Laboratory evaluation of egg white and milk external biomarkers for Wasmannia auropunctata (Hymenoptera: Formicidae)

Authors: MONTGOMERY, MICHELLE - University Of Canberra; Hagler, James; VANDERWOUDE, CASPER - University Of Canberra; LYNCH, A.JASMYN - University Of Canberra; ROBINSON, WAYNE - Charles Sturt University

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2019
Publication Date: 12/20/2019
Citation: Montgomery, M., Hagler, J.R., Vanderwoude, C., Lynch, A.J., Robinson, W.A. 2019. Laboratory evaluation of egg white and milk external biomarkers for Wasmannia auropunctata (Hymenoptera: Formicidae). Journal of Insect Science. 19(6):1-5. https://doi.org/10.1093/jisesa/iez121.
DOI: https://doi.org/10.1093/jisesa/iez121

Interpretive Summary: The little fire ant is a major invasive pest in Hawaii and is spreading throughout the pacific region. Unfortunately, despite being one of the most invasive species in the world, little is known about its population dynamics, foraging range, or distribution of food resources. Greater knowledge of this ant’s dispersal or movement patterns is critical for more effective control of this noxious pest. Insect dispersal is often studied using marked insects, but the marker must be easily and unambiguously detectable. An ARS scientist at Maricopa, AZ in collaboration with researchers at The Hawaii Ant Lab in Manoa, Hawaii marked little fire ants with two protein markers: egg albumin from chicken egg whites and casein from cow’s milk. In turn, sensitive assays were used to detect these specific proteins on the ants. Results indicated that the albumin biomarker was retained longer than casein and that more ants were successfully marked when a direct spray application method was employed. However, cross-contamination tests showed that the mark was frequently transferred from marked to unmarked individuals. Based on our results, the protein marks were useful for tagging little fire ants, but the potential for cross-contamination (false positives) of the samples must be considered.

Technical Abstract: Acquisition and retention of two protein-markers were tested on little fire ants, Wasmannia auropunctata Roger. Pure (100%) cow’s milk and a dilution (10%) of chicken egg whites were applied to W. auropunctata directly by contact spray plus residue or indirectly via residual contact only with protein-marked plant debris. Protein-marked ants were held in plastic shoe-box sized containers, collected at 0, 24 and 48 hours after exposure to their respective marks, and then examined for the presence of the marks by a chicken egg albumin and milk casein-specific enzyme-linked immunosorbent assay (ELISA).Cross-contamination rates were assessed by allowing an equal number of ants marked with egg whites and milk to interact for 24 and 48 hours after exposure, then collected either individually or in bulk. Results indicated that the egg whites biomarker was retained longer than milk, and that more ants were successfully marked when the direct spray application method was employed. Cross-contamination rates were highest among bulk-collected ants and lowest among ants collected individually 24 hours after exposure. However, the rates of cross-contamination among individually collected ants increased and were similar to that of bulk-collected ants 48 h after exposure. Based on our results, external protein marking may not be suitable if mass trapping is required or if the study extends beyond 24 h due to high cross-contamination rates among specimens collected in bulk and low marker detection rates beyond 24 hours.