La vessie natatoire chez Dicentrarchus labrax et Sparus auratus

Abstract

In sea bass and sea bream the primordial swim bladder can be observed in vivo by transparency (profile projection), as early as the third day after hatching. In both species, normal swim bladder development, from the initial vesicle, is characterized by two stages. The first stage, called “initial inflation”, occurs in 5-mm sea bass larvae (around 7 days old) and in 4-mm sea bream larvae (around 5 days old). Inflation coincides with oil globule resorption. When initial inflation fails, the swim bladder development is stopped at a stage resembling that prior to inflation and is non-functional. The second stage corresponds to an expansion phenomenon. In larvae greater than 12 mm long, the swim bladder looks like an ellipsoidal vesicle which progressively stretches backwards during growth. It becomes stable in 40–50-mm fish, reaching 20 to 30% of the total length. Among larvae that fail to inflate, the swim bladder development stops and the bladder never exceeds 3–5% of the fish length.