Invasive SpeciesCommon periwinkle

Littorina littorea
FOUND by 2018csb
2018-10-04
Falmouth Maine
Not Yet Reviewed by Expert
Quality checked by Mr. Wilson
Peer reviewed by Tanner
Field Notes
The day we went out was cloudy, cool, and misty. The tide was going out. The coast was divided into about 10 m sections that extended to the water and each group got 1 section. The coordinates of the area were 43.6902˚ N and -70.2265 W. We were searching for 6 different species within our area, and each one of our group members was assigned one of the species. The species our group was looking for are the green crab, the asian shore crab, the common periwinkle, rough periwinkle, knotted wrack, and rockweed. I was searching for the common periwinkle, and I think that I found it. Our area started dryish and empty with little seaweed and many periwinkles, to a wet, flat, and rocky ground with different types of seaweed covering the entirety of it. I found my periwinkle near the mainland part of our area, on a rock that was dry, indicating that it never went underwater. Out of all the periwinkles I saw, there were more invasive species than native. This poses a huge threat to the native periwinkles, as the invasive periwinkles may take up all of the natural resources that the native ones need and as a result drive the native species to extinction.
Supporting Evidence
Photo of my evidence.
As you can see, the tentacles of this periwinkle have horizontal black bands on them. This is a distinguishing feature of the common periwinkle and it differentiates this species from similar species, such as the rough periwinkle which have vertical lines on their tentacles opposed to horizontal.
Photo of my evidence.
The aperture meets the whorl at an angle that is less than 90 degrees. This is another feature of the common periwinkle to tell it apart from other species. The species similar to it, the rough periwinkle, has an aperture that meets the whorl at an angle greater than 90 degrees.
Photo of my evidence.
The aperture of this periwinkle is white, just like the aperture of a common periwinkle. This further indicates that this is a common periwinkle.
Species Observation: Species Looked For
Did you find it?: 
I think I found it
Scientific name:
Littorina littorea
Common name:
Common periwinkle
Sampling method: 
Transect
Photo of our sampling method.
Place Studied
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Map this species
Latitude: 
N 43.690200 °
Longitude: 
W -70.226500 °
Observation Site Information
A photo of our study site.
Habitat: 
Coastal - Rocky intertidal
Trip Information
Name:
2018 Mackworth Coastal
Trip date: 
Thu, 2018-10-04 07:26
Town or city: 
Falmouth Maine
Type of investigation: 
Species Survey
Ecosystem: 
Coastal
Watershed: 
Presumpscot
Time of low tide: 

Comments

Nice picture of the tentacles and those horizontal black bands.