                   Awaits Satan’s call.

Every thane of Satan                                                                                                                       Must disburse for entry                                                                                                                     Into gates of hell.

Fiera, inflamed with desire,                                                                                                               Will give her due payment                                                                                                                 By forming demons.

Ladies and gentlemen                                                                                                                     Lost in the night’s wassail;                                                                                                               Their fate undecided.

Fiera is sent before Satan,                                                                                                                 A harbinger
But to be naught more.

For fickle fairy Fiera                                                                                                                   Releases trinkets’ curses                                                                                                                   A thane never to be.

Fiera, like the horse
In the adage,
Drinks not from the chalice Of Satan.

Playground roundabout

A child, singing, round and round
The sound, a lovely ringing peal
A composition which, simply by existing                                                                                 Determines to trounce fate

Toes spin around above the ground
A petal drifts around that angelic face                                                                                               A smile touches your lips
Then a frown

A crease betwixt the eyebrows fixes
Your eyes widen as fate crouches to pounce
The toes stop going round; they hit the ground                                                                                   The petal touches the ground without a sound                                                                               The singing stops; the silence resounds
Someone should stop the playground roundabout                                                                                             but it goes round and                                                                                                                                       round

Deep space

She sinks into the blue                                                                                                                     and inverts her mind                                                                                                                         which is floating into blue                                                                                                                   of a different kind

A fish darts by
“Like a bird!” she thinks                                                                                                                        And the current it makes                                                                                                                    is like wind on her face

Darkness envelops
excitement mounts
life bioluminesces
like stars; she gazes into infinity

Enraptured by its beauty
like velvet sequined with burning diamonds                                                                                     she can feel it slide across her skin
so smooth it almost feels like liquid

The lights fade and disappear
nothing lives here
in the depths of space
where the emptiness is devoid even of air

Her eyelids drift shut
a smile dances on her mouth
she surrenders to the dark
and begins her journey to that otherworldy place