Recording-2025-03-13T21:04:46.004Z

Introduction to Gas Exchange in Aquatic Animals

• Animals need oxygen for cellular respiration, transporting it from air or water to mitochondria.

• The concept of partial pressure vs. concentration gradient is crucial.

Partial Pressure Gradient

• Partial Pressure Rule: Gases move down their partial pressure gradient, overriding concentration gradients.

• Example: Water beetles capture air bubbles and swim back to their underwater habitat, utilizing this principle.

Boundary Layer in Water

• The boundary layer is a stagnant layer of water that changes thickness based on the animal's swimming speed.

• Fast swimming results in a thinner boundary layer, facilitating oxygen exchange.

• In contrast, slow swimming leads to a thicker boundary layer, potentially limiting gas exchange.

Plastron and Organism Adaptation

• The water beetle and backswimmer have adaptations for gas exchange, such as a plastron (a layer of air on their body).

• Backswimmers exploit a niche that most aquatic bugs cannot due to their unique adaptations:

• Able to maintain neutral buoyancy allowing access to different prey items.

• Possess specific cell types with hemoglobin, unlike other insects which do not have hemoglobin in their blood.

Structure of Backswimmer

• Unique adaptations include:

• Air storage in their body.

• Limbs resembling oars for surface movement.

• Hydrophobic hairs on the belly helping prevent gas exchange with water.

Hemoglobin Function in Backswimmer

• Backswimmers use hemoglobin in cells to store oxygen, which is similar to its function in vertebrates.

• When surfaced, they:

• Open their spiracles to let in air when the partial pressure of O2 is low in trachea.

• This air rushes in and binds to hemoglobin, thus maintaining low O2 pressure in trachea, allowing more oxygen influx.

Process of Oxygen Uptake

• Oxygen will bind to hemoglobin, keeping the partial pressure of O2 low, allowing continuous oxygen uptake.

• Activation of hemoglobin leads to increased O2 saturation in both hemoglobin cells and trachea.

Dives and Buoyancy Control

• After sufficient oxygen uptake, the backswimmer can dive:

• Initially experiences positive buoyancy due to the oxygen in the trachea.

• Once this oxygen is utilized, they can maintain neutral buoyancy.

• CO2 produced during respiration gets bound to hemoglobin, keeping its free gas pressure low.

Carbon Dioxide Release and Its Importance

• As hemoglobin releases O2 back to tissues, it can now bind CO2 due to partial pressure gradients.

• If the trachea fills with CO2, it leads to increased density, causing the animal to sink.

• Emphasis on Control: Backswimmers cannot release CO2 freely during dives due to risk of water entry and drowning.

• Most CO2 binds with hemoglobin or converts to bicarbonate to manage buoyancy.

Conclusion

• Understanding the gas exchange mechanisms allows insight into aquatic adaptations.

• Key takeaway: both oxygen and carbon dioxide management are crucial for the survival of aquatic organisms, demonstrating the balance maintained by respiratory adaptations.