INFLUENCE OF TEMPERATURE ON THE DEVELOPMENT OF THE HEART VENTRICLE INHERRING (CLUPEA-HARENGUS) LARVAE

Spring spawning Atlantic herring (Clupea harengus L.) were reared at 5 degrees C, 8 degrees C and 12 degrees C. The effects of temperature o n the development of the heart ventricle at hatching were analysed. Ve ntricular shape, cross-sectional area, wall thickness and cell density were determined by Light microscopy. information on the cellular comp osition and ultrastructure of the myocardium was obtained by transmiss ion electron microscopy. The thickness of the ventricular wall increas ed by a factor of two between 5 degrees C and 12 degrees C. However, t he density of cells and the number of layers and organisation of the m yocytes increased in the series 8 degrees C > 12 degrees C > 5 degrees C. Thus, although the rate of development increased at higher tempera ture, the degree of differentiation of the heart ventricle at hatching showed an optimum at 8 degrees C. The results indicate different ther mal sensitivities for development and tissue differentiation in ontoge ny of the fish heart. (C) 1996 Wiley-Liss, Inc.