User:Shine.21/sandbox

Topic: The adaptation of shell thickening seen in Mytilus edulis

Elliot Shine

Freeman, Aaren. "Mussels Evolve Quickly To Defend Against Invasive Crabs." Mussels Evolve Quickly To Defend Against Invasive Crabs. University of New Hampshire, 10 Aug. 2006. Web. 13 Sept. 2014.

This article explores how Mytilus edulis was able to undergo evolutionary change in 15 years, which by it is amazing. The article supports this theory of such a quick evolutionary change by comparing blue mussels from Southern New England to blue mussels from above the Mid- coast of Maine. The Carcinus maenas commonly known as the Green Crab is an invasive species that was introduced to New England around 150 to 200 years ago and compares the mussel’s reactions to the Hemigrapsus sanguiens commonly known as the Asian Shore Crab, which was introduced to New Jersey in 1988. The study showed the adaptive ability for the Southern New England mussel to thicken it’s shell in the presence of both crabs, while on the other hand showed the inability of the Northern mussel to recognize and harden it’s shell in the presence of the relatively new invasive Asian Shore Crab.

"SCIENCE." Washington Post. The Washington Post, 14 Aug. 2006. Web. 13 Sept. 2014.

This news article gives a brief history of the introduction of the Carcinus maenas into New England. While also referencing the introduction of the Hemigrapsus sanguiens into the United States, and its recent effects on the mussel. The Washington Post also provided readers with specifics such as the specific date of introduction for the Green Crab being 1817.

Byers, James E., and Aaren Freeman. "Divergent Induced Responses to an Invasive Predator in Marine Mussel Populations." Divergent Induced Responses to an Invasive Predator in Marine Mussel Populations. Science Magazine, 13 June 2006. Web. 13 Sept. 2014.

This is the article that all the follow up articles have stemmed from. It explains how the same species of mussel is able to detect chemicals in the water after adaptation to trigger a defense system when in proximity to the predator. More importantly it explores the worldlier concept of how a species is capable of quickly adapting a defense to an invasive species. Also explaining how typically crabs will move on to easier prey if they find it is too hard to open the mussel.

Stokstad, Erik. "Native Mussel Quickly Evolves Fear of Invasive Crab." Science Magazine: Sign In. N.p., 11 Aug. 2006. Web. 14 Sept. 2014.

Something I found particularly helpful in this article was quantitative percentages on the thickness the shell incurs. It is actually several months for the shell to become only 5% to 10% thicker than it would have been otherwise. While this statistic alone would lead you to believe it isn’t quite as powerful of a mechanism this slight change in itself requires the crab 50% more time for the crab to open the mussel. This coupled with the knowledge I gained earlier about how the crab will move onto easier prey shows the pure effectiveness of this mechanism in deterring the predator.

Mooney, H. A., and E. E. Cleland. "The Evolutionary Impact of Invasive Species." Proceedings of the National Academy of Sciences of the United States of America. N.p., 8 May 2001. Web. 14 Sept. 2014.

While this article did not specifically reference the Blue Mussel nor its adaptative abilities. It did shed a unique light on the ramifications of envasive species, which is a primary focus. It explains how before the Age of Exploration the probability of the dispersion of such species was low. In contrast with today where now ecological systems can be greatly affected by the what may seem at the time as minor alterations. The article gives specific examples of ecological changes and responses which I feel would be very informative to reference because it shows the uniqueness of the scenario at hand and how adaptations aren’t always as easy and as timely as the shell thickening seen in blue mussels.

https://en.wikipedia.org/wiki/Blue_mussel

This article neglects to mention ″Hemigrapsus sanquiens″ also known as the Asian Shore Crab and ″Carcinus maenas″also known as the Green Crab as predators. Secondly the article also forgets to mention the defense capability of shell thickening. Lastly in the top of this notes section there is a question referring to the diet of Mussels, which is in fact entirely plankton and a mussel can filter up to sixty five liters of water a day doing so. Shine.21 (talk) 01:29, 2 October 2014 (UTC)

The capability of shell thickening by mussels has become a very effective defense mechanism. In the presence of predators a mussel is able to increase shell thickness 5 to 10 percent, which in turn makes opening the shell take 50 percent more time. [9]

FINAL DRAFT STARTS HERE

Phenotypic differentiation and defense mechanisms of Mytilus edulis with correlation to the Enviornment

Elliot Shine

Thursday 5:20 p.m.

