Effects of Mouth Brooding on Juvenile Behavior

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Tifftastic

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I don't know if anyone is interested but I have found some really cool stuff with this research so far.

Here's some general info:
Species: Malawi Eye Biter (Dimidiochromis compressiceps) (previous Haplochromis compressiceps)
SIMPLIFIED METHODS:

Spawning and Raising
  • Spawned group of wild caught D. compressiceps in a group tank, checked daily for holding females or spawning behavior
  • Holding females were isolated to reduce stress
  • After the third day 30-40 eggs were gently removed and raised in a 1 L Erlenmeyer flask with air stone and Methylene blue and checked daily
  • Female was removed, Elastomer tagged and returned to main tank
  • Juveniles raised in artificial environment were moved to same size and set up tank as naturally raised eggs
Size
  • All juveniles were measured on the day of release
  • Removed group was measured daily until the same size as the natural juveniles on day of release
Behavior Testing
  • The day after release 16 juveniles from the control (natural) group were individually placed into a 10 L opaque white bucket filled with approx. 3 L of tank water and filmed for 3 minutes upon being released from the net
  • Fish were left for 24 hours to acclimate
  • Eight individuals were randomly selected on the following day to be exposed to a startle and chase, filmed for one minute, chased with a net in the manner used to catch them for one minute, and then filmed for one minute following
  • The remaining eight individuals were exposed to a startle with a novel object (drop a marble in the bucket), filmed for one minute, marble dropped on opposite end of bucket and filmed for two more minutes
  • When treatment group (removed individuals) reached a size that was not statistically different from the first group on testing day the same procedure was followed
  • This was repeated with the spawn of three females
RESULTS SIMPLIFIED:

Size

  • Treated groups were significantly smaller upon the day of release than control
  • Treated groups were also less developed at day of release than control and still retained their yolk up to 20 days in some cases where control groups were fully free swimming at 14 days
Behavior Tests
  • Treated groups had significantly less activity in the novel environment and no difference in response to startle stimuli to the control
  • Boldness: treated groups were significantly more bold than the control
  • Predator avoidance: treated groups had significantly stronger predator avoidance tactics
  • Additionally: there was a significant difference in predator avoidance tactics between families
DISCUSSION SIMPLIFIED:
  • There is evidence that mouth brooding increases predator avoidance behaviors in offspring
  • There is evidence that mouth brooding increases bold behaviors in juveniles
  • Bold behaviors are associated with increased fitness due to increased foraging and finding of mates
  • There is evidence that maternal effects can differ among females: some females are better mothers
  • Unknowns: are effects stronger in different sexes? How long do the effects last? Does this hold true in other species? What is causing the faster development in fry raised in the mother's buccal cavity? How does this effect social behaviors?

The results haven't been published yet but we are confident that after adding in another family or two we will have a really good publishable paper. Currently, we could publish it now, but we'd like to get some of my stats that are borderline over the line and into significant which would really increase the amount I can conclude from my research.
The project I am working on at the moment is looking at maternal effects on shoal cohesion of juveniles and while I haven't waded through the massive data sheets my video analysis has generated, observations are suggesting that those raised in the artificial environment startle easier in a group, don't stick together as much and don't have a defined leader when they do shoal. Its been really interesting! Of course, obligatory pics of my gorgeous males.

(This is me avoiding my massive data sheets as long as I possibly can)

Slide1.JPG Slide2.JPG Slide3.JPG Slide4.JPG
 
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Cool reading. Thx.
 

Tifftastic

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Another interesting thing that happened is in two of the three families there were some jaw deformities. This deformity, bottom picture, only occurred in eggs that were removed from the female. The question raised by this is whether or not there is something in the environment of the buccal cavity that does not allow juveniles like this to hatch, or if there was something external in the flask (though each were raised in a new clean flask and at separate times) that caused the deformity? Another option is does the female somehow selectively remove these individuals from the clutch before I am able to see them? Or lastly, was it just random luck of the draw. Its impossible to tell at this point. However, one female from study one was used to produce fry for study two and though she produced fry with this deformity the first go round, none were present in the second.
The deformity present does not allow juveniles to properly consume food and all of them perished within four days of absorbing the yolk. Fish pictured are of the removed group at 20 days post hatching when the yolk was nearly fully absorbed.


JawDifferences.jpg
 

SnakeIce

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There is a third possible explanation, that the potentially deformed fry do hatch and that the physical parameters in the mouth prevent it from developing to such extreme. In other words they might get massaged into normalcy.

I suppose if you remove some in the future and some of them develop deformities, one method to test that the mouth conditions normalize fry could be found by finding a way to count the eggs that remain in the mouth before they hatch. Then compare that number with the number of released fry and whether they are all normal.

1. So if some removed fry are deformed and the number of eggs in the mouth and normal fry are equal, then the mouth normalizes potentially deformed fry or there is something damaging the removed fry/eggs.

2. If the number of eggs in the mouth is more than the number of normal fry released then the deformed fry are culled somehow by the mother.

This could possibly give you the answer on whether the cause of the deformities is nature or nurture.
 
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Tifftastic

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That is one way we were thinking about looking at it. The problem is figuring out how to determine that. With my current stock of females being wild caught they tend to stress and purge eggs much easier than tank raised individuals would. I had one female that simply removing her to the smaller tank caused her to cough up all of her eggs, it was very depressing. So, I do know that too much inspection of the fish would be an issue.

This particular deformity is potentially caused by an excess hormone that causes a change in the regulation of a specific enzyme, I can't remember which one, during skull formation. My supervisor purposefully bred some like this, of a different species, a few years ago to use as an extreme in the measurement of skull slopes based on the levels of that hormone.

It is something that we plan to find a way to investigate if I manage to get this PhD spot.
 

SnakeIce

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Not like you can walk up and tell them, "Say Ahhh". Surely a puzzle anyway.
 

Tifftastic

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Ahhh! If only I could!!!

Getting some interesting results on shoaling cohesion in a novel envinronemnt so far! Should be some great results!
 
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rufioman

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Great series of posts. It's clear you are an awesome enthusiast! Mouthbrooders are my favorite fish, haha. I used to watch my Afro cichlids brood around all the time.
 

Tifftastic

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Great series of posts. It's clear you are an awesome enthusiast! Mouthbrooders are my favorite fish, haha. I used to watch my Afro cichlids brood around all the time.
Thanks! I really do love this topic and posting here is great way for me to simultaneously procrastinate and get a better understanding of what I am trying to work on while not feeling too guilty lol. Mouthbrooders really are fantastic and I am so happy that I got to work with them!
 
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