Submit a preprint

Latest recommendationsrsstwitter

IdTitle * Authors * Abstract * Picture * Thematic fields * RecommenderReviewers▲Submission date
31 Jul 2024
article picture

Cross-transmission of resistant gastrointestinal nematodes between wildlife and transhumant sheep

What gets left behind? Shared nematode communities at the wildlife-livestock interface.

Recommended by ORCID_LOGO based on reviews by 2 anonymous reviewers

Gastrointestinal nematodes represent a major problem for livestock production across the globe, one that has intensified with the rapid and repeated evolution of multi-drug resistance (Wit et al., 2021). Understanding parasite exposure and how resistance is maintained over time are therefore of key importance for defining efficient management strategies. To date, the role wildlife play in these dynamics has been poorly studied. The work of Beaumelle et al. examine this essential question by studying the transmission dynamics of nematodes at the environmental interface between transhumant sheep and wild ungulates, more specifically with ibex (Capra ibex) that allochronically share alpine pastures when sheep are brought to graze in summer. By collecting fresh fecal material from both species and using a metabarcoding approach based on ITS-2 sequences, the authors characterise the nemabiome in each ungulate species and demonstrate that the two host species share a large portion of their parasite diversity. More importantly, by focusing on a gene (β-tubulin isotype 1) associated with resistance to a commonly used anthelmintic drug (benzimidazole), they demonstrate that both species carry resistant nematode strains, but that the diversity of strains, and particularly susceptible strains, is much higher in ibex. A key feature of the sampling design is that fecal material from both species was collected before seasonal transmission between the ungulate species could occur. Therefore, their results demonstrate that ibex are able to maintain resistant strains over long periods of time and therefore may be major nematode reservoirs for sheep infection. This important conclusion raises a series of key questions. How are resistant genotypes maintained in untreated ibex hosts? Is the cost of resistance so weak that they can coexist with susceptible strains in the absence of drug treatment or does anthelminthic contamination of the pastures maintain resistant genotypes directly in wild hosts? This work also opens several interesting perspectives: For example, what additional resistant parasites may be maintained by these wildlife hosts? What role do other wild ungulate species play in the evolution of nematode communities in transhumant sheep? An expansion of this work to the larger community of wild ungulates using alpine pastures, and an evaluation of the degree to which wild species are exposed to anthelminthic drugs released by grazing livestock into the environment is now required to understand the deeper consequences of drug treatment for shaping parasite communities and their cascading impacts for wildlife conservation, and the development of efficient and sustainable management strategies for pastoral livestock. 

References

Beaumelle et al. Cross-transmission of resistant gastrointestinal nematodes between wildlife and transhumant sheep. bioRxiv, ver. 5 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2023.07.21.550073

Wit, J., Dilks, C.M., Andersen, E.C., 2021. Complementary Approaches with Free-living and Parasitic Nematodes to Understanding Anthelmintic Resistance. Trends Parasitol. 37, 240–250. https://doi.org/10.1016/j.pt.2020.11.008

Cross-transmission of resistant gastrointestinal nematodes between wildlife and transhumant sheepCamille Beaumelle, Carole Toigo, Rodolphe Papet, Slimania Benabed, Mathieu Beurier, Lea Bordes, Anais Brignone, Nadine Curt-Grand-Gaudin, Mathieu Garel, Justine Ginot, Philippe Jacquiet, Christian Miquel, Marie-Therese Poirel, Anna Serafino, Eric ...<p>Wild and domestic ungulates can be infected with the same species of gastrointestinal parasitic nematodes. These parasites have free-living stages in the environment that contribute to the ease of transmission among different host species. In a...Ecology, Molecular biology, ParasitologyKaren D McCoy2023-07-25 10:36:28 View
08 Mar 2024
article picture

A comparison of the parasitoid wasp species richness of tropical forest sites in Peru and Uganda – subfamily Rhyssinae (Hymenoptera: Ichneumonidae)

Two sides of tropical richness, parasitoid wasps collected by Malaise traps in tropical rainforests of South America and Africa

Recommended by based on reviews by Mabel Alvarado, Filippo Di Giovanni and 2 anonymous reviewers

Insect species richness and diversity comparisons between samples of the tropics around the world are rare, especially in taxa composed mainly of cryptic species as parasitoid wasps.

The article by Hopkins et al. (2024) compares samples of parasitoid wasps of the subfamily Rhyssinae (Hymenoptera: Ichneumonidae) collected by Malaise traps in tropical rainforests of Perú and Uganda. The samples presented several differences in the time of collecting, covertures, and the sampling number; however, they used the same kind of traps, and the taxonomic process for species delimitation was made for the same team of ichneumonid experts, using equivalent characters.

