Growth in Fish Flashcards by Bryony Costello

Define Growth

A change in size (wight or length) over time

A change in calories stored as somatic or reproductive tissue

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What 3 things combine in the intake equation?

Growth + Excretion +Metabolism

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What is the equation for he specific growth rate (SGR)

SGR = 100 (logeSf - logeSi)/ tf-ti

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What is growth expressed as?

% change in body size per day

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What constitues weight growth?

Sort tissue growth
Muscle growth
Fat deposits
Gonadal development

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Is growth reversible?

Yes

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How is fish muscle organised?

In myotomes

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Give some characteristics of red muscle

Small and slow
Lipid and myoglobin rich
always active at moderate swimming speeds
oxidising metabolism with mitochondria

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Give some characteristics of white muscle

Large and fast
Glycotic metabolism
active at high swimming speeds only

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Give the two ways muscle fibres in fish grow

Increase in diameter (hypertrophy)

2. Fiber number increases (Hyperplasia)

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How is muscle fibre growth different in mammals compared to fish?

In mammals post-natal muscle fibre growth is only hypertrophy. (diameter) and not hyperplasia

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How do small, slow growing fish grow?

by increasing fibre size (hypertrophy)

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how do large, fast growing fish grow?

Hyperplasia (show continuous recruitment of new muscle)

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What happens as a fish grows and ages? (with regards to type of muscle growth)

There is a shift from hyperplasia to hypertrophy

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With the example Rainbow trout explain how they grow?

Under 20cm = hyperplasia
20 - 50cm = both plaisa+trophy
Over 50cm = Hypertrophy

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What are the 3 strategies of fat deposition?

High or low muscle fat
Large or small liver
little or lots of visceral fat

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Why do salmon stop feeding months before spawning?

Their gonads are growing; proteins and lipids are reabsorbed from muscles and replaced by water, then proteins and lipids are relocated to gonads and somatic growth slows/ is halted

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Weight and lent growth are different processes; what determines length growth?

Skeletal growth

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Is length growth permanent?

Yes

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What is the composition of organic bones (matrix)?

Collagen, ECF, proteoglucane

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How much weight and volume does organic bones contribute?

50% weight and 25% volume

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What is the composition of inorganic bones?

Na+, HCO3-, H20, Mg2+, Hydrocyapatit

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How much weight and volume does inorganic bones contribute?

50% weight and 75% volume

What would happen if there were no minerals in bones?

The bone would become bendy

What would happen If there was no collagen in bones?

The bone would become brittle and snap

Dows the condition factor increase or decrease in sexual maturation?

Increase

What does the condition factor depend on?

It is species specific and depends on fish shape

Dows the condition factor increase or decrease in salmon smoltification and starvation?

decreases

What is the feed composition ratio?

An animals efficiency to convert feed mass into body mass

what is the feed composition ratio of wild salmon vs farmed salmon?

wild salmon consume 10kg of feed but only convert to 1kg of growth; farmed salmon convert 1.1kg of food to 1kg of growth!

What is the GH-IGF-1 System?

A dual effector hypothesis (growth hormone and insulin like growth factor -1)

What does the GH do?

Stimulates cell growth and increases the sensitivity of cells to IGF-1

What does IGF-1 do?

stimulates cell growth and proliferates

What does the GH do in lipolysis?

Causes lipids to be converted to FAs and gycerol by TG-Lipase

What does GH do in protein accretion?

Increases protein synthesis and decreases grotein breakdown

How do fish grow faster?

1. GH increases appetite, dominance, aggression, and Feed conversion efficiency 2. GH decreases predator avoidance

Why dont fish normally grow faster in the wild?

It is a trade off - but other than that we dont actually know

Which hormones regulate appetite and growth?

GH-IGF-1 system, Insulin, T3 and T4, Ghrelin and Leptin

What internal factors affect growth an appetite?

Nutrients, Immune system, Metabolies

What external factors affect growth and appetite?

Photoperiod, temperature, Current Velocity, Water Quality and Salinity, Social Interaction

Describe the endocrine control of food intake (decrease)

1. The pancreas secretes insulin and the adipose tissue secretes leptin (both adiposity signals) 2. The GI-tract produces PYY,CKK,GRH (all endocrine/chemical a mechanical signals) called satiety signals. 3. The liver also produces satiety signals 4. Adiposity signals (secreted from pancreas and adipose tissue), and satiety signals produced by liver and GI-tract, send decreasing appetite signals to CAC in the. brain CAC = central appetite centre

Describe the endocrine control of food intake (increase)

The GI-tract secretes Ghreline which is a hyper signal and increases the appetite of an organism by influencing the CAC in the brain

What does leptin do in mammals?

Leptin is secreted by adipose tissue and decreases food intake and fat mass It increases energy expenditure, carbohydrate/lipid catabolism and FA oxidation

What does Grehlin do in mammals?

Increase food intake, fat mass, body weight and lipogenesis

What do Orexigens do?

Stimulate food intake

What do Anorexigens do?

Decrease food take

What are rexigens?

Hormones

Describe how leptin acts

leptin is produce by adipose tissue - into the blood - signals hypothalamus - changes appetite in CAC - decreases fat cells

Maintaining adiposity is not a ........ ........ ....... for vertebrates

viable metabolic strategy

How do vertebrates increasese adiposity

Icreasing appetite and foraging in summer to survive winter

What type of animals have the highest plasma lectin concentrations and why?

Hibernating animals as they need to use the fat cells (once broken down) to survive the v=winter - hibernating animals all have the lowest body adiposity

In freshwater species what is their metabolic strategy with regards to where energy is stored and liver size?

energy is stored in muscle and visceral as fat | and their liver is small sized

Where is ghrelin produced?

GI-tract (mainly in stomach), small amounts also released by the small intestine, pancreas and brain

What effect does ghrelin have on goldfish?

gherkin has a rapid stimulatory effect in goldfish on food intake through NPY and orexin in the CNS, also increases lipid deposition in females

What effect does ghrelin have on tilapia

Long term stimulatory effect and also increases lipid deposition in females

What effect does ghrelin have on brown trout?

Swimming activity stimulated

What effect does ghrelin have on rainbow trout?

decreased food intake