Perkinsus marinus is a prevalent pathogen of oysters, causing massive mortality in oyster populations. The disease it causes is known as "Dermo", and is characterized by proteolytic degradation of oyster tissues. Due to its negative impact on the oyster industry, parasitologists interested in helping oyster farmers are trying to find novel strategies to combat the disease. P. marinus are found in marine water, and grow especially well in warm waters during the summer months.

P. marinus are protozoa, and in particular belong to a group called the alveolates. The individual cells have two flagella, and have a partial polar ring used to attach to their hosts at the anterior. This is similar to structures found among the Apicomplexa, and Perkinsus was previously classified with them. However, genetic studies show that P. marinus is probably closer to the dinoflagellates, which also appear to have modified polar rings.