"You still don't understand what you're dealing with, do you? The perfect organism. Its structural perfection is matched only by its hostility. I admire its purity. A survivor … unclouded by conscience, remorse, or delusions of morality." - Ash to Ripley (Alien, 1979)
As human beings, we have thousands of different species of bacteria on our bodies, not including the other types of microorganisms. With all the different bacterial species, it would seem that no single bacteria is an indispensable member of our microbiome, however this is not the case. Lactobacillus acidophilus is a species of bacteria that women rely on just as much as the bacteria do. The L. acidophilus reside (among other places in the body) on the human vagina and use the woman as a resource host in exchange for protection from other potentially more harmful micro-organisms.
Description of the Relationship:
The presence of bacteria on the vagina was discovered over 100 years ago and is now one of the most well known examples of mutualism between humans and bacteria that there is. It is considered mutualistic because both the woman and the bacteria necessarily rely on one another. The L. acidophilus, once introduced to the vagina, begins to adhere to the vaginal epithelial cells and colonize. The bacterial colony consumes the natural sugars excreted by the skin and ferments them into lactic acid. This product lowers the pH to a level intolerable by most bacteria not of the Lactobacillus genus. During menstruation, many of the bacteria are killed, reducing them to an appropriate level.
Cost/Benefit Analysis:
The woman benefits from this mutualistic relationship by gaining protection from more harmful organisms that could potential cause a yeast, bladder, or urinary tract infection. This is at the cost of a slight decrease in reproductive fitness. L. acidophilus taking glucose molecules that the woman worked to obtain might not have a large negative affect on the woman by itself, but there are thousands of micro-organisms on and inside the human body that all contribute to a somewhat heavy, yet necessary burden. The bacteria (L. acidophilus) benefit from the relationship by gaining a steady food supply, and a habitable living place. This is at the cost a attack by the woman's defense system (daily hygiene, monthly menstruation, and immune response if levels get too high)
Orchids are widely distributed across
the world with 25,000 to 35,000
species except for Antarctica [1]. Orchid’s lifecyle begins after pollination
with the shivering of its petal and sepals. Then, it begins to form a seed; The
maturation period of the seed is unique to each orchid species. Next, the seed germinates into a seedling
resulting in the flowering of orchid and the process begins again. Since orchids’ seeds lack endosperm, they use
resources from fungus to complete the germination process [2].
Basidiomycetes
fungi provide energy and nutrients to orchids, from familyOrchidaceae. The fungi in the orchid mycorrhiza fulfill
the role of endosperm in orchid seed [3]. During
the non-photosythentic phase of the orchid’s lifecycle, the fungi provide the
orchid with energy and carbon compounds [4]. After the non-photosynthetic phase, the fungi
can also increase the nutrients and mineral intake of the orchid through the
roots. The fungi form pelotons that are
like the host cell. These pelotons are surrounded by a membrane similar to
plasma membrane. An infect orchid has altered microtubules and cell wall
microfibrils [3]. All these
alterations caused by the fungi help the orchid to absorb inorganic nutrients
and trace elements from the soil. The
fungi also benefits from these interactions by receiving some of the
photosynthesized carbohydrates [5]. Thus, the relationship between
orchid and orchid mycorrhiza is mutualistic.
Some orchid mycorrhiza have evolved to be specific based on the species
of the orchid therefore, can serve to be pathogenic to other orchid species [3].
Cost and Benefit
Analysis
As stated above, both the orchid and
fungi benefit from this relationship.
The fungi gains carbohydrates from the orchid while the orchid receives nutrients
and energy.
The orchid does not spend a
lot of energy in developing its roots in order to increase its volume of
nutrients and minerals absorption from the soil. Instead, the fungi fulfill that role. The fungi are not limited to the roots alone. They can explore other cavities and compounds
that are not near the roots[5].
Even though fungal infection can be
pathogenic to the orchid, the orchid is able to control the infection. The orchid has defense genes and compounds
such as orchinol that can control the fungal infection [3]. These defense mechanisms does not significantly
affect the reproductive success of the fungus.
Scientists approximate that bacteria first appeared on Earth
around 3.5 billion years ago, while the first eukaryotes were not thought to
inhabit Earth until approximately 1.5 billion years ago. What happened in this
time gap of 2 billion years? Well, scientists can only make an educational guess,
considering that primates likely did not come to be until approximately 65
million years ago (1). The endosymbiosis theory points to perhaps the earliest
known form of mutualism in which bacteria are thought to have inhabited a “primordial
eukaryotic cell” (2). The presence of a bacterial organism inside the larger
cell allowed cellular life to adapt to the harsh conditions of the time.
