Lecture14Fish - Ch 15 Marine Animals Marine Class...

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Unformatted text preview: Ch. 15 Marine Animals Marine Class Osteichthyes Class 27,000 + species of bony fishes Have a strong, lightweight skeleton for Have support support Most are in the order Teleostei (“perfect Most bone”), examples are cod, tuna, halibut, perch perch 77 million metric tons of bony fishes are 77 harvested from the oceans each year harvested Diversity of Bony Fishes Commercially-harvested Bony Fishes Movement, shape and propulsion and Buoyancy Gas exchange Osmotic Osmotic considerations considerations Movement, Shape & Propulsion Movement, Water is dense and viscous Viscosity = Internal resistance to flow; “thickness” of fluid (Higher salinity, higher viscosity) Small organisms have a particularly hard time swimming; viscous Small fluid impedes their progress (think fly in honey) fluid Active swimmers are held back by “drag” or the resistance to Active movement of an organism movement Drag is the force that resists the movement of a solid object through a fluid (a liquid or gas). Drag is made up of friction forces, which fluid friction act in a direction parallel to the object's surface (primarily along its sides), plus pressure forces, which act in a direction perpendicular pressure to the object's surface. to Amount of drag depends on viscosity and speed, shape, and size of the moving organism shape, (Turbulence) Drag depends on size, shape Large animals need to streamline as much energy is lost to turbulence Yellowfin tuna How Fish Move How Forward thrust comes from body muscles and Forward fins fins Slender, flexible fish (eels) undulate in long SSshaped waves (like snakes); eel pushes forward against water forward Not very efficient; much of body length has to Not push against water, results in lots of friction and lots of pressure perpendicular to the direction of movement (so lots of drag) direction Most fish have relatively inflexible bodies that relatively undulate through a shorter distance undulate Hinged tails transfer muscle energy to the water Fish’s body can be shorter, less surface area at Fish’s cross section to direction of movement so losses of energy to drag are minimized of Some fish also excrete mucous or oil onto their Some surface which minimizes friction between body and water, minimizes turbulent eddy formations and Any reduction in drag is energy saved that can Any then go into reproduction or growth then Swim fishy swim! Swim Big fish like swordfish and marlin can Big swim fast! (120 km/h in bursts) swim Some tuna (and sharks) can maintain their Some body temperature a few degrees above ambient, permits them to metabolize food faster, rapidly generating energy (greater muscle power per unit weight) muscle Maintaining buoyancy Maintaining Marine fish density is ~ 5% higher than Marine surrounding sea water surrounding Weight of marine organisms must be Weight counterbalanced by buoyancy counterbalanced Many swimming fishes have gas-filled swim Many bladders to compensate bladders Quantity of gas is controlled by secretion and Quantity absorption of gas from the blood and by muscular contraction of the swim bladder to compensate for temporary changes in depth compensate Gas Exchange Gas Fish are “water breathers” (Air breathers have to dissolve gas in a (Air thin film of water in our lungs before it can diffuse across a membrane) diffuse Fish take in water containing dissolved Fish oxygen through their mouths, then pump it past fine gill membranes, out via rearpast facing gill slits Gills are arranged in thin filaments and plates; water and blood circulate in opposite direction= counter current flow which increases transfer efficiency Higher O2 concentration in water causes O2 to diffuse (down conc gradient) into the fish; higher CO2 in fish than in water promotes diffusion of CO2 from the fish to the outside Osmotic considerations Osmotic Osmosis is the diffusion of water from high Osmosis to low concentrations to Marine teleosts have lower internal Marine concentration of salts than their environment (higher internal water concentration); hypotonic; would tend to concentration); lose water if not capable of osmoregulation osmoregulation This is the hypotonic solution S alinity and Osmosis • If body fluids are le s s s alty than surrounding water, then they are h ypotonic • If body fluids are m ore s alty than surrounding water, then they are h ype rtonic This is the hypotonic solution This is the hypertonic solution 1 2 Hypertonic Marine fish – body fluids are less salty (hypotonic) as compared to the surrounding water 1. Will tend to lose water by osmosis to the environment through their skin but mostly through their gills (but don’t want to shrivel up!) 2. Have developed mechanisms to compensate for this water loss; the kidneys are modified in such a way that very little water is extracted from the blood, results in concentrated urine. 3. Water is still being lost by the gills and this cannot be stopped, so the only method left is to somehow replace the water as quickly as it is lost, so marine fish actually drink water 4. However, drinking water cannot solve the problem because they are drinking salt water and therefore, Na+ and Cl- ions will accumulate in the body of the fish and must be eliminated; done by special cells in the gills called chloride cells, which move these ions out of the body F reshwater fish Body fluids are more salty than surrounding water (body fluids are hypertonic) 1. F reshwater fish are constantly taking on water by diffusion through their skin and, to a much larger extent, through the thin membranes of their gills. 2. To maintain the high concentration of their body fluids, they must continuously excrete the excess water they have absorbed. This is accomplished by highly efficient kidneys which produce a very dilute urine. Chondrichthyes do it differently… Chondrichthyes Sharks and rays supplement their internal fluids with urea so that the osmotic urea pressure is balanced across the gill membrane (prevents water loss) membrane Urea causes shark meat to have a bitter Urea taste unless it is soaked to remove the excess urea excess Final words on fish…for now Final Lateral line systems allow them to sense vibrations (small canals in the skin and bones around the eyes, over the head, and down the sides of the body sides Canals are highly innervated, connect to the skin Canals surface by tiny pores surface Nerves report changes in current direction, water Nerves pressure…can be used to detect prey pressure…can Next time: Deep Sea Fish…adaptations, etc. ...
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This note was uploaded on 02/22/2012 for the course MSCI 102 taught by Professor Benner during the Spring '10 term at South Carolina.

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