A Comprehensive Method for the Evaluation of Hermetia illucens Egg Quality Parameters: Implications and Influence Factors

SIMPLE SUMMARY: Manual methods for counting insect eggs have certain shortcomings, and automatic methods often record counting errors due to confusion of objects in the visual field. There is paramount interest in research and innovation in the case of Hermetia illucens. Reproduction represents the vital part of the biological cycle, where the number of eggs is of significant importance. The development of a preparation method and precise egg counting, as well as an accurate technique for evaluating egg biometric parameters are the main research objectives. This precise method of egg preparation and counting proposed consists of dispersing the egg clutch under a stereo microscope and counting the eggs by the operator on a photographic capture using the Clickmaster software. The accuracy of the method is over 99.4% and the appropriate dispersion solutions were 50% glycerin and 70% ethanol. The length and width of eggs can be accurately evaluated, and positively correlated with egg weight and with the number of eggs. The methods proposed allow for a precise evaluation of the reproductive parameters of H. illucens, highly applicable in the selection process of adult flies as well as in the optimal breeding technology. ABSTRACT: The significant momentum received by Hermetia illucens as a worldwide species is due to its biological traits and large applicability in scientific research, environmental entomoremediation, insect meal production, and for biodiesel yield. The aim of this research is to develop a method for the preparation and precise egg counting of the H. illucens egg clutch, as well as an accurate technique for evaluating egg biometric parameters. The precise proposed method for egg preparation and counting consists in dispersing the eggs clutch under a stereo microscope and counting the eggs on a photographic capture using the Clickmaster software. Five solution types were used to disperse the egg clutches: glycerin 50%, ethanol 70%, ethanol 80%, physiological serum 0.9% and purified water. The efficiency of the estimation method for eggs number evaluation was also tested by using the estimated egg weight as a conversion factor. The biometric parameters of single eggs (length and width) were determined using the free Toupview software. The precise method of egg preparation and counting allows for the registration of the eggs number manually identified by the operator. The appropriate dispersion solutions were glycerin 50% and ethanol 70%. The method has an error of 1.4 eggs for each 500 counted eggs, thus an accuracy of over 99.4%. The eggs number estimation method is not applicable without significant errors, the accuracy being less than 32%, due to egg heterogeneity in the clutch. Biometric parameters (length and width) are positively correlated with egg weight (r = 0.759) and with the number of eggs in the clutch (r = 0.645). In conclusion, the results clearly suggest the method of egg preparation and precise counting for an accurate evaluation of quality parameters of the H. illucens clutches, as well as the technique for evaluating egg biometric parameters.