Allometry of diving capacities: ectothermy vs. endothermy.

Area of Science:

• Comparative physiology
• Vertebrate biology
• Evolutionary biology

Background:

• Body mass is a critical factor influencing diving performance in air-breathing vertebrates.
• Understanding the relationship between body mass and dive duration is key to deciphering the evolution of diving.
• Previous studies primarily focused on endotherms, leaving a gap in knowledge regarding ectotherms.

Purpose of the Study:

• To investigate the relationship between body mass and dive duration across a diverse range of air-breathing vertebrates, including ectotherms.
• To compare the influence of body mass on dive duration between endothermic and ectothermic species.
• To explore the evolutionary implications of body mass on diving capacities in different vertebrate lineages.

Main Methods:

• Conducted a comprehensive review of existing literature on dive duration and body mass.
• Included a wide array of nonavian and nonmammalian diving vertebrates (sea snakes, iguanas, turtles, crocodiles).
• Analyzed data to assess the correlation between body mass and dive duration, comparing ectotherms and endotherms.

Main Results:

• The positive correlation between body mass and dive duration, widely observed in endotherms, was significantly weaker in ectotherms.
• No significant effect of body mass on dive duration was detected in ectothermic species.
• This suggests that factors other than body mass may be more influential for dive duration in ectotherms.

Conclusions:

• The influence of body mass on dive duration differs substantially between endotherms and ectotherms.
• Physiological differences, particularly the less direct link between body mass and respiratory demands in ectotherms, may explain the absence of a clear correlation.
• Future research on diving physiology evolution requires novel approaches that consider both endothermic and ectothermic strategies.