Keywords: Other invertebrates

Sterile insect technique reduces cabbage maggot (Diptera: Anthomyiidae) infestation in root crucifers in Canada

35337
Anne-Marie Fortier, Allen Bush-Beaupré, Jade Savage, et al.,  Journal of Economic Entomology,  118:2710–2717. 2026-01-07 11:20:58.
The cabbage maggot (Delia radicum (L.)) is a major pest of brassica vegetables in Canada that has traditionally been managed with soil-applied insecticides. However, recent regulatory restrictions on key products such as chlorpyrifos have created a pressing need for alternative solutions. This study evaluates the sterile insect technique (SIT) as a control method for the cabbage maggot in root crucifers. Large-scale field trials conducted from 2019 to 2022 in Quebec (Canada) demonstrated significant reductions in D. radicum infestations in radish and daikon crops. Quality control measures confirmed the effectiveness of sterilization on cabbage maggot, with minimal impact on male performance. The results suggest that the SIT is a promising, environmentally friendly alternative to chemical control for cabbage maggot management. The study further highlights the importance of optimizing release strategies and improving predictive models to guide deployment. Overall, the SIT offers growers a viable option to reduce reliance on insecticides while maintaining crop health and yield.

CRISPR/Cas9-germline editing of Biomphalaria glabrata: A breakthrough in genetic modification of snails that transmit schistosomiasis

35226
Kouhei Oonuma et al.,  Science Advances,  11. 2025-10-09 10:03:53.
Human schistosomiasis remains one of the most devastating parasitic diseases worldwide, and the development of genetically modified vector snails has long been a goal in the field. Here, we report the successful creation of genetically modified Biomphalaria glabrata, an important intermediate host, using CRISPR/Cas9 gene editing. We targeted the fibrinogen-related protein 3.1 (FREP3.1) gene, confirmed stable germline transmission of the mutated gene, and established two different homozygous FREP3.1-edited lines. Disruption of the FREP 3.1 gene did not alter snail susceptibility to Schistosoma mansoni infection, possibly due to a limited role of FREP3.1 in resistance or to functional redundancy and/or compensatory expression within the highly diverse FREP gene family. Our study demonstrates successful germline editing, effective ex ovo culture of decapsulated embryos, and the generation of viable, genetically modified B. glabrata snails, thereby establishing a foundation for future genetic strategies to control schistosomiasis.

Paratransgenesis: Overview, Current Perspectives, and Future Research Needs for Malaria Control

34874
Oziegbe, O., Okeke, C.C., Esho, D.O.,  Springer, Cham.,  2025-05-26 21:52:21.
Malaria is an insect-borne disease (IBD) that is responsible for significant human mortality and morbidity globally. Several effective vector and parasite control strategies have been considered to control malaria. However, paratransgenesis is a strategy targeted towards parasite development disruption rather than vector elimination which can potentially address insecticide resistance in mosquitoes. Genetically modified symbionts such as bacteria, fungi, or viruses secrete anti-plasmodial effector molecules that kill or inhibit the development of Plasmodium species without affecting the vector or the microorganism. Various anti-plasmodial effector molecules have been identified such as scorpin, a peptide from scorpion venom that acts by lysing the parasite, enolase- plasminogen interaction peptide (EPIP) which acts by inhibiting midgut invasion, A protein kinase (Akt) that acts by activating innate immune responses, and salivary gland and midgut peptide 1 (SMI) that acts by preventing binding to the parasite surface proteins. For this strategy to be successful, the selected symbiotic microorganism should be easy to culture and genetically manipulate, stable, as well as capable of producing effector molecules with anti-plasmodial activity while colonizing a wide range of the host species. Paratransgenesis presents a promising future for malaria control globally. However, its efficacy and safety as a malaria control strategy should be experimented with in large outdoor settings with more elaborate and collaborative studies carried out to sustain the approach in malaria-endemic countries.

