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Lecture 8

Lecture 8.docx

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ZOO 2090
Fred Laberge

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Lecture 8 October 2, 2013 ZOO*2090 Respiration Objectives - describe the variety of breathing organs and circulatory system in fishes - contract the modes of gill ventilation among fishes Respiration  gas exchange - exchange surface between environment and respiratory organs - transport of gases in blood - exchange surface between capillaries and tissues - respiratory and circulatory systems work together Diffusion – gas exchange follows physical rules of diffusion Need: - large surface between environment medium and blood - thin barrier - adequate contact time Fish Gills - designed for water breathing - large surface area, countercurrent exchange, thin water-to-blood barrier Evolution of Internal Gills 3 Types: - pouched - no gill covering (lamprey) - septal gills (shark) – each individual septum protects each gill chamber - opercular gills (teleost) – common operculum covers the gills (bony covering – like the perch) Pouched (lamprey) Septal (shark) Opercular (teleost) External pores Gill slits Operculum No septum Long septa Short/no septa No gill bar Gill bar Gill bar Small opening to pharynx Large opening to pharynx Larger opening to pharynx Trends: - reduction of number of gill bars and chambers - loss of spiracle and loss to septa Lecture 8 October 2, 2013 ZOO*2090 Gill Ventilation - hagfish  pulsating structure (velum) produces a current of water from the nostril to the gills - lamprey  tidal ventilation through compression/expansion of branchial cavity (mouth often attaches) - active fish can use ram ventilation (mouth open while swimming) - most common is dual pump o buccal and opercular components act like a two stroke pump with alternating cycles of negative and positive pressure Gas Bladder and Lungs - gas exchange in air - develop from outpocketings of pharynx endoderm - lungs are paired structures ventral to the gut - gas bladder is a single elongated sac dorsal to the gut used for buoyancy (swim bladder), but sometimes also help with respiration (respiratory gas bladder) - can also be involved in sound production and reception Gas Bladder: Two Types - physotomous can be filled by gulping air in the digestive tract - physoclisto
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