This gastropod is usually white or a purple-grey, but orange and striped specimens occur. The Dogwhelk , Nucella lapillus , is a carnivorous marine snail that is common on rocky shores where it feeds on acorn barnacles by smothering this sessile crustacean, and attacks and eats mussels by boring a hole in the hard shell and sucking out the rich orange flesh. The Dogwhelk can be kept in aquaria where it can be observed feeding. This marine snail comes in different colours but many of them are all white or a dirty grey-purple in colour. A white specimen in my tank fed on a mussel and in the succeeding weeks turned grey.
Further study is necessary.
Further Dogwhelks were introduced and most of these did not change colour. The results were inconclusive. There is still a lot to be learned about the life on the seashore.