wStri spread dynamics in Nilaparvata lugens via discrete mathematical models

34574
Zheng, B., Yang, H., Elaydi, S. et al.,  Journal of Mathematical Biology,  90. 2025-03-12 16:30:16.
Wolbachia, an intracellular bacterium, is well-known for inducing cytoplasmic incompatibility, which has become a promising and environmentally sustainable strategy for controlling pest populations. The strain wStri, specifically identified in Nilaparvata lugens (brown planthopper), has shown potential for such biocontrol applications. In this study, we develop a comprehensive discrete mathematical model to analyze the dynamics of wStri spread in a mixed population of wStri-infected, wLug-infected, and uninfected Nilaparvata lugens under both constant and periodically varying environmental conditions. Under a constant environment, the model identifies the critical threshold necessary for the successful establishment of wStri within the population. Our analysis reveals that the model exhibits a strong Allee effect, where a population must exceed a certain critical density-the Allee threshold-for the wStri strain to persist and spread. Below this threshold, the wStri strain is likely to be eliminated, failing in pest control efforts. When the environment varies periodically, the model transforms into a non-autonomous periodic discrete model, introducing additional complexity. In this scenario, we derive sufficient conditions that ensure the composition of finitely many Allee maps continues to function as an Allee map. Furthermore, we prove that a unique periodic orbit exists within such a periodic environment. This orbit is characterized as unstable and acts as a threshold, determining whether wStri will establish itself in the population or die out over time. The findings from this model provide critical insights into the conditions under which wStri can be effectively used to control Nilaparvata lugens, particularly in environments that are not constant but fluctuate periodically. These insights have significant implications for the practical deployment of Wolbachia-based biocontrol methods in pest management strategies.

Parental-effect gene-drive elements under partial selfing, or why do Caenorhabditis genomes have hyperdivergent regions?

33170
Matthew V Rockman,  Genetics,  2024-10-31 08:57:53.
Self-fertile Caenorhabditis nematodes carry a surprising number of Medea elements, alleles that act in heterozygous mothers and cause death or developmental delay in offspring that don’t inherit them. At some loci, both alleles in a cross operate as independent Medeas, affecting all the homozygous progeny of a selfing heterozygote. The genomic coincidence of Medea elements and ancient, deeply coalescing haplotypes, which pepper the otherwise homogeneous genomes of these animals, raises questions about how these apparent gene-drive elements persist for long periods of time. Here I investigate how mating system affects the evolution of Medeas, and their paternal-effect counterparts, peels. Despite an intuition that antagonistic alleles should induce balancing selection by killing homozygotes, models show that, under partial selfing, antagonistic elements experience positive frequency dependence: the common allele drives the rare one extinct, even if the rare one is more penetrant. Analytical results for the threshold frequency required for one allele to invade a population show that a very weakly penetrant allele, one whose effects would escape laboratory detection, could nevertheless prevent a much more penetrant allele from invading under high rates of selfing. Ubiquitous weak antagonistic Medeas and peels could then act as localized barriers to gene flow between populations, generating genomic islands of deep coalescence. Analysis of gene expression data, however, suggest that this cannot be the whole story. A complementary explanation is that ordinary ecological balancing selection generates ancient haplotypes on which Medeas can evolve, while high homozygosity in these selfers minimizes the role of gene drive in their evolution.

Stalk-eyed flies carrying a driving X chromosome compensate by increasing fight intensity

32712
Kimberly A. Paczolt, Macy E. Pritchard, Gabrielle T. Welsh, et al.,  Frontiers in Ethology,  3. 2024-10-22 17:39:40.
Exaggerated ornaments provide opportunities to understand how selection can operate at different levels to shape the evolution of a trait. While these features aid their bearer in attracting mates or fending off competitors, they can also be costly and influenced by the environment and genetic variation. The eyestalks of the stalk-eyed fly, Teleopsis dalmanni, are of interest because eyestalk length is the target of both intra- and intersexual selection and is also reduced by loci on a highly-divergent sex ratio X chromosome (XSR), a meiotic driver accounting for up to 30% of wild X chromosomes. Male stalk-eyed flies fight to control access to females and over food using a combination of low-intensity displays and high-intensity physical fights. We staged, filmed, and scored contests between pairs of eyespan-matched males to evaluate whether X chromosome type impacts the behavior and outcome of aggressive interactions. While our results broadly match expectations from previous studies, we found that XSR males used more high-intensity behaviors than males carrying a non-driving, standard X chromosome (XST), particularly when their eyestalks were of similar size or smaller than their opponents. Additionally, we found that when XSR males use high-intensity behaviors, they win more bouts than when they use low-intensity behaviors. Taken together, these results suggest that XSR impacts male aggressive behavior to compensate for the shorter eyestalks of XSR males and may help to explain how this selfish chromosome is maintained.

