wear your heart on your sleeve. to make your feelings and opinions obvious to other people John's always worn his heart on his sleeve, so there's no doubt who he'll be supporting. See also: heart, on, sleeve, wear. Related vocabulary: wear something on your sleeve.
In many bivalves and snails, and in cephalopods, part of the mantle is modified into a siphon, which can be used to pump water through the mantle cavity for respiration, feeding and/or jet propulsion. Freshwater and marine mollusks have gills (called ctenidia) for respiration, located in the mantle cavity. In most bivalves, these are enlarged and serve to trap food particles as well (Morton 1983).
Crayfish use their gills to breathe. A crayfish has a gill at the base of each leg. These gills are very delicate and are covered by the crayfish's carapace, or shield. This carapace is aligned backwards from the head, allowing water to run through in a channel over the gills, which provides a continuous source of oxygen that allows the crayfish to breathe.