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Effects of Maternal Experience with Predators on Offspring

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by

Gabriella Gao

on 19 November 2013

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Transcript of Effects of Maternal Experience with Predators on Offspring

Materials and Methods
Discussion
Conditions that a mother undergoes while pregnant can have a deleterious or a beneficial effect, depending on the condition itself
Results
Compared to control group, effects of predator exposure resulted in:
- eggs with higher cortisol concentration
- Eggs with increased oxygen consumption, attenuating over time
- No effect of treatment on growth
- Closer shoaling, prior to a disturbance


Female Sticklebacks Transfer Information via Eggs: Effects of Maternal Experience with Predators on Offspring
Questions?
Introduction
Exposure to predation risk in female fall field crickets

Prenatally stressed female monkeys

Prenatally stressed rats
Maternal experience can influence offspring via
non-genetic mechanisms

Growth and development of offspring can be affected by maternal experience with stressors in the environment such as predation



In vertebrates, there is evidence for hormonally mediated maternal effects



Role of cortisol of fish
Intergenerational transmission of antipredator behavior might occur through a
hormonal mechanism


Examples
Female birds deposit steroids in the yolk of their eggs

In mammals, including humans, during pregnancy stressors influence the development of offspring in utero via steroids transferred from mother to fetus

Disturbance protocol
Metabolic rate
The oxygen consumption rate of fertilized eggs from each treatment group was measured

Intermittent flow respirometry

allowed researchers to determine whether maternal exposure to predation risk influenced the oxygen consumption of fertilized eggs

Post-hatching characteristics
Fry hatched from clutches transferred to control or experimental tanks

matched to tanks by size to minimize dominance interactions over access to food

Each tank photographed 3 times on 6 different occasions over a 12 week period
‘Before’

‘Immediately following’: taken just after fish had been gently disturbed with piece of plastic tubing

‘After’ – taken two minutes after disturbance

Thank you!
Exposure to
predation risk
Produce larger eggs
give fry an advantage in a high predation environment
higher concentrations of cortisol in eggs
- time - no effect

respiration rate
mass-specific
metabolic rate

embryo can buffer any cortisol effects before hatching
Long-term consequences

Shoaling behavior

Maternal experience might cause intergenerational transmission of information about predation risk
Unknowns
Whether the effects on the offspring was directly due to cortisol exposure, increased size of eggs, or the egg qualities themselves.

Whether how long the effects that do appear will last and if they are just a response to predator exposure or could have the same response to other stressors.
Chandni Patel
Dima Yaser Kailani
Jiaqi Gao
Katie Dods
Margot Couse
Sidonie Swain Ward
Suramya Jeyaratnam











Biol 370
Nov 20/13
Less is known about hormonally mediated maternal effects in fishes

The purpose of this experiment was to determine the consequences of maternal exposure to predation risk on offspring in three-spined sticklebacks (
Gasterosteus aculeatus
)



Role of Cortisol of Fish
Female sticklebacks were randomly assigned to either a control or experimental tank

Fish were given unique spine clips to monitor length of time spent in the treatment tank

Tanks were covered in opaque plastic with small window to monitor the pregnancy of females


Predation risk was simulated by disturbing the fish with a model of a predator.

When a female from either group became pregnant, she was measured for standard length and weight while still bearing eggs

Average egg size of each clutch was calculated

Total # of eggs
= entire clutch mass/egg size

30-40 eggs from each female were artificially fertilized
Sperm collected from sacrificed males
Dissected out the testes
One testis used to fertilize an experimental clutch of eggs, other testis used to fertilize a control clutch of eggs

Of the eggs that were successfully fertilized, some were measured for metabolic rate and others were incubated and reared for analysis of post-hatching characteristics



Experimental group:
Fish chased with clay model of Northern Pike, a natural predator
This disturbance occurred for 30 seconds once per day at a randomly chosen time
The unpredictable and repeated exposure to cues of predators was designed to mimic natural conditions

Control group:
Remained undisturbed

10-15 eggs from each female were kept unfertilized and used in cortisol quantification
Cortisol content was measured using an ELISA (enzyme-linked immunosorbent assay)

Strong positive correlation between maternal and egg glucocorticoids concentrations in fishes

Cortisol plays an important role in the development of eggs

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