Angelfish and other loners

Dick wrote:
On 21 Nov 2005 00:52:45 -0800, "Cliff L"
wrote:


NetMax wrote:


For these loners, was the process of evolution so harsh that every other
variant was exterminated, or perhaps their environments were so
inhospitable to having more than one of something? If their survival was
so precarious, it gives me the feeling that it's only by the slimmest of
chances that we have them here today, and that many unique fishes simply
did not survive long enough to have been seen by modern man. Or perhaps
these unique fishes were so successful that they simply mastered the
niche they found and prevented any competition through diversification.

I'm grateful we have discus and angels. But what *is* their niche?
In what situation do they have an edge over standard-shaped
cichlids?

Cliff


You all are discussing part of my problem with "Evolution", how enough
survived accidents in particularly unique niches can survive twice
within a reproducible time frame, it does take two to reproduce. Think
male and female Peacock, sure you can argue the female is attracted to
the beautiful feathers, but also think how hard it is for the male to
run to catch her or evade destruction from a less beautiful display.
And, how did the female come to find the riot of colors and patterns
"sexy?"

What you are neglecting in your conception of evolution is time.
Evolution happens slowly over a long period of time. Species develop
gradually - a new species doesn't just spring fully formed from Zeus's
head. (Even when you hear about certain theories arguing for "quick"
speciation, they're talking about over dozens of generations, at least,
not in one generation.) "Species" as a distinct grouping only makes
sense if you look at a single period of time. If you look through time,
one generation blends into the next.

To take your example of peafowl, there wasn't one sunny day when a
peacock with a large tail and a peahen with a lust for large tails
hatched and found themselves together - the species developed over time.
"In the beginning" there was probably just a dull bird. For some reason,
there happened to be a subset of females which *slightly* preferred male
birds with larger, brighter tails. Just through natural variation within
the species, there were males with slightly larger, slightly brighter
tails (but nothing close to what we see in peafowl today). These birds
mated, and produced offspring which were more likely, on average, to
have bigger tails, and like mates with bigger tails (since offspring are
more like their parents than a random bird in the population).

It turns out that the females which preferred birds with big tails did
better in their mate choice than those who preferred ones with duller
tails, even if you ignore tail causing genes. It takes energy to grow a
bigger tail - birds with big tails are more likely to be good at finding
food than dull tails (the ones that weren't would die). Birds with
bright tails are healthier (sick animals look paler) - more likely to
have genes that protect against disease. Mating age birds with big tails
are better at avoiding predators - they're easier to spot, so if they
survive, they must be better. Females which pick males with big tails
will thus select mates which are more likely to survive - their children
will be more likely to survive than those of dull females who choose
dull males. There can be some "freeloaders", birds with bright tails who
don't have other good genes, and are just lucky to have survived that
long. But over time, their offsprings' luck will run out, and bright
tails will be correlated to good genes.

Over time a few things can happen: a) Some other influence becomes big
and disadvantages those birds with big tails (e.g. increased predation).
The species makes a turn and other traits besides big tails get selected
for. b) The bright females choose bright males, and the dull females
choose dull males. Over time, they get more and more selective in their
choices, and the two groups no longer interbreed - you now have two
species, one bright, one dull. c) The bright birds have enough of an
advantage from those other genes that they become more numerous than the
dull birds, and eventually, the dull subset fades away.

The important thing is this all happens over time, and works with
averages and populations - there isn't a single moment or single bird
which we can point to and say "this is the first peacock!" The peacock
grew slowly from its duller ancestor. Individuals don't evolve -
populations do.

Further, I would like to see a specific gene that can accidentally
change to create a pattern such as seen on the Clown fish (or
peacock). You may find a nich rational, but finding one survivable
gene change requires real imagination. To make things more
complicated, recent knowledge about genes suggest one gene does more
than one thing, then there are all those other cellular functions that
must cooperate for the gene to survive and do something useful.

You answer your own question. Genes do multiple things. There (probably)
is no single "peacock tail" gene. The tail is created by multiple genes
which are also involved in other things. A slight perturbation in this
network may cause death (and routinely does - look at the number of dead
baby animals in the wild), but it may be more-or-less neutral, or may
cause a slight change that makes the animal *slightly* more likely to
pass that gene onto it's children than a "normal" animal will pass its
"normal" gene onto it's children. Over time that slight advantage will
build up in the population. "Evolution" doesn't care by what mechanism
it happens, or what the result appears like to humans - as long as the
animal is more likely to pass it's genes on than its competitor, that's
all that matters.

"Alpha" wrote in message
...

