Doctoral defence Leonard Owuraku Opare “Rearing density effects on a commercially important insect species”

On 6 September at 10:15 Leonard Opare will defend his doctoral thesis “Rearing density effects on a commercially important insect species” for obtaining the degree of Doctor of Philosophy (in Zoology and Ecology).

Supervisors:
Associate Professor Toomas Esperk, University of Tartu
Research Fellow Sille Holm, University of Tartu

Opponent:
Associate Professor Cecilia Lalander, Swedish University of Agricultural Sciences (Sweden)

Summary

The use of insects for food and feed has recently attracted attention as a sustainable alternative to traditional livestock. Edible insects such as the black soldier fly (BSF) provide nutritional benefits similar to those of conventional animal products. However, the industry is still emerging, and much remains to be learned about utilising the species for mass-rearing purposes. Life history theory aids in understanding the complex life cycles of organisms and the evolution of their life history traits in changing environments. Life history traits are closely related to fitness and are frequently traded off against each other, so investing more in one trait typically comes at the expense of others. This profoundly influences how organisms grow, reproduce, and survive in various environments. For insects, a key environmental factor for insects is larval density. High larval density often leads to smaller body size, higher mortality, and faster or slower development. Our results revealed that optimal conditions for BSF larvae are low densities and temperatures around 27 °C. They grow larger, develop faster, and have higher fat content at low larval densities. Contrary to this, high densities, while boosting immune responses, often result in smaller larvae with longer development times. As the influence of larval density on BSF life history traits depends on temperature, fungal pathogen and substrate type, maintaining optimal larval density and controlling other key environmental factors is crucial. Fermentation serves as a way to alleviate some of the negative effects of high larval density. However, the effectiveness of fermentation depends on the substrate type and the environment. Our study highlights the importance of managing multiple environmental factors simultaneously. By understanding this, producers of insects for food and feed can optimise rearing conditions to maximise yields and increase production efficiency.

The doctoral thesis defense can also be followed online: https://ut-ee.zoom.us/j/99506408152?pwd=SUWm0wF9TC89bmYsNrImJcmq8Es3Ks.1 (Meeting ID: 995 0640 8152, Passcode: 209849).