Characterization of Incremental Markings in the Sagittal Otolith of the Pacific Sardine (Sardinops sagax) Using Different Imaging Modalities

Kelsey C. James, Uwe Kierdorf, Victoria Cooley, Viktor Nikitin, Stuart R. Stock*, Horst Kierdorf

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Teleost fish possess calcium carbonate otoliths located in separate chambers (utriculus, sacculus, and lagena) of their membranous labyrinth. This study analyzed the surface topography of the sagittal otolith of the Pacific sardine (Sardinops sagax) and the daily and annual increments in these otoliths. The otolith surface, characterized by laser scanning confocal microscopy for the first time, consisted of a system of prominent ridges and valleys (grooves), but it is unclear whether these structures are functional or represent time-resolving markings reflecting growth periodicity. Within the first-year volume, daily increments, each consisting of an incremental (more mineralized) and a discontinuous (less mineralized) zone, were resolved by optical microscopy and backscattered electron (BSE) imaging in the scanning electron microscope (SEM). Daily growth increments could, however, not be resolved in volumes formed after the first year, presumably because otolith growth markedly slows down and spacing of incremental markings narrows in older fish. Throughout otolith growth, the crystalline network continues across the discontinuous zones. Fluorochrome labeling provides additional information on growth after the first year. Compared with optical and BSE imaging, synchrotron microComputed Tomography of intact otoliths (with 0.69 µm volume elements) was less able to resolve daily increments; X-ray phase contrast reconstructions provided more detail than reconstructions with absorption contrast. Future research directions are proposed.

Original languageEnglish (US)
Article number705
JournalMinerals
Volume14
Issue number7
DOIs
StatePublished - Jul 2024

Funding

This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility, operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Argonne National Laboratory\u2019s work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract DE-AC02-06CH11357.

Keywords

  • fluorochrome labeling
  • laser scanning confocal microscopy
  • recording structure
  • scanning electron microscopy
  • sclerochronology
  • synchrotron microCT imaging

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology

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