Molecular components related to egg viability in the gilthead sea bream,Sparus aurata

Abstract

In pelagic egg spawners, the production of large numbers of sinking eggs, unable to develop into embryos, represents one of the major limiting factors in controlled reproduction. The aim of this study is to elucidate the molecular differences between floating and nonfloating eggs at cytoplasmic and nuclear level. Comparison of analyses between floating and nonfloating sea bream Sparus aurata eggs evidenced differences in vitelline envelope protein components, such differences being probably related with the hydration process but not with fertilization as supported by the assessment of DNA that doubled after in vitro insemination. These data clearly indicated that the absence of embryo development in nonfloating eggs is not due to lack of fertilization. The cytoplasmic composition was also different, the number of protein components being higher in floating eggs, and these extra components may generate the appropriate osmotic pressure at the base of the hydration process. Some lysosomal enzymes, such as cathepsin D and L both involved in yolk proteolysis, in virgin nonfloating eggs were significantly higher with respect to floating ones; the levels of these two enzymes significantly increased in the latter after fertilization. On the contrary, in nonfloating eggs cathepsin L significantly decreased after fertilization. These changes may be related with a series of metabolic processes vital for the production of viable offspring. The capacity of egg transcription and the protein synthesis in these two types of eggs, indicated by the RNA/DNA and RNA/protein ratios, evidenced that the status of cell transcription rate and protein synthesis capacity is significantly higher in floating eggs. This, in turn, suggested that the lack of embryo development may be due to low levels of proteins involved in cell cycle regulation. Mol. Reprod. Dev. 58:330–335, 2001. © 2001 Wiley‐Liss, Inc.

Dietary fatty acid enrichment during the spawning season increases egg viability and quality inHippocampus hippocampus

“…Egg viability represents one of the major limiting factors in controlled reproduction (Carnevali et al . ), especially in seahorses where egg viability is a key factor and where the frequency of unviable eggs is often higher than 50% (Saavedra et al . ).…”

Oogenesis and Egg Quality in Finfish: Yolk Formation and Other Factors Influencing Female Fertility

“…In barfin flounder (Verasper moseri), cathepsin B mediates this proteolysis [149] however, in gilthead seabream (Sparus aurata) cathepsin L does [36,37]. Dysfunctional cathepsin D and L levels in ovulated eggs and recently fertilized embryos are related to low fertility in seabream [38]. Low levels of cathepsin D and cathepsin B expression in recently fertilized red spotted grouper (Ephinephelus akaara) embryos (0-24 h post-fertilization) also are associated with poor egg quality [39], further suggesting that proper processing of vitellogenin derived yolk proteins is a critical step during vitellogenesis and ovarian maturation and may lead to reproductive failure if disrupted.…”

Evaluation of egg quality in broodstock cobia Rachycentron canadum L.

“…Essential fatty acids including docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), arachidonic acid (ARA) and their ratios in egg were related to blastomere morphology and/or hatching success in cod (Pickova et al 1997;Salze, Tocher, Roy & Robertson 2005) in Asian sea bass Lates calcarifer B. Di¡erences in the biochemical composition between non-viable and viable eggs have been characterized for Asian sea bass (Nocillado et al 2000) and gilthead sea bream Sparus aurata L. (Carnevali, Mosconi, Cardinali, Meiri & Polzonetti-Magni 2001;Lahnsteiner & Patarnello 2003). (Tveiten et al 2004).…”