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This chapter discusses the anatomy of the brains of the cartilaginous fishes and their learning capabilities. Sharks, rays, and chimaeras can learn as quickly as birds and mammals, and have brains of a comparable size and elaboration.

This chapter discusses the anatomy of the jaws and teeth of cartilaginous fishes as well as the role of the muscles and teeth in jaw extension, seizure, and handling of prey. Most sharks, rays, and chimaeras are tertiary consumers, occupying the same trophic level as the prey of the white shark. These species feed upon small fishes, cephalopods, and mollusks that in turn feed on zooplankton. There are three steps in active predation: approach, seizure, and handling of the prey. The extent of attachment of the jaws to the cranium has lessened over evolutionary time in the cartilaginous fishes. The ancient sharks needed to swallow their prey whole due to the rigid attachment of the jaws to the cranium. The jaws of the modern sharks trend toward a less rigid attachment to the cranium.

There are currently 503 species of sharks, 699 species of rays, and 49 species of chimaeras in the class Chondrichthyes. The name Chondrichthyes comes from the Greek prefix khondros meaning “cartilage” and suffix ikhthus for “fish.” These species are referred to as the cartilaginous fishes. This chapter provides an overview of the subsequent chapters, which describe benchmark studies on the cartilaginous fishes. The results are presented in diagrams and graphs to introduce readers to authentic scientific data. “Spotlights” are included in each chapter to focus attention on the sophisticated methods used by pioneer scientists to make important scientific discoveries.

This chapter discusses the long evolutionary history of the cartilaginous fishes. Topics covered include the sharks and chimaeras of the Paleozoic era (species diversification, Early Paleozoic sharks, Late Paleozoic sharks, Paleozoic chimaeras); the Paleozoic ecosystem (Permian extinctions, sharks and rays of the Mesozoic Era); the demise of the giant-tooth shark; and orders of extant the cartilaginous fishes.

This chapter discusses the swimming styles of sharks, rays, and chimaeras. It covers differences in their skeletal and muscular anatomy; their skin and the dermal denticles that cover their bodies; hypotheses in scientific literature explaining how they use their tail fins to propel themselves forward and the empirical evidence supporting them; and commonly used classification of the diverse modes of swimming exhibited by the cartilaginous fishes.

This chapter describes the internal hydro-mineral balance of the sharks, rays, and chimaeras, with special attention given to how species regulate the salt composition of their tissues in order to temporarily inhabit estuarine and freshwater environments or reside wholly in the freshwater environment. The discussion covers the process of osmoregulation and the osmoregulatory organs (rectal gland, kidney, gills).

This chapter discusses how sharks, rays, and chimaeras are able to locate their prey and avoid predators from large distances. This sense is called mechanoreception because mechanical disturbances of the water are detected by two organ systems. The free neuromasts, canal neuromasts, and vessels of Savi on the external body are sensitive to one-way displacements of particles of water. The inner ear is sensitive not only to these displacements but also to two-way displacements of water particles associated with pressure oscillations. The former receptors are active in the near field, where the one-way oscillations exceed the two-way oscillations; the latter receptor is active in both the near and far field, where the two-way oscillations are dominant. The boundary between these fields for a very low frequency of 10 Hz is 150 m while for 100 Hz it is only 15 m.

This chapter discusses the electromagnetic sense which enables sharks, rays, and chimaeras to find their way in the apparently featureless ocean by following the subtle patterns of magnetization on the sea floor or the earth's dipolar magnetic field. It covers the anatomy and distribution of ampullae of Lorenzini; prey detection; mate detection; orientation and navigation; and the hierarchy of senses.