Evaluation of a 3D-printed pipette tip for seeding housefly eggs

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Egg manipulation is crucial in insect breeding and research. Housefly eggs are small, delicate and susceptible to dehydration. Hence, researchers require rapid and gentle ways to manipulate specific quantities, with consistent quality. Therefore, a 3D-printed pipette tip was designed and tested. Three series of pipette tips, differing in volume (A: 12.7 mm3; B: 15.2 mm3; and C: 17.7 mm3), were printed in triplicate and subjected to four experimental procedures. Eggs from a housefly colony were suspended in water, sucked up with the 3D-printed tip mounted on a Pasteur plastic pipette and released on a piece of coffee filter. Repeatability intra-run and reproducibility inter-day were evaluated by counting the eggs manipulated with the experimental tips. Time needed for egg sowing via a pipette tip was compared to time needed for counting 100 eggs delivered by a Paster pipette (control). Potential damage to eggs due to the pipette tip was estimated by quantifying fecundity (egg eclosion and larval survival). Coefficients of variation intra-run and inter-day were similar over replicates. Pipette set B had the best repeatability (coefficient of variation intra-run between 4.4 and 4.7%), and pipette set C the highest reproducibility (coefficient of variation inter-day of 2.6%). Egg damage due to the tip was negligible, however the tips did reduce larval survival (between 46.1±7.2% and 63.4±18.9%), compared to the control (between 66.0±2.4 and 75.5±9.3%). The pipette size and number of dispensed eggs correlated well (R2=0.90,P<0.001), but the relation was non-linear (y = 0.051034 x2+ 12.356 x – 0.03627). The time needed to sow a fixed number of eggs on the rearing substrate was reduced by 73% (pipette A) – 80% (pipette C) by using the pipette tip, compared to visual quantification.