Publications about this kind of comparative study are difficult to find because cooperative projects on insect richness and diversity from South American and African continents are not frequent. In this sense, this study presented a valuable contrast that shows interesting results about the higher richness and lower abundance of the biota of the American tropics, even with a small sample, in comparison with the biota of the African tropics. The results are supported mainly by the rarefaction curves shown. This pattern of higher species richness and lower specimen abundance, observed in other American tropical taxa such as trees, birds, or butterflies, is observed too in these parasitoid wasps, increasing the body of information that could support the extension of the pattern to the entire biota of the American tropics. The authors recognize the study's limitations, which include strong differences in the size of the forest coverture between places. However, these differences and others are enough described and discussed.

This work is useful because it increases the information about the diversity patterns of the tropics around the world and because study a taxon mainly composed of cryptic species, with a small amount of information in tropical regions.

References

Hopkins T., Tuomisto H., Gómez I.C., Sääksjärvi I. E. 2024. A comparison of the parasitoid wasp species richness of tropical forest sites in Peru and Uganda – subfamily Rhyssinae (Hymenoptera: Ichneumonidae). bioRxiv, ver. 2 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2023.08.23.554460

A comparison of the parasitoid wasp species richness of tropical forest sites in Peru and Uganda – subfamily Rhyssinae (Hymenoptera: Ichneumonidae)Tapani Hopkins, Hanna Tuomisto, Isrrael C. Gómez, Ilari E. Sääksjärvi<p style="text-align: justify;">The global distribution of parasitoid wasp species richness is poorly known. Past attempts to compare data from different sites have been hampered by small sample sizes and lack of standardisation. During the past d...Biodiversity, Biogeography, InsectaGiovanny Fagua2023-08-24 18:30:26 View
19 Aug 2024
article picture

Dose, temperature and formulation shape Metarhizium anisopliae virulence against the oriental fruit fly: lessons for improving on-target control strategies

Optimizing fungal pathogen strategies for oriental fruit fly control

Recommended by ORCID_LOGO based on reviews by François Verheggen and Papa Djibril Faye

Using entomopathogenic fungi for biological control is an effective method for controlling certain crop pests, with the perspective of reducing the use of chemical pesticides. Yet, the efficiency of pathogenic fungi is dependent upon many factors that need to be evaluated to improve biological control potential in the fields (Lacey, 2001). The article by Chailleux et al. (2024) presents an exciting contribution to the field of biological pest control, specifically focusing on using entomopathogenic fungi to manage the oriental fruit fly, Bactrocera dorsalis. This fly, a member of the Tephritidae family, is a major threat to orchards in Asia, the Pacific and Africa, as it attacks fruit and causes considerable damage, in addition to having a relatively rapid biological invasion dynamic (Clarke et al. 2005). 

The objective of the Chailleux et al. (2024) study was to evaluate the virulence of Metarhizium anisopliae spores (strain Met69) on B. dorsalis adult flies according to various conditions: the inoculation dose and spore load, the formulation (adjuvant) and temperature conditions. The focus on host specificity and on-target applications was conducted to ensure minimal impact on non-target organisms, which is crucial for sustainable agriculture. The main challenge in this system was to achieve high strain virulence to kill wild individuals with a low number of spores—therefore limiting impact on non-target species such as natural enemies—but with a sufficient incubation period to allow transmission from mass-reared insects to wild conspecifics (Leite et al. 2022). A comparison of different inoculation methods is also provided and is interesting from a methodological point of view for future studies or even large-scale applications.

Using a well-designed experimental setup, the authors show that high pathogenicity (measured by LD50) is achievable even at low spore doses and independently of the fly's sex. Lethal action speed was, however, dependent on the dose. Regarding temperature, the authors demonstrated that mycelium growth was affected by the mean temperature but, most importantly, by daily fluctuation regimes; night and day temperature alternation allowed faster growth than constant temperature. These notions of thermal fluctuations are still under-researched in terms of their modulating role in biological control yet seem central to understanding them, as the authors demonstrate here. The correlation between increased virulence and specific abiotic factors, such as temperature, offers valuable additional insights into the bioecology of the insect host and the fungal pathogen. Chailleux et al. finally point out the need for careful selection of adjuvants in formulations and pay attention to interactions with the abiotic environment to avoid compromising the effectiveness of biological control agents. Indeed, the survival rate of inoculated flies increased in the presence of the corn starch adjuvant, but this effect decreased with temperature. As corn starch unexpectedly delayed mortality, the authors suggest a potential for enhancing conspecific transmission

From a broader perspective, the study emphasizes the importance of standardizing virulence evaluation to optimize biological control strategies like auto-dissemination or vectoring with sterile males, particularly in field conditions. The study contributions are timely and essential for advancing sustainable pest management strategies and improving inoculation methods. The findings underscore the need for field trials to refine these strategies, particularly in Africa, where climatic factors may affect pathogen efficacy and fly behavior. I recommend publishing this article in a referenced journal like the Peer Community Journal. 

