Evolutionary Origins of Animal Skeletal Biomineralization

Abstract

The evolutionary history of biomineralization in animals is crucial to our understanding of modern mineralized tissues. Traditional methods of unravelling this history have aimed to derive a theory of the development of biomineralization through evolution by the comparison of mineralized systems in model organisms. This has led to the recognition of the ‘biomineralization toolkit’ and raised the question of the homology of mineralized tissues versus convergent or parallel evolution. The ‘new animal phylogeny’ reveals that many of the groups known to biomineralize sit among close relatives that do not, and it favours an interpretation of convergent or parallel evolution for biomineralization in animals. In addition, the fossil record of the earliest mineralized skeletons presents a rapid proliferation of biomineralization across a range of animal phyla with fossil representatives of many modern biomineralizing phyla. A synthesis of molecular, developmental, phylogenetic and fossil evidence demonstrates the convergent or parallel evolution of biomineralization in animals at the phylum level. The fossil record of the Cambrian explosion not only provides vital evidence for the evolution of animal mineralized tissues but also suggests a mechanism for its rapid and synchronous convergent origin.

Proteomic analysis of skeletal organic matrix from the stony coral Stylophora pistillata

“…Highly acidic proteins also have been identified or hypothesized in mineralizing invertebrates, and several have recently been described, including the Asprich family in the pen shell, Atrina rigida (15), Pif and Aspein in the pearl oyster, Pinctada fucata (16,17), and the Adi-SAPs (highly acidic proteins proposed to be soluble or secreted) in the stony coral Acropora digitifera (18). Sequence-based homologs of each have been found in a variety of other invertebrates, yet these proteins, and their consequent biomineralization reactions, appear to have originated several times independently (19,20), and their sequence similarity is most likely explained by convergent evolution. Proteins containing acidic amino acids (Asp and Glu) or phosphorylation sites (on Ser residues) are thought to be used at various stages of aragonite and calcite mineralization to temporarily stabilize amorphous calcium carbonate or nucleate the mineral under appropriate conditions (reviewed in ref.…”

Causes of the Cambrian Explosion

“…This type of feedback is manifest in the origins of plankton/nekton, burrowing and biomineralization, which initially are de novo evolutionary products but then contribute a series of additional feedback loops that accelerated the evolutionary cascade and diversification. In the case of biomineralization, this is manifest in the near simultaneous appearance of both predatory and defensive hard tissues across a wide range of animal groups predominantly utilizing two separate calcium biomineral groups, the carbonate isomers and apatite (9,10). Although it has been argued that the emergence of complex food webs is the result of crossing a threshold or tipping point (7), it is equally likely that this is a downstream, distal result of complex feedback loops (see figure).…”

Calcifying tissue regeneration via biomimetic materials chemistry

“…(Online version in colour.) biomineralization toolkit has similarities between the original ancestors and the successors [10]. Materials chemists are striving to replicate this and have superior performing materials for medicine, optics and electronics, etc.…”