Respiratory System Fish

Respiratory efficiency R = rate of diffusion R = DA(Δp/d) D = diffusion constant (of the medium) Temperature Density A = surface area Δp = partial pressure differential across membrane d = distance (thickness)

Life (respiration) in Water Initial Problems: O2 must be dissolved from atmosphere O2 tension: 20° air at sea level - 210mL/L [O2] Fresh HOH – 6.6mL/L Salt HOH – 5.3mL/L

Generic Gills External Gills (Larval fish) Internal Gills (Adult fish) Sites of gas exchange

Gills

Gills of Elasmobranchs Branchial pouches Narrow chambers Lamellae on Septa “Septal” Gills

(Efferent flow to dorsal aorta)

Pump Ventilation in the Dogfish

Teleost Gills Operculum Opercular cavity or chamber “aseptal” gills Countercurrent exchangers

Teleost Gills

Scanning electron micrograph of a longitudinal cut through a gill filament

Elasmobranchs (C and G)and teleosts (D and H

% O2 in water % O2 in gills % O2 in water % O2 in gills

Accessory Respiratory Organs Low O2 conditions Drying pool Warm, anoxic swamps Allow for gaining O2 from air “Bimodal breathers” Extensions of Gills Air bladders

Examples of gill extensions Climbing perch, mud eels (perch), Siamese fighting fish, snakeheads, walking catfish, etc. Gulp air and remain on dry land Gulps of air – 30 minutes to 3 hours Remain on dry land for up to 6 months

Outpocketings of gill arches i.e. labyrinth organ, arborescent organs Climbing Perch Walking Catfish

Swim Bladder

Swim bladders and the evolution of lungs Two main types Physostomous Connected to esophagus by pneumatic duct Physoclistous Independent of esophagus (no duct)

Evolution of Lungs and Swimbladders