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Re: Sibling predation (stringing it all together)


On 9 Mar 2001, at 6:28, James Honaker wrote:

> 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.

Sorry but I chose my words poorly. Clearly they are all related but 
basis for natural selection is that 'your' genes must survive because 
you are the fittest. The farther gains nothing by rubbing out his 
sons but his sons and faugthers benefit by reducing the competion 
(i.e.: their younger siblings and eggs).

> 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.

Kin selection is a response to selective presures other than 
reseource linitations or territory. To survive the monkeys have to 
look out for each other. Fish look out for themselves. The furthest 
they go is to protect their offspring. This is visable in killies i.e.: In 
an article by Erbel et al. in FAMA in I think 1996 or 97, the aurthors 
describe seeing AUS in the wild. One large male was seen 
surrounded by females and a group of younger males (his 
offspring?). Kin selection does occur in fish and cannot be ignored 
but it is not at the level seen in primates except in 
Neolamprologous brichardi and pulcher. At least not to my 
knowledge.

> 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).  

Good question! Lionesses will kill outside females not of their pride 
(inadvertanly ensuring gentic isolation). While such intraspecies 
aggression may have its behavioural root in various reasons it could 
be a factor in species/strain isolation. 

However, logic suggests that such intraspecies aggression would 
be more prevalent in isolated populations where there is increased 
competion which is why stream living killies such as dageti, 
annulatus and striatum do not seem to be botherred by their 
offspring or brethren. Your opinion?

On 9 Mar 2001, at 18:02, wshenefelt wrote:

> Egg-fry eaters
> I can say the following.  I have raised  Fp.Mirabilis Takwai, Fp
> Spoorenbergi, and A bivitatum in a group adult environment with 
no
> "observable" predation of eggs or fry by companion adults..  That 
is not to
> say there is none within the group of fry, or that maybe the egg 
production
> is so large that they cannot eat them all, however.the fry  range 
from newly
> hatched  to 1/3 inch in size with no real place to hide from the 
parents or
> others living in the tank swimming directly in front of the mouths 
of adult
> fish...
> ...I do pull fry and move them to a new tank once they are about 
1/3 inch long
> since from this size up, there seems to be a lack of "new 
hatched" fry and
> the fry I pull seem to be well fed!

So the older, maturing fry are eating their brethren in some form...

>  I have other species that only seem to ignore fry if it is a single 
pair in
> the breeding tank.

Again, the parents have nothing to gain by consuming their fry.

>  I have never found more than a single fry in with a pr of A schioetzi 85/1,
> Fp gardneri Misaje, Fp sjoestedti, A lamberti, and a few other species even
> when only a single pair was present..
> I do not know if it is a characteristic of the particular pair or not but
> seems to be that way over at least two to three generations and different
> pairs.

Interesting...

On 9 Mar 2001, at 17:28, Charles n Sue Harrison wrote:

> I could go through a long list of gardneri, roloffia and sjoestedti 
> which produce fry in the tanks with a pair or trio until the young 
> get to be about 1/2 in. They seem to be more aggressive than 
the 
> adults at this young age and more interested in eating. or at 
least 
> that is the way things are in my ammonia contaminated tanks.

This brings us to Jake's comments:

On 9 Mar 2001, at 16:27, jake levi wrote:

> Rather then a 'survival strategy' much more likely
> that the strategy consists of getting a wholesome
> balanced meal, i.e., eggs are good food. 

Certainly we can't ignore the obvious. The implications are 
debatable but clear: you are directly reducing your competetion in 
the long run.

On 9 Mar 2001, at 5:03, Scott wrote:

> I think it is more likely
> that the male GAR will leave the young males alone
> because they are still not competitors for breeding. I
> would think that if the young males reach maturity
> that the "fighting" will begin again the first time
> one of the offspring decides to get in on the
> spwaning. Also I do not think there is any strategy
> involved in egg consumption in that case other than
> any organisms natural response to utilize any
> available resource. In other words they eat what they
> can :-)

Good points. I have however had mature GAR in with daddy (twice 
his size) and spawning with the young ladies without agression. 
naturally if he tries to displace his farther natural selection will be 
put to the test. Back tot he FAMA article Erbel et al described the 
AUS male as BIG and robust, not a young fish. Clearly the young 
males that surrounded him were not his first kids. Others must of 
came and gone, chased off by the big male when they tried to take 
his spot.

In a few simple experiments I did, movign the mop arround and 
changing mop colour the emerging trend revealed that the eggs 
which yielded the most eggs had to be a combination of colour and 
placement. For AUS dark mops in shade was prefered while for 
DAG light mops in bright light were prefered. This suggests to me 
that the female chooses where he eggs will be layed. So the male 
with the best spot gets the best girls. Defence of the "perfect" 
territory must be taken into account. Naturally daddy wants to 
leave his spot to his kids if not intentionally then simply by inborn 
accident.

Unfortunetly my experiments were never concluded as the female 
AUS passed away before all variables could be properly explored. 
The DAG also hit a reproductive speed bump...

Bye for now


Tyrone Genade
tyronegenade at yahoo_com
http://www.geocities.com/tyronegenade

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P450 Lab, Biochemistry Department
University of Stellenbosch, 7602, South Africa
Ph: +27-021-808-5876, fax: +27-021-808-5863
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"Those who trust in the Lord for help will find their 
               strength renewed."
                          Isaiah 40:31
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