Monday, August 15, 2005
Bridges of a Rainforest Friendship
I rushed down the hardwood stairs, pulled on my mud-caked hiking boots, and walked briskly into the depths of the forest. Although the break was only fifteen minutes long, I had enough time. Upon entering this newfound refuge, I felt the day’s meddlesome anxieties trickle away from my body with each successive step. This forest would soon prove to be a catalyst for change and learning in my life and my friendships.
Its misty, foggy depths intrigued me. I sat in the forest for long periods of time trying to assemble the big picture, picture large enough to remain in my memory that would capture all that I saw. Impossible. Sitting in the forest focusing on a plant or a rock, the intricacies of the forest could never be condensed into a simple rendering.
For when the veil is lifted,
love the void as the treasure
and know that it is worth
as much.
Nature’s empty coalescence
and its beautiful
meaningless therein. (“Null”)
I was boarding at La Estación Biológica Monteverde nestled in the beloved cloud forest of
The forest was always accessible, always conducive to the possibilities of discovery and exploration. The vibrant green unknown was a release, a way of escaping the inanities of life. Its mysterious chaos captivated a biology student like me.
The tropical rainforest, situated only two meters from my bedroom, was unlike any other place I had ever been in my entire life. Prior to this trip, I had never spent a considerable amount of time in any forest. Throughout my life, I had preferred to stay inside and read a book, choosing to experience the world through my friends glued into the binding. I was in a car watching the scenery rush by at fifty miles per hour. These intangible glimpses of my surroundings never affected me due to the confines of that metal and glass prison in which I remained. I needed to open the car door and experience the world.
During my freshman year of college, I realized that I had somehow worked my way into this hole of comfort, a hideaway where I could escape bitter reality at any given moment. I was guarding against a nonexistent, contrived danger. I resolved to branch out—dig a few connecting tunnels out into the real world
Therefore, after visiting the campus International Programs and Services office with piles of catalogs in hand, I “burrowed” my way home. Though programs at a Spanish university had been my aim, I came across a program that trekked through the forests of
I walked slowly through the forest, not wanting to miss a thing. I marveled at the vines seemingly floating along the side of a tree, attached to neither the branches nor the ground. Glass-wing butterflies parked on the flowers of the passing understory, totally reliant on their unique form of invisibility. I picked one up to ponder upon its distinctive transparency and replaced it on its leaf. Seemingly not troubled by this alien form of displacement, the butterfly remained perched on the leaf in apparent contemplation. A vine curled around itself and fell into the trail in front of me. Although predominantly green, the plant had chosen to color its tendrils red, a color that contrasted the green of the forest. Looking into the center of the spiral, I was astonished to see a tiny oblong egg, placed so carefully inside by a mother butterfly scattering her young. These presumably minute details of the forest drew me in and kept me coming back.
The ground was muddy with large flat rocks as structural support. The leaves and fruits that spread along the human-cleared trail hinted at the large trees overhead. A palm-shaped leaf of five lobes lay on the ground. It fingers were curling due to desiccation. I picked it up and carried it to my destination.
I stopped at the metal green bridge. It was not far into the forest—maybe only thirty meters. Sitting on the bridge with my feet dangling over the edge, I hung my arms over the railings with my head resting on my shoulder. Closing my eyes, I breathed. It was a breath of a final release, of utter calm, and of quietude.
I fell in love with the bridge. It is a partition between two worlds. As I looked over the edge, a stream of fresh ground water rushed below me. A natural trench of rock, barren save patches of moss, had been carved by this natural spring of water. Along the edges of the stream, life has flourished. The sound of the rushing water overcame me, and I lay down along the cool rungs of the bridge. Although they rubbed against my back, I stayed there as my problems were vindicated by the sheer tranquility of this sanctuary.
Above me were light-spotted Cecropia leaves. The leaf palms faded and swayed through the gaps of light created by the rock trench below. These beautiful trees are opportunists, grabbing any little moment to grow in the rays of the sun. Biologically known as gap-dependent, these trees wait for years even to grow from a small seed placed by another lucky seed from years before.
These trees reminded me of who I am and who I want to be. I want to seize all the chances I get. I want to always be ready to do so, sitting on the edge of my seat instead slumped back in an armchair. Gap-dependent trees, when the chance finally arises, grow at tremendous speeds, not willing to take any chance that this opportunity will wane.
“Friendship is unnecessary, like philosophy, like art. It has no survival value; rather it is one of those things that give[s] value to survival.” C.S. Lewis. Friendship is not essential to the sustenance of a person’s life, rather a person’s happiness. A friendship must be fostered and treasured because it is one of the greatest values in life. It is an opportunity to assimilate in a world where isolation seems to be a driving force. A friendship must be quickly appreciated because new friendships, though quick to form, can rapidly be lost in the breeze.
My friend Megan Smith and I wandered into the forest to have private talks of sorts, but instead we discussed life and what it meant to us. We lay on the bridge. We discussed our beliefs. We laughed, we sighed, and we looked over the edge.