References

Chailleux, A. Coulibaly, ON, Diouf B, Diop S, Sohel A, Brevault T (2023) Dose, temperature and formulation shape Metarhizium anisopliae virulence against the oriental fruit fly: lessons for improving on-target control strategies. bioRxiv, ver.2 peer-reviewed and recommended by PCI Zoology https://doi.org/10.1101/2023.12.14.571642

Clarke, A. R. et al. (2005). Invasive phytophagous pests arising through a recent tropical evolutionary radiation: the Bactrocera dorsalis complex of fruit flies. Annu. Rev. Entomol., 50, 293-319. https://doi.org/10.1146/annurev.ento.50.071803.130428

Lacey, L. A. (2001). Formulation of microbial biopesticides: beneficial microorganisms, nematodes and seed treatments. J Invertebr Pathol, 77, 147. https://doi.org/10.1006/jipa.2000.5005

Leite, M. O. et al. (2022). Laboratory risk assessment of three entomopathogenic fungi used for pest control toward social bee pollinators. Microorganisms, 10, 1800. https://doi.org/10.3390/microorganisms10091800

Dose, temperature and formulation shape Metarhizium anisopliae virulence against the oriental fruit fly: lessons for improving on-target control strategiesAnais Chailleux, Oumou N. Coulibaly, Babacar Diouf, Samba Diop, Ahmad Sohel, Thierry Brevault<p>​Entomopathogenic fungi are a promising tool for the biological control of crop pests provided low or no impact on non-target organisms. Selection for host specificity as well as on-target applications open new avenues for more sustainable stra...Biocontrol, Insecta, Pest managementKévin Tougeron2023-12-18 11:59:30 View
07 Jun 2024
article picture

Relationship between weapon size and six key behavioural and physiological traits in males of the European earwig

The unreliable signal: No correlation between forceps length and male quality in European earwigs

Recommended by ORCID_LOGO based on reviews by Luna Grey and 2 anonymous reviewers

In animals, male weapons such as antlers, horns, spurs, fangs, and tusks typically provide advantages in male contests and increase access to females, thereby enhancing reproductive success. However, such large and extravagant morphological structures are expected to come at a cost, potentially imposing trade-offs with life history traits, physiological functions, or certain behaviors (Emlen, 2001; Emlen, 2008). These costs should be manageable only by males in the best condition. The present study by Blackwell et al. (2024) examines this assumption through a comprehensive study on the European earwig, where males possess forceps-like cerci that vary widely in size within populations.

In the European earwig (Forficula auricularia), male forceps are used in male-male contests as weapons to deter competitors prior to mating (Styrsky & Rhein, 1999) or to interrupt mating pairs by non-copulating males (Forslund, 2000; Walker & Fell, 2001). Despite providing benefits in terms of mating success (Eberhard & Gutierrez, 1991; Tomkins & Brown, 2004), it remains unknown whether long or short forceps are associated with other important life-history traits.

In this laboratory study, Blackwell et al. (2024) investigated two European earwig populations, each divided into two subpopulations: one with the shortest forceps and one with the longest forceps. They examined the potential costs of long forceps on six different traits: one reproductive trait (sperm storage); three non-reproductive behavioral traits such as locomotor performance (involved in search for resources), fleeing reaction face to a risk (long forceps are supposed to be correlated with boldness), and aggregation behavior (European earwigs are facultative group-living organisms); and survival (when deprived of food and subsequently when exposed to an entomopathogenic fungus).

As males in the best condition are supposed to be those that can afford to develop large forceps, Blackwell et al. (2024) predicted that males with long forceps would perform better than those with short forceps across the investigated traits. However, their predictions were not validated, as no correlation between weapon size and male quality was detected in either population. Although the sample size is sometimes limited, the consistency of these results across different populations adds robustness to their conclusions.

By demonstrating that forceps length in the European earwig does not reliably indicate male quality, this paper challenges existing theories and highlights the complexity of evolutionary processes shaping morphological traits. Furthermore, the study raises important questions about the evolutionary mechanisms maintaining weapon size diversity, providing a fresh perspective that could stimulate further research and debate in the field, notably the search for other traits where costs might be incurred.

