The data is in and my hypothesis that putting up bits and pieces of mites would increase my frequency of posting is falsified (sorry Kaitlin). In fact, in spite of the interesting discussion the last posting generated, and my intent to propose a General Theory of Oribatid Mite Leg Well Ornamentation (sorry Dave, could not resist the pun), I have let other duties drag me away from macromite. Now all is snow and ice and bare trees, though, and so sitting at the computer on a Sunday morning no longer seems like chore. So how about a bit of a bat mite – or tick if you prefer?
As a general rule, mammals are an okay habitat for mites: primates, even lemurs, carnivores, even and odd toed ungulates, sloths, armadillos, shrews, hares, rabbits, rodents, and marsupials all sport specialized mite parasites. Even duck-billed platypuses and echidnas have to deal with ticks and chiggers. Whales, dolphins, and porpoises are an exception – as far as I know they seem to have left their mites behind when they moved into the ocean – but other marine mammals such as sea lions, elephant seals, fur seals, and walruses are hosts of nasal mites in the family Halarachnidae. It is the bats, however, that seem intent on outdoing all other mammals in terms of the diversity and creepiness of their acarine inhabitants with at least 18 families and over 1000 species known. Several of these families are restricted to bats and there is even a genus of soft ticks, Antricola, that are exclusively parasitic on bats (well, there was a genus, recent research submerges Antricola into Carios).
Of course, bats are ONE OF the most successful group of mammals, with about 1,100 species known (~20% of all mammals), so this is only about one species of mite per species of bat. In comparison, only about 3,000 species of bird mites are known (from ~10,000 species of birds). So, either a higher proportion of bat mite species have been found or bats are great hosts. A simple explanation for the success of mites on bats is that bats like to hang out close together in protected spots and tend to be philopatric – they like to return to the same spot. Presumably these behaviours help bats to survive, but they also make life easy for parasites: lots of bats to eat and if they get bored with one bat, it is relatively simple to move to another. One of my favourite families of bat mites is the Spinturnicidae. These mites spend their lives on the wing membranes of bats and suck their blood and, well, they are strange and rather creepy looking – all fat legs and long hairs, especially in males where the body behind the legs is highly reduced (somewhat as in sea spiders).
Spinturnicids have been the subject of a fair amount of scientific study and some of the most interesting has been published by a Swiss researcher at the University of Lausanne, Nadia Bruyndonckx, and her colleagues (from around the world). One of their recent papers (see below) tested for co-speciation between European bats and spinturnicid mites. They found some evidence for co-speciation, but also for failure to speciate and for host switching. So, like much of evolutionary history, that of bat mites is complicated. That may be especially true in North America. Those behaviours that have favoured mites in the past probably facilitate the spread of whatever agent causes white nose syndrome: bat mites here may be facing a lonely future.
For more on bat mites see:
Bruyndonckx, N., Dubey, S., Ruedi, M., Christe, P. (2009): Molecular cophylogenetic relationships between European bats and their ectoparasitic mites (Acari, Spinturnicidae) Molecular Phylogenetics and Evolution 51: 227–237
Krantz, G.W. & Walter, D.E. (eds.). (2009): A Manual of Acarology 3rd Edition. Texas Tech University Press, Lubbock, 807 pages
Walter, D.E. & Proctor, H.C. (1999): Mites: Ecology, Evolution and Behaviour. University of NSW Press, Sydney and CABI, Wallingford. 322 pp.