Ontogenetic variation in metabolic rate-temperature relationships during larval development

Area of Science:

• Ecology
• Physiology
• Evolutionary Biology

Background:

• Ectotherm environmental response models often use limited insect thermal performance data.
• Existing models frequently overlook ontogenetic variation and non-adult stages.
• Metabolic rate predictions often neglect body size and temperature interactions.

Purpose of the Study:

• Investigate ontogenetic variation in ectotherm physiology.
• Assess the impact of this variation on predictive modeling.
• Examine metabolic rate-temperature (MR-T) relationships across insect larval instars.

Main Methods:

• Studied routine metabolic rates (RMRs) in spongy moth (Lymantria dispar dispar) larvae.
• Assayed RMRs across eight temperatures for the first five larval instars.
• Accounted for body mass differences in allometric analyses.

Main Results:

• Larval instars exhibited significant variation in MR-T relationships, even after controlling for body mass.
• Temperature sensitivity and allometry of RMR peaked in the third instar.
• These MR-T parameters decreased in later larval instars (fourth and fifth).

Conclusions:

• Insect thermal physiology is dynamic throughout larval development.
• Ontogenetic shifts in physiology must be considered for accurate ectotherm predictive models.
• Current modeling approaches may be insufficient due to ignoring developmental changes.