Normally anomalous otoliths in adults of reef croaker, Odontoscion dentex

Abstract

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Odontoscion dentex is reef fish (Sciaenidae) commonly found in the coastal shallow waters of Florida (US) until Santa Catarina (BR). Sciaenids, in general, are highly acoustic fish, both producing and receiving water vibrations through the lateral line system. As consequence they have large and irregular otoliths, associated to a well-developed lateral line and swimbladder. Several irregularities have been observed in fish sagittal otoliths, but mainly restricted to the replacement of the mineral form, i.e. aragonite by vaterite, in the carbonate matrix. This is usually recorded in rockfishes, including one scianidae species. However, these structures have been assumed to be anomalous and occasional in some individuals. In sagittae of O. dentex a permanent structure was however recorded, as a deep hole near the otolith’s core, usually with a U-shape. This irregularity was observed in all specimens analyzed, in both optic and scanning electron microscopy images, during the grinding and polishing procedures, after embedding the otolith in epoxy resin, for ageing purposes. Our result suggests that this is a non-artifact and permanent structure observed in O. dentex sagittal otoliths, which biological meaning is, at present, unknown.

Keywords

• SEM
• Sciaenidae
• OP
• Deep hole
• rockyreefish