Rank in order of fastest to slowest B C

What type of caudal fin does this fish have?

What is the body form of this fish?

What are the structures to which the arrows point?

What type(s) of scales is these ain’t?

Barrel eye

Angler Fish

Structure of Fish Gills

Countercurrent exchange Countercurrent “multiplier system”. Occurs when: Transport of substance (e.g., O2) is by diffusion. Two fluids flow in opposite directions in close proximity. One of the most important of all adaptations for efficient diffusion. In gills, allows for as much as 90% of O2 in the water to diffuse into the blood. Found in many places throughout the vertebrate body where gases, salts, or heat are concentrated.

Source: http://www.geocities.com/aquarium_fish/how_fish_breathe.htm

Gills and Countercurrent Exchange of Gases Direction of water flow is counter that of blood flow in capillaries. Countercurrent exchange of gases across the gill epithelia (on gill lamellae)

Critical tradeoff for aquatic organisms: Large surface areas are necessary for oxygen exchange. Exposes individual to: Other dissolved compounds in water, including toxic compounds. Salinity and temperature fluctuations.

Gill Dimensions and Life Style in Teleost Fishes

Gills are controlled by muscles Any water that passes by gills without coming into close contact with blood represents wasted energy. But gills must sometimes be flushed. Adductor and abductor muscles control the positions of gill filaments.

Air-breathing fishes Hundreds of convergent cases of air-breathing using accessory structures. Most are facultative air-breathers. Some are obligatory: drown if kept from the surface. Adaptations to two ecological conditions: Depletion of oxygen in the water. Periodic droughts. Most species are tropical freshwater or estuarine. Oxygen-deficient water more common in tropics. Much decaying organic matter in water, consumes O2. High temperature increases bacterial action. Shaded jungle waters support little photosynthesis. Little temperature variation supporting thermal convection.

Gas bladder Gas-filled sac: Forms as diverticulum from anterior gut. Pressure regulated by countercurrent exchange system (gas gland, =rete mirabile, =rete). Connection to gut may be present or absent. Physostomous vs. physoclistous (=physocleistous) Functions: Original function: Respiration: in lungfishes and many primitive bony fishes. Derived functions: Buoyancy. Resonator: for producing or detecting sounds.

Connections of gas bladder with gut

Teleosts Gars, bowfin Bichir Lungfishes Amphibians

Teleosts Tetrapods Osteichthyes Sarcopterygians

Homologies of respiratory systems Gills and lungs are not homologous: Developmental patterns very different. Anterior vs. posterior pharynx. Some species have both. Lungfishes, early amphibians. Lungs of tetrapods are homologous with gas bladders of fishes: First observed in early placoderms (jawed fishes). Derived function in modern fishes: buoyancy.

Solubility of Oxygen in Water Solubility of oxygen in water is affected by: temperature salinity Freshwater in equilibrium with the atmosphere contains 1/23 the oxygen concentration, per unit volume, as does the atmosphere at 5oC. 1/43 at 35oC.

Solubility of Oxygen in Water At 35oC the oxygen concentration, at equilibrium, is 6.94 mg/l (ppm). At 5oC the oxygen concentration is 12.76 mg/l. Normoxic (normal oxygen) conditions are those at or near saturation, that is near 156-mm HG partial pressure of oxygen (PO2).

Dalton’s Law of Partial Pressures The partial pressure of an ideal gas in a mixture is equal to the pressure that gas would exert if it occupied the same volume alone at the same temperature. A consequence of this is that the total pressure of a mixture of ideal gases is equal to the sum of the partial pressures of the individual gases.

Dalton’s Law of Partial Pressures For example, given an ideal gas mixture of oxygen (O2), carbon dioxide (CO2) and ammonia (NH3): P = PO2 + PCO2 + PNH3

Relationship of PO2 and O2 Content.

Fish Respiration Summary Water severely limits the solubility (availability) of oxygen, yet fishes have numerous adaptations that allow them to survive in virtually all aquatic (and some terrestrial) habitats. Oxygen requirements vary among species, and with life history stage, size, and activity level. Oxygen requirements vary with temperature.

Hematological Characteristics of Fishes

Hematological Characteristics of Fishes

Fish Hemoglobin Fish hemoglobin of is two basic types: monomeric and tetrameric. Monomeric- single-heme polypeptide molecules with a molecular weight of about 17,000 daltons. Characteristic of lampreys and hagfish

Lamprey and Hagfish Lamprey (attached to lake trout) Hagfish

Tetrameric Hemoglobin Characteristic of all fishes except lampreys and hagfish. Composed of four amino acid chains (two a and two b chains) and have a weight of approximately 65,000 daltons. Within species, hemoglobin may be polymorphic: Four kinds of hemoglobin found in rainbow trout, two in American eels.

Tetrameric Hemoglobin Molecules

Ecological Significance of Hemoglobin Polymorphisms In catadromous American eels, one hemoglobin has a high affinity for oxygen in saltwater conditions and one with high affinity for oxygen in freshwater conditions. The desert sucker possesses a pH-insensitive hemoglobin that maintains a high oxygen affinity when binding efficiencies of other hemoglobins are reduced in the presence of elevated plasma lactic acid concentrations due to muscular activity.

American Eel

Desert Sucker

Hemoglobin Polymorphisms Changes in hemoglobin types have been observed in Coho salmon. Changes occur with the progression from fry to presmolt stages. Presence of multiple hemoglobins may negatively affect performance. In turbot (Scophthalmus maximus), individuals with two hemoglobin types grow more slowly than those with a single hemoglobin (one of which has relatively low and the other relatively high oxygen affinity).

Turbot

Oxygen Affinity of Hemoglobin Oxygen molecules bind reversibly to hemoglobin: Hb + O2 HbO2 High oxygen concentration in blood: Hemoglobin (Hb) combines with oxygen to form oxyhemoglobin (HbO2). Low oxygen concentration in blood: Oxyhemoglobin dissociates to hemoglobin + oxygen.

Bohr Effect and Root Effect Capacity Affinity

Blood Oxygen Saturation Curves

Blood Oxygen Saturation Curves

Oxygen Affinity of Hemoglobin Relationship between O2 concentration and PO2 saturation depicted by an oxygen dissociation curve: Curves can differ dramatically for different species and different environments. Max binding capacity Shift to right indicates decreasing binding affinity Each hemoglobin binds 4 O2 molecules. Because it is more “difficult” for the first O2 to bind than for subsequent O2s, the lower end of the dissociation curve is concave upward. The

Oxygen Dissociation Curves Trout: cool, highly oxygenated water Eels: warm, moderately oxygenated water

Oxygen Affinity of Hemoglobin Factors affecting O2 binding: pH: Decreasing pH (acidity) shifts curve to right (Bohr effect). Effect is greater in fishes than mammals. Temperature: Increasing temperature weakens bond, shifts curve to right. Beneficial: temperature increase causes increased metabolic rate. Counteracted by decreasing solubility of O2. CO2: Increasing CO2 lowers pH, shifts curve to right. Beneficial: high CO2 concentration causes more O2 to be given up to body tissues (Bohr effect, Root effect).