The pineal complex of the European sea bass (Dicentrarchus labrax): I. Histological, immunohistochemical and qPCR study

The pineal organ of European sea bass contains photoreceptor and presumed melatonin-producing cells.

• The pineal complex includes a narrow pineal stalk, a small end vesicle, a parapineal organ, and a convoluted dorsal sac.
• Histological analysis revealed abundant serotonin-positive cells in the pineal organ.
• Cone opsin-like and rod opsin-like photoreceptor cells were identified in the pineal stalk and vesicle.
• Both melatonin-synthesizing enzymes, AANAT2 and HIOMT, are expressed in the pineal organ.
• AANAT2 showed higher levels of expression at night, while HIOMT expression did not vary significantly between day and night.

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