Validation of fluorescent dust marking of Culicoides biting midges and the design of a self-marking technique

Abstract

BackgroundInvestigation of insect flight patterns frequently involves the use of dispersal studies. A common method for studying insect dispersal is mark-release-recapture (MRR) techniques using wild-caught insects in their natural environment; however, this requires a suitable marker. At present, no studies have been performed to identify markers that are suitable for use in midges within the Obsoletus Group, and visible by eye or down a light microscope.MethodsA series of 11 experiments were undertaken to determine the effectiveness of three colours of Brilliant General Purpose (BGP) fluorescent dusts in marking Culicoides midges. Three areas were focused on: 1) dust properties, 2) the effect on Culicoides, and 3) dust application in the field.ResultsAll three dusts were insoluble in water, 10% washing-up liquid and 70% ethanol. They were visible down a microscope, with and without the use of a black light, and two were highly visible without the need for a microscope. The dusts remained adherent to the marked Culicoides for the duration of the experiments, did not transfer between marked and unmarked individuals or the environment, and remained adherent when the Culicoides were stored in an ethanol or water-based solution. The dusts had no effect on the mortality rate of the insects over the 48 hrs of the experiment. There were no significant differences between the recorded behaviours undertaken by undusted control Culicoides and the BGP fluorescent dusted Culicoides. Field-based marking of Culicoides can be achieved using a ‘self-marking’ technique, whereby the trapping vessel is pre-dusted with fluorescent dust prior to trapping the individuals to be marked.ConclusionsThis is the first study to identify BGP fluorescent dusts as markers for use with Obsoletus Group Culicoides. BGP fluorescent dusts provide a quick and effective method of marking and identifying Culicoides for both field and laboratory studies. The self-marking technique minimises the time needed to handle specimens prior to release.

A standardised method of marking male mosquitoes with fluorescent dust

“…The initial dust amounts tested with An. arabiensis were 1000 and 500 mg of dust per 100 male mosquitoes, based on the amounts used by Kluiters et al [10] to mark Culicoides midges but these severely impacted immediate post-dusting survival. Therefore, a subsequent series of dust weights were investigated per 100 males and mortality assessed after 24 h, i.e.…”

“…Fluorescent paints [6], dyes [7,8] and dusts [9,10] in an array of colours are commonly used, in addition to methods involving the use of radio isotopes [11], trace elements [12], protein immunomarking [13] and genetic or transgenic techniques, including mutations leading to a distinguishable phenotypic difference or transfection of a symbiont such as Wolbachia [14][15][16]. Currently, there is no universal marking method applicable to all insect species.…”

“…For over five decades, fluorescent dust has been applied during the pupal stage, resulting in the emerging adults retaining their mark [19]. There are several types of fluorescent dusts that have been used in previous insect marking studies, from manufacturers such as Brilliant General Purpose [10], RADGLO [20] Brian Clegg [21] and DayGlo ® [21]. DayGlo dusts are available in a broad spectrum of bright colours, allowing separate cohorts to be marked with different colours.…”

A standardised method of marking male mosquitoes with fluorescent dust

“…Fluorescent paints [6], dyes [7,8] and dusts [9,10] in an array of colours are commonly used, in addition to methods involving the use of radio isotopes [11], trace elements [12], protein immunomarking [13] and genetic or transgenic techniques, including mutations leading to a distinguishable phenotypic difference or transfection of a symbiont such as Wolbachia [14,15,16].…”

“…There are several types of fluorescent dusts that have been used in previous insect marking studies, from manufacturers such as Brilliant General Purpose [10] Mosquitoes can be marked by placing them in a dusted plastic bag and gently shaking them. Previous studies that use a shaking procedure to mark delicate insects including mosquitoes have reported high mortality immediately after dusting in addition to coating them with too much dust [22].…”