Department of Genetics

Permanent URI for this community

https://scholar.sun.ac.za/handle/10019.1/21

Browse

Browsing Department of Genetics by Subject "Abalone -- Growth"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    The effect of triploidy on the growth and survival of the indigenous abalone, Haliotis midae, over a 24 month period under commercial rearing conditions
    (Stellenbosch : Stellenbosch University, 2008-03) Schoonbee, Lize; Brink, Danie; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
    ENGLISH ABSTRACT: Triploidy is the genetic state of containing three sets of chromosomes per cell in stead of two as in diploid organisms. The South African abalone (Haliotis midae) is naturally a diploid organism that sexually matures between four to eight years of age. Early sexual maturity is a disadvantage in cultured abalone stock, as the process of gonad development and spawning is energy demanding, causing energy to be diverted away from somatic growth. This same problem has been extensively experienced in diploid bivalve molluscs, where triploidy has since been applied as a means to prevent sexual maturation from occurring, thereby speeding up the growth process and shortening the time to marketing. Because triploidy was effective in bivalves, it was thought that it could contribute to faster growth in abalone as well. A procedure for the induction of triploidy in the abalone, Haliotis midae, was developed by De Beer (2004) and yielded up to 100 percent triploidy in treated abalone larvae. The next step was to compare the growth of the diploids and triploids to establish whether there was indeed a growth advantage on the part of the triploids, in view of commercial application. By using the same techniques as described by De Beer (2004), three groups consisting of triploid and diploid siblings were produced and subscribed to a comparative growth trial. The groups were spawned in three different seasons. The main objective was to establish whether there was in fact a difference in growth between diploid and triploid siblings, and whether seasonal effects were associated with growth advantages for either triploids or diploids. The two growth parameters measured were shell length and body weight. Measurements commenced at eight months of age, when the abalone could be individually tagged and continued up to the age of 24 months. The over-all results provided no convincing evidence of statistically significant faster growth of triploid juveniles compared to that of diploids up to two years of age. Growth differences were detected between seasons, but could not confidently be ascribed to seasonal environmental effects. The regression of shell length to body weight was similar for diploids and triploids.