Invertebrates exoskeletons

A major biological sink for CO9 that is often overlooked is the calcium carbonate shells of corals, molluscs, and Crustacea. These invertebrate animals deposit CaCOa in the form of protective exoskeletons. In some invertebrates, such as the sderaetinians (hard corals) of tropical seas, photosynthetic dinoflagellates (kingdom Protoctista) known as zooxanthellae live within the ani-... 

An inventory of known biomacromolecules is provided in Table 22.3. Many of these play essential metabolic roles in enabling growth and reproduction, such as the carbohydrates, lipids, proteins, and polynucleotides. Others are components of cell walls and exoskeletons. Some organisms, such as bacteria, plankton, plants, and lower invertebrates, synthesize biomolecules, called secondary metabolites, that are used to control ecological relationships, including predator/prey, host/symbiont, mating/spawning, and competition for food or space. 

Chitin, which is the structural component of the exoskeleton of invertebrates such as crustaceans, insects, and spiders, resembles cellulose with the exception that the hydroxy groups on carbon 2 are replaced by acetylamino groups. 

The only members of this group of interest here are the corals, which are a large group of invertebrates that live singly or in colonies. The hard corals construct elaborate, rigid calcareous exoskeletons, which can build up over generations, forming coral reefs. Soft corals are solitary, more flexible animals that have calcareous particles in their cell walls. 

Arthropods are invertebrates having a hard exoskeleton, a segmented body, and jointed appendages. The body is generally divided into three segments,... 

In museum collections, most invertebrates will be encountered as natural history specimens, which are divided into dry and wet-preserved. Those animals having a shell or tough exoskeleton, like starfish, shelled mollusks, and lobsters, may be dried after death. The tissue may be removed, but it is often left inside the shell or carapace to shrivel and dry. Wet-preserved specimens are usually fixed in a solution of formalin or some other preservative to prevent the tissues from deteriorating quickly after death. After a brief period, the specimen is usually removed from the toxic fixing solution, rinsed, and placed in a storage solution of 70% ethanol (alcohol) mixed with water. 

Invertebrates are common as fossils, and are found in rocks dating back almost to the beginning of life on Earth. Most animals that survive the fossiliza-tion process do so because their bodies include some hard part(s), such as a shell, exoskeleton, endoskeleton, or teeth. Some completely soft invertebrates, however, have been fossilized as impressions. These include jellyfish, insects, eggs, and larvae. 

Corals animals of the Cnidaria phylum (formerly Coe-lenterata), with a calcareous skeleton. Sea anemones and jellyfishes are Cnidaria without skeletons Dentine also called ivory, the inner hard tissue of the tooth. The bulk of a tooth is made up of dentine Enamel the outer layer covering the tooth Frustule the siliceous shell or exoskeleton of a diatom. It is composed of two valves (epitheca and hypotheca), one overlapping the other, like a pill box and its cover Mollusks invertebrates having a soft unsegmented body usually enclosed in a shell. Mollusca mainly includes Bivalvia, Gastropoda, and Cephalopoda... 

Chitin is isolated from the exoskeletons of crustaceans (e.g., crabs, lobsters, crayfish, shrimp, krill, barnacles), molluscs or invertebrate animals (e.g., squid, octopus, cuttlefish, nautilus, chitons, clams, oysters, scallops. 

Calcium Carbonate. A "salt" used by many marine invertebrates, such as corals and echinoderms, and by protists, such as coccolithophorids, to construct their exoskeletons. 

Chitin is derived from the Greek word chiton, which means a coat of nail. It is the major component of the exoskeleton of invertebrates, crustaceans, insects, and the cell wall of fungi and yeast (Knorr, 1984 Lower, 1984 Tan et al., 1996) in which chitin acts as a supportive and protective component. Chitin is the second most plentiful natural polymer on earth after cellulose (Brzeski, 1987 Ornum, 1992). At least 10 gigatons (1 x 1013 kg) of chitin... 

Reflect and Apply Why is the polysaccharide chitin a suitable material for the exoskeleton of invertebrates such as lobsters What other sort of material can play a similar role ... 

Chitin is a polymer of A acetyl-p-o-glucosamine, whereas cellulose is a polymer of D-glucose. Both polymers play a structural role, but chitin occurs in the exoskeletons of invertebrates and cellulose primarily in plants. 

Pheromones are used right across the animal kingdom because any molecule that gives a selective advantage can potentially evolve into a pheromone. This is in part a consequence of the combinatorial mechanisms of olfaction. Invertebrate and vertebrate olfaction, despite all the superficial differences between crustacean aesthe-tascs and mammalian noses, works in roughly the same way. Crustaceans, with an impermeable exoskeleton, have evolved olfactory windows in the exoskeleton. 

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