References

Blackwell, S.E.M., Pasquier, L., Dupont, S., Devers, S., Lécureuil, C. & Meunier, J. (2024). Relationship between weapon size and six key behavioural and physiological traits in males of the European earwig. bioRxiv, ver. 3 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2024.03.20.585871

Eberhard, W.G., & Gutierrez, E.E. (1991). Male dimorphisms in beetles and earwigs and the question of developmental constraints. Evolution, 45(1), 18–28. https://doi.org/10.2307/2409478

Emlen, D.J. (2001). Costs and the diversification of exaggerated animal structures. Science, 291(5508), 1534–1536. https://doi.org/10.1126/science.1056607

Emlen, D.J. (2008). The evolution of animal weapons. Annual Review of Ecology, Evolution, and Systematics, 39(1), 387–413. https://doi.org/10.1146/annurev.ecolsys.39.110707.173502

Forslund, P. (2000). Male-male competition and large size mating advantage in European earwigs, Forficula auricularia. Animal Behaviour, 59(4), 753–762. https://doi.org/10.1006/anbe.1999.1359

Styrsky, J.D., & Rhein, S.V. (1999). Forceps size does not determine fighting success in European earwigs. Journal of Insect Behavior, 12(4), 475–482. https://doi.org/10.1023/A:1020962606724

Tomkins, J.L., & Brown, G.S. (2004). Population density drives the local evolution of a threshold dimorphism. Nature, 431, 1099–1103. https://doi.org/10.1038/nature02936.1.

Walker, K.A., & Fell, R.D. (2001). Courtship roles of male and female European earwigs, Forficula auricularia L. (Dermaptera: Forficulidae), and sexual use of forceps. Journal of Insect Behavior, 14(1), 1–17. https://doi.org/10.1023/A:1007843227591

Relationship between weapon size and six key behavioural and physiological traits in males of the European earwigSamantha E.M. Blackwell, Laura Pasquier, Simon Dupont, Séverine Devers, Charlotte Lécureuil, *Joël Meunier <p style="text-align: justify;">In many animals, male weapons are large and extravagant morphological structures that typically enhance fighting ability and reproductive success. It is generally assumed that growing and carrying large weapons is c...Behavior, Evolution, Insecta, Invertebrates, Life histories, MorphologyOlivier Roux2024-03-26 08:56:27 View
19 Jul 2024
article picture

Museomics of Carabus giant ground beetles shows an Oligocene origin and in situ Alpine diversification

Natural history collections continue to inform ground beetle genetics.

Recommended by based on reviews by Michael Caterino, Julian Dupuis and 1 anonymous reviewer

Some of the biodiversity of our planet now exists only in museums, due to continuing habitat destruction and climate change. With more than 380 million entomological specimens already preserved in museums (Johnson and Owens 2023), there is much work left to document what we already have. Fortunately, new advances in DNA sequencing have given us the opportunity to get enormous amounts of information from dried specimens on pins.
 
One such advance is HyRAD-X, which uses RAD-derived probes originally developed using RNA extracted from a selection of specimens with high RNA-integrity (Schmid et al. 2017). These exome-limited probes can then be used to capture low-integrity DNA extracted from a single leg from museum specimens, followed by Illumina sequencing of the enriched libraries.
 
Ground beetles allow an excellent demonstration of this approach, as their diversity, large size, and charismatic appearance has led to them being well represented in museums. Using a HyRAD-X probe set previously developed for a higher phylogeny within the subfamily Carabinae (Toussaint et al. 2021), the authors have now applied the same probe set to produce a comprehensive phylogeny for Arcifera, a clade of four subgenera and ten species within the genus Carabus (Pauli et al. 2024).
 
Of the 96 specimens that they started out with, 90% were from natural history collections and 40% dropped out immediately due to poor DNA extraction yield. After filtering the resulting sequence reads for minimum coverage and minimum number of samples per locus, they ended up with 35 museum specimens with an average of 793 loci. Phylogenetic analysis of this data supported the current classification of these beetles.
 
Pauli et al’s. (2024) study has effectively shown the power of HyRAD-X methods for applications at the species level. In-house production of probes makes the method accessible, expanding the opportunity to use museum specimens for population genetic research.

