Physiology of Elasmobranch Fishes

There can be little doubt that, to use the parlance of the advertising world, the elasmobranch fishes have a "high profile image" in today's world. To most mem­ bers of the general public they are seen as terrors of the deep, perfect aquatic predators, and the stars (or more acurately, the villains) of major Hollywood movie films and innumerable television nature programmes. Such an image belies the fact that the vast majority of elasmobranch species feed on invertebrates and that, for man, the threat from shark attack is infinitesimal compared with even being struck by lightning! Similarly, there can be few biologists who have not carried out the classic vertebrate dissection of the dogfish at some stage early in the formative years of their scientific education. Yet elasmobranch species make up only a small proportion, perhaps little more than I %, of all vertebrates, and there are probably nearly 50 times as many teleost species as there are elasmobranchs. It is also curious that, as subjects for modern research, elasmobranchs seem to be chosen sometimes for their unique physiological characteristics and at other times because they represent excellent model systems for the study of some general process. Equally, it is for both these, seemingly contradictory, reasons that this book was proposed.

Contenu

1 Cardiovascular and Respiratory Systems.- 1.1 Functional Morphology of the Cardiovascular and Respiratory Systems.- 1.1.1 The Heart and Coronary Circulation.- 1.1.2 Branchial Circulation.- 1.1.2.1 The 'Respiratory' Blood Pathway.- 1.1.2.2 The 'Non-Respiratory' Blood Pathway.- 1.1.3 The Systemic Circulation.- 1.1.4 The Respiratory System.- 1.2 Gas Exchange.- 1.2.1 Properties of Oxygen and Carbon Dioxide in Water and Blood.- 1.2.2 Analysis of Gas Exchange in Relation to the Morphology of the Gills.- 1.2.2.1 Direction of Blood Flow.- 1.2.2.2 Diffusion Resistance.- 1.2.2.3 Shunts.- 1.2.2.4 Unequal Distribution of Water and Blood Flow.- 1.2.3 Effectiveness of Gas Exchange.- 1.2.4 Use of the Fick Equation for Calculating Cardiac Output.- 1.3 Control of the Cardiovascular and Respiratory Systems.- 1.3.1 The Heart.- 1.3.2 The Branchial Circulation.- 1.3.3 The Systemic Circulation.- 1.3.4 Ventilation.- 1.4 Supply of and Demand for Oxygen: Integrated Responses of the Respiratory and Cardiovascular Systems.- 1.4.1 Temperature.- 1.4.2 Exercise.- 1.4.3 Hypoxia.- References.- 2 The Central Nervous System.- 2.1 The Plan of the Elasmobranch Central Nervous System.- 2.1.1 The Environment of the Brain.- 2.2 Control of Motor Behaviour.- 2.2.1 Locomotion in the Spinal Dogfish.- 2.2.2 Is There a 'Central Pattern Generator' for Locomotion?.- 2.2.3 The Relationship Between Sensory Input and Control Circuits.- 2.2.4 The Organization of the Spinal Cord.- 2.2.5 Spinal Cord and Brainstem.- 2.2.6 The Reticular Formation.- 2.2.7 Control of Extrinsic Eye Muscles.- 2.2.8 Control of Intrinsic Eye Muscles.- 2.2.9 Control of Heart Muscle.- 2.2.10 Control of Jaw and Gill Musculature During Respiration.- 2.2.11 Control of Sensory Hair Cells.- 2.2.12 The Cerebellum.- 2.2.13 Function of the Cerebellum.- 2.2.14 Properties of Cerebellar Neurons.- 2.2.15 The Structure of Motor Programmes.- 2.3 Central Analysis of Sensory Information.- 2.3.1 Central Processing for Vestibular Function.- 2.3.2 Central Processing for Audition.- 2.3.3 Central Processing for Lateral Line Mechanoreception.- 2.3.4 Central Processing for Electroreception.- 2.3.5 Central Processing for Tactile Information.- 2.3.6 Central Processing of Vision.- 2.3.7 Central Processing of Olfactory Information.- 2.3.8 Sensory-Motor Integration.- 2.4 Concluding Remarks.- References.- 3 Sensory Physiology.- 3.1 Olfactory System.- 3.1.1 Behavioural Studies.- 3.1.2 Anatomy.- 3.1.3 Electrophysiology.- 3.2 Visual System.- 3.2.1 Behavioural Studies.- 3.2.2 Anatomy of the Visual System.- 3.2.2.1 Extraocular Muscles/Eye Movements.- 3.2.2.2 Eyelids.- 3.2.2.3 Optics.- 3.2.3 Retinal Anatomy and Electrophysiology.