Caterpillars have evolved lungs for hemocyte gas exchange

Area of Science:

• Insect Physiology
• Respiratory Systems
• Cell Biology

Background:

• Insect respiration relies on a tracheal system for gas exchange via diffusion.
• Insect hemocytes (blood cells) are typically not tracheated and float in hemolymph.
• Anoxia affects hemocyte structure and localization in caterpillars.

Purpose of the Study:

• To investigate the interaction between insect hemocytes and the tracheal system under anoxic conditions.
• To explore a novel respiratory function for specialized tracheal structures in insects.

Main Methods:

• Observation of hemocyte behavior and structure in caterpillars exposed to anoxia.
• Analysis of hemocyte accumulation in specific tracheal regions, particularly the 8th abdominal spiracles and tokus.

Main Results:

• Anoxia induces structural changes in hemocytes, leading to their release from tissues.
• Hemocytes aggregate in thin-walled tracheal tufts near the posterior spiracles.
• Residence in these tracheal structures restores normal hemocyte morphology.
• Hemocytes also adhere to tracheae within the tokus compartment.

Conclusions:

• The specialized tracheal system in the 8th abdominal segment and tokus may function as a 'lung' for hemocytes.
• This represents a novel concept in insect physiology, where hemocytes actively move to tracheal structures.
• Insect tracheae, usually supplying tissues, are shown to be sites visited by hemocytes.