Thesis (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Metals occur naturally in the environment but since the industrial revolution the amounts
ofbioavailable metals in the environment have increased significantly. There are various
anthropogenic sources of metals in the environment. In recent years there has been an
increasing interest in the use of biomarkers in terrestrial invertebrates for the assessment
of the potential adverse effects of chemicals in soil ecosystems. Terrestrial isopods are
one of the groups that play an important role in the decomposition process as fragmentors
of dead plant material in soil ecosystems. They are also known to accumulate
contaminants in their bodies, especially in the hepatopancreas. Cadmium has no known
biological function and is deposited in the environment through a variety of sources.
Zinc on the other hand is one of the essential metals and play an important role in the
normal metabolism of animals. Zinc too, is deposited in the environment through a
variety of anthropogenic sources. The aim of this study was to undertake an
experimental and field evaluation of the role cellular change in the hepatopancreas of
terrestrial isopods can play in conjunction with other sublethal responses to contribute to
the assessment of the impact of cadmium and zinc in terrestrial ecosystems.
Porcel/io laevis was used as test species in the laboratory experiments in this
study, to conduct sublethal toxicity tests. Cadmium- and zinc sulphate were used as the
contaminants, applied separately and as mixtures. The isopods were weighed before the
beginning of the exposures and every week throughout the exposure period of six weeks.
At the end of the exposure period they were dissected to remove the hepatopancreas. The
zinc and cadmium content of the hepatopancreases and rest of the bodies of the isopods were determined by atomic absorption spectrophotometry. Hepatopancreas samples were
also prepared for histological analysis, and measurements of the Percentage Cellular Area
(PCA) were made using image analysis. Specimens of Porcellionides pruinosus were
collected from contaminated- and uncontaminated field sites. Hepatopancreas- and rest
of the body samples of P. pruinosus were also analysed for cadmium and zinc.
Histological sections of the hepatopancreas were similarly prepared and analysed, as in
the laboratory experiments.
Exposure to cadmium- and zinc sulphate affected the mass of P. laevis negatively
in the single metal exposures. However, these two metals "neutralised" each other's
effects in the mixture toxicity exposures, pointing towards an antagonistic interaction.
Administered cadmium- and zinc sulphate resulted in the accumulation of cadmium and
zinc in the isopods, especially in the hepatopancreas. In the mixture toxicity experiments
cadmium and zinc influenced the accumulation of each other. Cadmium- and zinc
sulphate, whether administered separately or as mixtures, changed the structure of the
hepatopancreas and this was quantitatively shown through PCA measurements. PCA of
the hepatopancreas of terrestrial isopods was shown to be a good general biomarker of
exposure and effects for cadmium as well as for zinc. It is suggested that PCA could
serve as a general biomarker to predict possible impairment of growth or mass change of
isopods exposed to cadmium and zinc mixtures. The findings of the field survey also
suggest that PCA may be suitable to be used as a general biomarker to measure metal
induced stress in woodlice from contaminated field sites. / AFRIKAANSE OPSOMMING: Metale kom natuurlik voor in die omgewing, maar sedert die industriële revolusie het die
hoeveelheid bio-beskikbare metale in die omgewing betekenisvol toegeneem. Daar is
verskeie antropogeniese bronne van metale in die omgewing. Die afgelope paar jaar was
daar toenemende belangstelling in die gebruik van biomerkers by terrestriële invertebrate
vir die assessering van potensiële negatiewe effekte van chemiese stowwe in
grondekosisteme. Terrestriële Isopoda is een van die groepe wat 'n belangrike rol speel
III die ontbindingsproses as fragmenteerders van dooie plantmateriaal III
grondekosisteme. Hulle akkumuleer ook kontaminante in hul liggame, veral in die
hepatopankreas. Kadmium het geen biologiese funksie nie, en word vrygestel in die
omgewing deur verskeie bronne. Sink, aan die ander kant, is een van die essensiële
metale en speel 'n belangrike rol in die metabolisme van diere. Sink word ook in die
omgewing vrygestel deur 'n verskeidenheid antropogeniese bronne. Die doel van die
studie was om deur eksperimentele en veldondersoek die rol van sellulêre veranderinge in
die hepatopankreas van terrestriële Isopoda in samehang met ander subietale response te
evalueer om by te dra tot die assessering van die impak van kadmium en sink op
terrestriële ekosisteme.
Porcellio laevis is as toets-spesie in die laboratorium eksperimente gebruik om
subietale toksisiteitstoetse mee uit te voer. Kadmium- en sinksulfaat is as kontaminante
gebruik, en is apart en gemeng toegedien. Die houtluise is geweeg voor die begin van die
blootstellings en elke week deur die loop van die blootstellingsperiode van ses weke.
Aan die einde van die blootstellingsperiode is hulle gedissekteer om die hepatopankreas te verwyder. Die sink en kadmium inhoude van die hepatopankreas en res van die
liggame van die houtluise is bepaal met behulp van atoomabsorpsiespektrofotometrie.
Monsters van die hepatopankreas is ook voorberei vir histologiese analise, en metings
van die Persentasie Sellulêre Oppervlak (PSO) is gedoen met behulp van beeldanalise.
Eksemplare van Porcellionides pruinosus is versamel van 'n gekontamineerde- en 'n
ongekontamineerde gebied. Monster van die hepatopankreas en res van die liggaam van
P. pruinosus is ook geanaliseer vir kadmium en sink. Histologiese sneë van die
hepatopankreas was ook voorberei en geanaliseer, soos in die laboratorium eksperimente.
Blootstelling aan kadmium- en sinksulfaat het die massa van P. laevis negatief
beïnvloed in die enkelmetaal-eksperimente. Hierdie twee metale het egter mekaar se
effekte in die mengseltoksisiteitstoetse "geneutraliseer". Dit dui op 'n antagonistiese
interaksie. Toegediende kadmium- en sinksulfaat het gelei tot die akkumulasie van
kadmium en sink in the houtluise, veral in die hepatopankreas. In die
mengseltoksisiteitstoetse het kadmium en sink mekaar se akkumulasie beïnvloed.
Kadmium- en sinksulfaat, apart of as mengsels toegedien, het die struktuur van die
hepatopankreas verander, en dit is kwantitatief aangetoon deur die PSO metings. PSO
van die hepatopankreas van houtluise is 'n bruikbare algemene biomerker van
blootstelling en effek vir kadmium en sink. Dit word voorgestel dat PSO kan dien as 'n
algemene biomerker om negatiewe effekte op die groei of massaverandering van
houtluise te voorspel wat aan kadmium en sink mengsels blootgestel word. Die
bevindinge van die veldondersoek dui daarop dat PSO gepas mag wees om gebruik te
word as 'n algemene biomerker om metaal-geïnduseerde stres by houtluise vanaf 'n
gekontamineerde gebied te meet.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52877 |
| Date | 12 1900 |
| Creators | Odendaal, James Philander |
| Contributors | Reinecke, A. J., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 138 p. : ill. |
| Rights | Stellenbosch University |
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