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Cui W, Ge J, Chen D, Nie X, Dong L, Wang X, Kang L. Dibutyl phthalate released by solitary female locusts mediates sexual communication at low density. Proc Natl Acad Sci U S A 2024; 121:e2401926121. [PMID: 39018190 PMCID: PMC11287119 DOI: 10.1073/pnas.2401926121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 06/16/2024] [Indexed: 07/19/2024] Open
Abstract
Sex pheromones play a crucial role in mate location and reproductive success. Insects face challenges in finding mates in low-density environments. The population dynamics of locusts vary greatly, ranging from solitary individuals to high-density swarms, leading to multiple-trait divergence between solitary and gregarious phases. However, differences in sexual communication between solitary and gregarious locusts have not been sufficiently explored. Herein, we found that solitary locusts but not gregarious ones heavily rely on a single compound, dibutyl phthalate (DBP), for sexual communication. DBP is abundantly released by solitary female locusts and elicits strong attraction of male solitary and gregarious locusts. Solitary adult males display much higher electrophysiological responses to DBP than adult females. Additionally, LmigOr13 was identified as the DBP-specific odorant receptor expressed in neurons housed in basiconic sensilla. Male LmigOr13-/- mutants generated by CRISPR/Cas9 have low electrophysiological responses and behavioral attraction to DBP in both laboratory and field cage experiments. Notably, the attractiveness of DBP to male locusts becomes more evident at lower population densities imposed by controlling the cage size. This finding sheds light on the utilization of a sex pheromone to promote reproductive success in extremely low-density conditions and provides important insights into alternative approaches for population monitoring of locusts.
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Affiliation(s)
- Weichan Cui
- State Key Laboratory of Integrated management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
- Department of Entomology, College of Plant Protection, China Agricultural University, Beijing100193, China
| | - Jin Ge
- State Key Laboratory of Integrated management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
| | - Dafeng Chen
- State Key Laboratory of Integrated management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
| | - Xin Nie
- State Key Laboratory of Integrated management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
| | - Liushu Dong
- State Key Laboratory of Integrated management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
| | - Xianhui Wang
- State Key Laboratory of Integrated management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
| | - Le Kang
- State Key Laboratory of Integrated management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing100101, China
- Department of Entomology, College of Plant Protection, China Agricultural University, Beijing100193, China
- Institute of Life Science and Green Development, College of Life Science, Hebei University, Baoding071002, China
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Maeno KO, Piou C, Leménager N. Egg size-dependent embryonic development in the desert locust, Schistocerca gregaria. JOURNAL OF INSECT PHYSIOLOGY 2023; 145:104467. [PMID: 36528090 DOI: 10.1016/j.jinsphys.2022.104467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/26/2022] [Accepted: 12/11/2022] [Indexed: 06/17/2023]
Abstract
Phenotypic plasticity in body size is a product of modification of the developmental pathway. Although hatchlings of the desert locust, Schistocerca gregaria, show egg size-dependent plasticity in body size, it remains unclear how embryogenesis during egg development regulates final embryonic body size. To determine the developmental pathway causing body size variation at hatching, we examined egg and embryonic development at the early, middle, and late egg developmental stages in S. gregaria by comparing small and large eggs. Crowd-reared females produced larger eggs than isolated-reared females. The daily egg developmental rate was similar between small and large eggs: eggs dramatically absorbed external water after days 3 to 7 and nearly doubled the initial egg weight at the late stage of day 12. Morphological measurements of eggs and embryos at different days after oviposition revealed that large eggs were longer than small eggs throughout developmental stages. However, embryo length was similar between small and large eggs at the early stage (anatrepsis). Embryos begin to absorb yolk into their bodies after blastokinesis. The size of large-egg embryos increased significantly from the middle stage (katatrepsis) due to absorption of more yolk than small eggs. Egg length and embryo length were conspicuously larger in large eggs than in small eggs on day 12 of late katatrepsis. These results suggest that egg size did not influence the egg developmental rate and initial embryo size. Large eggs had more yolk and space, resulting in larger final embryos than small eggs. The amount of yolk and size of eggshells during katatrepsis could play a key role in determining hatchling body size in S. gregaria.