Modeling the efficacy of CRISPR gene drive for snail immunity on schistosomiasis control

23810
R. E. Grewelle, J. Perez-Saez, J. Tycko, E. K. O. Namigai, C. G. Rickards and G. A. De Leo,  PLOS Neglected Tropical Diseases,  16:e0010894. 2022-10-31 09:02:03.
CRISPR gene drives could revolutionize the control of infectious diseases by accelerating the spread of engineered traits that limit parasite transmission in wild populations. Gene drive technology in mollusks has received little attention despite the role of freshwater snails as hosts of parasitic flukes causing 200 million annual cases of schistosomiasis. A successful drive in snails must overcome self-fertilization, a common feature of host snails which could prevents a drive's spread. Here we developed a novel population genetic model accounting for snails' mixed mating and population dynamics, susceptibility to parasite infection regulated by multiple alleles, fitness differences between genotypes, and a range of drive characteristics. We integrated this model with an epidemiological model of schistosomiasis transmission to show that a snail population modification drive targeting immunity to infection can be hindered by a variety of biological and ecological factors; yet under a range of conditions, disease reduction achieved by chemotherapy treatment of the human population can be maintained with a drive. Alone a drive modifying snail immunity could achieve significant disease reduction in humans several years after release. These results indicate that gene drives, in coordination with existing public health measures, may become a useful tool to reduce schistosomiasis burden in selected transmission settings with effective CRISPR construct design and evaluation of the genetic and ecological landscape.

Modeling the efficacy of CRISPR gene drive for schistosomiasis control

19109
R. E. Grewelle, J. Perez-Saez, J. Tycko, E. K. O. Namigai, C. G. Rickards and G. A. De Leo,  bioRxiv,  2021.10.29.466423. 2021-11-01 14:51:40.
CRISPR gene drives could revolutionize the control of infectious diseases by accelerating the spread of engineered traits that limit parasite transmission in wild populations. While much effort has been spent developing gene drives in mosquitoes, gene drive technology in molluscs has received little attention despite the role of freshwater snails as obligate, intermediate hosts of parasitic flukes causing schistosomiasis -- a disease of poverty affecting more than 200 million people worldwide. A successful drive in snails must overcome self-fertilization, which prevents a drive's spread. Simultaneous hermaphroditism is a feature of snails -- distinct from gene drive model organisms -- and is not yet incorporated in gene drive models of disease control. Here we developed a novel population genetic model accounting for snails' sexual and asexual reproduction, susceptibility to parasite infection regulated by multiple alleles, fitness differences between genotypes, and a range of drive characteristics. We then integrated this model with an epidemiological model of schistosomiasis transmission and snail population dynamics. Simulations showed that gene drive establishment can be hindered by a variety of biological and ecological factors, including selfing. However, our model suggests that, under a range of conditions, gene drive mediated immunity in snails could maintain rapid disease reduction achieved by annual chemotherapy treatment of the human population, leading to long-term elimination. These results indicate that gene drives, in coordination with existing public health measures, may become a useful tool to reduce schistosomiasis burden in selected transmission settings with effective CRISPR construct design and close evaluation of the genetic and ecological landscape.Competing Interest StatementJT and EKON were seed funded by the Merck Innovation Cup 2016 for research on schistosomiasis, and previously employed as external consultants to the Global Health Institute of Merck (KGaA) which produces treatments for schistosomiasis. REG and GADL were partially supported by the National Science Foundation's grants DEB-2011179 and ICER-2024383.

A Maternal-Effect Toxin Affects Epithelial Differentiation and Tissue Mechanics in Caenorhabditis elegans

19128
C. Lehmann and C. Pohl,  Frontiers in Cell and Developmental Biology,  9. 2021-10-14 14:25:20.
Selfish genetic elements that act as post-segregation distorters cause lethality in non-carrier individuals after fertilization. Two post-segregation distorters have been previously identified in Caenorhabditis elegans, the peel-1/zeel-1 and the sup-35/pha-1 elements. These elements seem to act as modification-rescue systems, also called toxin/antidote pairs. Here we show that the maternal-effect toxin/zygotic antidote pair sup-35/pha-1 is required for proper expression of apical junction (AJ) components in epithelia and that sup-35 toxicity increases when pathways that establish and maintain basal epithelial characteristics, die-1, elt-1, lin-26, and vab-10, are compromised. We demonstrate that pha-1(e2123) embryos, which lack the antidote, are defective in epidermal morphogenesis and frequently fail to elongate. Moreover, seam cells are frequently misshaped and mispositioned and cell bond tension is reduced in pha-1(e2123) embryos, suggesting altered tissue material properties in the epidermis. Several aspects of this phenotype can also be induced in wild-type embryos by exerting mechanical stress through uniaxial loading. Seam cell shape, tissue mechanics, and elongation can be restored in pha-1(e2123) embryos if expression of the AJ molecule DLG-1/Discs large is reduced. Thus, our experiments suggest that maternal-effect toxicity disrupts proper development of the epidermis which involves distinct transcriptional regulators and AJ components.