References

Johnson KR, Owens, (IFP. 2023) A global approach for natural history museum collections. Science 379,1192-1194(2023). https://doi.org/10.1126/science.adf6434

Pauli MT, Gauthier J, Labédan M, Blanc M, Bilat J, Toussaint EFA (2024) Museomics of Carabus giant ground beetles shows an Oligocene origin and in situ alpine diversification. bioRxiv, ver. 5 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2024.03.21.586057

Schmid, S., Genevest, R., Gobet, E., Suchan, T., Sperisen, C., Tinner, W. and Alvarez, N. (2017), HyRAD-X, a versatile method combining exome capture and RAD sequencing to extract genomic information from ancient DNA. Methods Ecol Evol, 8: 1374-1388. https://doi.org/10.1111/2041-210X.12785

Toussaint EFA, Gauthier J, Bilat J, Gillett CPDT, Gough HM, Lundkvist H, Blanc M, Muñoz-Ramírez CP, Alvarez N (2021) HyRAD-X Exome Capture Museomics Unravels Giant Ground Beetle Evolution, Genome Biology and Evolution, Volume 13, Issue 7, evab112, https://doi.org/10.1093/gbe/evab112

Museomics of *Carabus* giant ground beetles shows an Oligocene origin and *in situ* Alpine diversificationMarie T. PAULI, Jeremy GAUTHIER, Marjorie LABEDAN, Mickael BLANC, Julia BILAT, Emmanuel F.A. TOUSSAINT<p style="text-align: justify;">The development of museomics represents a major paradigm shift in the use of natural history collection specimens for systematics and evolutionary biology. New approaches in this field allow the sequencing of hundre...Insecta, Phylogeny, SystematicsFelix Sperling2024-03-27 15:30:31 View
14 Oct 2024
article picture

Negative impact of mild arid conditions on a rodent revealed using a physiological approach in natura

Physiological Adaptations to Arid Conditions in South African Rodents: A Comparative Study of Rhabdomys Species

Recommended by based on reviews by 2 anonymous reviewers

Understanding how organisms are affected by environmental variations is a central question in ecophysiology and evolutionary ecology, particularly in the context of global changes(Fuller et al., 2016). Environmental variations challenge organisms' ability to maintain homeostasis leading to divergent adaptations between habitat specialists and generalists (Kawecki and Ebert, 2004). The article by (Keilani et al.) (2024) presents an original contribution to this field by focusing on the response to dry conditions in two rodent species from semi-arid regions of South Africa. The two species, Rhabdomys bechuanae and R.dilectus dilectus, have different environmental niches : R.dilectus dilectus occurring in mesic habitats while R. bechuanae is found in semi-arid and arid habitats. Previous studies highlighted morphological and behavioral adaptations to arid conditions in R. bechuanae (Dufour et al., 2019), the current study focuses on the physiological responses of the two species to seasonal dry conditions. By analyzing body condition, markers of kidney and liver functions, and habitat characteristics the authors aim to understand how aridity impacts parapatric populations of the two species. They hypothesize that i) the aridity of the habitat tend to increase during the dry season, ii) both species can adjust their physiology to dry conditions thanks to phenotypic plasticity, and iii)  R. bechuanae, having evolved in arid environments, will cope better with dry conditions than R. d. dilectus.
Consistent with their prediction, Keilani et al (2024) found physiological divergence between the two species. They also observed six blood markers (out of 12 tested) showing significant temporal changes, indicating resource depletion as the dry season progressed, even though the year of study was influenced by a relatively mild La Niña event (i.e. wet year). Both species displayed similar physiological responses to the dry conditions, such as reduced blood albumin level by the end of the dry season, confirming albumin as a reliable indicator of malnutrition and nutrient deficiency (AL Eissa et al., 2012). In terms of interspecific differences, R. bechuanae exhibited better water regulation, with lower sodium, potassium, and total bilirubin levels, which may indicate adaptation to drier environments. The study concludes that R. bechuanae appears better adapted to cope with arid conditions, highlighting the importance of physiological studies in understanding species' responses to climate change, and suggests that harsher dry seasons could further challenge R. d. dilectus, particularly in semi-arid zones. This study underscores the value of studying species in their natural environments to fully understand the scope and limitations of their responses to environmental changes.

References

Dufour, C.M.S., Pillay, N., Avenant, N., Watson, J., Loire, E., and Ganem, G. (2019) Habitat characteristics and species interference influence space use and nest-site occupancy: implications for social variation in two sister species. Oikos128: 503-516.
https://doi.org/10.1111/oik.05357 
 
AL Eissa, M.S., Saad, A., Al Farraj, S.A., Saud, A.A., Al Dahmash, B., and Hamad, A.Y. (2012) Seasonal variation effects on the composition of blood in Nubian ibex (Capra nubiana) in Saudi Arabia. Afr J Biotechnol 11: 1283-1286.
https://doi.org/10.5897/AJB11.2004
 
