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Sibling predation (was: hormones?)
Tyrone wrote:
>I have had group of gardneri spawn and get quite a number of fry
>grow up in the tank seeing no decline in egg production. Once the
>fry began to mature the egg production went down and no new fry
>emerged. I watched and saw the younger fish follow their parents
>and eat the eggs that they layed. I have not observed with aus yet.
>Ii is also common that other females will eat each other's eggs. I
>have never seen a male pick at a mop.
>
>This seems to be part of an inborn genetic survival stratergy: why
>allow other geneticly unrelated stock to occupy the space you
>want your children to occupy. This is partly also why there seems
>to be no aggression between a male GAR and his sons while they
>can be bloodthirsty towards each other.
Of course you don't mean that your siblings are not genetically related to
you, for example having two siblings survive would transmit as many
of your genes as having one child survive.
There are plenty of species that look after siblings for exactly this
reason. A classic example is Vervet monkeys (cite below) who signal the
presence of predators, which warns the whole group but raises the risk of
predation to the signaler, when the group of monkeys is closely related
genetically (for example an isolated family band) but in geographic
locations where lots of families intermingle, no monkeys signal predators,
because you are no longer saving your family who carry your genes, but
unrelated Vervet monkeys.
This is not to bash Tyrone, but he did raise the wonder in my mind if
anyone knows if predation on siblings, young, eggs etc. which seems to
vary significantly across different Killifish species might be a similar
function of the genetic isolation of the original species (or even
location strain). That is, perhaps Killies that come from smaller pond
systems where most of the other Killies you meet are related to you
genetically would be like the Striatums and Annulatus of the world, and
ignore eggs and young, and stock from more open systems with more mixing
of lineages and genes would be like my own gardineri Akure's who spend
most of their life rooting through the java moss for young and even chowed
3/4 inch fry I mistakenly returned too soon.
I'm not a biologist, but I do study evolution for a living. I would
welcome having my stylized facts corrected if I have paraphrased
incorrectly.
james.
Cheney and Seyfarth (1990). ``How Monkeys See the World.''
U.Chicago Press.
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