Relation between Fish Habitat and the Periodicity of Incremental Lines in the Fossil Otoliths

Hiroyuki Mishima,Yasuo Kondo,Tohru Hayakawa,Yasuo Miake,Fumio Ohe

doi:10.3390/cryst10090820

Abstract

There are few research reports on the relationship between fish habitats and the periodicity of the fishes’ incremental lines of otolith fossils. The present study examines this relationship through histological and analytical studies on otolith fossils from Nobori Formation, Pliocene, Japan. The specimens were observed and analyzed using light microscopy, polarizing microscopy, Miniscopy, Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis, electron probe X-ray microanalyzer (EPMA), Raman spectroscopy, and XRD. The otolith crystals were aragonite according to XRD and Raman analysis. The incremental lines contained C, O, and Ca, with Si as a trace element. In the layer between the incremental lines, Si was not detected. The circadian incremental lines were unclear and irregularly observed in both Lobianchia gemellarii and Diaphus gigas. Their behavioral pattern included a diurnal vertical movement. By comparison, for Cetonurus noboriensis, Ventrifossa sp., Sebastes scythropus, and Congriscus megastomus, the circadian incremental lines were evident. The habitat of the fishes that live exclusively on the continental slope is kept constant, and the circadian incremental lines are formed regularly. However, for fishes that spend the day in the deep sea and ascend to the shallow sea at night, the ecosystem, such as seawater temperature and pressure, fluctuates, and the circadian incremental lines become unclear and irregular. The period of the circadian incremental lines of otolith may vary due to differences in the ecosystems.

Highlights

The otolith is present in the bony fish’s internal ear and is the mineralized structure consisting of calcium carbonate with a small number of organic matrices [1,2,3]
The purpose of the present study is to examine the structure, the composition, and the periodicity of incremental lines in the otolith fossils due to differences in fish habitat through histological and analytical studies
On the Macrouridae spp. otolith fossil cross-sections, the inside of the otolith was found to consist of needle-like crystals crossed by some kind of incremental lines

Summary

Introduction

The otolith is present in the bony fish’s internal ear and is the mineralized structure consisting of calcium carbonate with a small number of organic matrices [1,2,3]. The main component of the otolith crystal is calcium carbonate (CaCO3 ) [1,2,3]. In fish otolith matrix proteins, two matrix proteins (OMP-1, Otolin-1) have been identified [4,5]. There are incremental lines with several types of periodicity in the otolith’s internal structure [1,8,9,10]. The daily incremental lines of otoliths are considered to be 1–4 μm [8,10]. There have been studies of the environmental history analysis of the fish [2]

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Discussion

Conclusion