Fuller, A., Mitchell, D., Maloney, S.K., and Hetem, R.S. (2016) Towards a mechanistic understanding of the responses of large terrestrial mammals to heat and aridity associated with climate change. Climate Change Responses 3: 10.
https://doi.org/10.1186/s40665-016-0024-1 

Hamilcar S. Keilani, Nico L. Avenant, Pierre Caminade, Neville Pillay, Guila Ganem (2024) Negative impact of mild arid conditions on a rodent revealed using a physiological approach in natura. bioRxiv, ver.9 peer-reviewed and recommended by PCI Zoology
https://doi.org/10.1101/2024.03.11.583554

Negative impact of mild arid conditions on a rodent revealed using a physiological approach in naturaHamilcar S. Keilani, Nico L. Avenant, Pierre Caminade, Neville Pillay, Guila Ganem<p>1. Understanding how organisms respond to seasonal variations in their environment can be a window to their potential adaptability, a classical problem in evolutionary ecology. In the context of climate change, inducing increased aridity and di...Ecology, Evolution, PhysiologyVincent Foray2024-05-02 18:38:29 View
01 Jul 2020
article picture

Sub-lethal insecticide exposure affects host biting efficiency of Kdr-resistant Anopheles gambiae

kdr homozygous resistant An. gambiae displayed enhanced feeding success when exposed to permethrin Insect-Treated Nets

Recommended by based on reviews by Thomas Guillemaud, Niels Verhulst, Etienne Bilgo and 1 anonymous reviewer

Malaria is a vector-borne parasitic disease found in 91 countries with an estimated of 228 million cases occurred worldwide during 2018. The 93% (213 million) of those cases were reported in the African Region (WHO 2019). Six species of Plasmodium parasites can produce the disease but only P. falciparum and P. vivax are the predominant species globally. More than 40 species of Anopheles mosquitoes are important malaria vectors (Asley et al. 2018). Intrinsic (genetic background, parasite susceptibility) and extrinsic (feeding host preference, host diversity and availability, mosquito abundance) factors affect the capacity of mosquitoes to vector the disease (Macdonald 1952). Malaria is prevented by chemoprophylaxis, vaccination, bite-avoidance and vector-control measures. The mainstays of vector control are long-lasting insecticide (pyrethroid) treated nets and indoor residual spraying with insecticides (Asley et al. 2018). The widespread use of pyrethroid insecticides forced the emergence of insecticide resistance in malaria vectors reducing the insecticidal effect. Mosquitoes can modify their behaviour avoiding insecticide contact and so potentially reducing vector control tools efficacy. In this sense, Diop et al. (2020) investigated whether pre-exposure to an Insecticide-Treated Net (ITN) modulates the mosquito ability to take a blood meal in Anopheles gambiae. By means of video recording experiments the authors analyzed how the feeding/bitting behaviour was affected by kdr mutation genotypes (homozygous susceptible – SS-, heterozygotes -RS- and homozygous resistant -RR-) when exposed to two different insecticides (permethrin and deltamethrin). According to the results, the blood-feeding success did not differ between the three genotypes in the absence of insecticide exposure. However, authors observed differences in the feeding duration and blood meal size. In example, RR mosquitoes spent less time taking their blood meal than RS and SS. On the other hand, RS mosquitoes took higher blood volumes than RR females. These differences can affect the mosquito fitness by decreasing/increasing the likelihood to be killed by the host defensive behavior or increase the oogenesis so enhancing fecundity. Regarding the effect of exposition to insecticides authors detected a strong relationship between kdr genotype and Knock Down (KD) phenotype when mosquitoes were exposed to Permethrin. Previously, the authors have evidenced that RR mosquitoes prefer a host protected by a permethrin-treated net rather than an untreated net and that heterozygotes RS mosquitoes have a remarkable ability to find a hole into a bet net (Diop et al. 2015, Porciani et al. 2017). With data here obtained, they demonstrated that kdr homozygous resistant An. gambiae displayed enhanced feeding success when exposed to permethrin ITN. The changes observed in the feeding/biting mosquito behaviour can affect their fitness shaping the evolution of the insecticide resistance in mosquitoes’ natural populations. Moreover, this may also alter parasite transmission dynamics by modifying vector/host interactions and so vector capacity.