Megan goes to the
I knew that our friendship was not based in the fluctuating phases of our lives. Friendship is an unselfish commitment to one another to always be there for the other regardless of convenience or distance. We valued our friendship and the bond that we had found despite the countries we had covered to find each other.
The camaraderie between Megan and me was different than most of the friendships I had maintained in the past. Many of my friendships were based upon common interests or similar lifestyles. The inherent flaw in this arrangement was that a person’s interests or lifestyle were not permanent.
A friendship that is susceptible to fluctuations serves as a poor base for a social growth, much like thin roots on a canopy tree. It just wouldn’t work. The trees must increase their roots in the ground as they continue to branch out. As a person branches out in life, it must have its main support system to keep it grounded.
In order for me to grow, I knew that I had to treat my friendships differently. They will not survive as give-take relationships, where one friend is only ready reciprocate a favor rather than give for the sake of giving. A friendship is not something that can vary as the direction of a person’s interests transform. It is a nonjudgmental relationship between two people who are there for each other as they grow and change in the world It is a stationery object to help them up to their next stair, much like a walking stick.
My friend Megan wrote,
What is the point in living
in this physical realm,
if you don’t feel it,
don’t let it move you? (“Pura”)
During my time in
The Monteverde Cloud Forest is famous for its huge species variety of epiphytes—plants that grow upon on other plants without extracting any nutrients from the plant. A common cloud forest epiphyte is the bromeliad. Bromeliads, by growing in a rosette form, create a tank where rainfall can collect. These small tanks form small ecosystems where various organisms live, from tadpoles to microscopic protozoans. In many ways these small communities are self-sustaining much like a relationship between friends. Although an isolated bond within the larger world, the interworkings of the connection are integral to the survival of both friends. They do not exploit the forest in their growth; instead, their growth creates an enhanced environment to many of the rainforests other gems. These bromeliad relationships are prevalent throughout the forest, but they are hidden among the leaves of the trees and vines. Only those who know where to look will find the cherished treasure.
I discovered immeasurable lessons from the flora and fauna sitting on that bridge during my time in Monteverde. It was an imprint on the sidewalk of my life—much like the handprint of a child on the front walkway of his first home. Although he will forget that innocent age, that little instance of his life will stay cemented in time. A handprinted depression would remain a reminder of what was and the possibilities of what could be.
I dropped the desiccated Cecropia leaf over the edge of the bridge and watched it float away into the depths of the forest. Who knows where it would go or where it would stop? All I knew was that it was floating on an unplanned path. At least, I would have my friends there to watch me.
Aloft in the branches, I find
a different kind of sanctuary,
one which blooms between
you and I, one in which
I know I am safe and feel so,
because you are too.
And I honestly don’t know
what I’d do without you
and these afternoons spent
weaving our lives together
with common conversational threads.
I have the feeling it will
keep my heart warm
after we must finally part. (“Treehouse”)
The Fight Against Fragmentation
A piece of art is an intricate web of colors and imagery that interact to form a collective message, like Picasso’s famous painting Guernica
Then, why is it that when a forest is torn apart into little pieces, not many come to the rescue? Forests—much like Picasso’s painting—are intricate and complex portions of the globe where all components collaborate to form a complete system. Problems arise because many of these forests are patched and separated by a sea of human civilization. These fragments of forest are unhealthy and do not represent what a true large forest could be. Unfortunately, the number of these patches is increasing. Many scientists call these patches of forest, islands, because although they are not isolated by large bodies of water, they are separated by regions where there is sparse exchange of organisms or energy.
Throughout the study of living things, islands have been studied to examine species interactions and the changes in a system through time. In David Quammen’s book The Song of the Dodo: Island Biogeography in an Age of Extinctions, he justifies this by saying, “
“Biogeography is the study of the facts and the patterns of species distribution” in David Quammen’s book. In this field of science, one is concerned with the location of all types of organisms, but also where they do not occur. Biogeography can usually be described by the formation of new species, the extinction of species, and separation of species due to geographical change such as the formation of mountains or the interruption of a forest by a new housing complex. Therefore, biogeography studies where one can find a particular species.
After these basic questions are answered, inquisitive scientists go into the past to figure out the background story. Why are these particular species remaining while others have disappeared? More importantly, it asks: why are these species going extinct in this area or all over the world? Biogeography can also be used in such specific questions as: Why are the species on the islands of
Many of these studies revolve around islands. For example,
Island biogeography began with
On islands fewer species are present; therefore, fewer species relationships will occur. Due to their isolation, islands are prime locations for evolution to occur. With a small population, there is a limited amount of genetic differences between individuals. This causes island organisms to have a higher likelihood of straying away from their original form. Evolution is the change of organisms over time. This can occur due to new conditions on the island that the immigrant must adapt to.