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Affiliation(s)
- Koutaro Ould Maeno
- Japan International Research Center for Agricultural Sciences (JIRCAS), Livestock and Environment Division, Ohwashi 1-1, Tsukuba, Ibaraki 305-8686, Japan.
| | - Cyril Piou
- CIRAD, UMR CBGP, INRAE, Institut Agro, IRD, Université Montpellier, F-34398 Montpellier, France
| | - Nicolas Leménager
- CIRAD, UMR CBGP, INRAE, Institut Agro, IRD, Université Montpellier, F-34398 Montpellier, France
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3
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Maeno KO, Ould Ely S, Ould Mohamed S, Jaavar MEH, Ould Babah Ebbe MA. Thermoregulatory behavior of lekking male desert locusts, Schistocerca gregaria, in the Sahara Desert. J Therm Biol 2023; 112:103466. [PMID: 36796911 DOI: 10.1016/j.jtherbio.2023.103466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 12/28/2022] [Accepted: 12/28/2022] [Indexed: 01/27/2023]
Abstract
Most terrestrial animals are constrained by extreme heat conditions such as midday desert environments, while a few terrestrial ectothermic insects are active in such ecological niches. Sexually mature males of the desert locust (Schistocerca gregaria) in the Sahara Desert remain on the open ground, despite the ground temperatures exceeding their lethal limit, to form leks and to mate incoming gravid females during the daytime. Lekking male locusts apparently suffer from extreme heat stress and greatly fluctuating thermal conditions. The present study examined the thermoregulatory strategies of the lekking male S. gregaria. Our field observations showed that lekking males changed their body orientation toward the sun depending on the temperature and time of day. In the relatively cool morning, males basked by orienting perpendicular to the sun's rays, maximizing the area of body surface exposed to the sun's rays. In contrast, around midday, when the ground surface temperature exceeded lethal high temperatures, some males tended to shelter inside the plants or remain in the shade. However, the remainder stayed on the ground, stilted (i.e., extending their legs to raise their bodies off the hot ground) and oriented parallel to the sun's rays, which minimized radiative heating. Measurements of body temperature throughout the hot middle period of the day confirmed that the stilting posture prevented overheating. Their critical lethal body temperature was as high as 54.7 °C. In this lekking system, gravid females enter male leks by flying. These incoming females usually landed on open ground, whereupon nearby males immediately approached, mounted, and mated the female, implying that males with greater heat-tolerance can increase mating chance. These results suggest that behavioral thermoregulation and physiologically high heat tolerance of male desert locusts allows them to endure extreme thermal conditions for lekking.
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Affiliation(s)
- Koutaro Ould Maeno
- Japan International Research Center for Agricultural Sciences (JIRCAS), Livestock and Environment Division, Ohwashi 1-1, Tsukuba, Ibaraki, 305-8686, Japan; The Mauritanian National Desert Locust Centre, Centre National de Lutte Antiacridienne (CNLA), Nouakchott, BP 665, Mauritania.
| | - Sidi Ould Ely
- The Mauritanian National Desert Locust Centre, Centre National de Lutte Antiacridienne (CNLA), Nouakchott, BP 665, Mauritania; Mauritania National Center of Agricultural Research and Development, Centre National de Recherche Agronomique et de Développement Agricole (CNRADA), BP 22, Kaedi, Mauritania
| | - Sid'Ahmed Ould Mohamed
- The Mauritanian National Desert Locust Centre, Centre National de Lutte Antiacridienne (CNLA), Nouakchott, BP 665, Mauritania
| | - Mohamed El Hacen Jaavar
- The Mauritanian National Desert Locust Centre, Centre National de Lutte Antiacridienne (CNLA), Nouakchott, BP 665, Mauritania
| | - Mohamed Abdallahi Ould Babah Ebbe
- The Mauritanian National Desert Locust Centre, Centre National de Lutte Antiacridienne (CNLA), Nouakchott, BP 665, Mauritania; Institut du Sahel (INSAH)/CILSS, BP 1530, Bamako, Mali
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4
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Vernier C, Barthes N, Chapuis MP, Foucaud J, Huguenin J, Leménager N, Piou C. Faeces' odours attract gregarious locust hoppers. JOURNAL OF INSECT PHYSIOLOGY 2022; 143:104454. [PMID: 36343666 DOI: 10.1016/j.jinsphys.2022.104454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 10/14/2022] [Accepted: 10/21/2022] [Indexed: 06/16/2023]
Abstract