Scientists believe that photosynthetic bacteria appeared 3.2 million years ago,
thereby releasing oxygen into the atmosphere. Oxygen can actually be a toxic
substance, but the first aerobic bacteria lived about 2.5 billion years ago,
very shortly before the first aerobic eukaryotes. These inferences, among many
other observations, point to the endosymbiosis theory as a plausible
explanation for adaption to an environment abundant in oxygen (1).
Why would we think that bacteria would crawl inside of
another cell? Well, we assume that in a mutualistic relationship, both parties
benefit due to the relationship. Additionally, the endosymbiosis theory suggests
that mitochondria and chloroplasts’ lineages can be traced back to ancient
bacteria. Not only are these structures about the size of a bacterium (70S),
but these organelles also contain their own DNA in the form of one circular
chromosome like bacteria (3). Both bacteria and the organelles replicate via
binary fission (1).
Although this background information is necessary in
understanding the basic evolution of the eukaryotic cell, I would like to
specifically examine the relationship between mitochondria (derived from ancient
bacteria) and the primitive eukaryotic cell. As previously stated, at the time
of the initial endosymbiotic encounter, few species were equipped to convert
oxygen into another substance to avoid oxidation. Therefore, the host cell
greatly benefitted from its smaller counterpart because mitochondria convert
oxygen to ATP via substrate-level phosphorylation. Today, researchers have
evidence to suggest the mitochondria are related to the proteobacterium Rickettsia prowazekii, “an obligate
intracellular parasite” (3) due to its similarity in genomic sequence. Although
it is not exactly clear why the bacterium benefitted from the relationship, it
can be inferred that the bacterium was provided a “safe” environment to reside
in a chemically stable environment. This idea applies to chloroplasts as well.
To understand the role of early bacteria in the cell, let us
look at the function of a mitochondrion. Ultimately converting oxygen to ATP, mitochondria
are the powerhouses of a cell through their production of energy. Mitochondria
have two membranes, of which the outer membrane, containing porins, resembles Gram-negative
bacteria. The inner membrane contains cristae, infoldings that greatly increase
surface area. The inside of the mitochondria, the mitochondrial matrix,
contains ribosomes (similar to size of those of bacteria), DNA, and calcium
phosphate granules. The DNA and ribosomes are used to synthesize some of its
proteins (3).
The mitochondrion is the location of the tricarboxylic acid
cycle (TCA), production of ATP, and oxidative phosphorylation. In the TCA cycle, pyruvate is oxidized and
cleaved to form CO2 and acetyl-coenzyme A (acetyl-CoA), an
energy-rich molecule. After a series of reactions on acetyl-CoA, NADH and FADH2
are formed, which are both electron carriers. This reaction also yields
four ATP molecules. The electron carriers formed in the TCA cycle are active
players in the electron transport chain, as electrons are transferred to
acceptors such as oxygen. The electron transport chain involves an energy
gradient within the inner membrane of the mitochondria in eukaryotes and in the
plasma membrane in prokaryotes. In this process, NADH is oxidized to NAD+,
while the electrons are transferred to other molecules (such as oxgygen) with
more positive reduction potentials. Oxidative phosphorylation is the result of
the electron transport chain, in which protons move across the mitochondrial membrane
and ultimately produce a maximum of 34 ATPs. These processes are very
simplified, as more complex explanations involve in-depth biochemistry (3).
Through these complicated processes in the mitochondria,
eukaryotic cells are able to reap the benefits of an abundant amount of energy
to sustain more complex forms of life. Although the TCA cycle and electron
transport chain produce small amounts of ATP, oxidative phosphorylation allows
for 34 molecules of ATP to be produced.
We already have an idea of how beneficial mitochondria are
to sustaining life, but what happens when mitochondria start to malfunction? As
already mentioned, mitochondria contain their own DNA. Mitochondria are passed
from mother to offspring in the cytoplasm of the egg. Over 200 human diseases
are caused by mutations in DNA due to mitochondrial DNA’s inability to repair,
unlike nuclear DNA. Most of these diseases come about in cells that require an
abundance of ATP, such as muscle and nerve cells. Several examples of dysfunctional
mitochondria-caused diseases are the following: optic neuropathy, often
resulting in blindness; neurogenic muscle weakness; maternal and
cardiomyopathy; and myoclonic epilepsy (2). Regardless of the primitive
bacteria-eukaryotic cell relationship, it is apparent that eukaryotic cells
have become very dependent on mitochondria to sustain life.