For example, on the mainland, the soil is dark brown and millipedes are camouflaged as such (they are dark brown). Let’s say some of these millipedes find their way onto the island. The island soil is a dark reddish brown. Slowly, through natural selection, it will be more like that millipedes with a reddish color will survive on the island because they are better camouflaged. They will survive better than the dark brown ones so they will produce offspring that also have the reddish color. Also, with less competition, the millipedes will become bigger due to better nutrition. Over time (millennia, mind you), the millipedes on the island will be large and dark red, while the millipedes on the mainland for the most part will remain the same. Islands push the fast forward button of evolution. Therefore, it is easier to see the complete chain of events on an island. Now, mainly due to size differences, the “mechanical parts” of the reproduction of the two populations of millipedes will not fit together. As a result, they have become two separate species.
As another example, in a wind storm, a couple of beetles get lucky and land on an island instead of the ocean. The island is a complementary habitat, but there are only a couple of them present. Let’s say that the only male present has extraordinarily long front legs. His offspring will be more likely to have longer legs than the offspring of the other beetles of the mainland. The offspring on the island will mate with each other causing the long legs of the new generation of beetles to become even more pronounced. As time passes (millennia, mind you) and new generation of beetles are born and mate, the trait could become a distinguishing feature of the beetles on the island. These beetles could, then, become a new species that cannot mate with those on the mainland anymore. This is why on islands new species are more likely to form due to small species populations. This demonstrates the way that an extremely limited population size can be a catalyst for a huge shift in the characteristics of a species.
The theory of island biogeography deals with the characteristics of an island and how they affect the rate of speciation and extinction on the island. On islands, species will immigrate from the mainland or from other islands. Sometimes, the species will already be present or the new organism may be the first on the island. The latter is called a species introduction. The number of species on an island is determined by the number of different species on the island and not by population size of the species (Henderson and Whittaker).
On any island, as the number of species on an island increases, the rate of immigration will decrease. This occurs because as the number of species on the island increases, it is likely that a new species from the mainland will be a repeat and not a newly introduced species. Repeats will not increase the number of species that are present on the island. Therefore, with time and as more species are present, it will be increasingly less likely that a new species will arrive on the island and more likely that it will be a repeat. As the number of species on the island increases, the rate of extinction increases because if more species are present, there are more than can go extinct. Additionally, there will be more competition for resources. In island systems, it is more likely for a species to go extinct because it is difficult for a species population to be maintained in isolation with only a few individuals present. Reverting to the beetles from before, if the male would not have been able to find the females to mate, the population would not have continued.
Two island characteristics will determine the rate of immigration and the rate of extinction on a particular island. They are the size of the island and the distance the island is from the mainland (Quammen). Let’s set up a scenario to portray how this affects the species diversity of the island:
A group of people stand on a beach each with three small similarly-sized pebbles in their hands. A line is drawn in the sand. Three feet behind the line, three circles are drawn to represent three different islands. They are all drawn at a similar distance away from the line. More importantly, they range in size. One is large, one is medium-sized, and the last is quite small. Lining up along the barrier, each with their back turned to the circles throws each pebble over their shoulder hoping one will land in one of the circles. Ten pebbles land in the large circle, five land in the medium-sized circle, and in the smallest circle, only one pebble lands.
A larger island is more likely to have new species colonize it due to a larger surface area for them to “land.” Following suit, a smaller island would have a overall lower immigration rate. The movement of organisms is represented by the pebbles in the scenario above. The smaller island would also have a greater rate of extinction because it is likely that even though a new species appears upon the island not enough of them will be present to replenish the population with their offspring. The larger island will have a lower rate of extinction because it is more likely that the mainland will “replenish” the population with new immigrants. Additionally, it would be more likely that more of them landed on the island allowing the population size to grow quicker and the possibility of extinction to decline (Henderson and Whittaker).
Now, the group of people plays a similar game, but the circles rather than being three differently sized circles, they the same size at different distances from the starting line. In the style of bozo buckets, it is much easier for the pebbles to fall into the “islands” closer to the line than the circles farther away.
The distance of an island is from the mainland also plays are a significant role in species distribution. If an island is closer to the mainland, its rate of immigration is going to be higher than that of a farther away island because of the short distance that a species would have to travel. Therefore, smaller species or those that cannot swim or fly very well will be more likely to colonize islands that are closer. If an island is closer to the mainland, its extinction rate will be lower. This is because it will become more likely that the mainland will replenish the population size with more immigrants (Henderson and Whittaker).
It would seem that an island that is closer to the mainland and larger would be ideal in terms of species diversity. This is true. (Quammen).
More recently, most habitat fragmentation has occurred due to the activities of humans where they are separated by human dwellings or even roads; it is the process in which fragments of natural habitat are formed. Habitats that were once continuous become separated into smaller fragments. Habitat fragmentation caused by natural processes that slowly alter the layout of the environment is characterized by gradual speciation of the surrounding species. Natural processes include the formation of mountains separating a large forest into two smaller sized forest fragments. (e.g. mountains form that separate a large forest in half) These processes can occur over millions of years and allow plenty of time for the surrounding animals and plants to adapt completely. Habitat fragmentation due to human activity is often sudden. This does not allow species time to react. Therefore, fragmentation caused by humans is characterized by a large rate of extinction (“Habitat”). Although fragments used to be catalysts for evolution, today with more of them due to human activities, they actually decrease the amount of overall species diversity.
