Browsing by Author "Stevens, Glen"

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Conspecific and heterospecific pheromones stimulate dispersal of entomopathogenic nematodes during quiescence
(Nature Portfolio, 2020-03-18) Kaplan, Fatma; Gentil, Abigail Perret; Giurintano, Julie; Stevens, Glen; Schiller, Karl C.; Mirti, Amaleah; Sampson, Edith; Torres, Cedric; Sun, Jiayi; Lewis, Edwin E.; Ilan, David Shapiro; Erdoğan, Hilal; Bursa Uludağ Üniversitesi/Ziraat Fakültesi/Biyosistem Mühendisliği.; 0000-0002-0387-2600; AAP-5834-2020; 57216199216
Ascaroside pheromones stimulate dispersal, a key nematode behavior to find a new food source. Ascarosides produced by entomopathogenic nematodes (EPNs) drive infective juvenile (IJ) emergence from consumed cadavers and dispersal in soil. Without ascarosides from host cadavers, Steinernema feltiae (EPN) reduce dispersal substantially. To determine whether other Steinernema spp. exhibit the same behavior, we compared S. feltiae and S. carpocapsae IJs without host cadaver pheromones. Unlike S. feltiae, S. carpocapsae IJs continued to disperse. However, S. carpocapsae IJs exhibited a temperature-dependent quiescent period. The IJ quiescent period increased at ≤20 °C but did not appear at ≥25 °C. Consistent with this, S. carpocapsae IJ quiescence increased from 30 min to 24 h at ≤20 °C over 60 days. The quiescent period was overcome by dispersal pheromone extracts of their own, other Steinernema spp. and Heterorhabditis spp. Furthermore, S. carpocapsae IJ ambush foraging associated behaviors (tail standing, waving, and jumping) were unaffected by the absence or presence of host cadaver pheromones. For S. feltiae, IJ dispersal declined at all temperatures tested. Understanding the interaction between foraging strategies and pheromone signals will help uncover molecular mechanisms of host seeking, pathogenicity and practical applications to improve the EPN’s efficacy as biocontrol agents.
Group joining behaviours in the entomopathogenic nematode steinernema glaseri
(Elsevier, 2023-03-28) Stevens, Glen; Erdoğan, Hilal; Pimentel, Eleanor; Dotson, Jenna; Stevens, Asa; Shapiro-Ilan, David; Kaplan, Fatma; Schliekelman, Paul; Lewis, Edwin; ERDOĞAN, HİLAL; Bursa Uludağ Üniversitesi/Ziraat Fakültesi/Biyosistem Mühendisliği Bölümü; AAP-5834-2020
Aggregations of foraging animals are key aspects of their ecology, driving spatial patterns, resource access, and successful resource exploitation. Entomopathogenic/insect parasitic nematodes demonstrate aggregated population structures. However, there are gaps in our understanding of how different behaviours affect aggregation. To understand joining behaviour as a mechanism of aggregation, we examined the group movement and joining behaviour of the EPN species, Steinernema glaseri, in conspecific (S. glaseri) and heterospecific (S. carpocapsae and S. feltiae) assemblages. We assessed group movement of S. glaseri using a glass olfactometer where nematodes were added to the central hub and allowed to disperse into six arms towards cues at the ends. 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. 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, S. glaseri readily moved towards and joined conspecific groups, particularly if those conspecifics had experienced host contact 48 h previously. When heterospecific nematodes were present in the ends, S. glaseri only appeared to preferentially join groups of S. feltiae with prior host contact. S. glaseri exhibited no propensity to join groups of S. carpocapsae regardless of prior host contact. Findings demonstrate context-dependent joining behaviours that may underlie aggregation in EPNs. These behaviours may lead to more effective mass attack and regulate interspecific competition among these insect parasites.
Nematodes follow a leader
(Frontiers Media Sa, 2021-11-04) Erdoğan, Hilal; Cruzado-Gutierrez, Karin; Stevens, Glen; Shapiro-Ilan, David; Kaplan, Fatma; Alborn, Hans; Lewis, Edwin; ERDOĞAN, HİLAL; Bursa Uludağ Üniversitesi/Ziraat Fakültesi/Biyosistem Mühendisliği Bölümü.; AAP-5834-2020
Aggregated movement and population structure are known in entomopathogenic nematodes, which are obligate insect parasites. Aggregation behavior in the absence of external stimuli suggests communication among individuals, often in the form of trail-following, which has not been shown by nematodes of any kind. Interactions among individuals are an essential basis of following behaviors and can have significant fitness consequences. We explored intraspecific and interspecific interactions among three Steinernema species (S. glaseri, S. carpocapsae, and S. feltiae) in terms of trail following, and fitness outcomes of following heterospecific individuals. We found that the following behavior is context dependent. Following behavior among conspecifics was significantly increased when the lead nematode had prior contact with host cuticle. However, we did not find a clear association between the following response to heterospecific IJs and their reproductive success in a co-infected host.