THE SKELETON | Cartilaginous Fish Skeletal Tissues

doi:10.1016/B978-0-12-374553-8.00276-8

Encyclopedia of Fish Physiology

From Genome to Environment

2011, Pages 428-433

https://doi.org/10.1016/B978-0-12-374553-8.00276-8 Get rights and content

Abstract

Most adult vertebrate animals have bony skeletons, with cartilage mostly restricted to joints and flexible structures. In contrast, the Chondrichthyes (sharks, batoids, and chimaeras) have endoskeletons made entirely of cartilage. Moreover, in sharks and batoids, most of the skeletal cartilage is tessellated, covered with mineralized, subperichondral blocks called tesserae. There are several other forms of cartilage found in the bodies of these fishes that likely serve distinct functional and metabolic roles. The structure and development of chimaeroid cartilage is essentially unknown.

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Cited by (9)

Ultrastructural, material and crystallographic description of endophytic masses – A possible damage response in shark and ray tessellated calcified cartilage
2017, Journal of Structural Biology
Citation Excerpt :
Tessellated cartilage has received the majority of research attention, and represents both a unique skeletal feature among vertebrates and a defining feature of the elasmobranch group for more than 400 million years (Long et al., 2015; Maisey, 2013). Several additional, but uncommon calcified tissues have been described to date for elasmobranchs, all of which appear to be modifications of tessellated calcified cartilage, but far less universal in their distribution, being found only in specific parts of the body and/or phylogenetic groups (for summaries of these see Dean, 2011; Maisey, 2013). For example, the skeletons of the rostra of modern lamnid sharks and large extinct sclerorhynchid batoids are covered with exceptionally tall “columnar” tesserae which, in sclerorhynchids, can exhibit a mineralized overlay apparently formed from mineralization of the perichondrium and obliteration of intertesseral spaces (Fig. 2A–C) (Compagno, 1988; Maisey, 2013; Mollen et al., 2012).
The cartilaginous endoskeletons of elasmobranchs (sharks and rays) are reinforced superficially by minute, mineralized tiles, called tesserae. Unlike the bony skeletons of other vertebrates, elasmobranch skeletons have limited healing capability and their tissues’ mechanisms for avoiding damage or managing it when it does occur are largely unknown. Here we describe an aberrant type of mineralized elasmobranch skeletal tissue called endophytic masses (EPMs), which grow into the uncalcified cartilage of the skeleton, but exhibit a strikingly different morphology compared to tesserae and other elasmobranch calcified tissues. We use materials and biological tissue characterization techniques, including computed tomography, electron and light microscopy, X-ray and Raman spectroscopy and histology to characterize the morphology, ultrastructure and chemical composition of tesserae-associated EPMs in different elasmobranch species. EPMs appear to develop between and in intimate association with tesserae, but lack the lines of periodic growth and varying mineral density characteristic of tesserae. EPMs are mineral-dominated (high mineral and low organic content), comprised of birefringent bundles of large calcium phosphate crystals (likely brushite) aligned end to end in long strings. Both tesserae and EPMs appear to develop in a type-2 collagen-based matrix, but in contrast to tesserae, all chondrocytes embedded or in contact with EPMs are dead and mineralized. The differences outlined between EPMs and tesserae demonstrate them to be distinct tissues. We discuss several possible reasons for EPM development, including tissue reinforcement, repair, and disruptions of mineralization processes, within the context of elasmobranch skeletal biology as well as damage responses of other vertebrate mineralized tissues.
Mineral homeostasis and regulation of mineralization processes in the skeletons of sharks, rays and relatives (Elasmobranchii)
2015, Seminars in Cell and Developmental Biology
Citation Excerpt :
The head skeletons of some large coldwater sharks (e.g., sleeper shark Somniosus, sixgill shark Hexanchus, sevengill shark Notorhynchus; pers. obs.; J. Maisey, personal communication; [30,180]), are almost entirely non-mineralized, with tessellation found only in restricted patches near jaw and cranial joints. Urist [30] showed that, at least for Notorhynchus, the plasma ion concentration is the same as for other species, meaning that this scant tessellation is not a function of the lack of the relevant materials for building mineral.
Sharks, rays and other elasmobranch fishes are characterized by a skeletal type that is unique among living vertebrates, comprised predominantly of an unmineralized cartilage, covered by a thin outer layer of sub-millimeter, mineralized tiles called tesserae. The mineralized portion of the skeleton appears to grow only by apposition, adding material at the edges of each tessera; maintenance of non-mineralized joints between tesserae is therefore vital, with precise control of mineral deposition and inhibition at the many thousands of growth fronts in the skeleton. Yet, we have only scattered evidence as to how the elasmobranchs mineralize and grow their skeletons. In this review, we take an “environment to skeleton” approach, drawing together research from a vast range of perspectives to track calcium and phosphate from the typical elasmobranch habitats into and through the body, to their deposition at tesseral growth fronts. In the process, we discuss the available evidence for skeletal resorption capability, mineral homeostasis hormones, and nucleation inhibition mechanisms. We also outline relevant theories in crystal nucleation and typical errors in measurements of serum calcium and phosphate in the study of vertebrate biology. We assemble research that suggests consensus in some concepts in elasmobranch skeletal development, but also highlight the very large gaps in our knowledge, particularly in regards to endocrine functional networks and biomineralization mechanisms. In this way, we lay out frameworks for future directions in the study of elasmobranch skeletal biology with stronger and more comparative links to research in other disciplines and into other taxa.
Resolving the identity of Platylithophycus, an enigmatic fossil from the Niobrara Chalk (Upper Cretaceous, Coniacian-Campanian)
2018, Journal of Paleontology
Phenotypic regionalization of the vertebral column in the thorny skate Amblyraja radiata: Stability and variation
2022, Journal of Anatomy
Endoskeletal mineralization in chimaera and a comparative guide to tessellated cartilage in chondrichthyan fishes (sharks, rays and chimaera): Endoskeletal mineralization in chimaera and a comparative guide to tessellated cartilage in chondrichthyan fishes (sharks, rays and chimaera)
2020, Journal of the Royal Society Interface
Evolutionary Development of the Postcranial and Appendicular Skeleton in Fishes
2019, Evolution and Development of Fishes

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