When fragments are created rapidly without allowing for evolutionary change, it is detrimental to the overall species diversity of a region. The overall amount of habitable area decreases. Plants are killed and animals must move to the remaining fragments. These remaining fragments will become very crowded, and consequently competition for resources will occur, as with population thinning (decline in population size). Few species can move between habitats (such as birds) but not many can or not many are “willing” to move across uncovered land that would increase their vulnerability to predators (“Habitat”).
A large piece of habitat is also necessary to maintain species diversity instead of a small patch. The larger an area of forest is, the more species diversity it will be able to maintain. This was discovered by Henry Allen Gleason in his article “On the relation between species and area” in 1922. In his study, he maintained patches of grass of different sizes. Each had the possibility of containing twenty-seven different types of grass. On average, a plot that was ten square meters contained ten different species of grass. A patch of twenty square meters had approximately thirteen species, compared to one of forty meters squared that had sixteen species. The best species diversity was found in the patch eighty square meters that was able to maintain twenty of the possible twenty-seven species comfortably. It was obvious that as the size of the plot increased, the number of species maintained also increased. This relationship can be used for all organisms (Quammen). In order for high species diversity to be maintained, a large area is necessary.
Additionally, a fragment is much like an island. The size of the fragment will determine the number of species present. Also it’s distance from the main forest and or other forests (or in the case of an island, mainland) will determine how many immigrants will colonize the fragment increasing species diversity. Fragments have small population sizes making them more susceptible to extinction. Small changes in environment due to climate or resources would be catastrophic in a small environment whereas in a large one could be corrected by another species (Henderson and Whittaker). For example, a certain bush that is the major food source to many small rodents cannot live under dryer conditions. For a couple of seasons, there is a drought and many of the bushes die out. In a small environment such as a fragment, there may not be other places for the rodents to get their nutrients but in a large forest, where there is increased species diversity, it is more likely that the problem can be fixed by another bush. Therefore, larger forests are more impervious to change than smaller ones.
Another consequence of habitat fragmentation is increased forest edge.
In conservation, a common procedure to decrease the effect of fragments is corridors. Corridors are small strips of forest between patches that to a certain extent, allow increased motion of organisms between different environments (“Habitat”). These corridors can also be “built” to the ocean to allow for animals that leave on coastal setting to interact with those of the interior land. With limited resources, this is the most that many conservation biologists can do. Unfortunately, the habitat is becoming increasingly fragmented, and the effects will be seen in all forests.
In conclusion, the best only way to preserve the true natural environment is to set aside the largest amount of continuous land with the smallest amount of edge to be saved. A large connected piece of land will allow species interactions to continue and relationships to thrive. Much like a work of art, all the pieces must be present to inspire the same message. Hopefully, people will realize that much like the necessity of maintaining the unity of all the pieces of
Works Cited
“Bombing of
“Edge Effects.” 31 October 2005. Wikipedia. 7 November 2005.
“Habitat Fragmentation.” 31 October 2005. Wikipedia. 7 November 2005.
Henderson, Scott J. and Whittaker, Robert J. “
Quammen, David. The Song of the Dodo:
Final Paper!
Defense mechanisms of Nyssodesmus python (Polydesmidae)
Sheiphali Gandhi
ABSTRACT
The purpose of this study was to examine the effects different characteristics of Nyssodesmus python had on the defense mechanisms of the organism. The defense mechanisms of N. python include: curling into a spiral and chemical defense. It was predicted that sex would not affect defense mechanisms, whereas size and level of calcification would. Populations were found in two locations: La Estación Biológica Monteverde and San Gerardo on different sides of the continental divide. One hundred and twenty millipedes were collected, 42 in Monteverde and 78 in San Gerardo. They were artificially threatened, and the time spent in a protective position and the release of toxin were recorded. The size of the individuals and level of calcification were also recorded. T-tests and chi-squared tests showed that there were significant differences in the defense mechanisms of males and females. Regression analysis showed a significant trend between size of an individual and the time it remained in the protected position, but the relationship may not be due to causation. The millipedes of different populations had some distinctive morphological and behavioral characteristics; additionally, there was a significant difference in their length of time spent in a curled position.
RESUMEN
El objetivo de este estudio fue examinar los efectos de las diferentes característcas de Nyssodesmus python sobre los mecanismos de defensa de estos organismos. Los mecanismos de defensa de N. python incluyen: doblarse sobre sí mismos y la defensa química. Se predijo que el sexo no afectaría a los mecanismos de defensa, mientras el tamaño y el nivel de calcificación si lo harían. Los individuos se encontraron en dos lugares: La Estación Biológica Monteverde y San Gerardo, en lados diferentes de la división continental. Ciento veinte milpiés se estudiaron en total, 42 en Monteverde y 78 en San Gerardo. Se amenazaron artificialmente, y se registraron el tiempo que pasaron en una posición protectiva y la presencia de la secreción de toxina. También se anotaron el tamaño de los individuos y el nivel de calcificación. Los experimentos indicaron una relación significativa entre el sexo de un milpiés y sus mecanismos de defensa. El análisis de regresión mostró una relación significativa entre el tamaño del individuo y el tiempo que pasó en una posición protectiva. Los milpiés de poblaciones diferentes mostraron diferencias morfológicas y etológicas características; hubo una diferencia significativa en el tiempo en que permanecieron en una posición protectiva.
