External gills usually contains muscle tissue, and may be moved by the animal as a free appendage, in order to stir up stagnant water. The stalk is lined by many thinly walled filaments (fimbriae), containing the majority of blood vessels used in gas exchange. Animals usually have one external gill originating on each gill arch (except the hyoid), which leads to there being three pairs of external gills in salamanders, and four in the gilled larvae of lungfish. External gills External gills are the gills of an animal, most typically an amphibian, that are exposed to the environment, rather than set inside
Gills Bay more common, this area having one of the largest British populations, however the common seal is also present. Wild dogs are often spotted around the Gills area which are believed to have come across on the ferry from Orkney. Porpoises can be seen all year round in all parts of the firth and at Gills Bay as they tend to favour shallower water. Usually seen singly or in small numbers although in the autumn many large groups may be seen in Gills Bay where they congregate. Basking sharks are rare but are being seen more often around May to August.