Introduction:
As we have seen with the Attine ant and Leucoprini fungus, animals have beaten humans to the act of farming. Another example of this would be the ambrosia beetles and ambrosia fungi. Ambrosia beetle is a general term used to describe several species of beetles from the two weevil subfamilies Scolytinae and Platypodinae [1]. One of the most rapidly diversifying, most widely distributed, and probably most ecologically and economically important group of ambrosia beetles is the tribe Xyleborini [1]. Ambrosia beetles can be found in all regions with tropical vegetation and even in some temperate areas [1].
Since there are several species of ambrosia beetles, it comes with no surprise that there are many species of fungi that have a long established relationship with these beetles. The most common are polymorphic asexual anamorphs from the general Ambrosiella, Raffaelea, Ambrosiozyma and Dryadomyces [1]. Most ambrosia fungi are not capable of living independently of the beetles [1].
The relationship between the beetles and the fungus has been describes as one of the most successful and widespread cases of insect-fungus symbiosis, ambrosia beetles are the product of sixty million years of intricate mutualism between the faster evolving beetles and some of the most bizarre fungi [2].
Ambrosia beetles have evolved a variety of morphological structures to carry their fungal symbionts from tree to tree. These structures are generally called mycangia [1]. As the beetles leave their initial home, they carry spores of the fungus in their mycangia. Once they find a suitable tree, they then create tunnels (galleries) inside the wood which will make small strings of compacted sawdust protrude from the tree [3].
The beetles will then cultivate the fungi inside the galleries within dead or decaying wood and feed on their mycelium. Once the "fungus farming" has started, the beetles can lay their eggs that will produce larva. The beetles will care for their young larva in the trees where they will become beetles and carry fungal spores to their next habitat.
Cost/benefit analysis:
The beetles are dependent upon the fungi, from which they require amino acids, vitamins, and sterols [5]. Certain immature stages of the beetles are unable to complete development in the absence of the fungus [6], At the same time, the activities of female beetles have been hypothesized to control the growth of composition of ambrosial gardens. If the female dies, the garden is quickly overgrown by contaminating fungi and bacteria, which ultimately results in the death of the brood [5].
The interaction is clearly mutualistic. The symbiosis allows the beetles to exploit a nutritionally poor resource (wood) and reduce interspecific competition, while providing the fungi consistent transport to a relatively rare and ephemeral resource (a new host of the appropriate condition and successional stage) [5].
Although both the beetle and the fungi are benefited by this relationship, there are also cost to pay. The beetle could die if the fungus is suddenly removed from its habitat as the beetles are too specialized to be able to use another species of fungus. The fungus has also evolved to where it does not reproduce sexually, thus reducing genetic diversity and ability to explore different niches without the help of the beetle.
The lizard, Podarcis
lilfordi, is found on the Balearic Islands off the coast of Spain [1].
However, unlike other lizards, this species shares a mutualistic relationship
with the shrub Daphne rodriquezii [2].
D. rodriquezii is characterized from
its beautiful white flowers and it also contains many fruits that the lizards
like to consume [3]. The lizards consume and disperse the seeds of the plant by
eating the fruits that grow from the shrubs [4].
P. lilfordi is a medium sized lizard that grows to a maximum of
80mm. Its body mass can be anywhere between 4.2 to 9.5 grams. The females
reproduce cyclically, producing 2-4 eggs per clutch. They can lay multiple
clutches in one season [3]. However, as new predators and lizards show up to
the islands and compete for resources, the population of P. lilfordi has slowly started to decline [1]. The shrub, D. rodriguezii, starts to grow during
the early spring season. They contain very small, white flowers. The sepals and
petals unite, forming a tube called the hypanthium that usually has purple dyes
and is 7 to 11 mm in length. During the summer, the shrubs mature and produce
red-orange, fleshy globose fruits. The shrubs rarely grows above 50 centimeters
in height [2].
P. lilfordi are
very productive seed-dispersers for the shrubs. It is a mutualistic
relationship, in which the lizards use the shrubs not only as a food source,
but also as a second home [1]. The lizard eats the fruits that D. rodriguezii produces, and it also
uses the shrub as a home, keeping it out of sight from other predators and the
hot sun [2]. In return, the shrub gets the benefit of having the lizards
disperse their seeds for them. They are then better able to spread their
offspring to other areas [3].
