Seed cleaning behaviour and their antimicrobial effect on seed germination by seed harvester ant, Trichomyrmex scabriceps

Harvester ants are a group of ant species known for collecting, storing and disperse the seeds, resulting in reciprocal advantages for both seeds and ants through dissemination as well as nutrition rewards from digesting the lipid-rich elaiosome. Harvester ants, which are granivores, predate seeds from many ecosystems providing multiple benefits, including seed germination. Only a few seed harvester ants from the Trichomyrmex genus, Trichomyrmex scabriceps (Mayr) (Myrmicinae: Formicidae), are regularly found in peninsular India, and no knowledge on seed collection and and storage. The current study aimed to investigate the seed cleaning behaviour of the worker ants in finger millet (Eleusine coracana L.) and little millet (Panicum sumatrense Roth. ex. Roem. and Schultz) as well as assess the role of seed cleaning behaviour and exocrine gland secretions of the worker ant as seed protectants though seed germination. The frequency of self-grooming, antennation, and seed cleaning behaviours were observed at (4.84 ± 0.19, 4.23 ± 0.27, and 1.72 ± 0.25) per hour, respectively. The data showed that ants completely removed the seed husk and a tiny amount of the elaiosome during storage in the granary. Ant-collected nest seeds in the nest granary had the highest rate of germination (71.67 ± 4.41). Despite the fact that the microbial load was similar across treatments, nest seeds showed much lower microbial growth than other seeds. The colony development rate for nest seeds, plant seeds, ant seeds, ground seeds, and control seeds was 12.33 ± 0.88, 25.00 ± 1.15, 16.33 ± 0.88, 17.33 ± 1.20, and 10.66 ± 0.88. The present study shows that seed cleaning behaviour can positively impact the germination of a seed. Accordingly, we suggested that benefits of seed cleaning for both ants as well as seed. Furthermore, our results contribute to the understanding the activity of antimicrobial compounds promotes significant seed germination while inhibiting the growth of fungal spores on the seed surface.