The brain is perhaps one of the most fundamental organs in all vertebrates. It determines not only an individual's ability to sense and process stimuli from the environment, but is also crucial in maintaining internal homeostatic processes as well as determining an individual's cognitive abilities. Brains come at a steep energetic cost however, with neural tissue requiring ~20 times the energy of muscle tissue. With such an important role to play, the 'expensive brain hypothesis' was been established to understand the evolutionary correlates of brain size. Maternal investment, defined as energetic investment during development, is a strong underlying factor in brain size evolution where higher energy investment from mothers is associated with increased brain size. However, much of what we know about brains comes from studying birds and mammals, while generally overlooking other vertebrate classes. Despite their diversity, all jawed vertebrate brains are comprised of similar components, a pattern that first appeared in sharks, rays, and chimaeras (Chondrichthyans). Chondrichthyans are often disregarded as unremarkable from a comparative perspective, which overlooks their true diversity of life histories and ecological niches. This thesis seeks to understand the evolution of brain size and organization in relation to life history and maternal investment using chondrichthyans as a model system. First, I reveal the sequence of reproductive evolution, finding that egg-laying is ancestral and that live-bearing and additional maternal investment (matrotrophy) have evolved independently several times, and are correlated with increasing body size. Second, I find that the evolution of reproductive mode and ecological lifestyle underlie the evolution of both brain size and brain organization, such that shallowwater matrotrophic species have large brains that are predominantly composed of regions related to enhanced cognitive abilities, the telencephalon and cerebellum. Conversely, deepwater lecithotrophic species have small brains composed predominantly of medulla oblongata. Lastly, I find that similar patterns of regional scaling in mammals, birds and chondrichthyans differ from those of teleosts, agnathans, and amphibians, and I propose that differing reproductive strategies may underlie this variation.

Since the theory of evolution by natural selection was first postulated, biologists have noted that life histories evolve following broad patterns across all organisms. Understanding the mechanisms causing these relationships is the central focus of life history theory; these insights can also be used to better estimate the biology and extinction risk of data-poor species. Sharks, rays, and chimaeras (class Chondrichthyes) are an ideal taxon to explore these relationships as they have evolved a broad range of life history strategies. In this thesis, I focus on two key time-related life history parameters that are often used as a measure of productivity: growth coefficient k, which is estimated from the von Bertalanffy growth function (VBGF), and maximum intrinsic rate of population increase rmax, estimated by simplifying the Euler-Lotka equation. I begin by clarifying two methodological problems regarding the estimation of growth and productivity. I first show that fixing the y-intercept in the VBGF, a common approach in chondrichthyan age and growth studies, often causes considerable bias in growth coefficient estimates, and recommend using the three-parameter VBGF instead. I then point out an important omission in a method commonly used for estimating r max in chondrichthyans and clarify the correct way to estimate it. Next I explore the effect of uncertainty on the estimation of r max and show that species with low annual reproductive outputs are bound to have very low productivities, thus focus should be placed into accurately estimating litter sizes, breeding intervals, and the variability of these traits. As an example of how these insights can be applied, I better estimate growth and productivity for a data sparse species of conservation concern, the Spinetail Devil Ray (Mobula japanica), and show it has a much lower somatic growth rate than previously thought and one of the lowest productivities among chondrichthyans. Finally, I show that productivity in chondrichthyans varies with temperature as well as depth, and that the scaling of this relationship changes with temperature according to the expectation from Bergman's rule. My thesis demonstrates that simple insights from life history theory can further our knowledge on the broad patterns that shape the evolution of life histories we see today, which can be used to inform management of data-poor species.

Biology of Sharks and Their Relatives is an award-winning and groundbreaking exploration of the fundamental elements of the taxonomy, systematics, physiology, and ecology of sharks, skates, rays, and chimera. This edition presents current research as well as traditional models, to provide future researchers with solid historical foundations in shark research as well as presenting current trends from which to develop new frontiers in their own work. Traditional areas of study such as age and growth, reproduction, taxonomy and systematics, sensory biology, and ecology are updated with contemporary research that incorporates emerging techniques including molecular genetics, exploratory techniques in artificial insemination, and the rapidly expanding fields of satellite tracking, remote sensing, accelerometry, and imaging. With two new editors and 90 contributors from the US, UK, South Africa, Portugal, France, Canada, New Zealand, Australia, India, Palau, United Arab Emirates, Micronesia, Sweden, Argentina, Indonesia, Cameroon, and the Netherlands, this third edition is the most global and comprehensive yet. It adds six new chapters representing extensive studies of health, stress, disease and pathology, and social structure, and continues to explore elasmobranch ecological roles and interactions with their habitats. The book concludes with a comprehensive review of conservation policies, management, and strategies, as well as consideration of the potential effects of impending climate change. Presenting cohesive and integrated coverage of key topics and discussing technological advances used in modern shark research, this revised edition offers a well-rounded picture for students and researchers.

A richly illustrated and comprehensive introduction to the world’s sharks Sharks are the top predators in many marine ecosystems. But tales of the killer instincts and fearsomely sharp senses of these hunters can obscure their full life histories. In fact, sharks are characterful, exhibit surprisingly complex behaviors, and lead secretive lives full of interest in every type of marine habitat. The Lives of Sharks is a fascinating and beautifully illustrated guide to these iconic marine creatures from two world-renowned experts. This book explores shark physiology, anatomy, behavior, ecology, and evolution, as well as conservation and the impact of human activity on shark populations. With stunning photographs and illustrations, as well as profiles of selected species, this is a comprehensive, authoritative, and inviting introduction to global shark life today.

The Biology of Sharks and Rays is a comprehensive resource on the biological and physiological characteristics of the cartilaginous fishes: sharks, rays, and chimaeras. In sixteen chapters, organized by theme, A. Peter Klimley covers a broad spectrum of topics, including taxonomy, morphology, ecology, and physiology. For example, he explains the body design of sharks and why the ridged, toothlike denticles that cover their entire bodies are present on only part of the rays’ bodies and are absent from those of chimaeras. Another chapter explores the anatomy of the jaws and the role of the muscles and teeth in jaw extension, seizure, and handling of prey. The chapters are richly illustrated with pictures of sharks, diagrams of sensory organs, drawings of the body postures of sharks during threat and reproductive displays, and maps showing the extent of the species’ foraging range and long-distance migrations. Each chapter commences with an anecdote from the author about his own personal experience with the topic, followed by thought-provoking questions and a list of recommended readings in the scientific literature. The book will be a useful textbook for advanced ichthyology students as well as an encyclopedic source for those seeking a greater understanding of these fascinating creatures.

"Ebert has herein assembled an enormous body of knowledge about California's 43 shark species ranging from shark and human behavior to taxonomic minutiae, along with up-to-date explanations of their ecology, status and fisheries. More importantly, his Herculean effort includes the often-overlooked 25 species of skates, rays and chimaeras. That, along with the fine illustrations of Mat Squillante, should answer any question that a student, diver, natural history buff, or recreational or commercial fisher might ask."—John E. McCosker, coauthor of Great White Shark "The timing of this publication is ideal given the status of some of California's elasmobranch populations and the need for a deeper understanding of their biology, ecology, and fishery management. The book is a comprehensive treatment—if one wants to find out the latest information on any species of shark or ray off California, this is the place to go. An outstanding work!"—Gregor M. Cailliet, Professor, Moss Landing Marine Laboratories, and Director, Pacific Shark Research Center