Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: When in close contact with the Yellow Dog Tick, Haemaphysalis leachi, dogs show
clear signs of disgust or even nausea. It is accepted that the secretion is produced by
the tick in order to prevent the dog from removing the tick from its body with its
teeth, thereby increasing the chances for the tick's survival.
The composition of this secretion was studied in order to identify the chemical
compounds responsible for the repellent action of the secretion.
Because of the dog's keen sense of smell, the tick only needs to produce minute
quantities of this repellant, which significantly complicated the detection of the
different components by conventional GC-methods. Several sampling and sample
enrichment methods were explored, including solvent extraction, SPME sample
enrichment, adsorption on active charcoal, cryoprecipitation, sorption in a phasecoated
open tubular trap, as well as solventless sampling, in order to determine which
method would ensure an appropriate amount of sample for gas chromatographic
detection.
Two of these sampling methods yielded acceptable results: The first method consisted
of rinsing irritated female ticks with dichloromethane and, after concentrating the
sample by evaporation, GC-MS analysis using normal splitless injection. The second
method entailed collecting secretions by wiping irritated ticks with glass micro fibre
filter paper after which the paper was inserted directly into the inlet liner of the GCMS
system, where thermal desorption of the volatile constituents of the secretion
preceded gas chromatographic separation and mass spectral detection.
Live dogs were needed for the evaluation of the isolated material to determine
whether the samples had an aversive effect on them. The extract was separated into
different fractions, which were further separated into subfractions. After each
separation process, all the fractions were tested for efficacy in order to determine
which fraction contained the active components, narrowing down the number of candidate target compounds. It was concluded that a combination of aldehydes,
namely hexanal, heptanal, octanal, nonanal, decanal, undecanal and dodecanal, is
responsible for the dog repelling action of the secretion.
In most cases the semiochemicals of insects and mammals are secreted in a more
complex matrix to ensure prolonged activity. For this reason some of the other
compounds in the complex cuticular secretion of this tick species were also identified
during the course of this study. / AFRIKAANSE OPSOMMING: Honde toon duidelike tekens van afkeer of selfs naarheid wanneer hulle in noue
kontak kom met die afskeiding van 'n sekere bosluisspesie, die geelhondebosluis,
Haemaphysalis leachi. Daar word aangeneem dat die bosluis die afskeiding produseer
om te verhoed dat die hond dit met sy bek van sy liggaam verwyder. Hierdeur word
die oorlewingskanse van die bosluis verbeter.
'n Studie is gemaak van die samestelling van die vlugtige komponente van hierdie
afskeiding om die chemiese verbindings, wat verantwoordelik is vir die afweer van
honde, te identifiseer.
As gevolg van die sensitiwiteit van 'n hond se reuksintuig, is dit vir die bosluis nodig
om slegs uiters klein kwantiteite van hierdie afweerstof af te skei, wat die waarneming
van die verskillende komponente deur middel van konvensionele GC-metodes baie
bemoeilik het. Ten einde die mees effektiewe metode te vind wat 'n gepaste
hoeveelheid monster vir waarneming op 'n gaschromatograafdetektor sou verseker, is
verskeie monsternemings en -verrykingsmetodes ondersoek, naamlik oplosmiddelekstraksie,
SPME-monsterverrykingsmetodes, adsorpsie op aktiewe koolstof,
kriopresipitasie, sorpsie in 'n fase-belaagde oopbuisval en oplosmiddellose
monsterneming,
Twee monsternemingsmetodes het aanvaarbare resultate gelewer: Met die eerste
metode is geïrriteerde wyfiebosluise met dichlorometaan afgespoel en die ekstrak is
na indamping met behulp van monsterinspuiting sonder inlaatstroomverdeling deur
middel van GC-MS geanaliseer. Met die tweede metode is die afskeiding van
geïrriteerde bosluise met mikroglasveselpapier afgevee en die papier is direk in die
binnebuis van die inlaat van die GC-MS-sisteem geplaas, waar die vlugtige
komponente termies gedesorbeer is vir gaschromatografiese skeiding en
massaspektrometriese waarneming.
Om die aktiwiteit van die geïsoleerde materiaal te evalueer, is van lewende honde
gebruik gemaak, om vas te stel of hulle aversie teenoor die betrokke monsters toon.
Die ekstrak is in verskillende fraksies geskei, wat weer in subfraksies verder geskei is.
Alle fraksies is na elke skeidingsproses getoets vir effektiwiteit om vas te stel watter
van die fraksies die aktiewe verbindings bevat. Sodoende is die aantal moontlikhede
vir die teikenverbindings met elke skeidingstap verminder. Daar is gevind dat 'n reeks
aldehiede, naamlik heksanaal, heptanaal, oktanaal, dekanaal, undekanaal en
dodekanaal, gesamentlik verantwoordelik is vir die afweer van honde.
Insekte en soogdiere skei dikwels semioverbindings in 'n draermateriaal af om
daardeur meer langdurige werking te verseker. In hierdie ondersoek is dus ook 'n
begin gemaak met die identifisering van die ander verbindings wat in die besonder
komplekse kutikulêre afskeiding van hierdie bosluisspesie aanwesig is.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49920 |
| Date | 12 1900 |
| Creators | Marx, Brenda |
| Contributors | Burger, B. V., Le Roux, M., Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | af_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 112 p. : ill. |
| Rights | Stellenbosch University |
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