This is the one.

http://www.aquahobby.com/gallery/gpantodon.html


I have to admit that when I was in the trade and could've ordered any fish I
wanted, I never bought any Butterfly fish. I'd have to research their
requirements, set up a tank, train the staff and have a story ready for
customers, and I wasn't even sure if they were appropriate aquarium fish.
Sure interesting looking though.
--
www.NetMax.tk

"Cliff L" wrote in message
ups.com...
NetMax wrote:

For these loners, was the process of evolution so harsh that every other
variant was exterminated, or perhaps their environments were so
inhospitable to having more than one of something? If their survival was
so precarious, it gives me the feeling that it's only by the slimmest of
chances that we have them here today, and that many unique fishes simply
did not survive long enough to have been seen by modern man. Or perhaps
these unique fishes were so successful that they simply mastered the
niche they found and prevented any competition through diversification.

I'm grateful we have discus and angels. But what *is* their niche?
In what situation do they have an edge over standard-shaped
cichlids?

Cliff


Stealth. Most predator fish register much more predominantly across a prey
fish's lateral line, due to their width. Because Angelfish are so narrow,
they can literally sneak up directly behind an unsuspecting meal, and gobble
them up. Most cichlids use speed, manoeuvrability and strength in their
attack. Angelfish lack those talents, but they can drift around like a flat
leaf toward unsuspecting prey.

I don't know Discus well enough to be familiar with their survival
techniques, but I assume their unique shape is for a reason. I have the
impression that they are more of a micro-predator grazer, so their shape
might have something to do with their environment (squeezing through tight
roots), but this is speculative on my part.
--
www.NetMax.tk

"Empty" wrote in message
news
On Sun, 20 Nov 2005 11:01:49 -0500, NetMax wrote:

Vote #3 is not so obvious. perhaps the Elephant-nose fish or Mono
(Monodactylus argenteus with one cousin, the Sebae). Hatchetfish are
quite unique (Silver or Marble species). Anyone have any other
suggestions?

The reedfish is the only fish in its genus, and the only fish in family
polypteridae to depart from the basic bichir body.

The FW butterfly is likely a good candidate for this honour as well.

Indeed it is.

"NetMax" wrote in message
...
"Alpha" wrote in message
...

This is the one.

http://www.aquahobby.com/gallery/gpantodon.html


I have to admit that when I was in the trade and could've ordered any fish
I wanted, I never bought any Butterfly fish. I'd have to research their
requirements, set up a tank, train the staff and have a story ready for
customers, and I wasn't even sure if they were appropriate aquarium fish.
Sure interesting looking though.
--
www.NetMax.tk


I have had great success with them in community tanks. They are one of the
few with their own genus and species.

"Alpha" wrote in message
...

I have had great success with them in community tanks. They are one of
the few with their own genus and species.
===================
So did I, until they reached sexual maturity and decided to breed. They'd
then take over most of the 55g tank for themselves. I wont keep Angels
anymore.
--
My Pond & Aquarium Pages:
http://bellsouthpwp.net/s/h/shastadaisy
~~~ }((((o ~~~ }{{{{o ~~~ }(((((o

Koi-lo wrote:
"Alpha" wrote in message
...

I have had great success with them in community tanks. They are one of
the few with their own genus and species.
===================
So did I, until they reached sexual maturity and decided to breed. They'd
then take over most of the 55g tank for themselves. I wont keep Angels
anymore.
--
My Pond & Aquarium Pages:
http://bellsouthpwp.net/s/h/shastadaisy
~~~ }((((o ~~~ }{{{{o ~~~ }(((((o
So did I, until they reached sexual maturity and decided to breed. They'd
then take over most of the 55g tank for themselves. I wont keep Angels
anymore.
--
Thank goodness!!!
Spawning Angelfish should be in a tank by themselves anyway.

"Tynk" wrote in message
oups.com...

Koi-lo wrote:
"Alpha" wrote in message
...

I have had great success with them in community tanks. They are one of
the few with their own genus and species.
===================
So did I, until they reached sexual maturity and decided to breed. They'd
then take over most of the 55g tank for themselves. I wont keep Angels
anymore.
--
My Pond & Aquarium Pages:
http://bellsouthpwp.net/s/h/shastadaisy
~~~ }((((o ~~~ }{{{{o ~~~ }(((((o

Thank goodness!!!
Spawning Angelfish should be in a tank by themselves anyway.
===================
Exactly. Since I had *no interest* in spawning them or raising Angel fry
they were not given a tank to themselves. I sold them.
--
Koi-Lo.... frugal ponding since 1995...
My Pond & Aquarium Pages:
http://bellsouthpwp.net/s/h/shastadaisy
~~~ }((((o ~~~ }{{{{o ~~~ }(((((o