Preopercular pores

These pores are found in loose groups, typically just anterior to the anal plates, although they may be much more widespread in some genera and species. They are ‘closed’ pores and are rather variable in shape. They may be small, flat, round to oval, relatively unsclerotised and may have a granular surface. In some genera, they are large, strongly convex, and heavily sclerotised; these pores can have quite deep, vertical margins, which give them a strongly ‘dark-rimmed’ appearance when viewed from above, and have a rough granular surface; they have also been called `discoidal pores' and `paraopercular pores'.