The first fossil immature of Elmidae: an unusual riffle beetle larva preserved in Baltic amber

PeerJ. 2022 Apr 7:10:e13025. doi: 10.7717/peerj.13025. eCollection 2022.

Abstract

Elmidae, riffle beetles, have both adult and immature stages that show specializations for water environments. Fossils of adults of Elmidae are already known from amber, however a record of immatures was so far lacking. We report here the first fossil larva of Elmidae, preserved in Baltic amber. To be able to access details of the body hidden by inclusions and "Verlumung" we conducted, in addition to optical documentation methods, micro-CT and synchrotron documentation methods. The larva is characterised by prominent dorso-lateral and lateral processes and a plate-like ventral operculum at the end of the abdomen. The new fossil has similarities in the general body shape and the prominent characters with some modern larvae of Elmidae. The posterior protrusions on the trunk end possibly represent gills, which would imply that fossil larvae of Elmidae also led a water-related life style similar to modern representatives.

Keywords: Amber; Elmidae; Eocene; Operculum; Processes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amber*
  • Animals
  • Baltic States
  • Coleoptera*
  • Fossils
  • Larva

Substances

  • Amber

Grants and funding

This work was supported by the Volkswagen Foundation with a Lichtenberg professorship and by the German Research Foundation (DFG Ha 6300/6-1). Support for imaging at the Imaging Center of the Department of Biology, University of Greifswald was received from the German Research Foundation (DFG INST 292/119-1 FUGG; DFG INST 292/120-1 FUGG). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.