Collective motion is one of the most impressive common features of gregarious locusts: once formed, bands and swarms get moving for long distances. It was shown that visual perception of neighbours plays a key role in maintaining marching behaviour at a local scale. But at a larger scale, mechanisms underlying band cohesion are less understood. It was shown in several field studies that individuals separated from the band were able to get back to the group, even after being separated since a night. In this context, faeces' odours could be a possible indicator of the recent passage of a group. In this study, we tested if nymphs are attracted by faeces' odours and if this effect is modulated by the age of the faeces. To this end, we conducted individual olfactometric behavioural assays of 3rd instar hoppers of desert locust, Schistocerca gregaria, exposed to odours of 1 h-old and 24 h-old faeces. We also used Gas Chromatography-Mass Spectrometry (GC-MS) to identify odours' volatile organic compounds from faeces. The results of behavioural assays indicated a strong attractive effect of faeces, with no preference for one of the two faecal age classes. Nymphs spent significantly more time in the side of the olfactometer where the faeces' odours came from, and 72.7% of tested individuals chose this side first. We filtered and annotated 11 volatile organic compounds present in both fresh and old faeces in GC-MS analyses, including guaiacol and phenol, which are known to cause an aggregative effect on desert locusts. As the attractive effect lasted over 24 h, band's faeces could still have an attractive effect when individuals are separated from the band since one day. In this situation, latecomers individuals would be able to get back to the group by following the traces of their predecessors.
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Affiliation(s)
- Camille Vernier
- CIRAD, UMR CBGP, F-34398 Montpellier, France; CBGP, Université de Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France.
| | - Nicolas Barthes
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul Valéry Montpellier, EPHE, IRD, F-34293 Montpellier, France
| | - Marie-Pierre Chapuis
- CIRAD, UMR CBGP, F-34398 Montpellier, France; CBGP, Université de Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
| | - Julien Foucaud
- CBGP, Université de Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France; INRAE, UMR CBGP, F-34398 Montpellier, France
| | - Joris Huguenin
- Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175, CNRS, Université de Montpellier, Université Paul Valéry Montpellier, EPHE, IRD, F-34293 Montpellier, France
| | - Nicolas Leménager
- CIRAD, UMR CBGP, F-34398 Montpellier, France; CBGP, Université de Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
| | - Cyril Piou
- CIRAD, UMR CBGP, F-34398 Montpellier, France; CBGP, Université de Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
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Cullen DA, Sword GA, Rosenthal GG, Simpson SJ, Dekempeneer E, Hertog MLATM, Nicolaï BM, Caes R, Mannaerts L, Vanden Broeck J. Sexual repurposing of juvenile aposematism in locusts. Proc Natl Acad Sci U S A 2022; 119:e2200759119. [PMID: 35969777 PMCID: PMC9407653 DOI: 10.1073/pnas.2200759119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 06/09/2022] [Indexed: 11/18/2022] Open
Abstract
Adaptive plasticity requires an integrated suite of functional responses to environmental variation, which can include social communication across life stages. Desert locusts (Schistocerca gregaria) exhibit an extreme example of phenotypic plasticity called phase polyphenism, in which a suite of behavioral and morphological traits differ according to local population density. Male and female juveniles developing at low population densities exhibit green- or sand-colored background-matching camouflage, while at high densities they show contrasting yellow and black aposematic patterning that deters predators. The predominant background colors of these phenotypes (green/sand/yellow) all depend on expression of the carotenoid-binding "Yellow Protein" (YP). Gregarious (high-density) adults of both sexes are initially pinkish, before a YP-mediated yellowing reoccurs upon sexual maturation. Yellow color is especially prominent in gregarious males, but the reason for this difference has been unknown since phase polyphenism was first described in 1921. Here, we use RNA interference to show that gregarious male yellowing acts as an intrasexual warning signal, which forms a multimodal signal with the antiaphrodisiac pheromone phenylacetonitrile (PAN) to prevent mistaken sexual harassment from other males during scramble mating in a swarm. Socially mediated reexpression of YP thus adaptively repurposes a juvenile signal that deters predators into an adult signal that deters undesirable mates. These findings reveal a previously underappreciated sexual dimension to locust phase polyphenism, and promote locusts as a model for investigating the relative contributions of natural versus sexual selection in the evolution of phenotypic plasticity.
