Band movement and thermoregulation in Schistocerca cancellata

Piou, Cyril; Zagaglia, Gustavo; Medina, Héctor E.; Trumper, Eduardo V.; Brizuela, Ximena Rojo; Maeno, Koutaro Ould

doi:10.1016/j.jinsphys.2021.104328

Cited by 14 publications

(6 citation statements)

References 41 publications

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“…Therefore, our aim in this study is to answer the question of the validity of those models, which if proven valid, would provide an even more trustworthy tool for solving the problem of the lack of standardised tools for S. gregaria sample categorization and phase assessment. That being said, we do not aim at characterising the phenomenon of locust outbreaks per se (an issue already approached in several earlier works [12][13][14]19,21,[29][30][31][32][33][34][35][36][37][38][39] and that is still being analysed in current research). Neither do we aim at a simple repeat of a previous work; thus, we will not discuss every single result in the present work as, having successfully replicated our previous results, such discussion can be found in our earlier extensive work [27].…”

Section: Discussionmentioning

confidence: 99%

The Multivariate Regression Models Suggested as Standardising Tools for Categorising Solitarious and Gregarious Groups of the Main Pest Locust, Schistocerca gregaria, Produce Reproducible Results

Saadi,

Bakkali,

Martín-Blázquez

et al. 2024

Insects

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Outbreaks of the desert locust Schistocerca gregaria affect some of the poorest parts of Africa, with devastating outcomes. The key to understanding and dealing with this problematic adaptation to environmental changes is comparing gregarious and solitarious locusts, either in nature or in laboratories. Categorising locusts and detecting changes in their phase status is key to such comparisons, which have been hitherto based on applying mathematical models that use behavioural parameters and that each laboratory has to build anew for each experiment. All the models used thus far are different from one another. This implies differences in the tools used for the different experiments and by the different laboratories and, thus, potential noise in the results and interpretations. Standardising the way locusts are categorised is necessary if we want to reduce noise and errors. It is crucial if we seek to make the results and interpretations transferable and comparable between experiments and laboratories for such an important research area. To tackle this problem, we suggested two models as possible standardising tools. However, the problem of a lack of standardised tools re-emerged due to the doubts cast on the validity of those models. Here, we use samples from independent S. gregaria populations in order to test and validate those models. We discuss how successful the two models were at categorising solitarious, intermediate (transient), and gregarious nymph and adult S. gregaria samples. We highlight shortcomings and make more specific recommendations on the use of those models based on the precision differences they show when categorising solitarious and gregarious S. gregaria nymph and adult samples. Overall, both models have proven to be valid since their results were largely replicated and seem reproducible.

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Section: Discussionmentioning

confidence: 99%

The Multivariate Regression Models Suggested as Standardising Tools for Categorising Solitarious and Gregarious Groups of the Main Pest Locust, Schistocerca gregaria, Produce Reproducible Results

Saadi,

Bakkali,

Martín-Blázquez

et al. 2024

Insects

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“…If food is readily available, animals can fill their guts faster than they can digest the food (Angilletta, 2001; Congdon, 1989; Grant & Porter, 1992; Harrison & Fewell, 1995; Levy et al, 2017; Miller et al, 2009; Yang & Joern, 1994). These digestive bottlenecks may be especially common in outbreaking herbivores such as grasshoppers and locusts that are surrounded by abundant food during the growing season (Belovsky, 1978; Hairston et al, 1980; Maeno et al, 2021; Piou et al, 2022). In our laboratory experiment, body temperatures near 40°C maximized the rate of digestion, as estimated by defecation rate (Figures 1–2).…”

Section: Discussionmentioning

confidence: 99%

Climate change expected to improve digestive rate and trigger range expansion in outbreaking locusts

