Results, Conclusions, and Reflections

During my transect survey out at Smith’s Cove, I only found small juvenile flat periwinkles, the large majority of which are <2 mm in shell height, inside broken rockweed air bladders. Juvenile flat periwinkles are smaller than 11 mm1 and they get bigger as they age. Therefore, the snails I found inside the air bladders were recently-hatched!

Additionally, I saw many more snails inside air bladders on the surface layers of the rockweed than the deeper layers. The surface layers, especially when it is sunny, are much more dry than the deeper layers because the surface layers are more exposed to the sun. In other words, the risk of desiccation for a snail on the surface layers is much higher. So in the natural environment, more snails are found inside air bladders where desiccation risk is high.

In my laboratory experiments, I found that the periwinkles leave the broken air bladders much less when the environment is dry and when there is a predation risk.

In summary, recently-hatched flat periwinkles use broken air bladders to avoid desiccation and predation.

These results are really exciting because it tells us that broken rockweed air bladders are in fact a juvenile habitat and are important in survival for the newly-hatched flat periwinkles. Rockweed is commercially harvested, and gaining this information can guide management to not threaten the snails.  

 

Throughout the course of this study, I’ve learned a lot about research and the scientific process. One lesson that I learned is that research requires a lot of planning, but even with planning, things don’t always go as planned. For example, I did some transect surveys when it was cloudy and I wanted to use agar pieces to measure desiccation rates during the same weather. However, after I did those transect surveys, I couldn’t prepare the agar in time for the next cloudy day and it didn’t get cloudy again after that. In the end, I had to simulate cloudy weather using an umbrella. I learned that there are many things I cannot control for, such as weather, and that is completely fine as long as I properly explain and account for them.

Before taking Research in Biology, I never imagined I would spend so much time studying snails. But what I learned goes beyond topics related to the flat periwinkle; I gained invaluable skills that I will carry with me to whatever the future brings.

Thank you for following me through this journey!

 

1. Goodwin, B. J. Studies on the biology of Littorina obtusata and L. mariae (mollusca: gastropoda). (University College of Wales, 1975).

Some Updates

Over the past few days, I’ve been running experiments and doing a transect survey to test for the functions of the broken rockweed air bladders for the flat periwinkle.

Last time, I mentioned that I was doing a laboratory experiment to test if the flat periwinkle uses the air bladders to avoid desiccation. So far, the experiment is running smoothly and they seem to like staying inside the broken air bladders when I place them inside the dry bowl.

To get even more convincing data, I decided to go out to Smith’s Cove again to see the snails’ usage of the air bladders in nature. I used a portable frame, called a quadrat, which I placed on random patches of rockweed, to guide my measurements.

Here’s what a quadrat looks like:

Within each quadrat, I measured the sizes of the snails I found, the amount of broken air bladders there were, and the number of snails inside and outside of the air bladders at different layers of the rockweed. If the flat periwinkles use the air bladders to avoid desiccation, more of them would be found inside on the upper layers, where it is more dry because it is more exposed to the sun.

 

At the same time, I also wanted to test if the flat periwinkles use the air bladders to avoid predators. So I did something a little similar to my other experiment. I placed three snails inside one of the broken air bladders I made and placed it into an observation bowl filled with water. I then placed an injured snail together with it and observed if they came out. For the control, I did the same thing except there was no injured snail.

Here’s what four trials at once looks like:

I’ll be back with my results soon. Stayed tuned!

08/03/17

Today, I started an experiment to test if juvenile flat periwinkles use the broken air bladders to avoid desiccation. To do these experiments I artificially made holes in air bladders using the eraser end of a mechanical pencil (with the eraser removed). Here are the results:

And here is a naturally-occuring hole in an air bladder:

I think they look pretty similar!

In my experimental setup, I placed three snails inside one of the broken air bladders that I made and placed it inside a dry observation bowl to see if they will come out. For the control, I added water to another observation bowl and placed inside another broken air bladder, also with three snails inside. I covered both bowls with mesh so that the snails cannot escape.

Here’s what one of the bowls look like:

While running my experiment, I went out to collect more flat periwinkles again. Here a couple of my finds:

I also found an egg mass!

Introduction to my Research Topic

The intertidal zone is an area between hide tide and low tide. Conditions in this area are constantly changing as the tides are always changing. For example, during high tide, the entire area may be submerged in water. But during low tide, most of the area may be relatively dry. One of the main groups of organisms that live in the intertidal zone is invertebrates, which include mollusks, insects, worms, and crustaceans. Because of the constantly changing environment, these organisms have to be able to survive many different situations. As one can imagine, doing this can be difficult, especially for juveniles. Once juveniles are hatched, they have to immediately be able to survive harsh conditions, such as varying water temperatures, salinity, and even lack of water at times. Nursery habitats in the intertidal are crucial in helping them survive.

One invertebrate commonly found in the intertidal zone is the flat periwinkle (Littorina obtustata), a herbivorous sea snail. These snails are direct developers, which means they hatch as mini snails. Because they are so small, they have to worry about a lot of things. With their small surface areas, newly-hatched juvenile snails can desiccate much more quickly than other snails. Another worry is predation. Adult flat periwinkles can protect themselves from predators using their thick shells, which can actually increase in size when there are more predators. Newly-hatched snails, however, have very thin and small shells that do not provide as much protection.

Last Saturday (07/29/17), I went to Smith’s Cove on Appledore Island to observe some flat periwinkles and learn more about them. There, I found a lot of the snails on Ascophyllum nodosum, more commonly known as rockweed, a long, string-like brown algae with small air bladders that keep it afloat during high tide. More surprisingly, there were holes in some of the air bladders of the brown algae. When I ripped them open, I discovered that they often housed several juvenile flat periwinkles!

Flat periwinkles have been seen inside broken air bladders of rockweed before1, but the benefits of being inside the air bladders have never been investigated. This led me to ask the question: why are flat periwinkles found inside the broken air bladders of rockweed?  To answer this question, I will use experiments in the lab to see if the flat periwinkles use the air bladders are important for the survival of juvenile flat snails.

1. Goodwin, B. J. THE GROWTH AND BREEDING CYCLE OF LITTORINA OBTUSATA (GASTROPODA : PROSOBRANCHIATA) FROM CARDIGAN BAY. J. Molluscan Stud. 44, 231–242 (1978).