RESEARCH QUESTION:

How does the amount of sunlight exposure alter the amount of gastropods that are stuck to rocks on the lower intertidal low-energy rocky shore?

BACKGROUND INFORMATION

Rocky intertidal shores contain a variety of organisms many of which are gastropods, organisms whose main feature is their muscular foot, which is their only source of transport. A number of gastropods that can be included in the investigation may be:

  • Constricted top snail
  • Hercules mudwelk
  • Striped mouth periwinkle

These species, and many more may be present at the experimental site and can be recorded for results.

Snails, as well as many other gastropods produce a sticky mucus through their muscular leg that allows them to travel seamlessly over sharp surfaces. This mucus also allows the organisms to adhere themselves to the surface in order to ingest food or to excrete. The substance that sticks to the surface is known as an epiphragm, “a closing membrane or septum (as of a snail shell or a moss capsule)” (Mariam-Webster, 2011) which is essentially dried mucus. The epiphragm also allows the organism to abstain from water loss and to retain as much moisture as possible, which would  be useful when in a area of high heat or low water content.

Many epiphragms are calcareous, or contain high calcium-carbonate content. This aids in the strength of the bond between the organism and the surface it wishes to attach itself to. “Gastropods can also create a calcerous epiphragm, prior to annual hibernation.” (Wikipedia, 2010) An epiphragm is not to be confused with an operculum, which is a physical attachment to the muscular foot which allows the organism to retain its moisture.

While any epiphragm does essentially allow the organism to stick to the surface indefinitely, the organism can be removed from the surface with a certain amount of force.

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Intensity of sunlight changes as the day goes by, so therefore if the independent variable is Sun exposure, it means that the variable is also time as well. So therefore the experiment will be conducted over a period of time where the Sun’s intensity changes as time goes by.

Throughout the year, the amount of sunlight (and essentially UV radiation) fluctuates according to the seasons and the Earth’s orientation to the Sun. Furthermore, cloud cover as well as weather conditions on the rocky shore may influence an organism’s inclination to be exposed to sunlight.

During summer, sunlight and UV radiation ...

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