Evolution of the Structure and Function of the Notochord

About this book

Although it is the defining organ of Chordates, the notochord is perhaps the least understood of vertebrate organs because it is usually considered a transient structure only present in early embryonic development. Most tetrapods replace the notochord with cartilaginous or bony vertebral bodies and remnants of the notochord persist as intra- or intervertebral spaces and intervertebral discs. The presence of cartilage in the notochord of some tetrapods raises further important questions on the evolutionary relationships between notochordal cells and cartilage cells. Evolution of the Structure and Function of the Notochord explores these patterns of relationships between the notochord and vertebral axial chondrogenesis.

Contents

- Introduction
- Structure and Fate of the notochord: Retained
- Structure and Fate of the notochord: Surrounded
- Structure and Fate of the notochord: Becomes the vertebral skeleton
- Cartilage in tetrapod notochords
- The notochord as a signalling centre
- Structure and Function of the Perinotochordal Sheath
- Segmentation of the notochord and of the axial mesoderm
- Notochord-Cartilage (chordoblast-chondroblast) relationships
- The evolutionary cell biology of notochordal cells

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Biography

Paul Eckhard Witten is Assistant Professor in the Departmenbt of Biology at Ghent University in Brussels. His research focuses on development, plasticity, and remodeling of skeletal tissues; in particular bone, cartilage and teeth of teleost fish. Processes are analyzed in a comparative developmental and evolutionary context.

Brian Keith Hall FRSC (born, 1941) is the George S. Campbell Professor of Biology and University Research Professor Emeritus at Dalhousie University in Halifax, Nova Scotia. Professor Hall has researched and extensively written on bone and cartilage formation in developing vertebrate embryos. He is an active participant in the evolutionary developmental biology (evo-devo) debate on the nature and mechanisms of animal body plan formation. Professor Hall has proposed that the neural crest tissue of vertebrates may be viewed as a fourth embryonic germ layer. As such, the neural crest – in Hall's view – plays a role equivalent to that of the endoderm, mesoderm, and ectoderm of bilaterian development and is a definitive feature of vertebrates (as hypothesized by Gans and Northcutt [1983]). As such, vertebrates are the only quadroblastic, rather than triploblastic bilaterian animals. In vertebrates the neural crest serves to integrate the somatic division (derived from ectoderm and mesoderm) and visceral division (derived from endoderm and mesoderm) together via a wide range novel vertebrate tissues (bone, cartilage, sympathetic nervous system, etc.). He has been associated with Dalhousie University since 1968. Since his retirement in 2007, he has been University Research Professor Emeritus and Emeritus Professor of Biology.