However, P. lilfordi
also has other priorities and responsibilities on the ecosystem found on the
Balearic Islands. It is also a pollinator of the aroid Dracunculus muscivorus, and a seed disperser for Withania frutescens and Phillyrea media [1].
As mentioned before, the mutualistic association between P. lilfordi and D. rodriguezii is very straightforward. D. rodriguezii serves as both a food source and a shelter for P. lilfordi, and in return P. lilfordi disperses the seeds of the
shrub through fecal defecation. Without D.
rodriguezii being present in nature, P.
lilfordi would still be able to survive and reproduce in nature. However,
it would have a better chance to pass its progeny if D. rodriguezii was present, as it would have an extra food source
and shelter [1]. D. rodriguezii,
however, would have a much harder time reproducing in nature as their seeds
would not get dispersed if P. lilfordi
was not present in the environment.
Many organisms living in the sea benefit from a symbiotic relationship with other organisms around them. One example of this is the relationship between the sea cucumber and the pearl fish. Sea cucumbers are echinoderms that have a shape very similar to soft cucumbers (1). They have “leathery skin” and their body is essentially one long digestive tube. These invertebrates crawl along the floor of the ocean and can reside in both shallow and deep areas of the ocean. They are omnivorous and usually eat small particles and detritus they find on the ocean floor. The sea cucumber can grow between 2 to 200 cm and can live to be between 5 and ten years old (2). Spawning for the sea cucumber usually occurs between June and August. The sea cucumbers release their sperm and eggs in the water and allow fertilization to take place. These fertilized eggs continue to develop into larvae, which become suspended in the water column for up to 70 days. Eventually, these planktonic forms settle on the ocean floor, where they change into tiny little juvenile sea cucumbers. Growth is slow for these invertebrates, and it can take up to 4 years for the cucumber to reach adult size (3).
The symbiont of the sea cucumber is the pearl fish. Pearl fish are “eel-shaped” fish that are found worldwide, but primarily in tropical, shallow areas around coral reefs. They have long, slender bodies that lack scales and they usually have transparent skin. The tail of the pearl fish is long and pointed, and the anus of this fish is located close to its neck. Pearl fish typically grow to be about 15 cm long (4). The female pearl fish releases clumps of eggs late in the summer to begin the life cycle. These eggs rise to the surface and hatch, turning into a specific type of larvae called vexillifers. These larvae live among the plankton until reaching a length of about 7 to 8 cm. At this point, the larvae develop into tenuis. These forms descend to the ocean floor and begin their search for food and a host (5). The pearl fish will constantly be on the lookout for sea cucumbers to create a symbiotic relationship.
Description of Relationship:
Once a pearl fish (Onuxodon or Carapus) finds a sea cucumber (Holothuroidea), it immediately begins to smell around to distinguish between the head and the anus of the cucumber (6). Once it finds the anus, the pearl fish works its way into the rectum of the sea cucumber, eventually being completely engulfed in the digestive canal of its host. There it will spend the day inside, using its host as a form of protection. At night, the pearl fish comes out to feed on small crustaceans, but it doesn’t go too far from its host (7). After feeding, the pearl fish returns to its host and waits for the sea cucumber to take a breath. When the anus opens for respiration, the pearl fish simply swims back inside, seeking shelter in the rectum of its host (8). The pearl fish and the sea cucumber have evolved a symbiotic relationship know as commensalism. In this relationship, the pearl fish benefits because it gains a place to live that is cozy and protected from predators as well as any nutrients that can be absorbed as they flow out of the cucumber’s anus. Meanwhile, the sea cucumber appears to be unaffected by this relationship. It doesn’t even seem to notice the pearl fish entering its anus. As far as we know, the pearl fish is not taking anything from the sea cucumber. The reproductive success of the cucumber remains the same. Therefore, since the pearl fish benefits and the sea cucumber is neither helped nor harmed, one can argue that this relationship is one of commensalism. Many other organisms have benefitted from relationships similar to that of the sea cucumber and the pearl fish. The pearl fish have also learned to penetrate the bodies of other invertebrates such a starfish, sea squirts, and clams. A number of crabs and polychaete worms have also evolved to live inside sea cucumbers and have become specialized for gaining protection from the cloaca of that host (9).
