P. Kestemont, J. Cooremans, A. Abi-Ayad, C. Melard-1999
Fish Physiology and Biochemistry, 21(1): 59-64 (from Current Contents)
Abstract:
This study describes changes in cathepsin L activity during early development in Eurasian perch (Perca fluviatilis) and determines to which extend a precocious proteolysis of the yolk reserves by activated cathepsin L could be involved in the seasonal decline of egg and larval quality. During embryogenesis and early larval stages, samples were collected for determination of fertilization and hatching rates, assays of cathepsin L activity, and evaluation of larval resistance to stress (osmotic shock and fasting). Cathepsin L activity increased significantly during the embryonic development, reaching a maximum of 177.1 +/- 12.3 nmol/min/mg fresh weight on day 1 post-hatching and significantly decreasing on day 3. Activity increased significantly during the spawning season and individual variations between egg strands became very high during the second half of the spawning period. An inverse relationship was established between the cathepsin L activity in 7-day old eggs and the decrease of hatching rate. A negative exponential regression was calculated between the cathepsin L activity of eggs and the resistance of corresponding newly-hatched larvae to osmotic shock. Resistance to fasting was significantly reduced in larvae from eggs with cathepsin L activity higher or lower than 20 nmol/min/mg (lethal time(50) = 4.7 +/- 0.7 and 3.5 +/-0.4 days, respectively). The involvement of cathepsin L in the degradation of yolk reserves and its potential consequences on the quality of perch eggs and larvae are discussed in relation to results reported in salmonid fishes.
(Fac Univ Notre Dame Paix, Unite Rech Biol Organ, 61 Rue Bruxelles, B-5000 Namur, Belgium, e-mail: Patrick.Kestemont@fundp.ac.be)