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Affiliation(s)
- Darron A Cullen
- Department of Biology, KU Leuven (University of Leuven), 3000 Leuven, Belgium
| | - Gregory A Sword
- Department of Entomology, Texas A&M University, College Station, TX 77843
| | - Gil G Rosenthal
- Department of Biology, Università degli Studi di Padova, 35131 Padova, Italy
| | - Stephen J Simpson
- Charles Perkins Centre, University of Sydney, Sydney, NSW, 2006, Australia
- School of Life Sciences, University of Sydney, Sydney, NSW, 2006, Australia
| | - Elfie Dekempeneer
- Department of Biosystems, KU Leuven (University of Leuven), 3001 Leuven, Belgium
| | | | - Bart M Nicolaï
- Department of Biosystems, KU Leuven (University of Leuven), 3001 Leuven, Belgium
| | - Robbe Caes
- Department of Biology, KU Leuven (University of Leuven), 3000 Leuven, Belgium
| | - Lisa Mannaerts
- Department of Biology, KU Leuven (University of Leuven), 3000 Leuven, Belgium
| | - Jozef Vanden Broeck
- Department of Biology, KU Leuven (University of Leuven), 3000 Leuven, Belgium
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Chen D, Hou L, Wei J, Guo S, Cui W, Yang P, Kang L, Wang X. Aggregation pheromone 4-vinylanisole promotes the synchrony of sexual maturation in female locusts. eLife 2022; 11:74581. [PMID: 35258453 PMCID: PMC8903828 DOI: 10.7554/elife.74581] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Accepted: 02/15/2022] [Indexed: 11/13/2022] Open
Abstract
Reproductive synchrony generally occurs in various group-living animals. However, the underlying mechanisms remain largely unexplored. The migratory locust, Locusta migratoria, a worldwide agricultural pest species, displays synchronous maturation and oviposition when forms huge swarm. The reproductive synchrony among group members is critical for the maintenance of locust swarms and population density of next generation. Here, we showed that gregarious female locusts displayed more synchronous sexual maturation and oviposition than solitarious females and olfactory deficiency mutants. Only the presence of gregarious male adults can stimulate sexual maturation synchrony of female adults. Of the volatiles emitted abundantly by gregarious male adults, the aggregation pheromone, 4-vinylanisole, was identified to play key role in inducing female sexual maturation synchrony. This maturation-accelerating effect of 4-vinylanisole disappeared in the females of Or35-/- lines, the mutants of 4-vinylanisole receptor. Interestingly, 4-vinylanisole displayed a time window action by which mainly accelerates oocyte maturation of young females aged at middle developmental stages (3–4 days post adult eclosion). We further revealed that juvenile hormone/vitellogenin pathway mediated female sexual maturation triggered by 4-vinylanisole. Our results highlight a ‘catch-up’ strategy by which gregarious females synchronize their oocyte maturation and oviposition by time-dependent endocrinal response to 4-vinylanisole, and provide insight into reproductive synchrony induced by olfactory signal released by heterosexual conspecifics in a given group. Since 2019, a plague of flying insects known as migratory locusts has been causing extensive damage to crops in East Africa. Migratory locusts sometimes live a solitary lifestyle but, if environmental conditions allow, they form large groups containing millions of individuals known as swarms that are responsible for causing locust plagues.Locusts are able to maintain such large swarms because they can aggregate and synchronize. When they live in swarms, individual locusts produce odors that are sensed by other individuals in the group. For example, an aggregation pheromone, called 4-vinylanisole, is known to help keep large groups of locusts together. However, it is less clear how odors synchronize the reproductive cycles of the females in a swarm so that they are ready to mate with males and lay their eggs at the same time. To address this question, Chen et al. examined when female locusts reached sexual maturity after they were exposed to odors produced by other locusts living alone or in groups. The experiments found that only 4-vinylanisole, which was abundantly released by adult male locusts living in groups, stimulated female locusts to reach sexual maturity at the same time. This odor increased the levels of a hormone known as juvenile hormone in less-developed females to help them reach sexual maturity sooner. These findings demonstrate that when migratory locusts are living in swarms, male locusts promote the female locusts to reach sexual maturity at the same time by promoting less-developed females to ‘catch up’ with other females in the group. A next step will be to investigate the neural and molecular mechanisms underlying the ‘catch up’ effect induced by 4-vinylanisole.
