Egg quality determination based on the shape of the lipid vesicle in common dentex, Dentex dentex Franz Lahnsteiner 1 , Gemma Gime¤ nez 2 & Este¤ vez Alicia 2 1 Department for Organismic Biology, University of Salzburg, Salzburg, Austria 2 IRTA, Ctra. Poble Nou Km 6,Tarragona, Spain Correspondence: F Lahnsteiner, Department for Organismic Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria. E-mail: Franz.Lahnsteiner@sbg.ac.at Abstract The shape of the lipid vesicle (the ratio between the maximal and the minimal diameter and the shape coe⁄cient) of the eggs of Diplodus puntazzo and Sparus aurata is correlated with larval survival rate (%) and can be used as an egg quality marker as re- ported previously by Lahnsteiner and Patarnello (2005). In the present study, this method for egg qual- ity determination has also been validated for com- mon dentex, Dentex dentex, after introducing several modi¢cations in the calculation and evaluation pro- cedure in order to obtain higher sensitivity. In the present study, it could be demonstrated that the shape of the lipid vesicle is not only correlated with the hatching rate but also with the survival rate of 1, 2 and 3 days post hatch larvae and therefore it can also be used as an indicator of larval viability at early stages of development. Keywords: Dentex dentex, lipid vesicle, egg quality, larvae, embryos Introduction Eggs and embryos of many marine ¢sh are transpar- ent and contain a large and clearly visible lipid dro- plet (Shields, Brown & Bromage 1997; Vallin & Nissling 1998). As the lipid droplet is a prominent characteristic of the eggs, it might be useful as an egg quality marker. Investigations on the eggs of Diplodus puntazzo and Sparus aurata established this hypothesis as they revealed that the ratio of the max- imal to the minimal diameter of the lipid vesicle (RD) and the lipid vesicle shape coe⁄cient (SC) were correlated with larval survival (%) (Lahnsteiner & Patarnello 2005). The relations were best described using quadratic regressions and showed that lipid vesicles with a spherical or a very ellipsoidal shape are indicators of low embryonic survival, while lipid vesicles with a moderately ellipsoidal shape are indi- cators of high embryonic survival. The parameters determining and in£uencing the shape of the lipid droplet are unclear (Lahnsteiner & Patarnello 2005), although it has been hypothesized that the shape de- pends on the lipid composition of the vesicle and on the interactions between the lipid molecules and the surrounding water (Kralj-Iglic, Svetina & Zeks 1993; Svetina & Zeks 2002). As the lipid vesicle is located between the egg membrane and the yolk, the internal osmotic force and turgor pressure of the egg might also in£uence its shape. On the other hand, mechan- ical stress during egg manipulation could also alter the shape of the lipid vesicle. It also remains uncer- tain whether the shape of the lipid vesicle is corre- lated with embryo and larval viability in species other than S. aurata and D. puntazzo and in ¢sh kept under di¡erent hatchery conditions as those used in the previous study. These questions were the purpose of the present study in which common dentex, Dentex dentex, eggs and larvae were used. Material and methods The daily spawnings of two broodstock groups of common dentex were collected from 30 March to 27 June 2006.The groups were composed of ¢ve females: eight males and four females:six males, respectively. The ¢sh were stocked in two 4000L circular tanks connected to a recirculation unit (Carbo¤, Este¤ vez & Aquaculture Research, 2008, 39, 144^149 doi: 10.1111/j.1365-2109.2007.01865.x r 2008 The Authors 144 Journal Compilation r 2008 Blackwell Publishing Ltd