Wednesday, 28 January 2009

Felis catus v Rattus norvegicus

Has one of the CFZ cats had enough of living at the headquarters in Woolsery? Helios 7 was spotted at the weekend sitting in one of the recycling bins - something that she was seen doing everyday after that - and one could only surmise that she was sitting there waiting for the collection to be taken away today. I am not sure where she thought she would be taken – perhaps to hunting pastures anew?

We have often thought that she may not be the sharpest pencil in the box, but this does rather take the biscuit.


As Helios 7 has started this blog today, I thought I would also add a little bit of interesting information I learned last night from my youngest daughter concerning toxoplasmosis, which is transmitted by contact with cat faeces.


There is a parasite that lives in cats’ intestines which, believe it or not, changes the behaviour of rats. This parasite is a single cell called Toxoplasma gondii and causes the above mentioned disease. You may all have heard of the threat this poses in human beings in respect of mental alterations, and the real threat it may cause in pregnant women whereby it may contaminate the foetus and cause mental illnesses, sight deficiencies and even death.


What you may not know, however, is the very interesting and somewhat fascinating fact (in a macabre feline sort of way) that when a rat is infected with this illness, the parasite takes on an inactive form in the rodent's brain causing it to basically lose its fear of cats. In some cases, rats even start to be attracted by a cat’s smell. This, of course, is not good news for the rat, which then becomes easy prey for its predator.


The cat then eats the rat and the protozoon returns to its original host and reproduces, thus completing its life cycle.


How’s that for an innovative and cunning way of catching your dinner? Infect them and lull them into a false sense of security. Isn’t nature wonderful?

Hmm, perhaps Helios 7 knew that all along, and was hoping to take her in-built rat-catcher to new hunting grounds after all. Trouble is, I think she needs to sit with the ordinary household waste rather than the newspapers and magazines. What was I was saying about sharpest pencils?

1 comment:

Dr Dan Holdsworth said...

I don't know if you've realised it, but this topic pertains very strongly to the subject of Cryptozoology, and in particular to the Large Eel Theory of lake monsters.

You see, not only land vertebrates get parasitised; fish do too, and by a lot more different varieties of protozoan and metazoan parasite; living in water gives a water-living single-celled parasite a lot more scope to attack than does a land-living parasite, though prey to predator relationships involving parasites have evolved many times in land vertebrates.

Anyway, consider what a fish parasite wants out of life: it wants to breed a lot, and infect a lot more host fish. A parasite of fish which infects a migratory fish such as an eel or a salmonid, say, faces a major obstacle in that its host will migrate at some point; in salmon the ectoparasitic sea lice (actually a crustacean) are killed by fresh water.

So, suppose a parasite evolves to exploit eels. It is rare, a poor swimmer (so likely a single-celled animal) and isn't found much in running water but only in still waters. Perhaps the parasite isn't actually a specific eel parasite, just as Toxoplasma isn't a human parasite but can easily infect us. This parasite would do two things to make its host a more suitable environment; it would neuter it to stop it wasting energy breeding (selective destruction of the pituitary gland would do this), and it would make the eel less likely to migrate.

This would mean you'd end up with an eel that would simply stay in fresh water, growing bigger and bigger. In a few cases, where the eel's immune system and the parasite managed an uneasy truce, such a parasitised individual could live far longer than is normal for an eel (Jon's research in the wilds of Blackpool demonstrates the longevity of eels in captivity).

Now, this could explain the presence of very big eels, and might explain morphological differences in eel bodyforms, and a modified known species is obviously a better candidate for a monster than is a prehistoric relic hanging on, but the point is, how do you prove it?

Ideas, anyone?

BTW, if you think this theory isn't completely barking, do let me know; my former PhD supervisor in Aberystwyth, Dr Mike Johnston, is a parasitologist with a particular interest in the parasitology of fish (I myself studied the sex pheromones of some common plant parasites).