Youngblood

Cease

Copa

et al. 2022

Ecological Monographs

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Global climate change will probably exacerbate crop losses from insect pests, reducing agricultural production, and threatening food security. To predict where crop losses will occur, scientists have mainly used correlative models of species' distributions, but such models are unreliable when extrapolated to future environments. To minimize extrapolation, we developed mechanistic and hybrid models that explicitly capture range‐limiting processes, and we explored how incorporating mechanisms altered the projected impacts of climate change for an agricultural pest, the South American locust (Schistocerca cancellata). Because locusts are generalist herbivores surrounded by food, their population growth may be limited by thermal effects on digestion more than food availability. To incorporate this mechanism into a distribution model, we measured the thermal effects on the consumption and defecation of field‐captured locusts and used these data to model energy gain in current and future climates. We then created hybrid models by using outputs of the mechanistic model as predictor variables in correlative models, estimating the potential distribution of gregarious outbreaking locusts based on multiple predictor sets, modeling algorithms, and climate scenarios. Based on the mechanistic model, locusts can assimilate relatively high amounts of energy throughout temperate and tropical South America; however, correlative and hybrid modeling revealed that most tropical areas are unsuitable for locusts. When estimating current distributions, the top‐ranked model was always the one fit with mechanistic predictors (i.e., the hybrid model). When projected to future climates, top‐ranked hybrid models projected range expansions that were 23%–30% points smaller than those projected by correlative models. Therefore, a combination of the correlative and mechanistic approaches bracketed the potential outcomes of climate change and enhanced confidence where model projections agreed. Because all models projected a poleward range expansion under climate change, agriculturists should consider enhanced monitoring and the management of locusts near the southern margin of the range.

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“…In reality, however, non-cannibalistic interactions among locust nymphs are exceedingly common (Ariel et al 2014;Ariel and Ayali 2015). Indeed, gregarious nymphs frequently stop marching and aggregate at high densities (often touching one another) during morning and pre-dusk stationary basking, midday sheltering, postprandial resting and night-roosting with no cannibalism of healthy non-molting kin (Ellis and Ashall 1957;Ariel and Ayali 2015;Maeno and Ould Babah Ebbe 2018;Dkhili et al 2019;Maeno et al 2021a;Piou et al 2022). In our studies of S. gregaria in the field during 11 years, we never observed cannibalism during marching or on healthy non-molting individuals.…”

Section: Marching and Cannibalism In Orthopteramentioning

confidence: 99%

How molting locusts avoid cannibalism

et al. 2023

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Group living has various benefits, but it also carries costs, such as risk of cannibalism. Molting is a vulnerable period of being cannibalized in juvenile arthropods, but how gregarious arthropods avoid this threat is poorly understood. Here, we examined how actively migrating gregarious nymphs of desert locust, Schistocerca gregaria, avoid cannibalism during molting, in the Sahara Desert of Mauritania. In the field, gregarious nymphs cyclically march and feed on grass during the day. Our field observations found that marching behavior helped separating pre-molting and cannibalistic non-molting nymphs. Cannibalistic non-molting nymphs marched away from roost plants, leaving sedentary pre-molting nymphs behind, creating cannibal-free spaces. Some non-molting nymphs reached a pre-molting state after daytime marching, thus both pre- and non-molting nymphs roosted on same plants at night. However, pre-molting nymphs moved away from conspecifics prior to molting. Starvation experiments confirmed that food-satiation decreased cannibalistic necrophagy. Physiological surveys of diel feeding and molting patterns revealed that nymphs molted at times when conspecifics were food-satiated rather than hungry. Hence, our results indicate that behavioral and physiological traits of gregarious locusts could function to spatiotemporally separate molting locusts from cannibalistic conspecifics, thus reducing molting-associated cannibalism. This is the first report of migration-dependent molting synchrony as a mechanism reducing costs of aggregation in gregarious arthropods.

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Band movement and thermoregulation in Schistocerca cancellata

Cited by 14 publications

References 41 publications

The Multivariate Regression Models Suggested as Standardising Tools for Categorising Solitarious and Gregarious Groups of the Main Pest Locust, Schistocerca gregaria, Produce Reproducible Results

The Multivariate Regression Models Suggested as Standardising Tools for Categorising Solitarious and Gregarious Groups of the Main Pest Locust, Schistocerca gregaria, Produce Reproducible Results

Climate change expected to improve digestive rate and trigger range expansion in outbreaking locusts

How molting locusts avoid cannibalism

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