Warm acclimation improves hypoxia tolerance in Fundulus heteroclitus

Area of Science:

• Environmental Science
• Aquatic Ecology
• Physiology

Background:

• Rising global temperatures and increased frequency of hypoxic events threaten aquatic ecosystems.
• The potential for acclimation to one stressor to mitigate another remains understudied.

Purpose of the Study:

• To investigate if acclimation to warm temperatures enhances hypoxia tolerance in Atlantic killifish (Fundulus heteroclitus).
• To compare hypoxia tolerance between northern and southern subspecies of Atlantic killifish.
• To explore the role of gill morphology in mediating thermal and hypoxia tolerance.

Main Methods:

• Measuring time to loss of equilibrium in hypoxia (LOEhyp) at varying temperatures.
• Assessing critical oxygen tension (Pcrit) and LOEhyp for different subspecies.
• Examining gill lamellar surface area and interlamellar cell mass (ILCM) following warm acclimation.

Main Results:

• Warm acclimation significantly increased hypoxia tolerance (time to LOEhyp).
• The southern subspecies exhibited greater hypoxia tolerance than the northern subspecies.
• Warm acclimation increased gill lamellar surface area via ILCM regression, but this did not fully explain subspecies differences in hypoxia tolerance.

Conclusions:

• Thermal plasticity in gill morphology enhances Atlantic killifish's capacity to tolerate hypoxia.
• Existing physiological plasticity may aid aquatic organisms in coping with interacting climate change stressors.
• Differences in routine metabolic rate may contribute to subspecies-specific hypoxia tolerance.