We See Sea Shells by the Seashore
Where can we find limpets?
Isabella and Evangeline Burns
Introduction
On holidays our family often goes to the town of Ulladulla on the New South Wales south coast. When we do we always visit the rock pools and rock platform. We always look forward to these trips. We look for pretty starfish and gooey limpets and dead, dried-out blue bottles that pop when we step on them. We enjoy these expeditions so much that we wanted to learn more about some of the animals that live on the rock platform.
Many animals live on the rock platform. There are starfish, sea snails and crabs. We decided to look at limpets because they have a pretty shell with many different coloured stripes and the rock platform is covered in them. Also, limpets are well known for being very strong and very difficult to pull off the rocks. This was an animal worth knowing about.
Aim
We wanted to find out where on the rock platform limpets live. Do they live in the wet or the dry areas of the rock platform?
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Background Research
The animal we are looking at is called the Variegated Limpet. Its scientific name is Cellana tramoserica. It is found on the south-eastern coast of Australia from Queensland to South Australia.
Source: www.mesa.edu.au
Limpets are gastropods. This means that that they are like snails. They have oval shells shaped like a tent to protect their soft squishy body. The soft squishy part is called their foot! They also have gills to breathe underwater. Limpets also have teeth on their tongue to scrape up green algae off the rocks to eat.
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Limpets can be found on the rock platform between the high and low tide marks and move around to feed on the algae during the high tide. Limpets travel about one metre when feeding but can always find their way back to the same spot on the rocks by following the smell of their slime trails!
They like living near water where there is lots of algae but too low down the shore and they are easily eaten by fish. Too high up the shore and they become easy food for birds. So limpets are mainly found in the middle of the rock platform close to areas that are wet.
Hypothesis
We think that we will find more limpets living in the wet areas of the rock platform than in the dry areas.
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Risk Assessment
We had to be careful of a few things while we were doing our project What is the Danger? How do we keep ourselves safe? Poisonous animals like blue bottle If we see them leave them alone jellyfish and blue-ring octopus and do not touch Big waves and deep water Don’t go near the water’s edge Sharp rocks and shells Wear good shoes to protect our feet Raining and wet We wore ponchos because it rained one day when we went to the rock platform
Some adult friends also came with us to help us and keep us safe on the rock platform
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Variables
Dependant variable (This is what we were measuring): The number of limpets.
Independent variable (This is what was different): Wet and dry areas of the rock platform.
Controlled variables (This is what was the same): - Location (same area of the same rock platform) - Time of day (all on one day at low tide) - Size of counting square (50cm sides) - Number of squares counted (20)
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Method
1. Construct a square made of PVC pipe with 4 corner joints so that it creates a square with 50cm sides
2. Use this square and throw it into wet areas of the rock platform at low tide.
3. Count and record the number of limpets in the square
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4. Repeat until 20 squares have been counted
5. Use the square and throw it into dry areas of the rock platform at low tide
6. Count and record the number of limpets in the square
7. Repeat until 20 squares have been counted
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Results
Square Number Wet areas Dry areas 1 11 0 2 5 0 3 12 0 4 6 0 5 23 0 6 4 1 7 19 0 8 14 0 9 41 0 10 27 0 11 25 0 12 32 0 13 39 0 14 20 2 15 28 0 16 9 3 17 22 0 18 26 1 19 16 0 20 11 0 Total 390 7 Average 19.5 0.35
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In wet areas of the rock platform we counted 390 limpets. This was an average of 19.5 limpets in each square. In dry areas we counted 7 limpets. This was an average of 0.35 in each square.
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During our investigation we noticed something else. All the limpets in the dry areas were a lot bigger. So we also decided to test this new hypothesis by measuring the shell size of the limpets.
Hypothesis #2 We think we will find bigger limpets in dry areas.
Variables #2 Dependant variable (This is what we were measuring): The size of the limpet shells.
Independent variable (This is what was different): Wet and dry areas of the rock platform.
Controlled variables (This is what was the same): - Location (same area of the same rock platform) - Time of day (all on one day at low tide) - Number of limpets counted (20)
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Method #2 1. Collect 20 limpets from wet areas and measure their shell height, length and width. Record results.
2. Collect 20 limpets from dry areas and measure their shell height, length and width. Record results.
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Results #2 Limpet Wet areas Dry areas Number Length Width Height Length Width Height (cm) (cm) (cm) (cm) (cm) (cm) 1 1 0.5 0.9 2.4 2.3 1.3 2 1 0.7 0.7 2.9 2.9 1.4 3 1 1 0.5 2.1 2.4 1.9 4 1.1 1.1 1.1 2.6 2 1.3 5 1.3 1 1.1 2.5 2.1 1.2 6 1.1 1 0.5 2.8 2.6 1.3 7 1 1 0.5 2.1 2.2 1.2 8 1 0.5 0.5 2.6 2.4 1.2 9 1 1 0.9 2.5 2.3 1.1 10 1 1 0.5 1.5 1.5 1 11 1 0.9 0.5 1.5 2 1.1 12 1 0.7 0.5 2.1 1.5 0.9 13 1 1.8 1 2.5 2.3 1.2 14 1 0.9 8 2.5 2.1 1.2 15 1.2 1 0.5 1.1 2.1 1.4 16 1 1 0.5 2.9 2.3 1.4 17 1 0.5 0.5 3 2.6 1.8 18 1 1 0.5 2.1 2 1.2 19 1 1 0.6 2.1 2.2 1.4 20 1 1 0.7 2.1 2.1 1.4 Average 1.035 0.93 1.025 2.295 2.195 1.295
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Limpets in wet areas had an average size of 1.035cm x 0.93cm x 1.025cm. Limpets in dry areas had an average size of 2.295cm x 2.195cm x 1.295cm.
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Discussion There were more limpets in the wet areas because there was more water and food (algae) near these wet areas. Even though there were more limpets in wet areas, all the limpets in dry areas were much bigger. We did some more research and found out that small limpets can dry out more easily and so live in wet areas. They can also live here because their shells are so small that waves cannot knock them off the rocks. Large limpets can easily be knocked off the rocks by the waves and so live in the drier areas. Because they have bigger shells this means that they don’t dry out as easily and can survive living in drier areas. Only the oldest limpets are big enough to live in drier areas and so there are fewer limpets in dry areas. There are a few ways we could improve our investigation. We could count more squares across a larger area of the rock platform. We could also look at other rock platforms to see if limpets are doing the same thing in other areas too. We could also have measured the height, length and width of more shells across a larger area of the rock platform. This investigation and the results we found were very interesting and we had some more questions we would like to answer if we were to do another investigation. We did this investigation in summer and so we want to know if the location of limpets changes in winter when it is wetter and cooler. We would also like to know if the limpets are more scattered around at high tide when there is plenty of water
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covering the rock platform. Also our research has found how important water is for limpets and we would like to know if this is the same for other snails and animals on the rock platform.
Conclusion There were more limpets in the wet areas than the dry areas. Limpets in the dry areas were larger than the limpets in the wet areas.
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Acknowledgements We would like to thank a few people for helping us with our science project …
Nathan Our brother helped us count limpets. Ruth Our sister took photos for us. Dad and Mum Helped take photos and measure all Joel the limpet shells.
Looked after us on the rock platform Emma and took photos for us. He made our Helped take photos and measure all counting square and helped us count the limpet shells. limpets and write up our logbook. He
also typed up our work for us.
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We also collected our research and pictures from a few different places … ARKive, Common limpet, viewed 10 August 2016,
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