Family studies on genetic variability in growth and reproductive performance between and within test fish populations of the zebrafish, Brachydanio rerio

Abstract

The results of ecotoxicological tests are most likely to a certain extent affected by the genetic structure of the test organism populations. In this investigation the genetic variability of reproduction and growth performance was studied in the zebrafish, which is the favourite candidate for ecotoxicological tests. Four B. rerio populations of different origins were available. Full-sib families of all populations were hatched and reared separately to maturity according to a standard test procedure. In total, 118 femilies were analysed. The following parameters were recorded; egg number, hatching rate, spawning interval, individual length and weight of progenies at the age of 2 weeks and continuously every 2 weeks to the age of 20 weeks. Coefficients of variation (CV) were high for all traits studied, ranging between 40 and 90%, except fish length, with a CV of 20%. Significant differences between populations were found for spawning interval, hatching and survival rate. Within populations significant differences among families were observed for all traits. Heritabilities derived from full-sib analysis ranged from 0.4 to 0.6 for all parameters studied. The results indicate that variability in available populations of zebrafish in all traits studied is too high, even in unpolluted water, to allow a reliable judgement of water pollution by life cycle test. The development of test fish populations with defined genetic variability is therefore inevitable. Strategies to establish such test fish populations are discussed.