Interspecific differences in hypoxia-induced gill remodeling in carp.

Area of Science:

• Comparative Physiology
• Aquatic Ecology
• Fish Biology

Background:

• Fish gills undergo remodeling in response to environmental changes like oxygen levels, temperature, and exercise.
• Crucian carp and goldfish are known for their remarkable gill remodeling capabilities.
• Hypoxia tolerance varies significantly among different fish species and populations.

Purpose of the Study:

• To investigate interspecific variation in hypoxia-induced gill remodeling and hypoxia tolerance within cyprinids.
• To determine the relationship between gill morphology, hypoxia tolerance, and phylogenetic relatedness in carp.

Main Methods:

• Assessed hypoxia tolerance by measuring the oxygen tension at which fish lost equilibrium (LOEcrit) in 10 carp groups.
• Quantified mass-specific gill surface area and interlamellar cell mass (ILCM) volume under normoxia and hypoxia.
• Analyzed the correlation between gill morphology, LOEcrit, and phylogenetic relationships.

Main Results:

• Significant variation in hypoxia tolerance (LOEcrit) was observed among the carp groups.
• Hypoxia-tolerant carp had smaller gills in normoxia and exhibited greater hypoxia-induced reductions in ILCM volume.
• Gill remodeling reduced interspecific variation in gill surface area and eliminated the link between gill size and hypoxia tolerance.

Conclusions:

• The extent of gill remodeling in cyprinids is directly associated with hypoxia tolerance.
• This association is phylogenetically independent, highlighting adaptive plasticity.
• Gill remodeling is a crucial mechanism for enhancing hypoxia tolerance in carp.