Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Abalone production is the largest financial contributor to aquaculture in South Africa and
practically all of the abalone produced is exported to Asia. This means that the product
must be globally competitive and many technologies have been applied to this cause.
One that specifically shows great promise for bivalve mollusc production is triploidy; more
precisely, sterility due to the induction of aneuploidy.
Under normal maturation, energy is diverted from somatic growth through sexual
maturation, therefore inhibiting or retarding gametogenesis through a process such as
aneuploidy is expected to increase growth and decrease the time to marketing.
Two studies preceding this one investigated the induction of triploidy through hydrostatic
shock (De Beer, 2004) and the comparative growth rate of triploid genotypes from 8 to 24
months, prior to the onset of sexual maturation (Schoonbee, 2008). During this
comparative growth stage, no convincing statistical evidence of faster growth or of
seasonal environmental effects could be obtained.
It was recommended that growth between triploid and diploid variants be compared
during the age period when sexual maturity becomes a factor to determine whether
triploidy in Haliotis midae is a useful biotechnological tool to improve biological
productivity and global competiveness of the abalone industry.
The growth measured as shell length and wet weight in the period from 29 to 62 months
showed a statistically significant difference in mean weight and mean length with diploids
showing a superior growth rate compared to their triploid siblings. This difference of 1.99
mm and 5.13 g was however not perceived as being commercially significant.
Important production parameters including canning yield percentage and gonadosomatic
index were also measured during this trial. For both these parameters, the triploid
genotype showed statistically and commercially significant improvement of 10.68%
increased canning yield and 28.42% reduction in gonadosomatic index when compared
to their diploid counterparts.
Triploid abalone was found to be not completely sterile; gametes and even mature
gonads were observed in some instances. Even though complete sterility was not
achieved there appeared to be a retarded gonadosomatic development in triploid variants. The delay in sexual maturation, together with the improvement in canning yield,
may justify triploidy’s commercial application, despite its reduced growth rate. / AFRIKAANSE OPSOMMING: Perlemoen produksie lewer die grootste finansiële bydra tot akwakultuur in Suid Afrika en
feitlik al die Perlemoen word uitgevoer na Asië. Dit beteken dat die produk moet
kompeteer op die wêreld mark en verskeie tegnologieë word reeds aangewend vir die
spesifieke doel. Een so tegnologie wat potensiaal toon ten opsigte van akwakultuur
produksie is triploïedie; meer spesifiek, sterieliteit veroorsaak deur aneuploïedie induksie.
Onder normale volwassewording, word energie weggeneem van somatiese groei
wanneer geslagsrypheid intree en daarom kan groeitempo verhoog word deur
gametogenese te inhibeer of te vertraag deur ‘n proses soos aneuploïedie en, word
korter tydperk benodig om bemarkingsgrootte te bereik.
Twee voorafgaande studies het gehandel oor die induksie van triploïedie deur
hidrostatiese druk skok (De Beer, 2004) en die vergelykende groeitempo van triploïede
genotipes vanaf ouderdom 8 tot 24 maande (Schoonbee, 2008) alvorens geslagsrypheid
intree. Tydens hierdie vergelykende groeifase kon geen statisties betekenisvolle
aanduidings van vinniger groei of seisoenale omgewingseffekte aangetoon word nie.
Die studie handel vervolgens oor die uitbreiding van die vergelykende groeistudies
tussen triploïede en diploïede genotipes tot ouderdom van 62 maande wat die intrede
van geslagsrypheid insluit, ten einde te bepaal of die induksie van triploïedie in Haliotis
midae voordele inhou ten opsigte van produksiedoeltreffendheid en mededingendheid op
wêreldmarkte.
Groei gemeet in terme van skulplengte en lewende massa oor die tydperk van 29 tot 62
maande het statisties betekenisvolle verskille getoon in gemiddelde massa en lengte van
diploïede genotipes bo die van triploïede verwante individue. Die verskille van 1.99 mm
en 5.13 g kan egter nie as kommersieel betekenisvol beskou word nie.
Belangrike produksie eienskappe waaronder persentasie opbrengs van eindproduk en
die gonadosomatiese indeks is ook bepaal. Vir beide die produksie eienskappe het die
triploïede genotipe statisties sowel as kommersieel betekenisvolle verbetering van 10.68% getoon vir opbrengs en 28.42% verlaging in gonadosomatiese indeks in
vergelyking met die diploïede genotipe.
Triploïede genotipes was nie volledig steriel nie, gegewe die aanwesigheid van gonades
en gamete in sommige individue. Selfs al is totale steriliteit nie bereik nie, het dit wel
voorgekom asof daar vertraging in gonadosomatiese ontwikkeling plaasgevind het in
triploïede genotipes. Die vertraging in geslagsrypheid tesame met die verhoogde
persentasie opbrengs van die eindproduk hou voordele in bo die andersins effense
stadiger groei van triploïede genotipes.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/18082 |
| Date | 12 1900 |
| Creators | Prins, Nico |
| Contributors | Brink, D., Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 113 p. : ill. |
| Rights | Stellenbosch University |
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