Extracellular matrix. 3: Evolution of the extracellular matrix in invertebrates.

Invertebrates comprise about 95% of animal species, yet most studies of extracellular matrices have centered on vertebrates. Comparative studies of invertebrates will enhance comprehension of evolutionary processes and appreciation of the diversity of extracellular matrices. Moreover, new functions and new structures will be revealed over a wide range of organismic needs. Another important perspective is that several invertebrate species have provided insight into developmental processes, and those processes often have direct relevance to vertebrate development. Thus, studies of fruit flies, nematodes, and sea urchins have revealed common features of cell biology, embryonic development, and matrix properties that pertain throughout the animal kingdom. The advantages of invertebrates are their rapid rates of embryonic development, their amenability to genetic manipulation, availability of innumerable mutants, and their ease of study in the laboratory. Extracellular matrices themselves are readily compared. Invertebrates display a wide diversity of such matrices, at the levels of both tissue architecture and molecular anatomy. Knowledge of that diversity leads to an appreciation of evolutionary variety and eventually to comprehension of the organization of extracellular matrices and of the properties of their constituent macromolecules. The expanding knowledge of unique matrix molecules from invertebrates also has economic potential and is beginning to provide new materials for biotechnology.