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Affiliation(s)
- Dafeng Chen
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Li Hou
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China
| | - Jianing Wei
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Siyuan Guo
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Weichan Cui
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Pengcheng Yang
- Beijing Institutes of Life Sciences, Chinese Academy of Sciences, Beijing, China
| | - Le Kang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China.,Beijing Institutes of Life Sciences, Chinese Academy of Sciences, Beijing, China
| | - Xianhui Wang
- State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, China
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Maeno KO, Piou C, Ghaout S. Allocation of more reproductive resource to egg size rather than clutch size of gregarious desert locust (Schistocerca gregaria) through increasing oogenesis period and oosorption rate. JOURNAL OF INSECT PHYSIOLOGY 2022; 136:104331. [PMID: 34838517 DOI: 10.1016/j.jinsphys.2021.104331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 08/24/2021] [Accepted: 11/19/2021] [Indexed: 06/13/2023]
Abstract
The desert locust, Schistocerca gregaria, shows a density-dependent reproductive trade-off by laying fewer but larger eggs in crowded conditions (gregarious phase) than in isolated conditions (solitarious phase). However, the physiological mechanisms controlling reproductive resource allocation remain unclear. We examined how egg production processes, including ovulation timing (i.e., oogenesis period), oocyte and ovarian growth rates, and oosorption rate (resorbing developing terminal oocytes), regulate reproductive outputs (egg biomass per clutch, egg size, and clutch size) during a reproductive cycle in S. gregaria by rearing them either under isolated or crowded conditions. We observed a common density-dependent negative correlation between egg size and clutch size, with no significant difference in egg biomass between the two rearing conditions. Dissection of female locusts after different days of oviposition revealed that the daily oocyte growth rate was almost similar between the two rearing conditions, but crowd-reared females ovulated later than isolated-reared ones, resulting in further oocyte growth in the former. Terminal oocytes were renewed by previous penultimate oocytes at the onset of a new reproductive cycle, and oosorption mainly occurred at an early stage in both rearing conditions; however, crowd-reared locusts displayed higher levels of oosorption compared to their isolated-reared counterparts. Crowding induced a high oosorption rate, resulting in a reduced clutch size and a prolonged oogenesis period, which in turn allowed oocytes to intake more yolk, which was probably recycled via oosorption. These results suggest that the length of the oogenesis period and oosorption rate are manipulated by maternal density, and these physiological modifications interactively regulate reproductive trade-off in S. gregaria.
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Affiliation(s)
- Koutaro Ould Maeno
- Japan International Research Center for Agricultural Sciences (JIRCAS), Livestock and Environment Division, Ohwashi 1-1, Tsukuba, Ibaraki 305-8686, Japan.
| | - Cyril Piou
- CIRAD, UMR CBGP, INRAE, Institut Agro, IRD, Université Montpellier, F-34398 Montpellier, France; Ibn Zohr University, Agadir, Morocco; Centre National de Lutte Antiacridienne (CNLAA), Aït-Melloul, BP 125, Inezgane, Agadir, Morocco
| | - Saïd Ghaout
- Centre National de Lutte Antiacridienne (CNLAA), Aït-Melloul, BP 125, Inezgane, Agadir, Morocco
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Density-dependent mating behaviors reduce male mating harassment in locusts. Proc Natl Acad Sci U S A 2021; 118:2104673118. [PMID: 34635592 PMCID: PMC8594575 DOI: 10.1073/pnas.2104673118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2021] [Indexed: 11/18/2022] Open
Abstract
Male mating harassment may occur when females and males do not have the same mating objectives. Communal animals need to manage the costs of male mating harassment. Here, we demonstrate how desert locusts in dense populations reduce such conflicts through behaviors. In transient populations (of solitarious morphology but gregarious behavior), we found that nongravid females occupied separate sites far from males and were not mating, whereas males aggregated on open ground (leks), waiting for gravid females to enter the lekking sites. Once a male mounted a gravid female, no other males attacked the pair; mating pairs were thereby protected during the vulnerable time of oviposition. In comparison, solitarious locusts displayed a balanced sex ratio in low-density populations, and females mated irrespective of their ovarian state. Our results indicate that the mating behaviors of desert locusts are density dependent and that sex-biased behavioral group separation may minimize the costs of male mating harassment and competition.
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