Investigating genetic and molecular aspects of growth of the tropical abalone Haliotis asinina

The tropical abalone Haliotis asinina is a wild-caught and cultured species that is found throughout the Indo-Pacific. It is also an emerging model species for the study of growth, reproduction and development of haliotids and other vetigastropods. H. asinina has the fastest recorded natural growth rate of any abalone and reaches sexual maturity within one year. As such, it is a suitable abalone species for studying genetic and molecular aspects of commercially important traits such as growth. This thesis reports the analysis of growth and other traits in a single cohort of H. asinina that consisted of 84 families that were generated via a full-factorial mating design consisting of 14 sires and six dams. Progeny were measured and then tested for parentage and RNA expression to explain the differences in size. During this study a shell disease was discovered and investigated. Estimating the amount of variation in size that is attributable to heritable genetic differences can assist the development of a selective breeding program. In Chapter 2, I estimated heritability for growth-related traits at 12 months of age in these 84 H. asinina families. Of 500 progeny sampled, 465 were successfully assigned to their parents based on shared alleles at five polymorphic microsatellite loci. Using an animal model, heritability estimates were 0.48 ± 0.15 for shell length, 0.38 ± 0.13 for shell width 0.36 ± 0.13 for weight. Genetic correlations were > 0.98 between shell parameters and weight, indicating that breeding for weight gains could be successfully achieved by selecting for shell length. A novel method for analysis of shell colour revealed that the proportion of blue in the shell was a very good indicator of shell length in this study. In Chapter 3, large and small abalone from the aforementioned experiment were compared for differences in RNA expression levels, using microarray gene expression profiling. Big and small abalone were each represented by three pools of RNA, which each contained RNA from four individuals from that size class. Comparison of these RNA pools identified 14 genes that were significantly differentially regulated between fast and slow growers (