Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Haliotis midae (HM) is one of five indigenous abalone species occurring along the coast of South Africa, and
is the only species commercially cultivated in open flow-through systems. Commercial production of HM
contributes the most to income generated from aquaculture species in South Africa. Exports in 2011 totalled
1036 ton, which amounts to an income of ZAR 369 million (40 million USD). Commercial production of HM is
characterized by a long interval (i.e. up to five years) to harvest. Genetic modification of HM to improve
growth rate in HM can potentially decrease the interval from hatch to harvest, which will contribute to
optimising the cost-efficient production of HM. However, a major concern in the production of genetically
modified (GM) abalone is their escape from production systems, and the potential impact of the GM animals
on the natural stocks in the surrounding environment. The implementation of containment methods to
prevent the escape from GM abalone from production systems will assist in the management of the potential
ecological risks escaped GM abalone may pose. Currently no containment strategies exist for the South
African abalone industry, which limits the use of transgenic biotechnologies to optimise the cost-efficient
production of HM. The study therefore investigated the potential of biological methods (triploid induction),
mechanical methods (polypropylene filter bags and obstructive materials), and chemical methods (sodium
hypochlorite and chlorine dioxide) to contain transgenic HM in open flow-through systems.
Histological evaluation of gonad tissue samples of 16 triploid male and 15 triploid female HM indicated that
triploid induction was unsuccessful in arresting gonad differentiation, development, and function. A
combination of immature and mature gametes was observed on both triploid male and female gonads. The
fertilizing potential of biopsied sperm obtained from triploid and induced diploid male HM was assessed in
fertilization trials using ova obtained from diploid HM. No larvae were observed from the fertilization
treatments of triploid male biopsied sperm, however, abnormal larvae (0.01% fertilization) were observed
when induced diploid sperm were used to fertilize diploid ova. Polypropylene filter bags (100 μm) were not effective in containing male and female gametes in the
broodstock section of the abalone culture system used in this study, and future studies should address
specialized methods of containment of HM gametes. Polypropylene filters (100 μm), resulted in effective
containment of larvae and settlement larvae, and in this study was not a more effective method of
containment than the current on-farm larvae containment protocol. The three obstructive materials were
effective in containing HM spat, and did not differ in their ability as containment methods.
Sodium hypochlorite and Biox™, chlorine-based chemicals, were effective in containing the five life stages of
HM, i.e. sperm, ova, larvae, settlement larvae and spat. The respective life stages were exposed to varying
concentrations of the respective chemicals (i.e. 10 ppm, 50 ppm and 100 ppm) over five exposure times (i.e.
4, 6, 8, 10 and 12 minutes). Sodium hypochlorite and Biox™, at the different concentrations and exposure times, resulted in mortalities in all five HM life stages, with higher incidences recorded at the higher
concentrations evaluated.
Future research on the effect of triploid induction on the endocrine system, and how effective gonad
maturation and function is suppressed, needs to be conducted. The aspects of mosaics occurring in induced
diploid animals warrant further investigation with a larger sample size to verify the findings of this study. The
production of true sterile individuals would improve the results to use of GM animals as a method of
biological containment. Incorporation of mechanical containment methods need to be kept in mind when
abalone production systems are designed. The use of chemical containment methods warrants additional
studies on the practical administration and the economic feasibility of the chemical into the water supply of
open flow-through abalone culture systems. / AFRIKAANSE OPSOMMING: Haliotis midae (HM) is een van vyf inheemse perlemoen spesies wat langs die kus van Suid-Afrika voorkom
en is die enigste spesie wat kommersieel in oop deurvloeistelsels geproduseer word. Kommersiële
produksie van HM dra die meeste tot kommersiële akwakultuur produksie by, met uitvoere van 1036 ton in
2011, wat gelykstaande aan ‘n inkomste van ZAR 369 miljoen (40 miljoen VSA dollar). Kommersiële
produksie van HM word gekenmerk deur 'n lang interval (d.i. tot 5 jaar) vanaf uitbroei tot oes. Genetiese
modifisering van HM om die groeitempo te verbeter kan potensieel die interval tot slagmassa verkort, wat
potensieel tot die optimalisering van die kostedoeltreffende produksie van HM kan bydra. 'n Groot bron van
kommer met die produksie van geneties gemodifiseerde (GM) perlemoen is hul ontsnapping uit
produksiestelsels en die potensiële impak van die GM diere op die natuurlike perlemoenpopulasies in die
omliggende omgewing. Die implementering van beheermetodes om die ontsnapping van GM perlemoen uit
produksiestelsels te voorkom sal die bestuur van die potensiële ekologiese risiko's wat GM perlemoen mag
inhou, vergemaklik. Tans bestaan daar geen inperking strategieë vir GM diere vir die Suid-Afrikaanse
perlemoenbedryf nie, wat die gebruik van transgeniese biotegnologieë vir die kostedoeltreffende produksie
van HM beperk. Die studie het dus die potensiaal van biologiese metodes (triploïed induksie), meganiese
metodes (polipropileen filters en obstruktiewe materiaal) en chemiese metodes (natriumhipochloriet en
Biox™) om as inperk strategieë vir die bestuur van transgeniese HM in oop deurvloei produksiesisteme
gebruik te word, ondersoek.
