X is for Xenopus Frog
Xenopus longipes, the Lake Oku clawed frog, lives in western Cameroon, high on the extinct volcano Mount Oku, in one lake that is held in an old volcano vent.
It is surrounded by montane forest.
The local people hold the lake sacred, which is lucky for the frogs, as the introduction of fish, always a possibility to feed an increasing population, would certainly be their demise.
These frogs live in the lake their whole lives. They are tongueless and feed by using their outstretched arms to feel for prey, and then use their hands to guide it to their mouths where it is drawn in by suction.
This frog is biologically extraordinary – instead of one pair of chromosomes in each cell of its body it has 12 pairs of chromosomes. Usually every organism has two sets of chromosomes, one inherited from the mother and one from the father.
If a species hybridizes or manages to breed with another species, where the chromosomes are of differing lengths, very rarely the chromosomes double, so that there are 4 of each instead of 2 . 12 chromosomes is incredibly rare.
Perhaps the frogs (which are the only frogs of this species in the lake now) bred with more than one other species a long time ago.
Species which have more than one set of chromosomes are known as polyploid. 12 sets of chromosomes makes this frog dodecaploid.
This gives it an evolutionary advantage as it will have many more choices of genes that would otherwise be unavailable to it. This might mean being able to cope with changes in environment more quickly than an individual with only two sets of chromosomes to choose from.
If the volcano erupted and the acidity of the water changed for instance, this might, if it did not kill them straight away, give them a better chance of survival.
But still these frogs will contain a great many silenced genes which are not expressed for generations – features of the frogs with whom they hybridised.
I will just say that much of what I was reading today about this was a complete mystery to me – above the bare facts I have been very suppositional.
© Liz Brownlee
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