References

World Health Organization (2019). World malaria report 2019. Geneva: World Health Organization; 2019. ISBN 978-92-4-156572-1
Ashley EA, Pyae Phyo A, Woodrow CJ (2018). Malaria. Lancet. 391(10130):1608‐1621. doi: 10.1016/S0140-6736(18)30324-6
Macdonald G (1952). The analysis of equilibrium in malaria. Trop Dis Bull 49: 813-828.
Diop MM, Chandre F, Rossignol M, Porciani A, Château M, Moiroux N and Pennetier, C. (2020). Sub-lethal insecticide exposure affects host biting efficiency of Kdr-resistant Anopheles gambiae. bioRxiv 653980, ver. 4 peer-reviewed and recommended by PCI Zoology. doi: 10.1101/653980
Diop MM, Moiroux N, Chandre F, Martin-Herrou H, Milesi P, Boussari O, et al. (2015) Behavioral cost and overdominance in Anopheles gambiae. PLoS ONE. 10(4):e0121755. doi: 10.1371/journal.pone.0121755
Porciani A, Diop M, Moiroux N, Kadoke-Lambi T, Cohuet A, Chandre F, et al. (2017) Influence of pyrethroïd-treated bed net on host seeking behavior of Anopheles gambiae s.s. carrying the kdr allele. PLOS ONE. 12(7):e0164518. doi: 10.1371/journal.pone.0164518

Sub-lethal insecticide exposure affects host biting efficiency of Kdr-resistant Anopheles gambiaeMalal Mamadou Diop, Fabrice Chandre, Marie Rossignol, Angelique Porciani, Mathieu Chateau, Nicolas Moiroux, Cedric Pennetier<p>The massive use of insecticide-treated nets (ITNs) has drastically changed the environment for malaria vector mosquitoes, challenging their host-seeking behaviour and biting success. Here, we investigated the effect of a brief exposure to an IT...Behavior, Ecology, Evolution, Medical entomology, Pesticide resistanceAdrian DiazAnonymous2019-05-29 19:40:25 View
21 Mar 2023
article picture

Population genetics of Glossina fuscipes fuscipes from southern Chad

Population genetics of tsetse, the vector of African Trypanosomiasis, helps informing strategies for control programs

Recommended by ORCID_LOGO based on reviews by 2 anonymous reviewers

Human African Trypanosomiasis (HAT), or sleeping sickness, is caused by trypanosome parasites. In sub-Saharan Africa, two forms are present, Trypanosoma brucei gambiense and T. b. rhodesiense, the former responsible for 95% of reported cases. The parasites are transmitted through a vector, Genus Glossina, also known as tsetse, which means fly in Tswana, a language from southern Africa. Through a blood meal, tsetse picks up the parasite from infected humans or animals (in animals, the parasite causes Animal African Trypanosomiasis or nagana disease). Through medical interventions and vector control programs, the burden of the disease has drastically reduced over the past two decades, so the WHO neglected tropical diseases road map targets the interruption of transmission (zero cases) for 2030 (WHO 2022).

Meaningful vector control programs utilize traps for the removal of animals and for surveillance, along with different methods of spraying insecticides. However, in existing HAT risk areas, it will be essential to understand the ecology of the vector species to implement control programs in a way that areas cleared from the vector will not be reinvaded from other populations. Thus, it will be crucial to understand basic population genetics parameters related to population structure and subdivision, migration frequency and distances, population sizes, and the potential for sex-biased dispersal. The authors utilize genotyping using nine highly polymorphic microsatellite markers of samples from Chad collected in differently affected regions and at different time points (Ravel et al., 2023). Two major HAT zones exist that are targeted by vector control programs, namely Madoul and Maro, while two other areas, Timbéri and Dokoutou, are free of trypanosomes. Samples were taken before vector control programs started.

The sex ratio was female-biased, most strongly in Mandoul and Maro, the zones with the lowest population density. This could be explained by resource limitation, which could be the hosts for a blood meal or the sites for larviposition. Limited resources mean that females must fly further, increasing the chance that more females are caught in traps. 

The effective population densities of Mandoul and Maro were low. However, there was a convergence of population density and trapping density, which might be explained by the higher preservation of flies in the high-density areas of Timbéri and Dokoutou after the first round of sampling, which can only be tested using a second sampling. 

The dispersal distances are the highest recorded so far, especially in Mandoul and Maro, with 20-30 km per generation. However, in Timbéri and Dokoutou, which are 50 km apart, very little exchange occurs (approx. 1-2 individuals every six months). A major contributor to this is the massive destruction of habitat that started in the early 1990s and left patchily distributed and fragmented habitats. The Mandoul zone might be safe from reinvasion after eradication, as for a successful re-establishment, either a pair of a female and male or a pregnant female are required. As the trypanosome prevalence amongst humans was 0.02 and of tsetse 0.06 (Ibrahim et al., 2021) before interventions began, medical interventions and vector control might have further reduced these levels, making a reinvasion and subsequent re-establishment of HAT very unlikely. Maro is close to the border of the Central African Republic, and the area has not been well investigated concerning refugee populations of tsetse, which could contribute to a reinvasion of the Maro zone. The higher level of genetic heterogeneity of the Maro population indicates that invasions from neighboring populations are already ongoing. This immigration could also be the reason for not detecting the bottleneck signature in the Maro population. 

