Carcinus maenas

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    because of mutation that allows for additional shell thickness to appear among the population. Another explanation is that possessing a thick shell is expensive in terms of energy costs. Other studies have found that thinner shells are favored when crab predators are absent because they are less expensive to produce and allow the snails to experience rapid growth (Palmer, 1985). Due to the lack of predation in this case, there was no need to maintain a thicker sized shell and over time slightly thinner shells became more prevalent. The third experiment showed that when survival is selective the snail population would evolve toward thicker shells. Research has shown that thin-shelled Littorina obtusata snails were readily consumed by 8 Carcinus maenas crabs in under a minute, whereas only one crab was able to consume a thick-shelled snail in over 8 minutes (Seeley, 1986). In the presence of an un-banded predator, the thin-shelled snails were readily consumed because it was easier to crack open their shells which reduced handling time. Without a predator to influence the variation of shell thickness, the distribution shifted slightly toward thinner shells, possibly because maintaining thick shells is expensive (Palmer, 1985). The factors that caused some variants to survive to reproduce at higher rates than others was predation and the allocation of energy put into reproduction rather than shell thickness. Other studies suggest if predator induced phenotypic plasticity…

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    Conservationists have had a tight focus on invasive species for decades. These species cross ecological boundaries and establish themselves in new areas where they affect the environment indefinitely. Conservationists are skeptical, and for good reason: Invasive species collide with natural environments and as follows, affecting biodiversity. Invasive species can benefit endangered environments; however, there should be stricter regulations of imported species to avoid the possibility of…

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    The Green crab is native to the north-east Atlantic Ocean and Baltic Sea, around the upper European/ North African coast. However, the Green crab has become an invasive species and has spread to areas such as South Africa, Australia, Japan, and both coasts of North America. With the increasing geographic range of the host, Sacculina has also extended its range and can be found in those new areas as well. The invasive crab has had serious impacts on fisheries as the crab continues to eat…

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    Littorea Case Study

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    With the introduction of the Carcinus maenas, the L. littorea with the thickest shell is strongly selective as an anti-predation technique against C. maenas (Hughes et al, 1979). The shell is the thinnest has lower survival against C. maenas predation, whereas, the thicker L. littorea shell is the bigger their survival rate is. L. littorea collection was performed at Fitzgerald J V Marine Reserve, Half Moon Bay California. About 120 snails were collected from the rocky intertidal zone, 60 from…

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    Salinity In Earth Harbor

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    (Thiet et al. 2014a), and healthy beds of submerged aquatic vegetation have reappeared (Portnoy et al. 2005; Smith & Medeiros, 2013). By 2005, healthy molluscan communities had reestablished in East Harbor (Thiet et al. 2014a), as well as populations of crustaceans, invertebrates and 15 species of estuarine fish (Portnoy et al. 2005). Molluscan community abundance has been documented regularly in East Harbor since the partial restoration in2002, and species such as the soft shell clam (Mya…

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