Dissecting the Gut of An Insect- How Does Black Soldier Fly Digestion Work So Well?

I received this paper this morning from my colleagues in Italy. If you have the time, please do take a look at it. They did an exceptional job detailing the digestive tract of the BSF larva. 

Such research is sorely needed as we are attempting to harness the BSF larval process for recycling wastes. They seem to be able to digest just about anything organic (sounds like a grand challenge- "find the organic waste streams BSF are NOT capable of digesting").  

Bonelli, M., D. Bruno, S. Caccia, G. Sgambetterra, S. Cappellozza, C. Jucker, G. Tettamanti, and M. Casartelli. 2019. Structural and functional characterization of Hermetia illucens larval midgut. Frontiers in Physiology 10.

In this study, the authors focused on the midgut of the fully developed larva, which had been raised on a standard grain diet. They dissected the full digestive tract and provide excellent images detailing the various anatomical features at a gross scale. 

Much like a previous study presented in this blog, the authors detailed the pH of the various regions of the gut. But, they also build on this knowledge with detailed description of the morphology (physical features) of the midgut cell lining (epithelium) while distinguishing the different regions. They then proceed with a description of the digestive enzymes (through a multitude of experiments) identified and their activity in the midgut. They accomplished this goal by adding temperature as a factor and determined if shifting temperature impacted such activity. I consider this a key part of the study as they demonstrate temperature impacts enzymatic activity- with peak performance at 45C. This is really interesting as it suggests BSF larvae are capable of handling these high temperatures during development; however, temperatures above 45C negatively impacted activity). 

A couple of questions for the authors and others to ponder:
1. How does the midgut vary across instars (larval development stages)?
2. How plastic is the digestive tract with regards to food provided (i.e., does the morphology shift when larvae are fed different diets)?
3. How much variation do we see across populations from around the world?
4. Any thoughts on how to better prepare larval diets to take advantage of the capabilities of the midgut of the BSF larva (i.e., can we better formulate diets to enhance digestion and protein production)?

Author

Jeffery K. Tomberlin, PhD, Boggled by Insect Physiology
Director, EVO Conversion Systems, LLC
​Twitter: @FliesFacility