Calcite precipitation forms crystal clusters and muscle mineralization during the decomposition of Cambarellus diminutus (Decapoda: Cambaridae) in freshwater

Abstract

The fossilization of soft tissues is generally the replacement of organic structures by pseudomorphs in which muscle tissue is mostly replaced by minerals (i.e., phosphate, carbonate or pyrite). Micro-CT observations of decomposing crayfish in tank and distilled water, show a precipitation of crystal clusters over time. In addition, a mineralized muscle was found by SEM analyses. Raman spectroscopy (CRS) revealed that crystal clusters and the muscle consist of well-ordered calcite. Inductively coupled plasma mass spectrometry (ICPMS) of the distilled water showed a calcium content below the detection limit at the beginning of the experiments, which indicates that most of the calcium ions needed for the precipitation were provided by the decomposing carcasses themselves. Volume measurements of 3D-reconstructed calcite clusters and gastroliths showed a general increase of the volume of calcite clusters and simultaneously volume reduction of gastroliths with progressive decay. Specimens that were in the postmoult phase showed a smaller total volume of precipitated calcite, compared to specimens, which were in the intermoult or premoult phase. In addition, measurements of the total amount of body calcium of Cambarellus diminutus by atomic absorption spectrophotometry (AAS) revealed a higher amount of calcium in individuals without gastroliths than in individuals with gastroliths. It is assumed, that the higher the body size, the higher the volume of precipitated calcite, if the individuals were in the intermoult phase at the time of death. If the individuals were in the postmoult or premoult phase, the phase itself seems to be important.

Report on ammonoid soft tissue remains revealed by computed tomography

“…Lowering of the pH (< 6.38 = the phosphatization window that favors the precipitation of apatite) suggests a "closed system" that keeps the acidic biproducts of microbial metabolism, such as CO 2 and H 2 SO 4 Briggs & Wilby, 1996, Clements et al 2017. Here, we argue that the phragmocone itself served as a "closed system" comparable to the cuticular envelope of crustaceans (Briggs & Wilby, 1996;Mähler et al, 2020). Within the phragmocone chambers, the ion concentrations and low pH levels generated by microbial decomposition were maintained, while the body chamber (that contained the largest part of the soft tissues) represents an "open system" allowing the complete degradation of soft tissues without (See figure on next page.)…”

“…6-7). Because the original soft tissue is not preserved, such structures are preferable called pseudomorphs: they are generally formed by the replacement of tissues by, e.g., phosphates, carbonates, or pyrite (see Mähler et al, 2020 for more details). The preservation of these organic structures suggests an early diagenetic phosphatization (Weitschat, 1986;Weitschat and Bandel, 1991).…”

Widespread mineralization of soft‐bodied insects in Cretaceous amber

“…Nonetheless, even if different insect groups have different body structures with a varying potential to resist degradation and mineralization potential (Parry et al, 2018), the diverse groups of insects in this study suggest that their taphonomic pathways do not depend on taxonomic affinity. The mineralization of exceptionally preserved fossils depends on the availability of oxidants and reactive chemical species in the microenvironment (water or resin) surrounding the decaying carcass (Briggs, 2003;Briggs & Wilby, 1996a;Mähler et al, 2020;Muscente et al, 2014Muscente et al, , 2017Schiffbauer et al, 2014). Insects generally do not have biomineralized tissues made of silica or calcium carbonate (Li et al, 2020); ergo, the silicification and calcification of the Kachin insects must have been caused by precipitation of chemical species from two sources: (1) decomposition of their tissues in response to microbial respiration and (2) fluid from the surrounding environment (e.g.…”

The complex role of microbial metabolic activity in fossilization

“…The mineralization step of fossilization can be studied in laboratory experiments (Fig. 1), as mineralization can occur within days, month or years after death (Mähler et al ., 2020; Li et al ., 2013; Sagemann et al ., 1999).…”

“…To date, a number of experimental studies on the direct influence of bacteria on mineralization and preservation have been conducted, but they are mainly limited to marine settings [Briggs & Kear, 1993 a , 1993 b , 1993 c ; Butler et al ., 2015; Eagan et al ., 2017; Hof & Briggs, 1997; Martin, Briggs & Parkes, 2005; Naimark et al ., 2018 a ; Raff et al ., 2008; Raff et al ., 2014; Sagemann et al ., 1999; but see e.g. Naimark et al ., 2016 b , Peterson, Lenczewski & Scherer, 2010 and Mähler et al ., 2020 for non‐marine investigations]. Experimental studies can give insights into the initial and probably the most important steps in decay and mineralization processes that pave the way to fossilization (Briggs & McMahon, 2016; Newman et al ., 2019; Sagemann et al ., 1999).…”