The process of evolution is commonly perceived as a timeless process that incurs small incremental changes over a long period of time. Mytilus edulis, commonly known as the blue mussel has shed light on the time duration of evolution. The characteristics of the M. edulis species, coupled with the nature of it’s surrounding ecosystem provide the pathway to the species evolution. This is shown through unique defense mechanisms shown by conspecifics in unique environments, but also by the means in which M. edulis reproduces. The phenotypic plasticity of M. edulis provides a unique insight into phenotypic differentiation responses as a result of environmental change. This ability to change allows for survival in varying environments, and also keeps predator species in those environments steadily evolving in order to exploit such a unique organism. M. edulis has the unique defense mechanism of shell thickening,  the shell becomes 5% to 10% thicker, which in turn requires the predator crab 50% more time to access the mussel (Stokstad 2006). While this change may seem insignificant it has been proven that crabs will move onto easier prey if they find it too hard to open the mussel (Freeman and Byers 2006). The shell thickening mechanism along with the quantifiable increase in byssal threads are the two primary defense mechanisms. These mechanisms are induced by water cues that include nearby proximity of predatory crabs along with broken conspecifics (Leonard, Bertness, and Yund 1999). These water borne cues have been further explored in the comparison of two species of M. edulis that reside in different locations. While the Southern New England M. edulis and Mid-Coast Maine M. edulis  are conspecific, they reside in unique environments and display different phenotypic plasticity  for the shell thickening defense mechanism. While both populations share a common predator in the Carcinus maenas, which is also commonly known as the Green Crab, the Southern New England blue mussel has also been exposed to the Hemigrapsus sanquiens. The Green Crab is an invasive species that was introduced to the North East around 150 to 200 years ago, enabling both the Southern New England and Mid-coast Maine blue mussels ample time to develop shell thickening defense mechanisms due to water cues (Freeman and Byers 2006). On the other hand, there is the recent introduction of the Asian Shore Crab as an invasive species in 1988. The Southern New England blue mussel was unable to recognize water cues given off by the Asian Shore Crab early on and suffered the consequences. Amazingly, the Southern New England blue mussel was able to adapt and recognize the Asian Shore Crab only 15 years later and use the waterborne cues in order to activate its shell thickening mechanism showing incredible phenotypic plasticity (Freeman and Byers 2006). This ability for M. edulis to adapt so quickly was shown experimentally through the exposure of the Mid-coast Maine blue mussel to the unrecognizable Asian Shore Crab. Suffering from the inability to recognize water borne cues given off by the predator, the Mid-coast Maine blue mussel was easy prey and showed the inability to enact the shell thickening defense mechanism against an unrecognizable predator. Showing that this phenotypic response was made by the Southern New England blue mussel due to the environmental changes that occurred during the introduction of a new invasive species (Freeman and Byers 2006). Invasive predator species however are not the only environmental change that can induce phenotypic change. In the Gulf of Maine, two conspecific M. edulis populations were studied in environments where the amount of water flow varied. Estuarine shore lines with low water flow are characterized by high crab predation on the blue mussel, versus nearby shore lines with high water flow that showed comparatively less predation (Leonard, Bertness, and Yund 1999). Higher water flow prevents the build up of chemicals exuding from damaged prey (Behrens 1998). M. edulis use these chemicals as waterborne cues for defense, which seemed counterintuitive, because the high water flow sights experienced less predation in the experiment. This indicates that other characteristics of the high water flow shorelines must make it less favorable to predation. The high predation sites were characterized by an increase in byssal threads, which enable mussels to attach more firmly to substrates. At these high predation sites, populations showed that predators required 140% more force to dislodge mussels from their substrate in comparison to the mussels at low predation sites (Leonard, Bertness, and Yund 1999). As previously discussed, crabs will move onto easier prey if it takes too much time to eradicate the chosen mussel. In the high predation populations, a robust lip margin was also found as a defense mechanism. This robust lip margin provides protection against perimeter tactics used by predators on mussels to pry open the lip of mussels that are too large to crush outright (Leonard, Bertness, and Yund 1999). While the populations of M. edulis may be close in proximity in this case, the mussels once again vary in phenotypic response due to the varying environmental factors. The M. edulis species is unique in its ability to change phenotypes so readily, due characteristics of the population. The potential in gene flow in mussels is high because they