Teleost Skeletal Plasticity: Modulation, Adaptation, and Remodelling

Abstract

The vertebrate skeleton is a plastic organ system and the skeleton of teleosts is no exception. Epigenetic factors during development influence skeletal anatomy, mechanical properties, and meristic characters. The adult teleost skeleton undergoes changes connected to mechanical adaptation, repair, mineral homeostasis, sexual maturation, and aging. Vestiges, rudiments, atavisms, hyperostotic bones, additional tooth rows, and variable numbers of vertebral bodies are prominent examples of variable characters. Morphological changes require changes of skeletal structures on the cellular level, including modulation, transdifferentiation, and remodelling. Alterations at the cellular level are best understood by acknowledging those characters that distinguish teleost skeletons from mammalian skeletons: (a) the absence of osteocytes in most species of teleosts; (b) abundant mononucleated osteoclasts that perform non-lacunar bone resorption; (c) a phosphorous- rather than a calcium-driven mineral homeostasis; and (d) a variety of tissue types intermediate between bone and cartilage. This brief account of teleost skeletal plasticity shows that the teleost skeleton is a lifelong plastic organ system. Using examples, also from our own studies, we provide examples of skeletal plasticity at various hierarchical levels.