Abstract
BackgroundMarking mosquitoes is vital for mark-release-recapture and many laboratory studies, but their small size precludes the use of methods that are available for larger animals such as unique identifier tags and radio devices. Fluorescent dust is the most commonly used method to distinguish released individuals from the wild population. Numerous colours and combinations can be used, however, dust sometimes affects longevity and behaviour so alternatives that do not have these effects would contribute substantially. Rhodamine B has previously been demonstrated to be useful for marking adult Aedes aegypti males when added to the sugar meal. Unlike dust, this also marked the seminal fluid making it possible to detect matings by marked males in the spermatheca of females. Here, marking of Anopheles gambiae sensu stricto with rhodamine B and uranine was performed to estimate their potential contribution.MethodsTwo fluorescent markers, rhodamine B and uranine, were dissolved in sugar water and fed to adult An. gambiae. Concentrations that are useful for marking individuals and seminal fluid were determined. The effects on adult longevity, the durability of the marking and detection of the marker in mated females was determined. Male mating competitiveness was also evaluated.ResultsRhodamine B marking in adults is detectable for at least 3 weeks, however uranine marking declines with time and at low doses can be confused with auto-fluorescence. Both can be used for marking seminal fluid which can be detected in females mated by marked males, but, again, at low concentrations uranine-marking is more easily confused with the natural fluorescence of seminal fluid. Neither dye affected mating competitiveness.ConclusionsBoth markers tested could be useful for field and laboratory studies. Their use has substantial potential to contribute to a greater understanding of the bio-ecology of this important malaria vector. Rhodamine B has the advantage that it appears to be permanent and is less easily confused with auto-fluorescence. The primary limitation of both methods is that sugar feeding is necessary for marking and adults must be held for at least 2 nights to ensure all individuals are marked whereas dusts provide immediate and thorough marking.
Highlights
Marking mosquitoes is vital for mark-release-recapture and many laboratory studies, but their small size precludes the use of methods that are available for larger animals such as unique identifier tags and radio devices
Acute dye toxicity Rhodamine acute toxicity Of the three cages of males exposed to 0.8% rhodamine, after 3 nights of exposure, all males in two of the cages had died and this dose was not pursued further
Mortality is not substantial and rhodamine can be detected permanently in adults and in the spermathecae of females mated to marked males
Summary
Marking mosquitoes is vital for mark-release-recapture and many laboratory studies, but their small size precludes the use of methods that are available for larger animals such as unique identifier tags and radio devices. Rhodamine B has previously been demonstrated to be useful for marking adult Aedes aegypti males when added to the sugar meal. Unlike dust, this marked the seminal fluid making it possible to detect matings by marked males in the spermatheca of females. One technique to determine some of these characteristics, mark-release-recapture (MRR), consists of releasing marked mosquitoes into wild populations and observing them in subsequent collections [1], the number of marking methods is limited. The rare earth mineral rubidium has been used to mark individuals and eggs [5] but its use is limited by the detection methods which include mass spectroscopy and X-ray fluorescence [6]. Paint marking patterns [1] have been applied in unique patterns and colours for individuals in at least one case [8] and can reportedly be performed quickly by skilled staff but do not allow detection of matings
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