One important concept is that typically used reinforcing (post-tensioning tendons and shrinkage-compensating concrete reinforcement are the exceptions) will not prevent the concrete from cracking. The reason for this is that the reinforcing cannot begin to start resisting significant tension until the concrete cracks.
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.he mantle also secretes the shell, in those mollusks that have one. In many gastropods and cephalopods, the mantle is brightly colored and important for communication. In giant clams, the outer mantle tissue is colonized by symbiotic algae that provide their host with food energy in exchange for shelter.
An internal organ called the mantle secretes calcium carbonate so that as the inner invertebrate grows, the outer shell provides a roomier home. Many bivalve species play important roles in aquatic and marine ecosystems by filtering the water and serving as habitat and prey for a variety of sea life. roughfile clam from the Flower Garden Bank National Marine Sanctuaryâjust one of many different bivalve mollusk species. Like fish, bivalve mollusks breathe through their gills. As filter feeders, bivalves gather food through their gills.