I’ve been thinking about a few posts on cichlid evolution at the moment, but don’t have too much time. These fish make Darwin’s finches look like absolute beginners in evolutionary terms. Lake Malawi alone has at least 500 species and many geographical variations – all thought to have evolved from a single (maybe 2) common ancestor(s) in a few million years. For anyone with some spare time, this site provides some photos of them. A small section on trophic (feeding) adaptations can be found here.
Anyway, as a short post, I would like to introduce some Central American cichlids. Parachromis dovii is a rather large and nasty predator. One problem it faces is the predation of its fry by other fish. Next up is Theraps (aka Hypsophorys, aka Copora) nicaraguense. This is a medium sized fish, but is easily bullied and can be out competed for breeding sites by the aggressive Archocentrus nigrofasciatus. A 12 cm male is a very big fish for this species and I have had 6-8cm fish attack me and draw blood when looking after their fry. There is another smaller species, Neetroplus nematopus, which by all accounts is even more aggressive. So, T. nicaraguense has a problem, these little fish get all the good breeding sites. The solution is rather unexpected. See if you can guess: P. dovii is a major predator of N. nematopus and A. nigrofasciatus………
Give up?
T. Nicaraguense helps bring up the fry of P. dovii and is therefore tolerated by them. Their own fry also benefit from the numbers of P. dovii fry in the area – a predator is more likely to grab one of them as they are more numerous. Som studies estimate that P. dovii would face extinction in some areas if it was not for this interspecific co-operation. There are some costs though, as P. dovii will also eat some juvenile T. nicaraguense too. Thre have also been some recorded incidents of T. nicaraguense “cheating” on the deal too. However, that is evolution for you – cheating can be of benefit to the cheats until their numbers rise and make it disadvantageous – if P. dovii numbers drop, so do T. nicaraguense numbers. Natural selection will then start to select against the cheats and a new equilibrium will be reached – this may then allow another cycle of cheating……
There are obviously some implications for the evolution of moral behaviour here – by helping others, you are actually being selfish and helping yourself. This is something the religious just don’t get – they think being selfish means that you kill and eat every thing – not cooperate.
Anyway, as a short post, I would like to introduce some Central American cichlids. Parachromis dovii is a rather large and nasty predator. One problem it faces is the predation of its fry by other fish. Next up is Theraps (aka Hypsophorys, aka Copora) nicaraguense. This is a medium sized fish, but is easily bullied and can be out competed for breeding sites by the aggressive Archocentrus nigrofasciatus. A 12 cm male is a very big fish for this species and I have had 6-8cm fish attack me and draw blood when looking after their fry. There is another smaller species, Neetroplus nematopus, which by all accounts is even more aggressive. So, T. nicaraguense has a problem, these little fish get all the good breeding sites. The solution is rather unexpected. See if you can guess: P. dovii is a major predator of N. nematopus and A. nigrofasciatus………
Give up?
T. Nicaraguense helps bring up the fry of P. dovii and is therefore tolerated by them. Their own fry also benefit from the numbers of P. dovii fry in the area – a predator is more likely to grab one of them as they are more numerous. Som studies estimate that P. dovii would face extinction in some areas if it was not for this interspecific co-operation. There are some costs though, as P. dovii will also eat some juvenile T. nicaraguense too. Thre have also been some recorded incidents of T. nicaraguense “cheating” on the deal too. However, that is evolution for you – cheating can be of benefit to the cheats until their numbers rise and make it disadvantageous – if P. dovii numbers drop, so do T. nicaraguense numbers. Natural selection will then start to select against the cheats and a new equilibrium will be reached – this may then allow another cycle of cheating……
There are obviously some implications for the evolution of moral behaviour here – by helping others, you are actually being selfish and helping yourself. This is something the religious just don’t get – they think being selfish means that you kill and eat every thing – not cooperate.
8 comments:
You don't need to go to the South American jungles to observe this behaviour. You see it all the time in Tom and Jerry, when Jerry gets the dug to beat up Tom.
True,
I've always thought the mouse was the evil one - it's always trying to steal stuff and cause trouble
For anyone with some spare time,....
I don't, I'm a very busy man.
Get on with it.
Hmmmm, aggressive fish. No problem, I come from Scotland and I wear shoes.
Seriously though Bill, you're asking for trouble having a 6-8 foot dangerous fish in your house and then try to steal it's fry up.
It's a fish eat fish world after all. It's interesting that one finds this behaviour a lot in nature, including ourselves.
Where are the altruistic fish, Zebras, Polar Bears, etc?
Are humans the only species that can show true altruism? I'm not even sure that we can.
As for the religious, this is their domain, to waste in whatever way pleases them.
Just so long as they say sorry at the end.
Reciprocal altruism is not that uncommon in nature, but the point is the others get something in return. I doubt some human motives too. It's a bit like if say, we went into a coffee shop with a complete and utter window licking retard with nae social skills and constantly listend to the incoherent inuedo filled ramblings of his barely functional mind (hypothetically speaking of course) for an hour every week - it may appear nice, but we are also letting the girls know that we are supportive and potential mate material that will stick around and look after the kids.
Of course. This (hypothetical) window licker with an obvious fear of women, would also make us look better, increasing our chances.
This easily intimidated creature would obviously back down when, say, threatened by another territorial male armed with Windolene. He's obviously an ideal subject for lengthy psychological testing.
On very rare occasions, as you know, the subject can display a mild form of Tourette's, uttering "Bum, Paps" over and over.
It's very sad.
I think we should put this hypothetical spacktard in a bin bag with some bricks and throw him in the canal, and get a puppy instead. It's the humane thing to do really
This hypothetical character - drive a motorbike does he?
Ah, must be a different hypothetical character to the hypothetical character I'm thinking of.
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