Ontogeny of the sinus gland and of the organ of Bellonci in larvae and postlarvae of the European lobsterHomarus gammarus

Abstract

The topography of larval (stages I, II, III) and postlarval (stage IV) eyestalk of Homarus gummarus was studied by light and electron microscopy. The general structure (ommatidian layer and the three nervous masses) at hatching is similar to the adult eyestalks' organization. The sinus gland is present and contains neurosecretory granules as easly as stage I. Its size and the density of granules increase through development. The presence of neurosecretory granules and exocytosis vesicles in the sinus gland of stage I larvae demonstrates that the sinus gland is functional at the beginning of the larval development. The organ of Bellonci is also present at the first larval stage; it is located at the opposite side of the sinus gland and presents two aspects: a vesicular form and the classical onion bodies.