Selfing is the safest sex for Caenorhabditis tropicalis

15953
L. M. Noble, J. Yuen, L. Stevens, N. D. Moya, R. Persaud, M. Moscatelli, J. L. Jackson, G. Zhang, R. Chitrakar, L. R. Baugh, C. Braendle, E. C. Andersen, H. S. Seidel and M. V. Rockman,  eLife,  10:e62587. 2021-01-11 16:59:39.
We generated a chromosomal-scale genome for C. tropicalis and surveyed global diversity. Population structure is very strong, and islands of extreme divergence punctuate a genomic background that is highly homogeneous around the globe. Outbreeding depression in the laboratory is caused largely by multiple Medea-like elements, genetically consistent with maternal toxin/zygotic antidote systems. Loci with Medea activity harbor novel and duplicated genes, and their activity is modified by mito-nuclear background. Segregating Medea elements dramatically reduce fitness, and simulations show that selfing limits their spread. Frequent selfing in C. tropicalis may therefore be a strategy to avoid Medea-mediated outbreeding depression.

Ubiquitous Selfish Toxin-Antidote Elements in Caenorhabditis Species

15947
E. Ben-David, P. Pliota, S. A. Widen, A. Koreshova, T. Lemus-Vergara, P. Verpukhovskiy, S. Mandali, C. Braendle, A. Burga and L. Kruglyak,  Current Biology,  2021-01-07 16:57:04.
Here, we report the discovery of maternal-effect TAs in both C. tropicalis and C. briggsae, two distant relatives of C. elegans. In C. tropicalis, multiple TAs combine to cause a striking degree of intraspecific incompatibility: five elements reduce the fitness of >70% of the F2 hybrid progeny of two Caribbean isolates. We identified the genes underlying one of the novel TAs, slow-1/grow-1, and found that its toxin, slow-1, is homologous to nuclear hormone receptors. Remarkably, although previously known TAs act during embryonic development, maternal loading of slow-1 in oocytes specifically slows down larval development, delaying the onset of reproduction by several days. Finally, we found that balancing selection acting on linked, conflicting TAs hampers their ability to spread in populations, leading to more stable genetic incompatibilities. Our findings indicate that TAs are widespread in Caenorhabditis species and target a wide range of developmental processes and that antagonism between them may cause lasting incompatibilities in natural populations. We expect that similar phenomena exist in other animal species.

Ubiquitous selfish toxin-antidote elements in Caenorhabditis species

13751
E. Ben-David, P. Pliota, S. A. Widen, A. Koreshova, T. Lemus-Vergara, P. Verpukhovskiy, S. Mandali, C. Braendle, A. Burga and L. Kruglyak,  bioRxiv,  2020.08.06.240564. 2020-08-07 17:38:23.
We discovered five maternal-effect Toxin/Antidotes (TAs) in the nematode Caenorhabditis tropicalis and one in C. briggsae. Unlike previously reported TAs, five of these novel toxins do not kill embryos but instead cause larval arrest or developmental delay. Our results show that TAs are common in Caenorhabditis species, target a wide range of developmental processes, and may act as barriers preventing gene flow.

Selfing is the safest sex for Caenorhabditis tropicalis

13747
L. M. Noble, J. Yuen, L. Stevens, N. Moya, R. Persaud, M. Moscatelli, J. Jackson, C. Braendle, E. C. Andersen, H. S. Seidel and M. V. Rockman,  bioRxiv,  2020.08.07.242032. 2020-08-07 13:24:52.
Frequent selfing in Caenorhabditis. tropicalis may be a strategy to avoid gene drive-mediated outbreeding depression. Mating systems have profound effects on genetic diversity and compatibility. Caenorhabditis tropicalis is the least genetically diverse among 3 species of Caenorhabditis that have evolved a mating system dependent on self-fertilization and is the most afflicted by outbreeding depression.

Public health concerns over gene-drive mosquitoes: will future use of gene-drive snails for schistosomiasis control gain increased level of community acceptance?