Cost/Benefit Analysis:
The relationship between the pearl fish and the sea cucumber is not obligatory, but the pearl fish benefits from its symbiosis with the sea cucumber. The costs for the pearl fish in this relationship are very small. They must expend energy searching for a sea cucumber and for wiggling their way into the anus of the host. On the other hand, the benefits for the pearl fish are immense. The fish is provided protection from predators when it resides within the rectum of the cucumber. They also can take up any nutrients found in the waste products being excreted from the rectum of the sea cucumber. Another benefit for certain species of pearl fish is that they can use the rectum of the sea cucumber as a place to develop into their adult forms and complete their life cycle (9). While the pearl fish is provided with shelter, the sea cucumber has nothing to gain from this relationship. Nor does it have anything to lose. Both the cost and benefit for the sea cucumber is nothing. The reproductive success of the sea cucumber is not affected and the pearl fish benefits, it is likely that this relationship will persist as commensalism. Eventually, there may even be an adaptation that would benefit the sea cucumber, creating a relationship that is more like mutualism.
(Image from a scanning electron microscope of the phoretic mite Kennethiella tristosa) [7]
The phoretic mite Kennethiella tristosa attaches itself to
the wasp Ancistrocerus antilope. This pair exhibits both vertical and
horizontal transmission. Vertical transmission occurs when a female wasp lays
an egg and the larva, or deutonymphs, leave the wasp and transmit to the egg.
Horizontal transmission happens during mating from wasp to wasp [1].
Kennethiella tristosa gains a mode of transmission and housing, from a special
cavity solely developed for housing mites, from the wasps without harming it. However, it has been shown that large numbers
of Kenethiella tristosa can actually become parasitic and harm the wasp. It was observed that when large number of
mites was present, juvenile wasp’s mortality rate increased by 30% [2]. According to the distribution map (from the encyclopedia
of life) these mites are only found in two select areas [3]. Since the distribution is so small, these
mites are rarely researched. The life cycle of these mites includes a
deutonymph stage where the mites attach themselves to the propodeum of the
female wasp after she has mated with an infected male. After they have attached
to the wasp, they travel to a new nesting site via the females and feed in
order to complete their life cycle. After reproduction, the cycle starts all
over again [1] [4].
(Distribution Map for Kennethiella tristosa)[3]
Description of the Relationship:
(Life cycle of K. tristosa compared to the life cycle of A. antilope) [8]
This species of phoretic mites comes from the genus
Kennethiella and the species is tristosa [1]. The second partner in this
relationship comes from the genus Ancistrocerus and the species antilope. These
tiny mites gain a mode of protection and transportation during their
non-feeding stage of a deutonymph. The
wasps are not harmed in the process if the number of mites is kept at a
manageable rate [2]. These two species
exhibit commensalism where the mite obtains transportation, protection, and food
while the wasp is not harmed [5].
Cost/Benefit Analysis:
Benefit for Kennethiella tristosa: The mites gain protection
from the propodeum in the wasp. This area only has one function and that is to
provide protection for the mites. It
also gains transportation and food.
These mites feed on the larva of the wasp and in order to finish their
life cycle they must transfer to new nests with fresh larva. [1] [2]
Benefit for Ancistrocerus antilope: There is no recorded
benefit thus far for the wasp in the relationship. [2]
(K. tristosa on the propodeum of the A. antilope) [6]
Cost for Kennethiella tristosa: If there are too many mites
on a single wasp, the host is killed and there are no more resources for the
mites. Therefore, they cannot finish
their life cycle and produce the next generation.
Cost for Ancistrocerus antilope: If the wasp becomes too
heavily parasitized, it will die.
There are no specific strategies employed by either partner
in order to make contact easier.
Researchers are still uncertain as to why this commensalism relationship
continues, but they have notices that the only function of this cavity in the
wasp is to protect and house the phoretic mites [2].
6.Cowan, D. P. (Photographer). (2002). A male a. antilope wasp with a large cluster of k. trisetosa deutonymphs clustered on the right side of the propodeum and thorax. [Web Photo]. Retrieved from http://homepages.wmich.edu/~cowan/research/VenTransMItes.html
Introduction: Rhizobium are motile, rod shaped, gram negative
bacteria. They are particularly interesting because of their ability to
form nodules with the roots of leguminous plants. Legumes are herbaceous
plants that produce seeds in pods. Examples include peas, beans,
trefoils, and mimosa.
This relationship is common in nitrogen limited environments. [1]This
relationship occurs hen the rhizobium responds chemotactically to flavonoids
produced by the plant.
The rhizobium cause conformational changes in the root itself, asides from
the nodule. It causes the root hairs to change the direction of their
growth, which ultimately plays a large role in infection. The root hair
curls around the bacterium and traps it and brings it into the root [2, 3].
