osmoregulation immunity stress and disease osmoregulation immunity stress and disease

OsmoregulationImmunity

Stressand Disease

OsmoregulationImmunity

Stressand Disease

HK

Adrenalin

Head Kidney

CardinalVein Chromaffin

Cells

Brain

Nerve

The Beneficial effects of epinephrine/adrenaline are…

Better “fight or flight” capabilities

• Increases heart rateIncreases heart rate• Increases breathing Increases breathing

(respiration) rate(respiration) rate• Opens gill circulatory systemOpens gill circulatory system• Open muscle circulationOpen muscle circulation• Decreases blood to gutsDecreases blood to guts• Releases sugar from liverReleases sugar from liver

There is no such thing as a free lunch !

Gill Anatomy

Lamella

AfferentArtery

EfferentArtery

AfferentArtery

CartilageRod

Efferent Artery

WaterFlow

Freshwater Fish

Water

Salt

Saltwater Bony Fish

Water

Salt

Saltwater Shark

Water

Salt

=Trimethylamine oxide (TMO) and Urea

Epinephrine makes all osmoregulatory problems

•FW fish gain more water and loose more salt

•Saltwater fish gain more salt and loose more water

•Sharks gain more salt•Hagfish.. well…they stay

hagfish!

worse

•Starvation•Entrapment•Injury•Social problems

Brain

HK

InterrenalCells

ACTHAdrenocorticotropic Hormone

Cortisol

Good Effects of Cortisol ?

•Protein catabolism–Breaks down protein for energy

There is no such thing as a free lunch !

Complement molecules begin to assemble a complex on the wall of a bacterium

Complement finishes forming a channel through the bacterial cell wall.

Lysozyme•Dissolves bacterial cell walls

•Found in–Blood–Mucus–(tears)

Antibodies bind all over a Rhabdovirus and block it from infecting a cell.

Antibodies recognize foreign antigens on an “ich” parasite and mark it for destruction.

Uh-Oh!• Some proteins are really important !

– Antibodies: kill things, flag things for destruction

– Lysozyme: dissolves bacterial cell walls– Complement: pokes holes in bacteria,

flags things for destruction• Macrophages: need those flags• Neutrophils: need those flags• Eosinophils: need those flags

Cortisol Downsides• Cortisol triggers catabolism of

immune system proteins• Cortisol saves scarce resources

by reducing expenditures on immunity– Less white blood cells– Less production of immune proteins

Epinephrine: Makes osmoregulatory problems worse

Cortisol: Screws up the immune

system

The Case

•Bluegills harvested in July

•75-95% die from columnaris infections

The Problem• When fish are loaded onto the

trucks and into raceways, they perceive it as life-threatening

• They make cortisol and epinephrine

• Osmoregulation problems• Immunity problems

The Cure

•No treatment–95% die

•Gentle harvest–90 % die

•Add salt–85% die

•Add penicillin–5% die

The Case•Threadfin shad are harvested and loaded on trucks

•100 % die within 1 hr

The Problem•When threadfin shad are loaded onto the trucks, they perceive it as life-threatening

•They make epinephrine•Osmoregulation problems

The Cure•No treatment

–100 % die•Gentle harvest

–100 % die•Add salt

–95 % die•Add antibiotic

–95% die

The Case•Catfish develop ulcers and die 3-7 days after delivery

•Cultures show common soil bacteria

The Problem•Stress triggered cortisol production

•Cortisol screwed up the immune system

•The fish became susceptible to bacterial infection

What was the stress?•Normal fish: 1,000,000 bacteria

required to cause infection•Oxygen depleted fish: only 100•The neat part: It turns out that the

fish truck had an oxygen accident!•Bacteria levels were probably high

in the pond

The Cure

The Case

• Catfish look normal in aquariums

• Turn rigid if handled• Much worse if fish

aren’t feeding

The Problem•Stress triggered epinephrine release

•The fish had osmoregulatory problems

Why is it a problem here?

•Very low mineral levels in the water

•Minerals from the feed are needed

The Cure

The same thing happens with grass carp:

They are tough in hard waterbut

Fragile in soft water

The same thing happens with grass carp:

They are tough in hard waterbut

Fragile in soft water

Many common procedures used in aquaculture and fisheries are

perceived by fish as life threatening, but really aren’t

•Hauling in trucks•Seining•Weighing•Holding in tanks•Aerator noise…

If the fish make a bunch of epinephrine or cortisol, they

suffer the ill effects, but get no benefit.

The answer is to 1. reduce their perception of danger,

calm them with tranquilizers (if appropriate)

2. deal with the side effects using salt manipulation and antibiotics if appropriate

If conditions really are life threatening…

•Rapid temperature changes•Poor water quality•Handling injuries•Disease

Then, the hormones and their effects are vital to fish

survival…

But, you mustBut, you must

1.help the fish deal with the negative side effects

2.try to reduce improve the dangerous situation

Cures• Epinephrine

– Gentle handling– Salt adjustment for osmoregulation– Tranquilizers1 for open water fish

• Cortisol– Gentle handling and holding– Antibiotics1 for immune problems

1. Use only if required, safe, and LEGAL

Problem - Solution• Epinephrine Epinephrine

– great for fight and great for fight and flightflight

– screws up screws up osmoregulationosmoregulation

• CortisolCortisol– great to provide great to provide

energy in long energy in long lasting emergencieslasting emergencies

– screws up the screws up the immune systemimmune system

• EpinephrineEpinephrine– Gentle handlingGentle handling– Salt adjustment for Salt adjustment for

osmoregulationosmoregulation– Tranquilizers for open Tranquilizers for open

water fishwater fish• CortisolCortisol

– Gentle handlingGentle handling– Antibiotics for immune Antibiotics for immune

problemsproblems