Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The indigenous abalone, Haliotis midae has been a successfully cultured aquaculture
species in South Africa since 1990. It has a slow growth rate and takes from two to five
years to reach market size. Like for most other commercially important abalone species,
the slow growth rate of H. midae is a cause of concern with regard to the profitability of
farming and global competitiveness of the species.
Ploidy manipulation of the maternal genome, a universally growing practice in shellfish
culture, is considered a promising method to improve the growth rate of abalone - a
desirable trait in aquaculture organisms from a commercial perspective. This
manipulation technique is employed to achieve sterility, which results in limited gonad
development. The consequent re-allocation of resources to somatic growth results in
improved growth.
The purpose of this study was to establish a viable method for the induction and
validation of triploidy, on a commercial scale, in the South African abalone, H. midae. The
focus was on hydrostatic pressure as a method of induction and flow cytometry as the
method of validation.
The results obtained confirm hydrostatic pressure as an effective method for the
induction of triploidy in H. midae, delivering high percentages of triploidy (>80%) over a
wide range of pressures and times, in 48 hour-old larvae. Hydrostatic pressure had a
negative effect on survival in 20 hour-old larvae. Flow cytometry was validated as a
reliable, fast and accurate, though expensive, method for identification of triploidy in
H. midae.
As an outcome of this study a manual of “Procedures for the Induction and Validation
of Triploidy in the abalone” is presented (Appendix 1) together with recommendations for
further studies on triploidy in the South African abalone, H. midae. / AFRIKAANSE OPSOMMING: Die inheemse perlemoen, Haliotis midae, is sedert 1990 ‘n suksesvol gekweekte
akwakultuur spesie in Suid-Afrika. ‘n Kenmerk van die spesie is die stadige groeitempo
van tussen twee en vyf jaar ten einde bemarkbare grootte te bereik. Soos vir die
meerderheid perlemoen van kommersiële belang, is hierdie stadige groeitempo rede tot
kommer met betrekking tot die winsgewende kweek en wêreldwye mededingendheid van
die spesie.
Die manipulasie van ploïdie van die moederlike genoom is ‘n toenemende praktyk in
skulpvisboerdery en word gereken as ‘n belowende metode om die groeitempo van
perlemoen te verbeter. Hierdie manipulasietegniek word gebruik om steriliteit te verkry
wat manifesteer as onderdrukte ontwikkeling van die geslagsklier. Die gevolg is die
herkanalisering van bronne na somatiese groei.
Die doel van hierdie studie was om ‘n lewensvatbare metode vir die induksie van
triploïdie op ‘n kommersiële skaal in die Suid-Afrikaanse perlemoen, H. midae, te vestig.
Daar is op hidrostatiese druk as metode vir die induksie en vloei-sitometrie as metode vir
die geldigverklaring van triploïdie gefokus.
Die resultate van hierdie studie bevestig dat hidrostatiese druk ‘n effektiewe metode
vir die induksie van triploïdie in H. midae is. Hoë persentasies van triploïdie (>80%) is oor
‘n wye reeks van drukke en tye in 48 uur oue larwes verkry. Daar is gevind dat
hidrostatiese drukbehandeling ‘n negatiewe effek op die oorlewing van 20 uur oue larwes
het. Vloei-sitometrie is bevestig as ‘n betroubare, vinnig en akkurate, maar duur metode
vir die identifikasie van triploïdie in H. midae.
As ‘n uitvloeisel van die studie word ‘n handleiding “Procedures for the Induction and
Validation of Triploidy in the abalone” (Appendix 1) aangebied tesame met aanbevelings
vir verdere studies rakende triploïdie in die Suid-Afrikaanse perlemoen, H. midae.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/16299 |
| Date | 12 1900 |
| Creators | De Beer, Mathilde |
| Contributors | Brink, D., University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | ix, 105 leaves : ill. (some col.) |
| Rights | University of Stellenbosch |
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