MEPS 192:287-294 (2000)  -  doi:10.3354/meps192287

Daily variations of the saccular endolymph and plasma compositions in the turbot Psetta maxima: relationship with the diurnal rhythm in otolith formation

A. Edeyer1, H. de Pontual1,*, P. Payan3, H. Troadec1, A. Sévère2, N. Mayer-Gostan4

1Laboratoire de Sclérochronologie des Animaux Aquatiques, IFREMER, DRV/RH/LASAA, and 2Laboratoire de Physiologie des poissons, IFREMER, DRV/RA, BP 70, 29280 Plouzané, France
3Laboratoire de Physiologie et Toxicologie Environnementale EA 2138, and 4Laboratoire de Physiologie Cellulaire et Moléculaire UMR CNRS 6548, Université de Nice-Sophia Antipolis, Faculté des Sciences, BP 71, 06108 Nice Cedex 2, France
*Corresponding author. E-mail:

ABSTRACT: We studied the circadian variations of the ionic composition ([Na+], [K+], [Cl-]), total CO2 ([tot CO2]), and protein concentration ([protein]) in the plasma and endolymph in the distal and proximal sides of the sacculus in the turbot Psetta maxima. Daily variations in total plasma calcium ([tot Ca]) were also recorded. Significant diurnal fluctuations occurred in most parameters and the spatial heterogeneity of the endolymph composition was maintained throughout a 24 h period. The main parameters implicated in otolith calcification, endolymph [tot CO2] and endolymph [protein], fluctuated diurnally. [tot CO2] was highest and [protein] lowest at night; the relative concentrations were reversed during the day. The inverse, alternating relationship of maximal and minimal [tot CO2] and [protein] implies that calcium carbonate and organic matrix rates of deposition vary in antiphase. We therefore propose that in the turbot P. maxima, in autumn, the incremental zone (L-zone) is formed at night whereas the discontinuous zone (D-zone) is formed during the daytime.

KEY WORDS: Daily cycle · Endolymph · Otolith · Chemical composition · Teleost

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