Fish Flashcards
Explain the fresh water habitat
-As temperature rises amount of dissolved oxygen in water decreases
- thus warm standing water has less oxygen than moving water
- Temperature of water effects: rate at which chemical reactions take place and metabolic rate of fish and other aquatic organisms
- because water absorbs and releases heat much slower than air the temperature changes are relatively gradual
-thus sudden change to water temp( hailstorm, cold front, melting snow) may cause mortalities
What two categories are freshwater habitats divided into ? And give examples
Standing water or lentic water(calm) habitats
Eg lakes,ponds, pans, swamps and vleis
running water or lotic(washed) habitats
Eg springs, spruits, estuaries, streams and rivers
What effect does silt have on a freshwater habitat ?
More silt = less light penetration= reduce photosynthesis and thus has impact on life there
What are the 3 zones of lentic(calm) habitats ? And explain them
Littoral zone- shallow water light penetration to the bottom, occupied by rooted plants
limnetic zone- open water zone to the depth of effective light penetration, plankton and microscopic life here
profundal zone- bottom and deep water area beyond the effect of light penetration
The littoral zone is the most important and is divided into three sub zones name and explain them
Emergent vegetation- rooted plants with leaves above water- the emergent plants + those of moist shore provide important link between land and water. Used for food and shelter amphibians. Provide easy means of entry and exit of water for insects that spend part their lives in water and part on land
zone of rooted plants with floating leaves, like water lilies- the under surfaces of lily pads provide resting places for animals and a place for attachment of eggs
zone of submerged vegetation - rooted or fixed plants that are completely submerged. Leaves if these plants are generally thin
In what zone/zones will you find lake and pond fish species?
They move between the littoral and limnetic zones but mostly the littoral zone
What are the two zones within lotic habitats (running streams and rivers)
Rapids zone- shallow where water keeps bottom clear of silt(firm bottom) occupied by life forms adapted to clinging, stonefly and mayfly nymphs have adapted to be flat and cling to the underside of rocks
Larvae of various Caddisfly construct cases of small pebbles that they anchor to rock surfaces
pool zone deeper water where velocity of the current is reduced, resulting in soft silted bottom, favourable for burrowing forms of life
How do fish breath ? Briefly describe fish respiration
-Fish breath via extracting oxygen that is dissolved in water by means of a gill system
-the gills are covered with a moveable flap called operculum
- found inside the back of the mouth
- arranged in rows along four or five pairs of gill arches
What are gills ?
Are rows of bony rods to which are attached thin feathery like filaments rich in blood capillaries to absorb oxygen
Each filament has a thin epidermal membrane that is repeatedly folded into fine secondary plate like flaps(lamellae)
Explain in point form how the respiratory system of fish works
- water enters the mouth and passes through the gill chamber over the gills
- flow maintained by pumping of the mouth, synchronised to the opening and closing of the operculum
- water exits via operculum
- oxygen absorbed by blood capillaries
- water passes over gills against capillary blood flow( ensures water, rich in O2, flows over deoxygenated blood, no O2, maximum absorption of oxygen
- blood circulated through whole body by blood vessels
Explain how some fish species can live outside of water with an example
They can do this for different lengths of time
Lungfish can stay in stagnant water by coming to the surface and gulping air into its single lung formed via the swim bladder
As water levels drop the fish burrows into the soft sediment secreting mucus that is mixed with mud to form a hard cocoon
Fish becomes dormant, breathing through a small opening
He does this till the habitat is filled with water again !
Explain osmotic regulation in fish
-Freshwater fish are hyper- osmotic regulators in that they deal with the balance and differences in water and salt concentrations between the fresh water they live in and their body liquid-salt concentrations.
-Salt content in water less than in fish
-Thus water enters body of fish through osmosis and salt lost outwards through diffusion
- water gain and salt loss takes place across thin gill membrane
- freshwater fish regulate these balances through pumping out excess water by means of the kidney, very dilute urine, salt ions moved from water to blood by means of salt absorbing cells in the gill epithelium.
Absorbed salt and salt found in food replace salt lost through diffusion
Briefly explain osmotic regulation of saltwater fish
-Must drink sea water to replace water lost osmotically to salty environment
- sodium chloride and water absorbed from stomach.
- excess is secreted outwards by gills
- divalent sea salts and most magnesium sulphate, are eliminated with faeces and secreted by tubular kidney
Explain neutral buoyancy and the swim bladder of fish
- fish slightly heavier than water due to weight of skeletons and other tissue
- swim bladder keeps them from sinking
- lies in the coelom just beneath vertebral column
- by adjusting level of gas in the bladder a fish can achieve neutral buoyancy and remain at the same depth for infinite period of time
- when a fish moves deeper gas is compressed=fish heavier
-gas needs to be added to bladder in order to establish new equilibrium buoyancy. - when fish swims up it is made lighter due to expanding gas
- unless gas in the bladder is released the fish will rise faster and faster while bladder swells until it pops out and floats to the surface
Name and describe the two ways in which fish adjust the volume of gas in the swim bladder
Less specialised fish eg. Trout = pneumatic duct that connects their oesophagus to the swim bladder. These fish need to come to the surface and gulp air in order to charge the bladder and are restricted to shallow depths
more specialised fish secrete gas into swim bladder via blood make use of a highly specialised gas gland that secretes gas into the bladder and resorptive area(ovale) that is able to move gas from the bladder
This gland is supplied by a blood capillary network called the rete mirabile
Acts as a counter current exchange system to trap gasses, particularly oxygen, preventing their loss to circulation
In three steps explain the action of the swim bladder and its anatomy
A) swim bladder just below vertebral column in the coelom
B)-gas secreted into swim bladder via gas glad.
- gas from blood moved to gas glad via rete mirabile(complex array if tightly packed capillaries that act as counter current multipliers to build up oxygen concentration)
C)- the array of venous arterial capillaries in the rete
- in order to release gas during ascent muscular valve opens and allows gas to enter ovale where gas is removed via circulation