INTRODUCTION
Nyssodesmus python, commonly known as the large forest-floor millipede, is usually found on the Caribbean slope of
Adult N. python have twenty body segments, nineteen of which display a pair of horizontal keels that are large and flat, resembling a large isopod. Individuals are dull light yellow with two dark brown longitudinal stripes running down their backs. Sex can be easily determined because on the ventral side of the seventh body segment of male individuals, the first pair of legs is modified into a set of small curved “gonopods.” These structures are used in the transfer of sperm to the female millipede. Additionally, female N. python at 70-100 mm in length are larger than males, who measure on average 65-90 mm (Heisler 1983).
Nyssodesmus python molts throughout its entire life cycle even after it has stopped growing; after each molt, an adult N. python is soft and unpigmented. Approximately a month passes until the process of calcification and pigmentation is complete (Heisler 1983). The calcified exoskeleton plays an essential role in resisting the large pressures developed while burrowing. It is thought that calcium salts increase resistance without making the keel unwieldy. In general, the exoskeleton of males is stronger and more resistant than females. Also, as the body mass of females increases, the strength of their exoskeleton increases as well; while this trend does exist in male exoskeletons, it is much less apparent (Borrell 2004).
N. python has two forms of protection: an extremely rigid exoskeleton and a toxic chemical excretion. When threatened, it curls into a spiral, protecting its vulnerable underside, and secretes a toxin from its hindgut (Heisler 1983). The predominant components of their cyanogenetic defense secretions are hydrogen cyanide and benzaldehyde, together with other compounds such as phenol, benzoic acid, benzoyl cyanide, and mandelonitrile (Kuwahara et. al. 2002). Their characteristic secretion glands are known as oxadenes. They open laterally on the individual diplosegments to exude the repugnant liquid (Wright 1999). The composition of each toxin secretion is species-specific (Kuwahara et. al. 2002), and the secretion of N. python is commonly known for its pleasing cherry-almond scent. This liquid can be expelled violently up to a distance of 30 cm (Heisler 1983).
Research has been done on the reproductive behavior of this species by Hyatt (1993) and Arnold (1998), but little else is known about the natural history of N. python (Heisler 1983). The present study explored significant trends in defense mechanisms dependent on sex, size, and population. It was predicted that sex would not affect defense mechanisms, whereas size and level of calcification would. The hypothesis was based on the fact that little distinction exists between the morphology of males and females, whereas a clear disparity can be seen in size and calcification.
MATERIALS AND METHODS
Study site
Nyssodesmus python were collected in two locations: the forest close to La Estación Biológica Monteverde and the forest in San Gerardo. The forest close to La Estación Biológica is on the Pacific slope in the lower montane wet forest life zone with an elevation of 1400-1800 m (Haber et al. 2000). San Gerardo sits at approximately 1300 meters in elevation on the Atlantic slope in the premontane rain forest life zone. Collection occurred close to trails due to accessibility (Fig. 1).
Data collection
The millipedes from the forest above La Estación Biológica Monteverde were collected in plastic bags and brought to the station by CIEE students. The millipedes collected in San Gerardo by Alan Masters were placed in a plastic container containing leaf litter and brought back to La Estación Biológica Monteverde to be tested. All subjects were collected between July 21, 2005 and August 1, 2005. They were kept at the biological station in terraria containing leaf litter collected on station property and covered with plastic wrap to maintain a moist environment. The millipedes from the two life zones were kept in separate terraria. The millipedes were left alone for one day to allow for acclimation. Multiple terraria were maintained so that simultaneous acclimation periods could be used for millipedes collected on different days. No more than ten millipedes were kept in a terrarium at the same time.
After the acclimation period, the millipedes were taken out of the terraria individually. The subject was then placed on a table and was artificially threatened by roughly turning it over onto its dorsal side. The amount of time the millipede remained curled in a spiral was recorded. The presence of toxin was determined by the presence of a sweet/cyanide smell and recorded. The length and width of the millipede were measured in millimeters by holding the millipede on it ventral side against a ruler on the table. These measures were multiplied to produce a size index for the comparison of different individuals. The new layer of exoskeleton, after molting, is unpigmented; therefore, the amount of calcification of the exoskeleton can be determined by its pigmentation. This was rated on a scale from one to ten with ten being the darkest and one the lightest. Calcification was recorded for only the Monteverde population because the pigmentation trend is only known for this population of millipedes (Heisler 1983).
Statistical analysis
Parametric tests were used to compare values. The log of the time of protection was taken to generate a normal data set. Unpaired t-tests were used to compare the protection time and size index of millipedes found in different locations. A chi-squared test was used to determine if the secretion of toxin differed between populations at the two sites. Unpaired t-tests were used to compare the curling time of males and females. Because there is a significant size difference between the two sexes (Heisler 1983) (Fig. 2), separate tests compared the size index and the protection time of each sex using simple regression analysis. Similarly, separate unpaired t-tests were run comparing the size index and presence of toxin of each sex. A chi-squared test was run to compare the presence of toxin for both sexes. Lastly, simple regression analysis was used to see if the protection time was a function of calcification.
