The parasite theme that Vanessa began seems to be continuing. The second text I wrote for her was about pentastomids, or tongue worms, which primarily inhabit the lungs of snakes. Then last week I met a biologist in Dundee who told me about a professor who had specialized in parasitism, at one stage studying rattlesnakes and their lung parasites in the basement of one of the departments there. He described going into that room and that the moment you stepped inside they all began to rattle inside their perspex walls. He said that inevitably as you crossed the room one would strike out, hitting the side of the case sharply, and at this point he found it impossible not to leap backwards. He said that the professor never jumped, and in fact was bitten several times, until even the anti-venom became extremely toxic and he could no longer use it.
The same professor made a field trip several years ago to the mangrove swamps of Democratic Republic of Congo, to study pygmy crocodiles and their parasites. The crocodiles are now facing extinction, because of their size and the fact they are not enormously strong and they can be easily hunted. The Congo river floods annually, replenishing pools in savannah regions with fish – the crocodiles live in these pools and feed off the fish stocks. When the waters recede, they burrow into litter and earth at the bottom and eat crustaceans and eventually have to wait out the dry season. This means that they are quite easy to find and catch. Hunters wrap their legs and jaws and tie them onto their backs. They live off their fat stores and can be carried like this for several weeks, then sold as fresh meat at markets.
Unexpectedly the next day I had an email from a naturalist and beekeeper who has been sending me fascinating information on bees and pesticides, and he told me a story about bird parasites too. One day walking, Graham found a gannet on the beach, healthy but unable to fly. He said that he learned that they are often found in that region, in Dunbar, exhausted after their migration from Africa. He wrapped the bird in a dog blanket and drove it home. The man from the SSPCA who collected it parted the bird’s feathers to show him lice that live in the web of the feathers, and can easily jump onto humans hosts, and even though they won’t live on them for long, they can bite.
On bird lice, he told me, “Almost every species of bird has its own specific species of louse – and the evolutionary relationship is extremely ancient; each species has hosted its own commensal parasite for millions of years.”
Apparently DNA analysis of the lice revealed entirely unexpected evolutionary information. It had always been assumed that bird with similar forms and habits could be related, like swifts, swallows and martins. However, when the swift lice were examined, against all expectations they found that the swift louse was closest in evolutionary terms to the peregrine falcon. And so, they came to understand that swifts descended from hawks which evolved to eat flying insects.