New insights into the plasticity of gill structure

Area of Science:

• Physiology
• Ichthyology
• Environmental Biology

Background:

• Some fish species, like crucian carp and goldfish, exhibit remarkable gill plasticity.
• Gill lamellae can be covered by an interlamellar cell mass (ILCM) under normoxic, cold conditions.
• ILCM regression in hypoxia, warm water, or exercise increases respiratory surface area and oxygen uptake.

Purpose of the Study:

• Investigate the adaptive significance of gill remodeling in fish.
• Explore potential benefits beyond oxygen uptake, such as osmoregulation, toxin limitation, and infection prevention.
• Present evidence supporting the role of gill structure changes in defense against parasites.

Main Methods:

• Observation of gill morphology changes in response to varying environmental conditions (hypoxia, temperature, exercise).
• Comparative analysis of gill structure in infected versus uninfected fish under hypoxic stress.
• Review of existing literature on gill remodeling across different fish taxa.

Main Results:

• ILCM regresses under hypoxia, warm water, and exercise, enhancing oxygen uptake capacity.
• Evidence suggests ILCM maintenance in hypoxia-infected crucian carp, indicating a potential role in parasite defense.
• Gill remodeling is observed in various fish groups, including cyprinids, killifish, eel, salmonids, and anabantoids.

Conclusions:

• Fish gill remodeling is a widespread adaptation with multiple potential benefits.
• While enhancing oxygen uptake is a primary function, protection against environmental challenges like infection may also drive this plasticity.
• The osmo-respiratory compromise hypothesis requires further investigation.