RESULTS
A total of 120 Nyssodesmus python were collected. Close to La Estación Biológica Monteverde, 42 millipedes were collected, whereas 78 were collected in the San Gerardo forest. There were 46 females collected (16 in Monteverde and 30 in San Gerardo), while 74 males were collected (26 in Monteverde and 48 in San Gerardo). The ratio of females to males for each population was approximately 5 to 8.
Effect of sex
The protection time for the different sexes was found to be significantly different (p=0.0034). The mean protection time for females was 266.322±48.530 seconds, the mean protection time for males was 141.597±22.641 seconds. There was also a significant relationship between the sex of a millipede and the secretion of toxin (X2=10.781, DF=1, p=0.0010). Females were more likely to secrete toxin than males.
Effect of size
The millipede’s size index was found to have a significant effect on the protection time between sexes (males:p=0.0410, r2=0.057; females:p=0.0109, r2=0.138), but due to a low r2 value denoting a weak fit of the regression relationship, this may not be caused by millipede size. The trend showed that smaller millipedes tended to remain in the protected position for a longer span of time than a larger millipede of the same sex (Fig. 3 and Fig. 4). It was found that the size of a millipede did not have a significant relation to the secretion of toxin within each sex.
Results of different locations
The difference between the secretion of toxin in the two populations of millipedes was not significant (X2=0.001, DF=1, p=0.9693), as well as their differences in size (p=0.7893). There was a significant difference in the mean time of each group in the protected position (p=0.0018). The millipedes from Monteverde stayed in a spiral for 137.618±26.921 seconds, whereas the millipedes from San Gerardo averaged 217.295±33.311 seconds.
The two populations of millipedes showed divergent morphologies. The coloration of the group found in Monteverde consisted of yellow- and brown-striped keels (Fig. 5), whereas the keels of millipedes found in San Gerardo were black with yellow coloration on the outer edges (Fig. 6). A smell difference was also noted between the two groups. The millipedes on the Pacific slope secreted the characteristic cherry-almond smell, whereas the millipedes from the Atlantic slope secreted a substance that had a sweet smell that was neither as pleasing nor as strong as the secretion of the other group.
Other results
Calcification ratings were recorded for the millipedes found on the Pacific slope. Thirty-five of the 42 millipedes had complete calcification based on their pigmentation. It was observed that three millipedes had a rating of 1, one millipede had a rating of 2, one millipede had a rating of 4, and two had a rating of 8. There was no apparent relationship between the calcification of the exoskeleton of the millipedes found in Monteverde and its protection time.
DISCUSSION
Sex
Females remained, on average, in the protected position for a longer period of time and were more apt to secrete toxin, in comparison to males. The exoskeletons of male Nyssodesmus python are stronger than that of females (Borrell 2004). This may have been a contributing factor to this significant difference between the two sexes. Less protective measures would be necessary for the survival of the males since their exoskeletons provide them with better protection; therefore, the females with weaker calcification must compensate by using a longer time period in the spiral position or by relying on cyanogenetic secretions to deter predators.
Size
This slight negative relationship may be explained by the results of a study that found that as the size of female millipedes increased, the strength of the cuticle increased as well (Borrell 2004). It would not be necessary for large female millipedes to take as many defensive precautions as smaller female millipedes. Exoskeleton strength also increases with size in males, but the relationship was not nearly as defined as it was with females (Borrell 2004). This was mirrored in the relationship between protection time and the size of male millipedes. Therefore, although there is a significant relationship between the protection time of males, the relationship may not be strong due to the fact that the strength of their exoskeleton does not significantly increase with size.
Location
The two populations are comparable because they have very similar ratio between the numbers of males to females. In terms of patterns of toxin secretion and size, the two populations of millipedes differed little, but the distinctions between the protective times of the two groups were significantly different. It may have been due to the fact that the San Gerardo millipedes were moved to a much greater distance and to a new environment that caused them to remain in a protective position for a longer span of time. No prior research has been done on the San Gerardo population in particular, so no inferences can be made of this difference in times spent in the protective position.
The two populations have characteristics that may grant them to be considered as different species or subspecies. First of all, morphologically, the coloration of the species was very different. According to some definitions, this would be enough justification to separate the populations taxonomically. Additionally, the secretions of the two populations smelled very different. Within the family Polydesmidae, the compositions of the secretions are species-specific (Kuwahara et. al. 2002), further supporting that the two populations should be distinguished taxonomically.
Calcification
Molting causes fluctuations in the exoskeleton strength of N. python (Heisler 1983), but these fluctuations may not impact the defense mechanisms of the organisms as much as the gradual increases of calcification due to size (Borrell 2004). So, although calcification due to molting cycles did not show a significant relation, it says little of the overall calcification of an individual. Additionally, only seven millipedes were found to have exoskeleton strength differences due to a recent molt. This small sample size may have hindered the soundness of the data found.
