When Anne Youngman first asked me to do this presentation I put the phone down and found myself looking at the slides, jars and vials, containing hundreds of specimens of bat parasites, which as you can see take pride of place on my desk. I found myself wondering what the collective noun for a group of parasites might be. You get a herd of cattle, a parliament of owls, a murder of crows and even a boogle of weasels: what about parasites?
My first thought, given the reaction of most people to parasites was a yeeuch of parasites. Then I reflected that that doesn't match my own view: I find these strange creatures quite fascinating. Then I considered an omnibus of parasites, given the number of times I have searched in vain for specimens of a particular species, only to have several come along at once. I finally settled on a conundrum of parasites: there are many gaps in our knowledge and unasnwered questions about the parasites hosted by bats, so conundrum seems an appropriate noun.
What I would like to do today is introduce you to just a few of these conundrums or unaswered questions and hopefully show you how we, as active bat-workers, can make a contribution to answering these condundrums.
First though, for the benefit of those who haven't recently looked at page 54 of "The Bat Worker's Manual", which gives an excellent summary, here's a brief overview of British bat parasites, to put what follows into context.
The basic definition of a parasite is an animal (or plant), which lives on another animal and gains nourishment from the host, without benefitting it or killing it. It is also useful to understand the difference between ectoparasites, which live outside the host's body (e.g. fleas and ticks) and endoparasites, which live within the host's body (e.g. tapeworms or helminths). In this talk I will be concentrating on ectoparasites, and specifically those which are large enough to be found by us when handling live bats.
We should also consider host specificity: some parasites are generalists and may parasitise almost any warm-blooded animal. For example the ticks or hravest mites that pester me are as likely to pester my dog or a passing fox or deer. On the other hand, some parasites are highly host specific and will only parasitise a single species or perhaps a genus or small group of hosts which share a roost. Many bat parasites are highly host specific.
Let's briefly consider parasites taxonomy. British bat ectoparasites fall easily into five convenient groups. The arachnids are closely related to spiders and this is reflected in the fact that adults have 8 legs. These comprise the ticks and mites. Insect parasites of bats comprise fleas, bat bugs and bat flies.
There are two species of bat fly believed to be present in the UK, usually found on Daubentons and Bechsteins Bats. A third species is believed to be extinct. These animals are highly adapted to life on a bat. Although they are flies, their wings are reduced to simple buds.
A fascinating aspect of this subject for me is the lessons that bat parasites can teach us about their hosts. For example, when sampling mites on Natterer's and Daubenton's Bats in autumn I have often noticed a significantly higher parasite load on females and juveniles than on adult males. This presumably reflects the fact that the females and juveniles have been confined together within the maternity roost for a number of weeks, giving the mites the opportunity to reproduce and spread from host to host. The males on the other hand, will have been in smaller groups and able to move between roost sites much more frequently, reducing the opportunity for the parasites to spread.
My first conundrum relates to the Spinturnix family of mites: the Spinturncidae. These are the largest mites found on bats and often the most obvious to the naked eye. They are between 0,5 and 1.5mm long and are only found on the win and tail membranes of the bat, making them easy to see. This slide shows a Daubenton's Bat and you can just make out something within the red circle.
In 2003 Anne Baker of the Natural History Museum and Jenny Craven of Leeds University published a paper which brought together a piece of work funded by the british Ecological Society. They set out to gather all the known records of bat mites in Britain and to examine all available specimens. Their paper set out a checklist of species. This slide summarises their results for the Spinturnix family: eight species, each with the main hosts. However, there are two problems.
Conundrum two concerns the geographic distribution of ectoparasite species. To illustrate this I have chosen to use the Blyborough Tick Argas vespertilionis. This slide shows dorsal and ventral views of an adult. The ruler alongside shows millimetre divisions. I have selected this species because it is easily identified: it is almost entirely round and usually looks like a little 5p coin, either lumbering about the roost as an adult or as a larva, attached to a host, lying vertically within the fur.
The main chart here shows the existing distribution records in Scotland: just four records, some of them quite old. Does this indicate that this species is scarce? Or that it is declining, or limited in range to the west?
Conundrum 3 relates to the so-called Chigger Mites or Trombiculidae. This picture shows the larav of a member of this family. You can make out the mouth-parts to the left, sourrounded by the legs: only six of them as this is a larva. The remainder of it looks pretty much like a little orange jelly-baby.
This slide shows them attached to a host: in this case a Soprano Pipistrelle, with four larvae attached to her ear. They remain attached whilst taking a blood-feed, which provides what they need to metamorphose. After a few days they leave the host and as nymphs and adults they predate on smaller arthropods within the bat roost.
The final conundrum concerns bat bugs. This amazing picture was sent to me recently by Paul Hope and shows a Noctule with two bat bugs attached to it's forearm. My question is: are they Cimex pipistrelli or Cimex dissimilis? There is a long-standing uncertainty about whether both these species are present in the UK or not, fuelled by the fact that the differences are tiny and the taxonomy is the subject of some uncertainty. A DNA study in the Czech Republic aims to resolve these issues and specimens of bat bugs, especially from Pipistrelles, are sought to assist in this.
This slide shows how the bug uses it's stylet to go about feeding. You'll notice I have coloured the host a fetching pink, to reflect the fact that human bed bugs feed in exactly the same way!
This is where it gets interesting. The stylet is both flexible and prehensile and it commences probing around the flesh...
...until it finds a capillary and commences feeding. The probing and cutting through the flesh creates a contusion and slight swelling which is occasionally visible on the wing of bat. You may also find it on your own body if your choice of last-minute bargain holiday doesn't wuite work out as you had hoped!
I hope you have found this talk interesting and that one or two of you may still feel like eating your lunch. Hopefully I have also shown what an opportunity there is for us, as active bat workers to make a very real difference to the sum of human knowledge in this area. The four conundrums I have described barely scratch the surface: the simple fact is that any and all parasite records are useful.