How to Stay Cool in the Intertidal

We are lucky to have the privilege of using the weather forecast to prepare for the weather. We can dress warmly when we expect cold temperatures, or wear a hat and carry around a water bottle to stay hydrated during extreme heat.

intertidal zone

Intertidal zone during low tide (PC: http://www.thoughtco.com)

 

The intertidal zone is an area in marine environments that are alternately covered by the sea in high tide and exposed to air during low tide. Other hazards include exposure to dangerously high temperatures and desiccation. Organisms that inhabit this environment must have adaptions for extreme conditions in both wet and dry conditions. Sea stars keep themselves cool after heat exposure by soaking up water to protect themselves from the blazing temperatures that persist when the tide goes out. Hermit crabs use their shells to shelter themselves from high temperature and retain water in their shells. How do intertidal snails, Littorina Littorea, adapt to heat and desiccation stress?

L.Littorea

L. littorea in its shell in hot & dry environment (PC:Juhae Oh)

 

Snails have shells and are able to store water in their mantle cavity.  Would they store more water and take longer to come out of their shells after suffering desiccation and heat stress? In my experiment, different temperature treatments representing hot, warm, regular, and cold environmental conditions were set up. Each temperature treatment was paired with wet and dry environments representing respective high and low tide conditions. The effects of temperature, water level, and the combined effect of both were examined by quantifying amount of water stored in the snail’s mantle cavity, and the time it takes to come out of its shell. Water stored in the mantle cavity was calculated by change in weight. The initial weight of individual snails was measured before exposure to treatment conditions. After treatment exposure, they were placed in regular seawater to give them time to store water, then reweighed. Any change in weight was assumed to be from water stored in mantle cavities. The time it takes the snails to come out of their shells was also observed to see if shells were utilized as a form of protection. Results revealed a significant difference in the time it takes for them to come out of shells. Snails in hot temperatures did not come out of their shells regardless of wet and dry conditions. Snails in regular and warm temperatures took significantly longer to come out of their shells in dry conditions than wet conditions whereas in cold temperatures, they took longer to come out in submerged conditions. There was no significance in change in weight there. My experiment suggested that snails prefer to use their shells to protect themselves instead of storing water in their bodies, just like some people choose to stay away from the sun rather than carrying around water while exposing themselves to the stinging sun rays.

 

Click here to learn more about how plants and animals survive in the intertidal.

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