Bacteria play an important role in the fossilization of soft tissues; their metabolic activities drive the destruction of the tissues and also strongly influence mineralization. Some environmental conditions, such as anoxia, cold temperatures, and high salinity, are considered widely to promote fossilization by modulating bacterial activity. However, bacteria are extremely diverse, and have developed metabolic adaptations to a wide range of stressful conditions. Therefore, the influence of the environment on bacterial activity, and of their metabolic activity on fossilization, is complex. A number of examples illustrate that simple, general assumptions about the role of bacteria in soft tissue fossilization cannot explain all preservational pathways: (i) experimental results show that soft tissues of cnidaria decay less in oxic than anoxic conditions, and in the fossil record are found more commonly in fossil sites deposited under oxic conditions rather than anoxic environments; (ii) siderite concretions, which often entomb soft tissue fossils, precipitate due to a complex mixture of sulfate‐ and iron reduction by some bacterial species, running counter to original theories that iron reduction is the primary driver of siderite concretion growth; (iii) arthropod brains, now widely accepted to be preserved in many Cambrian fossil sites, are one of the first structures to decay in taphonomic experiments, indicating that their fossilization processes are complex and influenced by bacterial activity. In order to expand our understanding of the complex process of bacterially driven soft tissue fossilization, more research needs to be done, on fossils themselves and in taphonomic experiments, to determine how the complex variation in microbial metabolic activity influences decay and mineralization.

About 50% of all animal species are considered parasites. The linkage of species diversity to a parasitic lifestyle is especially evident in the insect order Hymenoptera. However, fossil evidence for host–parasitoid interactions is extremely rare, rendering hypotheses on the evolution of parasitism assumptive. Here, using high-throughput synchrotron X-ray microtomography, we examine 1510 phosphatized fly pupae from the Paleogene of France and identify 55 parasitation events by four wasp species, providing morphological and ecological data. All species developed as solitary endoparasitoids inside their hosts and exhibit different morphological adaptations for exploiting the same hosts in one habitat. Our results allow systematic and ecological placement of four distinct endoparasitoids in the Paleogene and highlight the need to investigate ecological data preserved in the fossil record.

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.

Fossilization processes and especially the role of bacterial activity during the preservation of organic material has not yet been well understood. Here, we report the results of controlled taphonomic experiments with crayfish in freshwater and sediment. 16S rRNA amplicon analyzes showed that the development of the bacterial community composition over time was correlated with different stages of decay and preservation. Three dominating genera, Aeromonas, Clostridium and Acetobacteroides were identified as the main drivers in the decomposition of crayfish in freshwater. Using micro-computed tomography (µ-CT), scanning electron microscopy (SEM) and confocal Raman spectroscopy (CRS), calcite clusters were detected after 3–4 days inside crayfish carcasses during their decomposition in freshwater at 24 °C. The precipitation of calcite clusters during the decomposition process was increased in the presence of the bacterial genus Proteocatella. Consequently, Proteocatella might be one of the bacterial genera responsible for fossilization.

Abstract:Beaked whales or ziphiids are the least known cetaceans, and are among the least studied of all mammalian groups. In August and September of 2002, a male and a female beaked whale stranded alive on the Argentine coast, 110 km away from each other. The specimens died shortly after the stranding and their bodies were collected for dissection and analysis. The specimens were identified as belonging to the genus Mesoplodon. Further measurements of the skulls, shape and location of teeth as well as molecular analyses of the mtDNA control region and cytochrome b, allowed unambiguous identification of both specimens as Hector's beaked whale, Mesoplodon hectori. The color pattern was different between male and female. Standard length was 3.94 meters for the male and 3.84 meters for the female. The female's vertebral formula was C7 + T10 + L11 + Ca21 = 49. Histo-pathological analysis of the female revealed the presence of Sarcocystis sp. in the skeletal muscle, and lung lesions related to parasitic damage and pneumonia or chronic infection. The stomach of both individuals was empty. The digestive tract of both specimens was infected by larval stages L4 of Anisakis sp. The female was also infected by Tetrabothrius sp. and Bolbosoma sp. while Braunina cordiformis was only found in the male. Different composition of parasitic fauna suggests possible sex-related differences in the diet or individual variability. Total length, teeth eruption (in the male) and the degree of vertebral epiphyses fusion suggest that both individuals were mature.Resumen: Las ballenas picudas o zífidos son los cetáceos menos conocidos y además están entre los mamíferos existentes que menos se conocen. En agosto y septiembre de 2002 un macho y una hembra de ballenas picudas vararon vivas en la costa de Argentina, a 110 kilómetros una de otra. Los especimenes murieron poco después del varamiento y sus cuerpos fueron colectados para su disección y análisis. Los especimenes fueron identificados como pertenecientes al género Mesoplodon, a partir de medidas del cráneo, la forma y posición de los dientes y el análisis del ADNmt, región control y citocromo b, permitiendo identificar sin ambigüedad ambos especimenes como ballenas picudas de Héctor, Mesoplodon hectori. El macho y la hembra presentaron diferente patrón de coloración. La longitud estándar fue de 3,94 metros para el macho y de 3,84 metros para la hembra. La fórmula vertebral de la hembra fue C7 + T10 + L11 + Ca21 = 49. Análisis histopatológicos de la hembra revelaron la presencia de Sarcocystis sp. en el músculo esquelético, y lesiones pulmonares relacionadas con daño producido por parásitos y pneumonía o infección crónica. El estómago de ambos ejemplares se encontró vacío. El tracto digestivo de ambos especimenes se encontraba infectado por el estadio larval L4 de Anisakis sp. La hembra tenía Tetrabothrius sp. y Bolbosoma sp. Mientras que el macho tenía Braunina cordiformis en su estómago. La diferente composición de la fauna parasitaria de ambos individuos sugiere la existencia de po...