Rhizobium are able to fix nitrogen with the aid of the enzyme
nitrogenase. The presence of oxygen would decrease the efficiency of the
nitrogenase. Leghemoglobin protects the nitrogenase from oxygen.
There is dispute as to the leghemoglobin's origin. In the school of
thought we will follow, the protein portion is contributed by the plant and the
heme group is contributed by the bacteria. [3].
It should be noted that rhizobium has been shown to be an enivronmentally
friendly and effective fertilizer and has great potential for the agricultural
industry [5].
Cost Benefit: Both species benefit from this relationship, but
they can exist independently of each other as well. The roots of the
legume plants provide energy to the rhizobium in the form of nutrients and
carbohydrates [4]. While the plant gives energy to the rhizobium, it does
not give so much so that the plant itself suffers. The rhizobium benefit the
plant by fixing nitrogen to ammonia. Some species on fix up to 220 lbs of N2
per agricultural acre per year [1]. The lack of negative aspects of this
relationship leads me to conclude that this non-obligatory relationship should
continue.
Sources
1.) http://filebox.vt.edu/users/chagedor/biol_4684/Microbes/rhizobium.html
2.) Bisseling, T; Geurts, R. Rhizobium Nod Factor Perception and
Signalling. The Plant Cell, Vol. 14, 239-249. May 2002.
3.) Van Rhijn, P; Vanderleyden, J. The Rhizobium-Plant Symbiosis.
MICROBIOLOGICAL REVIEWS. Vol 59(1). 124–142. Mar. 1995.
4.) Combes, C. Parasitism: The Ecology and Evolution of Intimate
Interactions.
5.) Mia, M;
Shamsuddin, Z.
African Journal of Biotechnology Vol. 9 (37), pp. 6001-6009, 13 September, 2010
Spider Crabs, Libinia
emarginata, are from the species of crab, stenohaline. They live in the Atlantic Ocean on the coast of North America, but can be found
from Nova Scotia to the Florida Keys, and the Gulf of Mexico.
[7]
They have long
legs, round spiny bodies, and 9 spines down their back. They live at depths up
to 150 feet Females can only reproduce after molting. The young hatch from eggs
as zoea larvae [5]. Since predation is a concern for these crustaceans, these
crabs will attach pieces of shell, seaweed, and algae to the sticky hairs on
their bodies for camouflage [1]. The crabs also use the greenish-brown algae on
their back to help hide it from predators [2].
[8]
DESCRIPTION OF THE
RELSTIONSHIP
Spider crabs come from
the genus and species Libinia emarginata. These crabs can grow to be up to 12 inches from claw
to claw [5]. They have different claws than other crabs do in order for them to
scoop up algae [3]. Spider crabs and algae share a mutualistic relationship. “A mutualistic relationship is when two organisms of
different species ‘work together,’ eachbenefiting from the relationship” [2]. Even though this
is a mutualistic relationship, it is a facultative relationship
for both meaning it is not obligatory for either organism. Both organisms benefit from the relationship with the
other: the crab gets to blend in with its surroundings and the algae get a
place to live [2]. The relationship is established when L. emarginata scoops up the
algae. This relationship is not unique to spider crabs. Spider crabs are not
the only animals that use algae for camouflage. Devil scorpionfish are
camouflaged to their environment because they allow algae to grow on them.
Also, other types of crabs use this camouflage technique by allowing algae and
dirt to stick to hairs on their body [4].
[6]
COST/BENEFIT ANALYSIS
Benefit for spider
crabs: As previously
stated, the spider crabs benefit from the relationship with algae by using it as
camouflage. Because of this, the crabs have a better chance of surviving
predators.
Benefit for algae: Since the crabs pick up the algae, they get a
permanent place to live. It is also protected from predators now because it has
a permanent home on the crab [2].
Cost for spider crab: The spider crab spends energy to find, collect, and
scoop algae onto its back.
Cost for algae: Even though the algae get a place to live, the
crabs possibly could take them into a new, unfamiliar environment. Therefore,
it might not be as successful there.
Since this is a
mutualistic relationship, there is not a great amount of cost for either the
spider crab or the algae. Any “cost” is outweighed by the benefits. Even though
the crab spends energy recruiting the algae, it pays off since it can hide from
predators.
Since this symbiotic
relationship shows strong, beneficial qualities for both organisms, it seems
like this relationship will proceed.