are broadcast spawners and produce long-lived larvae (Leonard, Bertness, and Yund 1999). Broadcast spawning is a method of reproduction in which the female releases ample unfertised eggs into the water, coupled by males releasing a great deal of sperm into the water which fertilizes some of the eggs. While many species are broadcast spawners the success for M. edulis in increasing their genetic diversity is because of the long-lived larvae. Due to the high volume secreted into the water and currents contributing to the dispersion of these larvae, genetic diversity is more likely because sperm and eggs from different populations have a higher probability of fertilization. The spatial arrangement of genetic variation of a marine taxon, with a large population size and potential for large-scale dispersal, is dependent on the amount of genetic exchange between different populations. The higher the amount of genetic differentiation between population the smaller the genetic exchange between these separated groups, the larger the intrinsic barriers that contribute to reproductive isolation (Grosberg and Cunningham 2001). This evidence helps show the genetic exchange in the M. edulis populations, that allow it to readily adapt to environmental changes readily. M. edulis populations do not observe the intrinsic barriers that many populations suffer from due to broadcast spawning and long-lived larvae. While all these defense mechanisms favor the prey, it is important to realize that the predators in this case also exhibit phenotypic change in order to survive. “Our results and those of Smith and Palmer (1994) suggest that an inducible arms race between crab predators and mussel prey must commonly occur in intertidal habitats. Smith and Palmer show inducible plasticity for claw strength in crabs fed resistant versus susceptible M. edulis ” (Leonard, Bertness, and Yund 1999). Crabs grown experimentally on fully shelled prey developed larger and stronger claws than those raised on nutritionally equivalent unshelled prey. When one claw was immobilized, claws also became asymmetrical (Smith and Palmer 1994). Induction or reversal of claw asymmetry after autotomy in certain heterochelous species suggests substantial developmental liability (Smith and Palmer 1994). The development of a larger and stronger claw is a clear indication of a phenotypic change in a population. Providing evidence of the arms race between M. edulis and their respective crab predators. The Biomechanical analyses of decapod crustacean claws have shown that it is mechanically impossible to design a claw that is both fast and strong (Alexander 1968). Fast claws typically have fine, sharp denticles and fast muscles with short sarcomeres. Strong claws, on the other hand, have greater propal heights and widths, a higher mechanical advantage, blunt broad molars, and more slowly contracting strong muscles with longer Sarcomeres. The claws in some families, such as the Xanthide and Portunidae, are dimorphic with each crab possessing both a fast and a strong claw (Warner 1977). This claw dimorphism may allow these species to potentially feed on both fast and hard prey (Kalio and Warner 1984). In the Portunidae family, Callinectes sapidus is a dimorphic species where the specialization on hard-shelled prey is only somewhat specialized due to its dimorphic claws allowing a diet that varies including fish, snails, and mussels. On the other hand Cancer pagurus part of the Cancidae family is monomorphic, leading to a high degree of specialization towards hard-shelled prey with a diet limited to strictly molluscs (Behrens 1998). Thus different species of crabs are better equipped to for varying types of prey. Blunt and broad claws will have a higher success rate of predation on mussel species such as the M. edulis, but due to the defense mechanisms in M. edulis , crab species must also have other characteristics that allow it to compete. After green shore crabs have successfully broken 5-6 prey items, they required 30% less time to break open subsequent prey of the same type and size (Cunningham and Hughes 1984). These observations strongly suggest that learning plays an important role in becoming a more efficient predator. The Red Queen Hypothesis can explain all of this phenotypic change between corresponding predator and prey. Prey must evolve in order to circumvent selection from their enemies. M. edulis has demonstrated its relatively quick ability to adapt to waterborne signals produced by invasive species in order to enact defense mechanisms, and the ability to activate these defense mechanisms more readily in an environment where it is considered necessary. In order to counter this, predators must continue to evolve in order to better exploit the target population. Crabs specifically have been able to adapt and compete. Much like the M. edulis, crabs will increase the size and strength of their claws on a needed basis, and will also move on to look for easier prey if they decide the amount of time isn’t worth the meal. These capabilities, along with the ability of a crab to learn, make it not only a competitive predator, but an intelligent one as well. This arms race is present in all environments, and is the driving force in the constant coevolution of organisms with their biological enemies. This race is as old as evolutionary time, and shows no signs of a finish line anytime soon.

