B-liners:
Some thoughts about the Tracheal mite resistance in honey bees.
In recent years, we have learned about mechanisms of honey
bee resistance to varroa mites, Thanks to Apis cerana and to Peng et
al. 1987's study in China. A contrast comparative study showed that
the hygienic mechanism is an effective method of keeping varroa mites
under control in the Asian bee colonies. Several studies followed this
study and shed more lights on other mechanisms of resistance to
varroa.
On the other hand, there are few studies which have focused on
resistance to tracheal mites. These studies are not as advanced as the
varroa study due to several factors:
1. There is no race or line of bees known for resistance as we have
in the case of cerana bees. All the known resistant bees such as the
Buckfast bees or tracheal mite resistant bred bees were recently
confirmed as resistant bees using sophisticated bioassay tests. In
addition, we need to test the bee lines to make sure that they are
resistant before conducting any study. Thus, any study will
take more time and will cost more money to conduct.
Who is going to pay the bill?
2. The microscopic size of tracheal mites and the nature of the
parasite as an internal obligatory parasite cause difficulty in
handling the mites and conducting this type of detailed study.
Although the above mentioned difficulties, there are several
reports about possible mechanisms for tracheal mite resistance in
honey bees. Several studies (Lee 1963, Gary and Page,1987, Gary et
al. 1989, Nasr et al. (Unpublished data) and others reported
differences in abundance and prevalences of mites in honey bees. These
tested bees had different relative attractiveness to tracheal mite as
they age. Tracheal mites preferentially infest bees <24 h-old and
the frequency of infestation declines quickly thereafter; Bees >4
days old were rarely infested. Bees of mite resistant lines could be
attractive to mites for a relatively shorter period of time than
susceptible lines or bees of mite resistance could be less
attractive to mites during that window of time in their age than the
susceptible lines. The end result in both cases is that fewer
migratory female mites migrate into their tracheae over the four day
period when bees are attractive to mites. There is recent unpublished
research showed that tracheal mite resistant bees are less attractive
to infestation by tracheal mites during that window of their age than
susceptible bees.
Based on the deferential attractiveness of honey bees to
tracheal mites, we (Ontario Bee breeders, Canada) are using a bioassay
test to identify bees less attractive to mites within the first 7 days
of their life. The identified lines are then subjected to a breeding
system to increase the frequency of the criteria in the subsequent
generations.
There was also an early study showed that the presence of
spiracular hairs had no effect on mite infestation. Recently, some
researchers restudied this mechanism. Early results showed that bees
with hairy spiracles had less mites!
Researching the mechanisms of resistance to tracheal mites will
progress and advance in the coming years. More focus will be on the
biology of bees (population dynamics, broodless periods, etc.) in
relation to mite population. In addition physiological, physical, and
behavioural mechanisms to explain the resistance to tracheal mites
will be investigated.
Medhat Nasr, Ph.D.
Ontario Beekeepers' Association
Ontario, Canada
>
>
>
> > On 30 Jan 97
> at 18:13, Stan Sandler wrote: mechanisms of tracheal mite > tolerance
> >
> > > The interesting discussion about varroa mite resistance / tolerance has me
> > > curious about tracheal mites now. In the types of bees that have shown
> > > greater tolerance what mechanisms contribute to this?
> >
> > We have been working with Dr.Nasr and the Ontario Breeding program for a
> > number of years now. They can tell us wether our strain of bees are
> > resistant or tolerant to T-mites, but not a word about the mechanisms. It
> > has been known, for a long time, that the mature mite moves out and looks
> > for a new host under 4 days old. Beyond that, nothing.
> > It is thought that the mites don't like the taste of the new host and
> > move back out, as there is record of bite marks in some tracheae but no
> > mites.
> >
> > *********************************************************
> > The Bee Works, 9 Progress Drive Unit 2, Orillia,
> > Ontario, Canada. L3V 6H1
> > David Eyre, Owner. Phone/Fax 705 326 7171
> > Dealers for E.H.Thorne & B.J.Sherriff UK
> > http://www.muskoka.net/~beeworks
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> >
>
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