Cichlid conundrum. Any theories?

[PUHUCBLMX2]

Thanks modest man & Top Dog & others for replying to my last post and IDing a cichlid for me. It got me doing a little research on the fairly common Midas cichlid.

Anyway, a lake in neighboring Nicaragua (Lago Apoyo) has a few species of cichlids in it, the most famous probably being the Arrow Cichlid endemic to Lago Apoyo (a close relative of the Midas). The lake is a volcanic lake, rain water over time has filled in an extinct volcano crater. All the water that enters the crater stays in the crater or evaporates out, only rain water maintains the lake level. No rivers flow out and no rivers flow in (an endorheic lake).

My question: How did they get into there?

I have looked high and low on the internet and can't find much of a theory.

I have heard that carp and other egg scatterers can colonize a lake with eggs on birds feet. However, that seems unlikely with most cichlids, or any nest builders for that matter.

I have heard that some species like bass can be picked up in hurricanes or tornados and dumped in bodies of water close to where they were captured by the high winds (sounds unlikely, but there's some merit to the theory). However we are at 11 degrees, there are no hurricanes or tornados this close to the equator.

Any theories how a lake with no rivers running in or out of it gets fish in it? There are a few lakes in the area that have the same phenomenon.

 

[jagster]

birds that catch a fish drop it accidentally? sounds unlikely but only other explanation i can think of is humans

 

[Drstrangelove]

Lago Apoyo was formed 23,000 years ago and the volcano is not extinct. Over that span of time, it's possible that a hurricane moved some animals (via flood or wind), or birds, or people. Birds are the most likely culprit as they could have had eggs sticking on their feet which were deposited into the lakes.

Anyway, while this seems "unlikely", it only does so when one refers to a short period of time. What is unlikely to happen over a span of 50 years can be extremely likely if you extend it to 23,000 years.

 

[luvinbluegills]

Some of the historic recordings of "raining" fish and frogs over cities miles from any body of water have been tracked to freak storms and/or waterspouts that lifted fish into the air and carried them for some distance, dropping them alive and far from "home". It may not have required a particularly vicious storm to lift the debris from a shallow section of water containing eggs or swimming fish and deposit them there.

These events have a long history on record, and here's one from 2010 that happened in Australia;

The fish were all alive when they hit the ground so they would have been alive when they were up there flying around the sky.

'When I told my family, who live in another part of Australia, about the fish falling from the sky, they thought I'd lost the plot.

'But no, I haven't lost my marbles. All I can say is that I'm thankful that it didn't rain crocodiles!'

Meterologists say the incident was probably caused by a tornado. It is common for tornados to suck up water and fish from rivers and drop them hundreds of miles away.

Mark Kersemakers from the Australian Bureau of Meterology said: 'Once they get up into the weather system, they are pretty much frozen and, after some time, they are released.'

Lajamanu is located half-way between Darwin and Alice Springs, on the edge of the Tanami Desert.

This is not the first time residents of the small town have experienced fish falling out of the sky.

Resident Les Dillon, 48, said: 'In the early 1980s I was at the Alice Springs Tavern Hotel and, when I walked out the door, I saw all these little fish, fallen out of the sky.

source - http://www.dailymail.co.uk/news/art...stralian-town-Lajamanu.html?printingPage=true

 

[jgentry]

Just because there is no water entry doesn't mean there will not be fish. It just means that over a long period you may have some genetic diversity compared to other close by bodies of water. If you dug a 1/2 acre pond that relied only on rain water to fill it within a couple of years if would be full of life and likely contain several different fish species. Like mentioned above, they typically are moved by birds. Nature finds a way.

 

[PUHUCBLMX2]

Thanks guys for all the theories.

I figured that 23,000 years old is actually pretty young for a lake. Lake Baikal is 25 million y/o, and Clear Lake in California is 1/2million, for example. But then again I have never been much of a lake-age-guesser. j/k. On a serious note, I am utterly ignorant on lake ages, evolution times, etc.

I was thinking about lakes like Crater Lake in Oregon that are also volcanic lakes that have been around a while, and prior to human introduction, they contained no fish species (surely storms and birds contact it too).

I thought the Arrow Cichlid an interesting specimen because it is only found in the lake, no where else (suggesting that it wasn't put in there by humans, birds feet, or storms, however its predecessor probably could have been). The bird and water spout theory are supported geographically, Lake Nicaragua is only about 30-40k away and 200m lower. Does anyone know if Arrow Cichlids are mouth brooders?

thanks again.

 

[neutrino]

Touches on a larger subject I've done a good bit of reading on. There's actually a good bit of study of Lake Apoyo by biologists as to species radiation in an environment without geographical barriers to separate different populations. One theory as to how the lake was colonized:
http://www.hras.org/sw/sw4-06.html

Amphilophus species in other lakes resemble the Midas cichlid more than the Arrow cichlid, so Meyer believes the former is the ancestral form that may have blown into the lake on a hurricane.

But that's just one theory. I haven't seen anything indicating solid evidence or general agreement by scientists, not that I've spent as much time reading science stuff on Lake Apoyo as the African rift lakes or other areas of interest.

 

[PUHUCBLMX2]

Thanks neutrino,

That article was a good little read, sound logic. I would like to know how he estimated 10,000 years of evolution. Too bad there isn't a way to know what weather looked like back then, we don't seem to have tornados or hurricanes at 12degrees latitude anymore. I wonder how powerful of a storm is necessary to transport fish/fry/eggs/etc.

 

[neutrino]

I would like to know how he estimated 10,000 years of evolution.

I'm assuming it's a result of molecular dating, since it's not like there's fossils to work from and I haven't come across any sort of date or theoretical date for when a hypothetical hurricane seeded Lake Opoyo with cichlids, based on some other type of evidence (geological, etc.). All I've seen is the suggestion that it was a one-time event, not a series of events.

Basically, molecular dating tries to estimate biological events (species divergence, age of biological lineages, etc.) by looking at differences in DNA or protein sequences from either a known or presumed relative or ancestor and using a theoretical rate of change or 'clock' to come up with those kind of dates. Often, dates cited in television science and nature programs for the age of a species or other biological events are based on this methodology, though these programs rarely explain this.

Without getting too verbose or too technical, the whole molecular clock thing is tricky to problematic. It's actually controversial and was right from the early 1960s when the theory was first developed. How controversial it's presented as being depends on the source and the extent to which they rely on or are critical of the MCH (molecular clock hypothesis). MCH dates are often at odds with fossil dates or even with MCH dates arrived at by different researchers, depending on a variety of assumptions and methodologies.