7950
D. O. Famakinde,  Pathogens and Global Health,  2020-02-26 20:49:43.
With the advent of CRISPR (clustered regularly interspaced short palindromic repeat)-based gene drive, present genetic research in schistosomiasis vector control envisages the breeding and release of transgenic schistosome-resistant (TSR) snail vectors to curb the spread of the disease. Although this approach is still in its infancy, studies focussing on production of genetically modified (GM) mosquitoes (including gene-drive mosquitoes) are well advanced and set the pace for other transgenic vector research. Unfortunately, as with other GM mosquitoes, open field release of gene-drive mosquitoes is currently challenged in part by some concerns such as gene drive failure and increased transmission potential for other mosquito-borne diseases among others, which might have adverse effects on human wellbeing. Therefore, not only should we learn from the GM mosquito protocols, frameworks and guidelines but also appraise the applicability of its current hurdles to other transgenic vector systems, such as the TSR snail approach. Placing these issues in a coherent comparative perspective, I argue that although the use of TSR snails may face similar technical, democratic and diplomatic challenges, some of the concerns over gene-drive mosquitoes may not apply to gene-drive snails, proposing a theory that community consent will be no harder and possibly easier to obtain for TSR snails than the experience with GM mosquitoes. In the future, these observations may help public health practitioners and policy makers in effective communication with communities on issues regarding the use of TSR snails to interrupt schistosomiasis transmission, especially in sub-Saharan Africa.

Gene drives for schistosomiasis transmission control

6341
T. Maier, N. J. Wheeler, E. K. O. Namigai, J. Tycko, R. E. Grewelle, Y. Woldeamanuel, K. Klohe, J. Perez-Saez, S. H. Sokolow, G. A. De Leo, T. P. Yoshino, M. Zamanian and J. Reinhard-Rupp,  PLoS Neglected Tropical Diseases,  13:e0007833. 2019-12-19 18:18:55.
Schistosomiasis is one of the most important and widespread neglected tropical diseases (NTD), with over 200 million people infected in more than 70 countries; the disease has nearly 800 million people at risk in endemic areas. Although mass drug administration is a cost-effective approach to reduce occurrence, extent, and severity of the disease, it does not provide protection to subsequent reinfection. Interventions that target the parasites' intermediate snail hosts are a crucial part of the integrated strategy required to move toward disease elimination. The recent revolution in gene drive technology naturally leads to questions about whether gene drives could be used to efficiently spread schistosome resistance traits in a population of snails and whether gene drives have the potential to contribute to reduced disease transmission in the long run. Responsible implementation of gene drives will require solutions to complex challenges spanning multiple disciplines, from biology to policy. This Review Article presents collected perspectives from practitioners of global health, genome engineering, epidemiology, and snail/schistosome biology and outlines strategies for responsible gene drive technology development, impact measurements of gene drives for schistosomiasis control, and gene drive governance. Success in this arena is a function of many factors, including gene-editing specificity and efficiency, the level of resistance conferred by the gene drive, how fast gene drives may spread in a metapopulation over a complex landscape, ecological sustainability, social equity, and, ultimately, the reduction of infection prevalence in humans. With combined efforts from across the broad global health community, gene drives for schistosomiasis control could fortify our defenses against this devastating disease in the future.

To reduce the global burden of human schistosomiasis, use ‘old fashioned’ snail control

4015
Sokolow, SHW, Chelsea L.; Jones, Isabel J.; Lafferty, Kevin D.; Kuris, Armand; Hsieh, Michael H.; De Leo, Giulio A.,  Trends in Parasitology,  34:23-40. 2018-01-13 00:00:00.
Control strategies to reduce human schistosomiasis have evolved from ‘snail picking’ campaigns, a century ago, to modern wide-scale human treatment campaigns, or preventive chemotherapy. Unfortunately, despite the rise in preventive chemotherapy campaigns, just as many people suffer from schistosomiasis today as they did 50 years ago. Snail control can complement preventive chemotherapy by reducing the risk of transmission from snails to humans. Here, we present ideas for modernizing and scaling up snail control, including spatiotemporal targeting, environmental diagnostics, better molluscicides, new technologies (e.g., gene drive), and ‘outside the box’ strategies such as natural enemies, traps, and repellants. We conclude that, to achieve the World Health Assembly’s stated goal to eliminate schistosomiasis, it is time to give snail control another look.

A maternal-effect selfish genetic element in Caenorhabditis elegans

14450
E. Ben-David, A. Burga and L. Kruglyak,  Science,  356:1051. 2017-06-09 17:13:17.
We discovered a selfish element causing embryonic lethality in crosses between wild strains of the nematode Caenorhabditis elegans.

Poisons, antidotes, and selfish genes

14448
N. Phadnis,  Science,  356:1013. 2017-06-09 16:55:51.
On page1051 of this issue, BenDavid et al . (3) chase down a serendipitous observation of an anomaly in genetic crosses to unmask a toxin-antidote type of selfish system in worms.