Future research
In order to improve the validity of this study for future replications, some adjustments must be made. Differences between adult and juvenile millipedes were not considered. Juveniles have fewer segments because segments are added with age (Heisler 1983). The exoskeleton of juveniles is generally weaker than that of the adults (Borrell 2004); therefore, this may have adversely affected the data. Results derived from this study indicated that smaller millipedes took more protective precautions; when in fact, this could be attributed to the age of the millipede. A more intensive study should be performed to obtain more robust results to test the difference in cuticle strength between sexes and its effect on defense mechanisms. The strength of the exoskeleton of each individual could be tested to determine its relationship to defense mechanism. This can be done by following methods used by B.J. Borrell, in which fracture force and density of keels were determined (2004). It is necessary to clarify the relationship between the populations of the opposite slopes. Morphologically, the population from Monteverde matches known natural history of Nyssodesmus python (Heisler 1983). Little is known of the San Gerardo population because there is no known existing literature describing its characteristics, or even stating if it is a subspecies of N. python. No tests were run on the possible reproductive interactions between the two groups to confirm relationship. Another population of Polydesmidae millipedes was found within the Monteverde collection site. In terms of coloration, they resemble those found in San Gerardo, but in general, they are smaller than those found in San Gerardo (Appendix 1).
ACKNOWLEDGEMENTS
I would like to acknowledge all the people who helped me with my data collection of the Monteverde population: Gina Rozinka, Mary Oppold, Stephanie Place, Kent Melchiors, Nathaniel Talbot, and Carlos Guindon. An appreciative hug goes to Alan Masters who provided the entire San Gerardo population. I am still astounded by his thoughtfulness and generosity. I would not have smelled like hydrogen cyanide for a week without all of you. Thank you to Javier Méndez and Carlos Guindon for all of your professorly advice and explanations of statistics. For helping me with my spur of the moment questions throughout the process, I appreciate all the help of my teaching assistants, Maria Jost and Nathaniel Talbot. Plus, they danced around the station, made me smile, and made sure that I didn’t measure my millipedes in millipedes. Additionally, the teaching staff was amazing in their efforts of trying to figure out the taxonomic information of the San Gerardo population of millipedes. The support of all my fellow CIEE students helped me get through the exhilarating process of the scientific method, and the group wallowing alleviated my problems more than I could have ever imagined. Kathy Rockwell was a huge support and help for taking me to the doctor twice when both of my feet decided to stop being functional. Thanks to telepathy, I was able to understand all my good times with my friend Meg Smith, without whom, I would be lost in the Costa Rica. All the people back home were a great support during hard times, especially my sister Sonali and my friends at USI. I will never be able to forget the concern of la familia Cruz Solís of my plight of finding a large sample size. It was wonderful to come home to such kind people. And, of course, thank you to the staff at La Estación Biológica Monteverde for the Costa Rican brewed coffee that always made my day and night.
LITERATURE CITED
Arnold, N. 1998. Mating behavior of millipedes, Nyssodesmus python. Educational Abroad Program, spring 1998. Monteverde, Costa Rica.
Borrell, B. J. 2004. Mechanical properties of calcified exoskeleton from the neotropical millipede, Nyssodesmus python. Journal of Insect Physiology. 50:1121-1126.
Haber, W. A., Zuchowski W. and Bello, E. 2000. An Introduction to Cloud Forest Trees Monteverde, Costa Rica, p. 11. Mountain Gem Publications, Monteverde de Puntarenas, Costa Rica.
Heisler, I. L. 1983. Nyssodesmus python (Milpies, Large Forest-floor Millipede). In D. H. Janzen (Ed). Costa Rican Natural History, pp. 747-749. University of Chicago Press, Chicago, Illinois.
Hyatt, P. 1993. The mating behavior of the tropical millipede Nyssodesmus python. CIEE, summer 1993. Monteverde, Costa Rica.
Kuwahara, Y., Omura, H., and Tanabe, T. 2002. 2-Nitroethenylbenzenes as natural products in millipede defense secretions. Naturwissenschaften. 89:308-310.
Wright, Johnathon C. 1999. Myriapoda (Including Centipedes and Millipedes). Encyclopedia of Life Sciences. John Wiley & Sons, Ltd: Chichester. (http://www.els.net/)
Saturday, August 13, 2005
Friday, August 12, 2005
i gave my symposium presentation yesterday and afterwards i felt really really sad. it felt like another large part of the program had just ended. i did fine though if u guyz care, i got a 9.6 out of 10.
afterwards me and meg went to Santa Elena and did some souvenir shopping. then we went to this coffee shop called the treehouse coffee shop. there is honestly this large tree growing through the middle of the place. it is soo sweet. we sat and talked for like 3 hours there. it was amazing. i had a chocolate mint milkshake and she had a passion fruit shake and coffee.
it was sooooo hot when we went there. then it started to cool down because a CLOUD came through the middle of town. hehehe. then it started pouring like no other. then it stopped and we left. it was awesome.
we came back and there was a barbecue and javier's house (one of our ecology profes) it was pretty fun. i've never eaten so much meat in my entire life. (shrimp and chicken) then we laid on the balcony talking to michael and stuff wrapped in blankets that gave me the sniffles. i went to bed cuz i was really tired, but her and michael stayed up til 2am to watch the meteor shower. i didn't want to miss it, but i knew even if i was there i would be sleeping.
i'm going to miss meg so much. we had a long conversation about religion and things like that and i believe i have found one of the only people that has introspectively analyzed their religion as much as i have. i told her that we have to make an effort to keep in touch b/c i can't bear to lose her as a friend.
