A Small World

To study physiology is to examine how organisms have evolved solutions to the business of living in an inanimate world. Our world is and has always been dominated by physical and chemical forces. A physicist might tell us that all things are physical, while a chemist is more concerned with the elementary nature of reactions. A physical chemist sees the bonds between these views, and a biochemist draws out the organic symphony of the vital pathways. A structural biologist adds shape to the chemical building blocks of life, while a molecular biologist tinkers with these structures. A cell biologist is closely related to a molecular biologist and cousin to an anatomist that is intrigued by the variety of phenotypes. Mapping the fabric between these fields is a developmental biologist that not only seeks to understand the mechanisms of cell signalling and differentiation, but place them in an evolutionary context. To understand how an organism functions, and adapts to changes in its external and internal environment, a physiologist must dabble in each of these fields. Consequently modern physiologists face a daunting task of acquiring a rich tapestry of knowledge and methods that will lead them from the whole organism to the depths of sub-cellular compartments and molecules responsible for life.

This book is intended as a resource for students and researchers interested in developmental biology and physiology and specifically addresses the larval stages of fish. Fish larvae (and fish embryos) are not small juveniles or adults. Rather they are transitionary organisms that bridge the critical gap between the single-celled egg and sexually immature juvenile. Fish larvae represent the stage of the life cycle that is used for differentiation, feeding and distribution. Like the juveniles and adults, however, they face the same physical and chemical challenges imposed by their aquatic environment, yet lack many of the cells, tissues or organs present in the more advanced stages to deal with such adversities. Many fish larvae, particularly those of the marine forms of teleosts, are small, in fact tiny, necessitating the use of magnifying devices just to see them. A common size of a newly hatched marine teleost is four mm or less, the same size as a one month old human embryo. As a consequence traditional physiological investigation of fish larvae has tended to be of the “black box” whole organism nature. With the advancement of molecular tools, and miniaturisation of manipulation instruments, investigators can now peer deep inside the developing systems and explain how they work. The genomic revolution might be regarded as the cavalry in this regard, where physiologists can not only investigate the ontogeny of expression, but modulate the genes through insertional mutations, or regulate them via hybridisation techniques. When coupled with more classical methods, an entirely new level of understanding emerges.

From a biodiversity perspective, fish champion the vertebrates, accounting for almost half of the known species of craniates. The most recent count is ~28 000 species spread among more than 500 families. The physiological diversity of fish larvae, in all of their myriad forms, is only beginning to be chartered. This book aims at providing a single-volume treatise that explains how fish larvae develop and differentiate, how they regulate salt, water and acid-base balance, how they transport and exchange gases, acquire and utilise energy, how they sense their environment, and move in their aquatic medium, how they control and defend themselves, and finally how they grow up. We hope that the reader learns as much from this text as we have editing it.

Contents

Part 1: Ontogeny

o Pattern Formation: Thomas E. Hall

o Pigmentation: Robert N. Kelsh and David M. Parichy

o Bioluminescence: Andrey V. Suntsov, Edith A Widder and Tracey T. Sutton

Part 2: Respiration & Homeostasis

o Gas Exchange: Bernd Pelster

o Cardiovascular Anatomy and Physiology: Warren Burggren and Brian Bagatto

o Osmo-and Ionoregulation: Toyoji Kaneko and Junya Hiroi

o Acid-base balance: Colin J. Brauner

Part 3: Nutrition and Energy

o Digestion: Ivar Rønnestad and Sofia Morais

o Nitrogen Excretion: Bendik F. Terjesen

Part 4: Sensory Physiology

o Mechanoreception: Patricia M. Pankhurst

o Chemoreception: Kjell B. Døving and Alexander Kasumyan

o Photoreception: Ellis R. Loew and Christina M. Wahl

o Electroreception: Frank Kirschbaum and Jean-Pierre Denizot

o Magnetoreception: Krzysztof Formicki

Part 5: Movement

o Buoyancy: John J. Govoni and Richard B. Forward Jr.

o Swimming and Muscle: Ulrike K. Müller

Part 6: Control and Defense

o Enteric Control: Anna Holmberg, Susanne Holmgren and Catharina Olsson

o Immunology: Agustín G. Zapata and Alfonso Cortés

Part 7: Functional Changes in Form

o Metamorphosis: D.M. Power, N. Silva and M.A. Campinho

o Smoltification: Sigurd O. Stefansson, Björn Th Björnsson, Lars O.E. Ebbesson and Stephen D. McCormick