Chapter 9
The Unique Invention of the Siliceous Sponges:
Their Enzymatically Made Bio-Silica Skeleton
Werner E.G. M€ uller, Xiaohong Wang, Ailin Chen, Shixue Hu, Lu Gan,
Heinz C. Schr€ oder, Ute Schloßmacher, and Matthias Wiens
Contents
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
9.2 The Key Innovation During the Proterozoic: The Skeleton of Metazoa . . . . . . . . . . . . . . 253
9.2.1 Proterozoic, Silica-Rich Ocean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
9.2.2 Emergence of the Animal Organic Hard Skeletons . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
9.3 Well-Preserved Fossils in Body Preservation at the Ediacaran/Lower Cambrian
Border: The Siliceous Sponges from Chengjiang . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
9.4 Morphology and Synthesis of Spicules in Demosponges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
9.5 Morphology and Synthesis of Spicules in Hexactinellids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
9.6 Phases of Silica Deposition During Spicule Formation Along the Proteinaceous
Filament . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
9.7 Silicatein: Emergence of one Protein Allowed the Establishment of an Organized
Body Plan in Sponges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
9.8 Catabolic Enzyme: Silicase . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 271
9.9 Biosintering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
9.10 Implication of the DUF Protein in the Axis Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
9.11 Final Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
Abstract Sponges are sessile filter feeders that, among the metazoans, evolved
first on Earth. In the two classes of the siliceous sponges (the Demospongiae and the
Hexactinellida), the complex filigreed body is stabilized by an inorganic skeleton
composed of amorphous silica providing them a distinct body shape and plan. It is
proposed that the key innovation that allowed the earliest metazoans to form larger
specimens was the enzyme silicatein. This enzyme is crucial for the formation of
the siliceous skeleton. The first sponge fossils with body preservation were dated
W.E.G. M€ uller (*)
ERC Advanced Grant Research Group at the Institute for Physiological Chemistry,
University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6,
D-55128 Mainz, Germany
e-mail: wmueller@uni-mainz.de; http://www.biotecmarin.de
W.E.G. M€ uller (ed.), Molecular Biomineralization, Progress in Molecular
and Subcellular Biology 52, DOI 10.1007/978-3-642-21230-7_9,
# Springer-Verlag Berlin Heidelberg 2011
251
The Unique Invention of the Siliceous Sponges:
Their Enzymatically Made Bio-Silica Skeleton
Werner E.G. M€ uller, Xiaohong Wang, Ailin Chen, Shixue Hu, Lu Gan,
Heinz C. Schr€ oder, Ute Schloßmacher, and Matthias Wiens
Contents
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
9.2 The Key Innovation During the Proterozoic: The Skeleton of Metazoa . . . . . . . . . . . . . . 253
9.2.1 Proterozoic, Silica-Rich Ocean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
9.2.2 Emergence of the Animal Organic Hard Skeletons . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
9.3 Well-Preserved Fossils in Body Preservation at the Ediacaran/Lower Cambrian
Border: The Siliceous Sponges from Chengjiang . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
9.4 Morphology and Synthesis of Spicules in Demosponges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
9.5 Morphology and Synthesis of Spicules in Hexactinellids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
9.6 Phases of Silica Deposition During Spicule Formation Along the Proteinaceous
Filament . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
9.7 Silicatein: Emergence of one Protein Allowed the Establishment of an Organized
Body Plan in Sponges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
9.8 Catabolic Enzyme: Silicase . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 271
9.9 Biosintering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
9.10 Implication of the DUF Protein in the Axis Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
9.11 Final Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
Abstract Sponges are sessile filter feeders that, among the metazoans, evolved
first on Earth. In the two classes of the siliceous sponges (the Demospongiae and the
Hexactinellida), the complex filigreed body is stabilized by an inorganic skeleton
composed of amorphous silica providing them a distinct body shape and plan. It is
proposed that the key innovation that allowed the earliest metazoans to form larger
specimens was the enzyme silicatein. This enzyme is crucial for the formation of
the siliceous skeleton. The first sponge fossils with body preservation were dated
W.E.G. M€ uller (*)
ERC Advanced Grant Research Group at the Institute for Physiological Chemistry,
University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6,
D-55128 Mainz, Germany
e-mail: wmueller@uni-mainz.de; http://www.biotecmarin.de
W.E.G. M€ uller (ed.), Molecular Biomineralization, Progress in Molecular
and Subcellular Biology 52, DOI 10.1007/978-3-642-21230-7_9,
# Springer-Verlag Berlin Heidelberg 2011
251