Physiological and molecular correlates of the screwworm fly attraction to wound and animal odors

Authors: Hickner, Paul; MITTAPALLI, OMPRAKASH - University Of Kentucky; SUBRAMONIAM, ANJANA - University Of Kentucky; SAGEL, AGUSTIN - US Department Of Agriculture (USDA); WATSON, WES - North Carolina State University; SCOTT, MAXWELL - North Carolina State University; Arp, Alex; Perez De Leon, Adalberto - Beto; SYED, ZAINULABEUDDIN - University Of Kentucky

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2020
Publication Date: 11/27/2020
Citation: Hickner, P.V., Mittapalli, O., Subramoniam, A., Sagel, A., Watson, W., Scott, M.J., Arp, A.P., Perez De Leon, A.A., Syed, Z. 2020. Physiological and molecular correlates of the screwworm fly attraction to wound and animal odors. Scientific Reports. 10. Article 20771. https://www.nature.com/articles/s41598-020-77541-w.
DOI: https://doi.org/10.1038/s41598-020-77541-w

Interpretive Summary: The screwworm fly, Cochliomyia hominivorax (Coquerel), is an important pest of livestock that was successfully eradicated from the United States by the sterile insect technique (SIT). Surveillance, a key component of screwworm control programs, utilizes traps baited with rotting liver or a blend of synthetic chemicals such as swormlure-4. Because SIT depends on the released sterile males mating with wild females, lures designed to attract males would help assess the survival and density of the released males. However, the current lure attracts mostly females. In addition, many non-target flies are captured such as the secondary screwworm fly, C. macellaria. Here we studied sex-specific responses to chemical components of swormlure-4. An insect antenna is functionally equivalent to a nose in mammals. Therefore, we used electroantennography (EAG) to measure the olfactory response of mated and unmated female, and male screwworm and secondary screwworm flies to the swormlure-4 chemical components. We also analyzed the antennal transcriptome by RNA-sequencing to determine if there are differences in the expression of chemosensory genes between male and female screwworm flies.

Technical Abstract: The screwworm fly, Cochliomyia hominivorax (Coquerel), was successfully eradicated from the United States by the sterile insect technique (SIT). However, recent detection of these flies in the Florida Keys, and increased risk of introductions to the other areas warrant novel tools for management of the flies. Surveillance, a key component of screwworm control programs, , utilizes traps baited with rotting liver or a blend of synthetic chemicals such as swomrlure-4. In this work, we evaluated the olfactory physiology of the screwworm fly and compared it with the secondary screwworm flies, C. macellaria, which occurs in geographically overlapping regions and greatly outnumber screwworm flies in the existing monitoring traps. Olfactory responses to swormlure-4 constituent between gender and mating status (mated vs unmated) in both species were recorded and compared. Overall, the olfactory detection by two fly species was apparent to the tested odorants, and distinct. We also present detailed analyses of the antennal transcriptome by RNA-Sequencing that reveal significant differences between male and female screwworm. The differential expression patterns were confirmed by quantitative PCR. Taken together, this integrated study provides insights into the physiological and molecular correlates of the screwworm’s attraction to wounds, and identifies molecular targets that will aid in the development of odorant-based fly management strategies.