Sponges Spicule

Table 10. Distribution of amino acids (residues/1000) in cell contents and cell walls of 6 species of diatoms from various habitats. Column a distribution in cell contents Column b cell walls. Bottom of table emphasizes the difference (Column b - Column a) between cell-wall composition and cell contents for those amino acids which show consistent trends. The sponge spicules are from Ctiona celata, and the sponge tissue is from an unidentified siliceous sponge. AA amino acids HA hexosamines... 

Schwab, D. W, and Shore, R. E. Fine structure and composition of a siliceous sponge spicule. Biol. Bull. 140, 125-136 (1971). 

The hydrated amorphous mineral silica (opal) is widely used by many plants and animals for structural purposes. Most skeletons are formed by unicellular organisms (diatoms Figure 2(a), radiolarians Figure 2(b)), but silica is also present within multicellular organisms (sponge spicules, plant... 

Brasier M., Green O., and Shields G. (1997) Ediacarian sponge spicule clusters from southwestern MongoUa and the origins of the Cambrian fauna. Geology 28, 303—306. 

Opal is related to the very common Si02 mineral species, quartz. Oceans are at present undersaturated with respect to opal (Broecker, 1971) possibly because of the biological formation of animals with silicified skeletons such as the diatoms. These delicate structured creatures, which proliferate in the upper photic zone, dissolve at depth. Therefore, only robust siliceous skeletons such as sponge spicules are retained in sediments that accumulate in deep waters, although some diatoms survive on the continental shelf under zones with high productivity. The initial deposition of the amorphous hydrated silica, opal, converts first to opal-CT and eventually to crystalline quartz (Kastner, 1981). 

The range of specific surface areas from Recent radiolarians to sponge spicules may vary by nearly three orders of magnitude. Since Alexander (25) has shown that for a series of silica gel sols, solubility varies as a function of both specific surface area and internal structure, only general trends in solubility can be discussed, and those, conservatively. 

Figures 1 and 2 show the change in solubility of the acid-cleaned radiolarian and sponge spicule assemblages at 26° 1°C and 3° 1°C as a function of geologic age. Also shown are the estimated values of the high and low cristobalite and low quartz solubilities at these two temperatures. The open and crossed circles represent the initial leveling off of the concentration of Si (OH) 4 vs. time curves, and the dots are the...

Figure 6, Late Miocene age radiolarmn assemblage having 118 gm specific surface area Hollow branching rod on the left is a sponge spicule.

Figure 8. Late OUgocene age radiolarian and sponge spicule assemblage having 39 gm specific surface area...

Jones, W.C., 1967. Sheath and axial filament of calcareous sponge spicules. Nature, 214 365. 

Jones, W.C. and James, D.W.F., 1969. An investigation of some calcareous sponge spicules by means of electron probe micro-analysis. Micron, 1 34—39. 

Jones, W.C. and Jenkins, D.A., 1970. Calcareous sponge spicules a study of magnesian calcites. Calcif. Tissue Res., 4 314—329. 

Diatom frustules and sponge spicules in terrestrial environments are derived chiefly from fresh and brackish water species and from unconsolidated fossiliferous sediments exposed to surface winds and water. 

As is the case with other forms of non-crystalline silica, the conversion to quartz of phytoliths, diatom frustules, and sponge spicules under sedimentary conditions on land can be expected to be accelerated by elevated temperature, elevated pressure, and the presence of an aqueous phase of high pH (>9) or containing electrolytes. 

Monaxon a simple uniaxial sponge spicule with a single axial filament or axial canal, or one developed by growth along a single axis. 

Framework - phyllosilicate/microcrystalline quartz fault rocks This class of fault rock is introduced here to describe fault rocks which form in sediments with concentrations (>20%) of dissolvable sponge spicules and varying amounts (15-40%) of phyllosilicates (Fig. 2d). Although not common, sediments with high sponge spicules contents are prone to the development of fault rocks by the cataclasis, dissolution and reprecipitation of silica. The process may be initiated by the collapse of secondary pores created by spicule dissolution and induce the redistribution of more soluble material by mixing. 

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