Vertebrate Zoology Chapter 4 Living in Water PDF

 Challenges of Living in Water Buoyancy Movement through water (dense medium) Heat loss (difficult to maintain different temperature from water) Maintaining a stable internal environment (water and ions move rapidly) Ammonia very soluble (positive) Oxygen concentration lowe...

 Challenges of Living in Water Buoyancy Movement through water (dense medium) Heat loss (difficult to maintain different temperature from water) Maintaining a stable internal environment (water and ions move rapidly) Ammonia very soluble (positive) Oxygen concentration lower Physical Properties of Fresh Water and Air at 20°C Gills are Used to Obtain Oxygen from Water The movement of water across the gills is unidirectional – in through the mouth and out through the gills (buccopharyngeal pumping) – Fish have flaps in their mouths and at the edges of their opercula that keep water from flowing backwards into the gills – The part of the gills that perform gas exchange project from each gill arch (gill filaments)  2 columns of gill filaments extend from each gill arch Gills Gas exchange occurs at the secondary lamellae, which are microscopic projections from the gill filaments The fish’s mouth and the pharyngeal region create a respiratory current that is almost continuous Fish such as sharks don’t pump water, so they must constantly swim to breathe (ram ventilation) – (also mackerel, tuna and swordfishes) Counter-current Exchange Each gill filament has 2 arteries: – Afferent vessel runs from the gill arch to the filament (O2 depleted) – Efferent vessel runs from the filament to the gill arch (O2 rich) – Blood flows in the opposite direction of water to maximize O2 diffusion into the blood  Fish that live in water with low dissolved Oxygen from Air O2 have other structures for gas exchange Betta fish draw air in through their Electric eels go to the surface about mouth and gas exchange occurs in a every 10 minutes to breathe. Their structure called a labyrinth located in main source of oxygen is through their the back of their heads. Considered highly vascularized mouth. facultative air breathers. Considered obligate air breathers.  Lungfish Lungfish have lungs with 1 or 2 lobes that are derived from the swim bladder (gas bladder) Live in lakes and rivers in South America, Africa, and Australia During the dry season, they burrow down into the riverbed and secrete a mucous that eventually hardens and they enter a dormant period which may last months. West African Lungfish | National Geographic Society Adjusting Buoyancy in Bony Fish Most are neutrally buoyant – Same density as water – Able to hover in the water Have a gas bladder or swim bladder When a fish swims down, it secretes air into the gas bladder to counteract the increased pressure at deeper depths. When it swims up, it removes gas to balance the decreased pressure of shallower depths.  Rete mirabile moves gas from the blood to the swim bladder – Attaches to the gas bladder at the gas gland, which creates a countercurrent for gas exchange Gas gland releases lactic acid and CO2 , which acidifies the blood in the rete mirabile and causes the hemoglobin to release O2 When the O2 levels in the rete mirabile become greater than in the swim bladder, it diffuses into it  Physostomus fish have retained a connection (pneumatic duct) between the gas bladder and the gut, so they can gulp air through their mouths to fill their swim bladder and can burp it out to release it. (Eels, herrings, salmon, anchovies, and minnows). Physoclistous fish do not have that connection. To release oxygen, they have a sphincter muscle that allows oxygen to enter the ovale, where oxygen diffuses back into the blood. Adjusting Buoyancy in Cartilaginous Fish Don’t have gas bladders (sharks, rays, & chimaeras) Use the liver to create neutral buoyancy – High oil content – Can be as much as 25% of total body mass Also have compounds in their blood that help with buoyancy (TMAO and urea) Buoyancy in Deep-Sea Fish Many have lightweight oil or fat in the gas bladder Rete mirabile is longer so oxygen can be secreted at high pressure; will have a large gas gland Some have lost it entirely and have fats distributed throughout the body  Vision in the Aquatic World In aquatic vertebrates, the lens focuses light on the retina; spherical lens is moved back and forth In terrestrial vertebrates, the cornea bends light and focuses it on the retina; have a flatter lens which changes thickness Cornea index of refraction is 1.37, so terrestrial cornea important in image focusing; in water, refractive index nearly same (1.33) so vision blurry under water; masks restore.  Hearing Sound travels 4 times faster in water than in air. Sound travels faster in open water than in air Solid objects reflect sound waves while vegetation absorbs sound energy. In air, sound energy obeys the inverse square law meaning that as sound propagates, the energy spreads over larger and larger areas. If the distance is doubled, the energy is reduced by a factor of 4. In the open ocean, sound waves reflect off thermoclines and remain in a sound channel. This means that sound waves can travel for kilometers in open water.  