Histologiese evaluering van gonadeweefsel monsters van 16 manlike en 15 vroulike triploïed HM het
aangedui dat triploïed induksie onsuksesvol was om gonade differensiasie, ontwikkeling, en funksie te
onderdruk. 'n Kombinasie van onvolwasse en volwasse gamete is in gonades van beide manlike en vroulike
triploïed HM waargeneem. Die bevrugtingsvermoë van sperme wat versamel is met behulp van ʼn biopsie
metode van triploïed en geïnduseerde diploïed HM is geëvalueer in bevrugtingsproewe met ova wat van
diploïed HM versamel is. Geen larwes is waargeneem met die gebruik van die triploïed sperme nie, maar
abnormale larwes (0.01% bevrugting) het wel voorgekom met die evaluering van sperme versamel van
geïnduseerde diploïed HM. Die voorkoms van mosaïek diere (d.i. ʼn kombinasie van beide diploïed en
triploïed selle in een individu) wat ontstaan a.g.v. onvolledige triploïed induksie noodsaak verdere navorsing
met ʼn groter monster diere om die vermoë van triploïed induksie om HM steriel te maak, te verifieer. Polipropileen filters (100 μm) was nie effektief om beide manlike en vroulike gamete wat in die teelafdeling in
die perlemoenkultuursisteem in hierdie studie geproduseer is, vas te vang nie. Toekomstige studies moet
gespesialiseerde metodes wat insluiting van HM gamete moontlik sal maak, ondersoek. Polipropileenfilters
(100 μm) was effektief met die inkamping van larwes en vestigingslarwes, met die filters wat nie meer
doeltreffend as die bestaande inkampingsmetodes in die produksiesisteem was nie. Die drie obstruktiewe
materiale was doeltreffend ten opsigte van die inkamping van onvolwasse perlemoen individue, met die 3 materiale wat ewe doeltreffend in hulle vermoë was om die onvolwasse HM se ontsnapping uit die sisteem
te voorkom.
Natriumhipochloriet en Biox™, chloor-gebaseerde chemikalieë, was effektief om die onderskeie 5
lewenstadiums, d.i. HM sperme en ova, larwes, vestigingslarwes en onvolwasse HM se voorkoms tot hulle
onderskeie afdelings binne die produksiesisteem te beperk. Die onderskeie lewensstadiums is blootgestel
aan verskillende konsentrasies van die onderskeie chemikalieë (d.i. 10 dpm, 50 dpm en 100 dpm) oor vyf
tydsintervalle (d.i. 4, 6, 8, 10 en 12 minute). Natriumhipochloriet en Biox™ het ʼn letale effek op al vier
lewensstadia gehad, met hoër sterftes wat met hoër konsentrasies aangeteken is.
Toekomstige navorsing oor die uitwerking van triploïed induksie op die endokriene stelsel en hoe
doeltreffend die rypwording en funksie van die gonades onderdruk word, moet aandag geniet. Die voorkoms
van mosaïek diere regverdig ook spesifieke aandag in toekomstige navorsing. Die produksie van ware
steriele individue sou die gebruik van GM perlemoen as 'n metode van biologiese inkamping moontlik maak.
Inlywing van meganiese inkampingmetodes moet in gedagte gehou word wanneer perlemoen
produksiestelsels ontwerp word. Die gebruik van chemiese inkampingmetodes benodig verdere studies om
te verseker dat die chemiese middels so bekostigbaar en prakties as moontlik in water van 'n oop deurvloei
perlemoen produksiestelsel toegedien kan word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86530 |
| Date | 04 1900 |
| Creators | Fourie, Lize |
| Contributors | Lambrechts, Helet, Brink, Danie, Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xv, 104 p. : ill. |
| Rights | Stellenbosch University |
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