Larval development of decapod crustaceans investigated by confocal microscopy: an application to Hippolyteinermis (Natantia)

The main goal of the present research was to devise and test an experimental protocol to follow the morphological evolution of the internal anatomy, during the larval development of the shrimp Hippolyteinermis. Larvae born in the laboratory were reared under controlled conditions and sampled at 2-day intervals, from hatching to the adult stage. After fixation, selected individuals were treated with a fluorescent carbocyanine dye (DiI) and analysed by a confocal laser scanning microscope. Images, acquired along the z-axis, were three-dimensionally reconstructed through image analysis software, and the structure of internal organs was analysed for each zoeal stage. The first zoea of H.inermis was characterised by the presence of a large tetralobate digestive gland occupying most of the space in the thoracic chamber. During development, formation of the eyestalks was accompanied by a progressive differentiation of the medullae, whereas the heart moved in the caudal direction and the gonadic buds appeared in the cephalothorax. The main arteries and anterior part of the midgut were analysed, during their differentiation, from dorsal views of the zoeae, whereas the structure of the nervous system and the main ganglia along the pleon were described from ventral scans. Received: 17 March 2000 / Accepted: 25 November 2000