Last one Lab animal

Marine elasmobranch fish

They are hypoionic to seawater but hyperosmotic. Their blood concentrations of inorganic ions are similar to other fish (much less than seawater) but their blood osmotic pressure is slightly hyperosmotic to seawater so they have a tendancy to gain water

How do marine elasmobranch fish gain water from seawater if they are very hypoionic?

They are slightly hyperosmotic to seawater so they have a tendancy to gain water. They do this by producing and retaining urea within their blood which keeps their osmotic pressure higher than seawater. Deal with excess salt via the kidneys and rectal glands

What is a stenohaline animal

Able to survive within only narrow ranges of ambient salinity

Euryhaline animal

Able to survive within broad ranges of ambient salinity

Anadromous

Grow in ocean but migrate to freshwater for reproduction

Xeric animals are capable

of living in dry water-poor environment

Humidic animals are restricted to

humid water rich microenvironments

How do terrestrial animals lose water

1. Evaporative water loss

2. Urinary water loss

What is atmospheric water vapor pressure (WVPa)

The portion of the total atmospheric pressure that is exerted by the water vapor present.

What is water vapor pressure of a solution

A measure of the tendency of the liquid water to inject water vapor into the air. It increases with temperature of the solution and decreases as solute concentration increases

Rate of evaporation

J = K ((WVPs - WVPa) / X)

• x is distance separating two water vapor pressures

• K is permeability of integument to water

How do xeric animals different from humidic to reduce evaporative water loss

Microscopically thin layers of lipids are responsible for low integumentary permeability. Xeric vertebrates have layers of lipids and keratin in stratum corneum. Insects and arachnids have thin lipid layer.

How does water loss change with increasing temperatures

When lipids melt they become less effective at preventing water loss so the rate of water loss will increase dramatically above a certain species-specific temperature point

How are frogs an exception of terrestrial animals with very low integumentary permeability but very low water loss

They secrete protective lipids from their skin glands and spread them over their skin

What do humidic animals do for respiratory water loss

Their skin as a respiratory surface is limited to humidic animals as the water loss exceeds the minimum required for gas exchange

What do Xeric animals do for respiratory evaporative water loss

They have evolved invaginated respiratory structures to control access of air to respiratory surfaces. Limit the amount of air to levels necessary for gas exchange. They may have mechanisms for cooling exhalant air as a means of water conservation as warmer air holds more water than cooler air

What are countercurrent nasal exchange systems

Systems to allow for the recovery of water prior to exhalation where incoming air is warmed and humidified. Outgoing air is cooled and loses water, wetting the nose

Rate of water loss =

Rate of oxygen consumption x water loss per unit of O2 consumed

Water loss per unit of oxygen consumed is dependent on

• Relative temperature of exhalant air

• Oxygen extraction coefficient

How does total rate of evaporative water loss relate to body size

They are dependent. Small animals have very high rates of evaporative water loss and it plummets with body size

What does excretory water loss depend on

1. Concentrating ability of excretory organs

2. Amount of solute that needs to be excreted

How does concentrating ability of excretory organs effect water loss

Humidic animals and most non-avian reptile have UP less than or equal to 1

How does total rate of water loss compare to body size

It is allometric where increasing body size causes lower rates of weight-specific water loss

What is estivation

A dormancy response some terrestrial animals have for tolerating water stress where metabolic depression minimizes O2 and food requirement as well as waste production

What is Anhomeostasis

The ability to remain functional despite major changes in body fluid composition which some terrestrial animals can do to tolerate water stress

How does the amount of solute that needs to be excreted effect water loss for terrestrial animals

Producing insluble nitrogenous end products of protein catabolism like uric acid and urate salts would conserve a lot of water while urea and urine would require it to carry the solutes

why do Invertebrates like isopods have higher total rates of evaporative water loss than vertebrates

Xeric animals will have less evaporative water loss than humidic animals.

Why does body size matter for evaporative water loss

Smaller animals have greater surface area to volume ratio in whcih they can lose more water. Also smaller animals have higher weight specific metabolic rates so they need more ventilation, exposing their respiratory surfaces to air and causing more evaporative water loss.