Tuesday, August 5, 2008

Lovell's Island Observations

We went to explore the tidal pool at low tide. The bottom of the pool was very rocky. I saw two different types of crabs while I was there.  The first crab that I saw was found underneath a rock. It was about 2" wide and was a dark brown-black color, very similar to the rock color. The crab appeared to lighter brown bands along its shell and legs. Its legs were a little longer than the crabs body and very thin. Its pinchers were short, about 1/3". Im not sure what type of a crab this is. I thought it was a Say's mud crab, but it was too large as they only grow to be less than an inch wide. 

The second crab was yellow with dark spotting that looked either red or purple. Its legs were short and thick, and its eyes protruded out to the sides. The crabs pincher claws were about 1/2 the length of its legs and it had a circular body about 2" wide.  I think that this crab is the Atlantic Rock Crab. Although they can grow to be almost 6" this may have been a young specimen. They are often found in rocky or sandy bottoms, ranging from intertidal zones to open water. 

There were plenty of periwinkle snails in the tidal pool. All of the snails were a brown color that was very similar to the rocks on the bottom of the pool. However, the snails all had different markings. Some appeared to be striped while others appeared to be mottled. Additionally, the striations on the snails' shells were very different. On some of the snails the striations followed the curvature of the shell and on other snails they went perpendicularly across the shell. 


When we gathered all of our samples together it became clear that there were many different types of periwinkles. I noticed that the snails could be grouped together in different categories based upon their color and size. I did a quick grouping of the snails we had and I found three different categories. In one group of sails, the point of their shells was a single solid color and the rest of the shell was another color. These snails were the smallest, and they were all very close in size to one another. The second group of snails I found were those with mottled shells. The third group of snails that I found were those that appeared to be a solid color. The last two groups were very close in size to one another. This lead me to believe that there were different species of periwinkle snails and definitely observable variations. 

I did find a piece of tunicate that looked very similar to some of the tunicate that we found on the dockside at the barking crab. I think that it is Orange Sheath Tunicate. However, there wasn't much of it found on the island. 

Searching for land snails was not as easy as I thought it was going to be! My group started a little further inland than the other groups. After a long period of time where we didn't find anything I found 2 baby snails. They were on the leaves of some sumac trees, about 4 feet off the ground. They were both about 2mm wide and had translucent shells with a brown stripe down the middle. Their bodies were both an opaque off-white. I was able to take a better look at land snails after regrouping with the class and seeing the examples they had brought back in.
I saw a great variety of snails. All of their shells were very similarly shaped, however they were different in their colors and markings. There were snails with yellow shells and snails with brown shells. For each color there were snails that had a single brown stripe or multiple brown stripes ranging from 3-5. Initially I thought that the darkly colored snails had darker bodies and the lighter colored snails had lighter bodies, but then we saw a light colored snail with a very dark body. I think that all the land snails are the same species with different traits. If the lighter snails had light bodies and the darker snails had dark bodies only I might have thought that there were multiple species that we were seeing. However, after seeing a light shell with a dark body, I believe that they are all the same species.... Although now that I'm typing it out, I remember someone suggesting that two species could have interbred.  To be honest, Im not sure how many different species of land snails we saw. It was very frustrating because there were so many different ways that the snails could have been sorted into groups. Overall they all looked very similar to one another, and in the end Im guessing that there is only 1 species. 

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