- 3.2.4 Visual Pigment.- 3.2.5 Retinal Electrophysiology.- 3.3 Octavolateralis System.- 3.3.1 Mechanoreceptors.- 3.3.1.1 Behavioural Studies.- 3.3.1.2 Hair Cell Mechanoreceptors.- 3.3.1.3 Anatomy of the Vestibular System.- 3.3.1.4 Anatomy of the Lateral Line Canals.- 3.3.1.5 Electrophysiology.- 3.3.2 Electroreception.- 3.3.2.1 Behavioural Studies.- 3.3.2.2 Anatomy of Ampullae of Lorenzini.- 3.3.2.3 Electrophysiology.- References.- 4 Muscles and Locomotion.- 4.1 General Organization of the Locomotor System.- 4.1.1 Sharks.- 4.1.2 Batoids.- 4.2 The Locomotor Muscle Fibres.- 4.2.1 Structure.- 4.2.2 Motor Innervation.- 4.2.3 Sensory Innervation.- 4.3 Physiology.- 4.3.1 Electrophysiology.- 4.3.2 Mechanical Properties.- 4.3.3 Biochemical.- 4.4 Buoyancy and Lift.- 4.5 Swimming.- 4.5.1 Swimming Speeds.- 4.5.2 Body Form and Fin Distribution in Sharks.- 4.5.3 Kinematics of Shark Swimming.- 4.5.4 Drag-Reducing Adaptations.- 4.5.5 Warm-Bodied Sharks.- 4.6 Concluding Remarks.- References.- 5 The Autonomic Nervous System.- 5.1 Anatomy of the Autonomic Nervous System.- 5.1.1 Terminology.- 5.1.2 Cranial Autonomic Nerves.- 5.1.3 Spinal Autonomic Nerves.- 5.1.4 Enteric Autonomic Nerves.- 5.1.4.1 Anatomy of the Elasmobranch Gut.- 5.1.4.2 Arrangement of the Enteric Nervous System.- 5.1.4.3 Extrinsic Nerves.- 5.1.4.4 The Myenteric Plexus.- 5.2 Chromaffin Tissue.- 5.3 Circulatory System.- 5.3.1 The Heart.- 5.3.2 The Branchial Vasculature.- 5.3.3 The Systemic Vasculature.- 5.4 The Spleen.- 5.4.1 Nerve Supply to the Spleen.- 5.4.2 Physiological Functions of Splenic Autonomic Nerves.- 5.5 Gut.- 5.5.1 Neuron Types of the Enteric Nervous System.- 5.5.2 Functions of Extrinsic Nerves.- 5.5.2.1 Vagal Innervation.- 5.5.2.2 Splanchnic Innervation.- 5.5.3 Transmitter Functions in the Gut.- 5.5.3.1 Cholinergic Innervation.- 5.5.3.2 Adrenergic Innervation.- 5.5.3.3 Serotonergic Innervation.- 5.5.3.4 Peptidergic Innervation.- 5.6 Uro-Genital Organs.- 5.7 The Iris.- 5.8 Concluding Remarks.- References.- 6 Salt and Water Balance - Extrarenal Mechanisms.- 6.1 Overall Hydromineral Status.- 6.2 The Retention of Urea and TMAO.- 6.3 Water Fluxes and Permeabilities.- 6.4 Ion Fluxes and Permeabilities.- 6.5 Elimination of Excess Ions.- 6.6 Rectal Gland.- 6.6.1 Structure and Histology.- 6.6.2 Secretion Rate.- 6.6.3 Mechanism of Secretion.- 6.6.4 Mechanism of Cyclic AMP Action.- 6.6.5 Control of Secretion.- 6.6.5.1 Hormonal Control - Peptides and Adenosine.- 6.6.5.2 Hormonal Control - Steroid Hormones.- 6.6.5.3 Gland Blood Flow and Secretion.- 6.6.5.4 Initiation of the Secretory Response In Vivo.- 6.7 Euryhaline and Freshwater Elasmobranchs.- 6.8 Osmoregulation During Development.- References.- 7 Kidney Function.- 7.1 Gross Morphology.- 7.2 Blood Supply.- 7.3 Microanatomy of the Nephron.- 7.4 Kidney Function.- 7.4.1 Urea Reabsorption.- 7.4.2 Reabsorption and Secretion of Ions.- 7.5 Control of Kidney Function.- References.- 8 Acid-Base Regulation.- 8.1 Steady-State Acid-Base Regulation.- 8.1.1 Release of Acid-Base-Relevant Substances.- 8.1.2 Steady-State Acid-Base Status.- 8.1.3 Imidazole Alphastat Regulation.- 8.2 Acid-Base Stress Conditions.- 8.2.1 Temperature Changes.- 8.2.1.1 Transients of Extracellular Acid-Base Regulation.- 8.2.1.2 Bicarbonate - Equivalent Ion Transfer Processes.- 8.2.1.3 Contribution of Buffering and Ion Transfer to the Acid-Base Regulation.- 8.2.1.4 Adjustment Kinetics of Intracellular pH.- 8.2.2 Hypercapnia.- 8.2.2.1 Environmental Hypercapnia.- 8.2.2.2 Hyperoxia - Induced Hypercapnia.- 8.2.3 Lactacidosis.- 8.3 Site and Utilization of Transepithelial Ion Transfer Mechanisms.- 8.4 Conclusion.- References.- 9 Nitrogen Metabolism.- 9.1 Nature and Routes of Excretion.- 9.1.1 Urea.- 9.1.2 Trimethylamine Oxide (TMAO).- 9.1.3 Ammonia.- 9.1.4 Amino Acids.- 9.2 Biochemical Pathways of Formation.- 9.2.1 Urea.- 9.2.2 Trimethylamine Oxide (TMAO).- 9.2.3 Ammonia.- 9.3 Urea Toxicity and Counteraction by Trimethylamine oxide.- 9.4 Physiological and Evolutiona…