Cretaceous mycelia preserving fungal polysaccharides: taphonomic and paleoecological potential of microorganisms preserved in fossil resins

Authors

  • M. SPERANZA Departamento de Bioquímica y Ecología Microbiana, Museo Nacional de Ciencias Naturales. Consejo Superior de Investigaciones Científicas, Serrano 115 bis, E-28006, Madrid, Spain.
  • C. ASCASO Departamento de Bioquímica y Ecología Microbiana, Museo Nacional de Ciencias Naturales. Consejo Superior de Investigaciones Científicas, Serrano 115 bis, E-28006, Madrid, Spain.Departament d’Estratigrafia, Paleontologia i Geociències Marines, Universitat de Barcelona Martí i Franquès s/n, E-08028 Barcelona. Spain.
  • Xavier DECLÓS Departament d’Estratigrafia, Paleontologia i Geociències Marines, Universitat de Barcelona Martí i Franquès s/n, E-08028 Barcelona. Spain.
  • E. PEÑALVER Museo Geominero, Instituto Geológico y Minero de España. Ríos Rosas 23, E-28003 Madrid, Spain.

Keywords:

Amber, Taphonomy, Paleoecology, Biomarkers, Fungi

Abstract

The cortices of pieces of Cretaceous amber around the world commonly are constituted by networks of filamentous structures. Based on their morphological characteristics, such structures have previously been classified in different microorganismal groups. Their correct interpretation, however, is of great importance to establish the conditions of the resin’s burial in the forest litter, and can provide important clues regarding the ecology and environmental conditions of Cretaceous resinous forests. Because these networks of filamentous structures present typical fungal morphological features we conducted a study in order to resolve their origin. The cortices of several pieces of Cretaceous amber from Spain were examined using light and scanning electron microscopy, energy dispersive X-ray spectroscopy and confocal laser scanning microscopy. This is the first time that Calcofluor white and Wheat germ agglutinin conjugated with fluorescein isothiocyanate have been employed as fungal markers in amber, and their use enabled us to detect preserved polysaccharides in the filamentous structures using confocal laser scanning microscopy. These results provide the first and oldest record of ß-1,3 and ß-1,4-linked polysaccharides, and specifically N-acetylglucosamine residues from chitin in a fossil fungus preserved in amber and to demonstrate that the networks of filamentous structures are mycelia composed of profuse hyphae of a resinicolous fungus. This type of mycelium constitutes one of the largest fungal fossil records known. Using taphonomic data it is demonstrated that the cortices originated during the Cretaceous due to fungal growth within non-solidified resin. The fossil diagenetic degradation sequence of the fungal hyphae and the surrounding amber is described. This degradation changed the microscopic appearance of the hyphae; thus, some of the previously indicated taxonomic features of this microorganism may actually be fossil diagenetic artifacts. The paleoecological implications with regard to fungal trophic requirements and forest environmental conditions are discussed.

Author Biographies

M. SPERANZA, Departamento de Bioquímica y Ecología Microbiana, Museo Nacional de Ciencias Naturales. Consejo Superior de Investigaciones Científicas, Serrano 115 bis, E-28006, Madrid, Spain.

Scientific researcher (Dpto. Biología Ambiental)

C. ASCASO, Departamento de Bioquímica y Ecología Microbiana, Museo Nacional de Ciencias Naturales. Consejo Superior de Investigaciones Científicas, Serrano 115 bis, E-28006, Madrid, Spain.Departament d’Estratigrafia, Paleontologia i Geociències Marines, Universitat de Barcelona Martí i Franquès s/n, E-08028 Barcelona. Spain.

Scientific researcher (Dpto. Biología Ambiental)

Xavier DECLÓS, Departament d’Estratigrafia, Paleontologia i Geociències Marines, Universitat de Barcelona Martí i Franquès s/n, E-08028 Barcelona. Spain.

professor and scientific researcher (Dept. d' Estratigrafia, Paleontologia i Geociencies Marines)

Universitat de Barcelona

E. PEÑALVER, Museo Geominero, Instituto Geológico y Minero de España. Ríos Rosas 23, E-28003 Madrid, Spain.

Scientific researcher (Museo Geominero, IGME)

Museo Geominero, Instituto Geológico y Minero de España

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Published

2015-11-16

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Articles