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BIOLOGY 457/657 PHYSIOLOGY OF MARINE & ESTUARINE ANIMALS

BIOLOGY 457/657 PHYSIOLOGY OF MARINE & ESTUARINE ANIMALS. March 1, 2004 Physiology of Respiration. METABOLIC RATE. MR = energy metabolism per unit time Significance: Measurement of overall chemical energy state Suggests utilization of particular energy sources

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BIOLOGY 457/657 PHYSIOLOGY OF MARINE & ESTUARINE ANIMALS

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  1. BIOLOGY 457/657PHYSIOLOGY OF MARINE & ESTUARINE ANIMALS March 1, 2004 Physiology of Respiration

  2. METABOLIC RATE MR = energy metabolism per unit time Significance: Measurement of overall chemical energy state Suggests utilization of particular energy sources Serves as a measure of physiological state or adaptation Often is related to the organism’s ecological status

  3. MEASURING METABOLIC RATE Energy is measured in units of force • distance, or Joules (kg • m2 • s-2), but metabolism is often expressed in calories, where 1 calories = 4.184 J Direct Technique: MR = (Food – Excreta)/Time. Very tedious and often inaccurate Calorimetry: Measure heat output. Is technically complex and difficult. O2 Consumption: In absence of anaerobic metabolism, can be technically simple. However, VO2 varies with substrate being metabolized.

  4. O2 CONSUMPTION Substrate kcal/g l O2 / g kcal/l O2 R.Q. Carbohydrate 4.2 0.84 5.0 1.00 Fat 9.4 2.0 4.7 0.71 Protein 4.3 0.96 4.5 0.81 (Note that energy per unit O2 is almost constant (~5 kcal/l O2) R.Q. (Respiratory Quotient) = CO2/O2. If R.Q. is measured as well as excretion of N, a complete description of substate utilization can be obtained.

  5. OXYGEN IN THE MEDIUM Air:In almost any habitat, concentration depends strictly on barometric pressure Water: concentration varies with S & T Volume ratio of O2 is low in water (~5 ml/l) Mass ratio of O2 is low in water (~7 – 10 mg/kg) Viscosity of water is very high (compared to air) Amount of O2 in water is highly variable: varies with depth, mixing, substrate consumption, photosynthesis, respiration, etc.

  6. VARIATIONS IN A TIDE POOL

  7. DIFFUSION OF GAS IN WATER Diffusion of gas in water is described by Fick’s Law: D ≡ diffusion constant A≡ area u≡ concentration x≡ distance Note that concentration (u) depends on the solubility coefficient (α ) and the partial pressure P. Since α is constant for a given gas, the rate of diffusion depends heavily on the partial pressure gradient across the respiratory surface.

  8. EXTRINSIC FACTORS AFFECTING METABOLIC RATE • Temperature May be adjusted by acclimation Both kinetic and denaturation effects influence rates Respiratory Q10 : Change in metabolic rate caused by a 10° rise in temperature Q10 varies with temperature, and may also be different for active vs. standard metabolic rates – this affects the scope for activity (active MR – standard MR)

  9. SCOPE FOR ACTIVITY

  10. EXTRINSIC FACTORS (continued) • Salinity. Effect is variable, depending on euryhalinity of the species and its ability to regulate or conform. • PO2. Conformity vs. Regulation. Pc: Critical PO2 (PO2 below which regulation is impossible.) (From Burggren & Roberts 1993)

  11. METABOLIC COMPENSATION Means of regulating metabolic rate: (1) Behavioral compensation (2) Ventilatory compensation (3) Adjust contribution of anaerobic metabolism

  12. ANAEROBIC METABOLISM AND RECOVERY FROM HYPOXIA During hypoxia, anaerobic endproducts are produced: • Dispose by excretion • Oxidize them to products • Resynthesize to substrate (builds an oxygendebt)

  13. OXYGEN DEBTS Whenever the demands of exercise exceed oxygen supplies, an oxygen debt may accumulate. Paying off of the debt can occur once lower levels of exercise are possible, or when free access to oxygen is possible (e.g. after diving).

  14. INTRINSIC FACTORS • Body Size. M = aWb(b is typically ~ 0.75) • Activity Level. (Basal, standard, routine, and active metabolic rates.) • Physiological State. (feeding, molt cycle, reproductive condition, health • Cyclic (Rhythmic) Changes. (season, tidal state, time of day)

  15. OXYGEN TRANSFER: THE GILL

  16. GILL DESIGN: CRUSTACEANS • The circulatory system is open in design. • Despite this, blood flow through the gill is countercurrent. • A gill-bailer, or scaphognathite, is required to pump water over the gills. In some crabs, it can pump air!

  17. Oxygen exchange in crustaceans is limited by the relatively low oxygen-carrying capacity of hemocyanin, which is much lower than hemoglobin. Consequently, blood volumes are often very high in active crustaceans: Species Circulatory Respiratory Blood VolumeBlood O2 ml of O2 System Pigment (% of Body Mass) Capacity Stored(vol%) Platichthys Closed Hb 6%6% 1.1 (flounder) Cancer Open Hcy 30% 1.3% 1.3 (crab)

  18. GILL DESIGN: FISHES Gills include a series of arches, or bars, that suspend the gill filaments. Each filament is made up of numerous gill lamellae, where gas exchange occurs. Blood and water flow are countercurrent to each other.

  19. GILL VENTILATION Most fish ventilate gills using pumpventilation. Buccal and opercular pumps produce a nearly continuous flow over the gill surface.

  20. GILL VENTILATION (2) Some fish, however, use ramventilation. Many elasmobranchs (particularly pelagic sharks) have no pump system at all and must rely on ram ventilation at all times. www.oceanicresearch.org/ sharkstv.html

  21. ADAPTATIONS FOR TERRESTRIAL RESPIRATION IN CRABS Semiterrestrial or terrestrial life brings new stresses to marine organisms associated with temperature extremes, dessication, loss of buoyancy/support, and hyperosmoticity. The most successful marine group to invade the land is the crustacea, although most still require water to reproduce (isopods are an exception). The most impressive of these are the crabs, both brachyuran (true crabs) and anomuran (hermit crabs). Characteristics: • Most are nocturnal • Many species are social • Most live in burrows • All require access to water (sea or fresh) for reproduction. • Short-term energy output of these crabs can be impressive. http://www.mbi.nsysu.edu.tw/~fiddler/figure/fig_crab/carnif_1.jpg

  22. ADAPTATIONS FOR TERRESTRIAL RESPIRATION IN CRABS (2) • Gills and gas exchange: (i) Reduction of surface area

  23. ADAPTATIONS FOR TERRESTRIAL RESPIRATION IN CRABS (3) (ii) Sclerotization (iii) Enlargement of the branchial chamber http://www.gulfspecimen.org/photographs/Ar-1530.GIF

  24. ADAPTATIONS FOR TERRESTRIAL RESPIRATION IN CRABS (4) (iv) Use of “gas windows” in the legs http://www.buiosch.edu.hk/z/crabs/cat5/images/big1.jpg

  25. ADAPTATIONS FOR TERRESTRIAL RESPIRATION IN CRABS (5) (v) Use of the branchial chamber surface as a “lung” (From Innes et al. 1987)

  26. ADAPTATIONS FOR TERRESTRIAL RESPIRATION IN CRABS (6) • Ventilation (i) Continue to use the scaphognathite, but as an air pump. (ii) Use movements of the shell or internal organs for breathing. (From Innes et al. 1987)

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