Fish have taste-bud organs in their mouths and around their heads and anterior fins Olfactory organs around their Chemosensation: snouts to detect substances that Taste and Smell are dissolved in the water Sharks can detect odors at concentrations < 1ppb Use timing of sensing odors on each side of their head to determine direction of the stimulus Salmon use permanently imprinted chemical signature from home stream  Lateral Line System Detects water displacement (aka vibration detector) Made of sensory cells called hair cells that are clustered together to make neuromast organs Located in a series of canals on the head, and one that goes down the side of the body to the tail Found only in aquatic vertebrates.  Each hair cell has an asymmetrical kinocilium within a cluster of stereocilia Lateral Line System A single neuromast contains several hair cells Hair cells are arranged in pairs with the kinocilium on opposite sides of the cell; allows detection of direction of displacement Each hair cell has 2 nerves, one to transmit movement in each direction The kinocilia are embedded in a gelatinous secretion called a cupula If water pushes the cupula, it causes the kinocilia to bend, which excited or inhibits the nerve This tells the fish which direction water currents are flowing  Schooling fish use their lateral lines to help maintain a Schooling Fish constant distance from each other. Dense schooling fish have greater concentrations of neuromast cells on their head rather than on lateral sides. Neuromasts help them to sense turbulence in the water created by their neighbors. The large group movement and quick adjustments made in direction confuses predators. Electrical Discharge ~350 fish species can create electric fields around themselves – Use modified nerve or muscle cells to create an action potential Creates a dipole along the length of the fish – Positive pole at the head, negative end at the tail Near head or tail is stronger shock than in the middle of the body Electrical Discharge Most are weakly electric, and use it for – Orientation, predator/prey detection, identification, courtship, and social interactions Only a few are electric enough to stun prey and deter predators – Electric eel can produce up to 600 V – Shock depends on location that you touch https://www.youtube.com/watch?v=97UjZHLGseY Electroreception by Sharks and Rays Sensitive electroreceptors on the heads of sharks and the heads and pectoral fins of rays, known as Ampullae of Lorenzini, detect electrical activity from their prey’s muscle contractions. The sensory cells are connected to pores by canals filled with a gel that conducts electricity. In addition to aquatic vertebrates, monotremes use electroreception to detect prey. Electrolocation Capacity of Sharks  Proteins and nucleic acids are metabolized and Nitrogen Excretion reduced into ammonia (toxic) Animal groups have different ways of excreting ammonia Bony fish excrete ammonia ammonotely (as ammonia) through their skin and gills and in their urine Ammonia is very soluble in water; since breakdown product of proteins, no energy required to make Mammals excrete primarily urea (ureotely) Requires energy to make, but it is less toxic than ammonia Reptiles and birds excrete ammonia as mostly uric acid (uricotely) Excreted as a paste, which is requires a lot of energy, but helps them conserve water Vertebrate Kidneys Remove excess water and waste from the body Made of hundreds to millions of nephrons, which make urine Blood is first filtered through the glomerulus Blood is filtered, and water, amino acids, and glucose are returned to the body and the remaining fluid is urine Stenohaline vs. Euryhaline Stenohaline fish inhabit either fresh water or salt water; tolerate only small changes to salinity. Most fish are stenohaline Euryhaline fish move between fresh water and salt water; tolerate large changes in salinity Examples include salmon and tilapia Water and Salt Regulation – Freshwater Fish The body fluids of freshwater teleosts are more concentrated than the water surrounding them They gain water by osmosis and lose sodium and chloride by diffusion They do not drink water; they actively absorb sodium and chloride through the gills; and they have kidneys with large glomeruli that produce a large volume of dilute urine Water and Salt Regulation – Marine Fish Marine teleosts have body fluids that are less concentrated than the water they live in They lose water by osmosis and gain sodium and chloride by diffusion Marine teleosts drink seawater and actively excrete sodium and chloride through the gills Their kidneys have small glomeruli that produce small volumes of concentrated urine