TA's singing something in
Wednesday, August 10, 2005
I MISS DDR!
Sheiphali: hi! i am once again on top of things. i finished my power point already. aren't you proud of me?
Sheiphali: tomorrow
Sheiphali: i know... WHAT"S HAPPENING TO ME!?!?!
Sheiphali: NEVA... i won't let you
Sheiphali: meh : P
Sheiphali: is DDR one of those steps?
Chad: all 12
Sheiphali: well if its DDR....
i'm a-going to post some pictures of me and meg today and some other random ones. in a bit.
Yesterday was brilliant!!!!!!!!!
people might be surprised that i say that considering i had a final yesterday but it was easy and confidence-building.
so after we went to San Luis which is this little farming town close by in the valley of the tilaran mountains kinda. we went to this families house and ate some of the best arroz con pollo EVER (chicken and rice). man it was sooo good. then they taught us about the history of their family and how the land had been his great-grandparents'. then we went out and helped him cut sugar cane and clean it. they have a really old fashioned sugar mill that has the thing that oxen run around to do it but for us Elizabeth and Colin had to do it. it was hilarious and great. everyone kept hitting them on the butts telling em to go faster. (i didn't :P). so we got to drink FRESH sugar cane juice. then we hiked about an hour to one of the most gorgeous waterfalls in the world. we
then we came back and went to Kathy's house for dinner and fun times. omg it was so fun. people drank and things and the got everyone to take shots or drinks even our professor Carlos Guindon. (well everyone except me of course... don't worry i haven't changed THAT much) it was just a fun time playing with her two ADORABLE daughters and the plethora/cornucopia of animals. since the waterfall had been so great, i was in one of my awesome sheiphali-moods and i think that i'm starting to open up in front of people more... to bad the program's almost over.
some people went to La Taberna but most of us came back to the station. i hung out with mary and nathaniel in the TA's office and we just layed on the hard wood floors, listened to music, and fell asleep. it was really nice. mary and nathaniel were talking but i was too tired to think and all i just slept. o ya and we did this thing that mary likes to do on hardwood floors. she moves her legs back and forth like she's making a snow angel because "it feels cool." uh right. but i did it anyways ~.o
so they have created a "sheiphalipop" song in my honor apparently and its hilarious. i'll try to see if i can figure out some way of taping it. it amuses me immensely. i don't even know the lyrics, but tyler and nathaniel made them up last night. nathaniel is one of the best musicians i have ever met. (probably ever met) he's amazing. when i tape it they're going to put it to music hehe. o man.
today i have to finish my symposium presentation that's tomorrow. public speaking won't be so bad especially if it's in front of people i know well. they cut you off at 10 minutes though so i'm going to have to practice a bunch. at about 1-2 pm me, meg, and mary are going to santa elenato buy souvenirs and things and i might try to buy something to wear to the symposium so i look nice. THEN! i'm going to teach a bunch of people how to indian dance because they want to learn. how cool is that? it's not like that one night in
i think i'm going to miss these people.
piano stuff in comp lab
Monday, August 8, 2005
ZIPLINES ARE AWESOME!
OH MY FREAKING GOD!!!!!!!!!!!!!!!!!!! (yes, it warranted more than just a omg)
zip lines kick ass.
i've realized that being here has really been worthwhile. as we hiked around in Sky Trek (we had to hike from zip line to zip line) i could name different plants to the species. how cool is that? i can be like, "hey look guys, that Xanthosoma robustum has started to infloresce." then someone else'll be like "oooh are there scarab beetles inside mating the sterile part?" OR "look at those Clusia leaves in that Quercus costarricensis. it hasn't reached the secondary stage of a primary epiphyte yet." MAN we're such biodorks. but seriously i know this sounds dumb, but it truly is exhilerating to walk through a forest and know what
and April, to answer your question, i truly am having the time of my life.
and a funny biojoke for all to enjoy... Quercus costarricensis just happens to belong to the family Fagaceae. (it's the costa rican oak tree)
tomorrow we have our ecology final, then we're going to san luis to see the awesomest waterfall ever (not going to swim b/c it's too cold), and finally, going to Kathy Rockwell's (the logistic coordinater) for a hot dog BBQ (chicken dogs for me). other people want to go to La Taverna to dance and stuff... but we'll see about that. i'm not antisocial, i just think i'll be tired and stuff
"busy, busy, busy" Cat's Cradle Kurt Vonnegut. time to go study. w00t!
wind through the trees
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