Periwinkle snails (Littorina littorea) are sea snails which are abundant on rocky shores, beaches, and marshes (Brawley, 2009) 

They are herbivorous, typically eating algae, rockweeds, and marsh grasses (Brawley, 2009) 

They are unisexual, self-fertilizing and laying 10,000-100,000 eggs on the sea floor anually (Brawley, 2009) 

Periwinkle snails are native to Great Britain, but now spread across the coasts of North America as well as the Northeastern coast of the Atlantic ocean (Brawley, 2009) 

• They are considered invasive in North America 

Chemoreception: using chemical senses to detect the odor or taste of a substance in the environment

• Many animals use this as an alarm response, telling them a predator is nearby by detecting the smell/taste of injured tissue of crushed conspecifics (Hadlock, 1980) 

The common predators of the Periwinkle Snail include crabs, lobsters, and shore birds (Cohen, 2011) 

The brown/black colors of the snails shell allows it to easily hide on or under rocks along the coast or in the water (Brawley, 2009) 

Square line: Control group (Introduced to live snails) 

Circle: Introduced to crushed snails

Triangle: Introduced to snail "juices" 

After introduction of the test stimuli, the control group had a significantly larger percent of snails visible, in comparison to the experimental groups which were exposed to snail "juices" or crushed snails 

In addition, the snails exposed to stimuli's rate of locomotion increased significantly. Before introduction of snail juices, the rate of locomotion was 0.32± 0.07 cm/min, and after was increased to 1.40± 0.31 cm/min. (Hadlock, 1980)