Experimental Study Of Phosphate-based Simulation Embryo Fossils

A considerable number of phosphatized spheroidal fossils were found in the Ediacaran Doushantuo Formation and the early Cambrian phosphorus strata in South China. Because of the special mineral that is preserved, many ultra-fine structures (cellular and sub-cellular levels) of the biological specimens can be three-dimensionally preserved. These fossils provide important material for the study of origins and early ontogeny of metazoan.For the Doushantuo spherical microfossils, ornamentation and morphology are important criteria for judging the biological properties of the fossils. Researchers usually study the fossils’ biological properties by a comparative analysis between the characteristics of the spherical fossils (including the size, the cleavage pattern, and the overall split mode) and the modern biological characteristics. According to the complexity of the structure of these fossil cell structures and their similar characteristics with the morphology features of modern animal tissues, the Doushantuo spherical fossils have been widely interpreted as originating from a variety of sources. Such hypotheses are based on the remarkable similarities between modern eukaryotic embryos and the Doushantuo spherical fossils in size and cell division boundaries. However, recognition of the same types of fossils relied on comparisons between living organisms and fossilized remains. As fossils have all experienced death, corruption, decay and digenetic alteration, few specific characteristics can be used as standards to identify the same biological species. The relationship between the corruption and the remnant morphology of soft tissues has yet to be explored. Because there is a different understanding between fossil characteristics and the biological structure correspondence of the fossil, the understanding of these characteristics is at odds with the identification of fossils, which usually causes controversy. A more complex explanation for the fossil assemblage appears to contain more difficulties (especially with regard to establishing the genetic relationship between individuals).Although many mineralization experiments confirmed that vulnerable tissues can be exceptionally preserved, it provided only limited information on the initial biological decomposition. There are insufficient data to separate the primary structures and the corruption changes. The direct evidence may be concealed by subsequent diagenesis, and the remaining traces of the primary structure were not recognized. Clearly, the spatial pattern will not be measured by chemical analysis. Steep chemical gradients that originally existed in the environment (e.g.,O2, nitrate, pH, and redox) may be the main factors that cause morphological changes. The ability to measure morphological changes over time is vital as the decomposition process itself is dynamic. The mineralization experiments, which focus on mineralization, provide an indication of understanding the processes. Providing the possibility of measuring single factors at fine spatial resolutions with minimum disturbance can reveal this process. Whether the native structure changed in a dynamic environment should be explored by the researcher.Modern artificial simulation experiments of phosphate animal eggs can provide scientific evidence to settle the aforementioned disputes. This experiment simulated environmental changes to observe the early morphological changes of the Bluntnose black bream eggs(Megalobrama amblycephala). This study in a laboratory confirmed the occurrence of morphological variations under different conditions and that the eggs decomposed in different ways. It was found that the eggs can show a different morphology in the phosphate environment and that these eggs exhibited considerable morphological variations under different conditions. By comparing the perservational state in this experiment with those of other states, the results showed diversified morphological changes that may also have occurred in the real environment. These results may indicate that diversified morphological changes may be widely occurred in geological history. Thus, those eggs cannot be ascribed to the same species based only on the features. The experimental results are expected to provide a useful reference for the identification of phosphatized microfossils and provide a more empirical basis for their genesis.