Group joining behaviors in the entomopathogenic nematode Steinernema glaseri

Authors: STEVENS, GLEN - University Of Idaho; ERDOGAN, HILAL - University Of Idaho; PIMENTEL, ELEANOR - University Of Idaho; DOTSON, JENNA - University Of Idaho; STEVENS, ASA - University Of Idaho; Shapiro Ilan, David; KAPLAN, FATMA - Pheronym, Inc; SCHLIEKELMAN, PAUL - University Of Georgia; LEWIS, EDWIN - University Of Idaho

Submitted to: International Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2023
Publication Date: 3/28/2023
Citation: Stevens, G., Erdogan, H., Pimentel, E., Dotson, J., Stevens, A., Shapiro Ilan, D.I., Kaplan, F., Schliekelman, P., Lewis, E. 2023. Group joining behaviors in the entomopathogenic nematode Steinernema glaseri. International Journal of Parasitology. 181 : 105220. https://doi.org/10.1016/j.biocontrol.2023.105220.
DOI: https://doi.org/10.1016/j.biocontrol.2023.105220

Interpretive Summary: Beneficial nematodes (also called entomopathogenic nematodes) are small round worms that are used as natural bio-pesticides. These nematodes kill insect pests but do not harm humans or the environment. How beneficial nematodes move in soil and find their insect hosts to attack is not fully understand. We know that the nematodes move in groups, like a pack of wolves in the soil. However, we did not know if one group would join another. Therefore, we tested "joining behavior" in a particular beneficial nematode species called Steinernema glaseri. The nematodes readily joined other groups of the same species when moving in soil, especially if the group they were joining had recently had contact with and insect host. However, the species tested (Steinernema glaseri) was not as apt to join groups of other nematode species, perhaps due to potential competition. Understanding how and why beneficial nematodes move will help us to design improved control programs for important insect pests.

Technical Abstract: Aggregations of foraging animals are often key aspects of their ecology, driving spatial patterns, resource access, and successful resource exploitation. In this study we examined the group movement and joining behavior of an insect parasitic nematode. We assessed group movement of a single species (Steinernema glaseri) using a glass olfactometer where nematodes were added to the central hub and allowed to disperse into six arms towards cue pots at the end. We measured movement in the absence of external cues, when host cues were present but uniform, and in response to both con- and heterospecific entomopathogenic nematodes. We observed that S. glaseri dispersed in a highly aggregated fashion both in the presence and absence of host cues. When conspecific nematodes were present in the olfactometer ends, we found that S. glaseri readily moved towards (joined) conspecific groups, particularly if those conspecifics had experienced host contact 48 hours previously. When heterospecific nematodes were present in the ends, S. glaseri only appeared to preferentially join groups of one species (S. feltiae), and only when those S. feltiae nematodes had experienced host contact. S. glaseri exhibited no propensity towards joining groups of S. carpocapsae, contrasting with previous research on trail following among these species. These findings expand on recent work assessing group dispersal and following behaviors and demonstrate context-dependent joining behaviors in these nematodes. These behaviors may lead to more effective mass attack and also promote interspecific competition among these key insect parasites.