References: Abby-Kalio NJ, Warner GF. Effects of two different feeding regimes on the chela closer muscles of the shore crabCarcinus maenas(L). Marine Behaviour and Physiology Marine Behaviour and Physiology. 1984 Apr 3 [cited 2014 Oct 26];11(3): 209-218. Alexander RM. Animal mechanics,. Seattle: University of Washington Press; 1968. Behrens YS, G BE. Claw morphology, prey size selection and foraging efficiency in generalist and specialist shell-breaking crabs. Journal of Experimental Marine Biology and Ecology Journal of Experimental Marine Biology and Ecology. 1998;220(2): 191-211. Cunningham P, Hughes R. Learning of predatory skills by shore-crabs Carcinus maenas feeding on mussels and dogwhelks. Mar. Ecol. Prog. Ser. Marine Ecology Progress Series. 1984;16: 21-26. Freeman A, Byers J. Divergent induced responses to an invasive predator in marine mussel populations. Science (New York, N.Y.). 2006 [cited 2014 Oct 14];313(5788): 831-3 Grosberg RK, Cunningham CW. Genetic Structure in the Sea: from populations to communities. Marine Community Ecology. 2001. Leonard GH, Bertness MD, Yund PO. Crab predation, waterborne cues, and inducible defenses in the blue mussel, Mytilus edulis. Ecology. 1999;80(1). Smith L, Palmer A. Effects of manipulated diet on size and performance of brachyuran crab claws. Science (New York, N.Y.). 1994 Apr 29;264(5159): 710-2. Stokstad E. Native mussel quickly evolves fear of invasive crab(EVOLUTION). Science. 2006 Aug 11 [cited 2014 Oct 14];313(5788). Warner GF. The biology of crabs. New York: Van Nostrand; 1977.

WIKIPEDIA EDIT:

https://en.wikipedia.org/wiki/Bioadhesive

Under the section "Examples of bioadhesives in nature" I added "mussels increase amount of byssal threads enabling mussels to more firmly attach to substrates induced by waterborne cues such as predator proximity and broken conspecifics" In the previous bullet point the section eluded to mussel bioadhesives but lacked an indication that it was a defense along with the term byssal threads. Importantly in order to show that it was a defense mechanism I talked about the waterborne cues mussels used, which I feel added a very important explanation.

Also, Under the section "Permanent Adhesion" I added "these numbers are dependent on the environment, mussels in high predation environments have an increased attachment to substrates. In high predation environments it can require predators 140% more force to dislodge mussels[4]", while the article used quantifiable values to indicate the adhesion of mussels they were not a range of values which I felt did not indicate that mussels have different levels of adhesion due to their environment. It has been shown that mussels in high predation environments require 140% more force in order to dislodge mussels which could greatly affect these values. My citation is also found as reference number 4 in the References Section "Leonard GH, Bertness MD, Yundo PO. Crab predation, waterborne cues, and inducible defenses in the blue mussel, Mytilus edulis. Ecology. 1999;80(1)."