The two HAT areas need different levels of attention while implementing vector eradication programs. While Madoul is relatively safe against reinvasion, Maro needs another type of attention, as frequent and persistent immigration might counteract eradication efforts. Thus, it is recommended that continuous tsetse suppression needs to be implemented in Maro.  

This study shows nicely that an in-depth knowledge of the processes within and between populations is needed to understand how these populations behave. This can be used to extrapolate, make predictions, and inform the organisations implementing vector control programs to include valuable adjustments, as in the case of Maro. Such integrative approaches can help prevent the failure of programs, potentially saving costs and preventing infections of humans and animals who might die if not treated.

References

Ibrahim MAM, Weber JS, Ngomtcho SCH, Signaboubo D, Berger P, Hassane HM, Kelm S (2021) Diversity of trypanosomes in humans and cattle in the HAT foci Mandoul and Maro, Southern Chad- Southern Chad-A matter of concern for zoonotic potential? PLoS Neglected Tropical Diseases, 15, e000 323. https://doi.org/10.1371/journal.pntd.0009323

Ravel S, Mahamat MH, Ségard A, Argiles-Herrero R, Bouyer J, Rayaisse JB, Solano P, Mollo BG, Pèka M, Darnas J, Belem AMG, Yoni W, Noûs C, de Meeûs T (2023) Population genetics of Glossina fuscipes fuscipes from southern Chad. Zenodo, ver. 9 peer-reviewed and recommended by PCI Zoology. https://doi.org/10.5281/zenodo.7763870

WHO (2022) Trypanosomiasis, human African (sleeping sickness). https://www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness), retrieved 17. March 2023

Population genetics of Glossina fuscipes fuscipes from southern ChadSophie Ravel, Mahamat Hissène Mahamat, Adeline Ségard, Rafael Argiles-Herrero, Jérémy Bouyer, Jean-Baptiste Rayaisse, Philippe Solano, Brahim Guihini Mollo, Mallaye Pèka, Justin Darnas, Adrien Marie Gaston Belem, Wilfrid Yoni, Camille Noûs, Thierr...<p>In Subsaharan Africa, tsetse flies (genus Glossina) are vectors of trypanosomes causing Human African Trypanosomiasis (HAT) and Animal African Trypanosomosis (AAT). Some foci of HAT persist in Southern Chad, where a program of tsetse control wa...Biology, Ecology, Evolution, Genetics/Genomics, Insecta, Medical entomology, Parasitology, Pest management, Veterinary entomologyMichael Lattorff Audrey Bras2022-04-22 11:25:24 View
25 Aug 2021
article picture

Up and to the light: intra- and interspecific variability of photo- and geo-tactic oviposition preferences in genus Trichogramma

New insights into oviposition preference of 5 Trichogramma species

Recommended by ORCID_LOGO based on reviews by Kévin Tougeron and Eveline C. Verhulst

Insects exhibit a great diversity of life-history traits that often vary not only between species but also between populations of the same species (Flatt and Heyland, 2011). A better understanding of the variation in these traits can be of paramount importance when it comes to species of economic and agricultural interest (Wilby and Thomas, 2002). In particular, the control of the development and expansion of agricultural pests generally requires a good understanding of the parameters that favour the reproduction of these pests and/or the reproduction of the species used to control them (Bianchi et al., 2013; Gäde and Goldsworthy, 2003).

Parasitoid wasps of the genus Trichogramma are a classic example of insects involved in pest control (Smith, 1996). This genus comprises over 200 species worldwide, which have been used to control populations of a wide range of lepidopteran pests since the 1900s (Flanders, 1930; Hassan, 1993). Despite its common use, the egg-laying preference of this genus is only partially known. For example, all Trichogramma species are often thought to have positive phototaxis (or negative geotaxis) (e.g. Brower & Cline, 1984; van Atta et al., 2015), but comprehensive studies simultaneously testing this (or other) parameter among Trichogramma species and populations remain rare.

This is exactly the aim of the present study (Burte et al., 2021). Using a new experimental approach based on automatic image analysis, the authors compared the photo- and geo-tactic oviposition preference among 5 Trichogramma species from 25 populations. Their results first confirm that most Trichogramma species and populations prefer light to shade, and higher to lower positions for oviposition. Interestingly, they also reveal that the levels of preference for light and gravity show inter- and intraspecific variation (probably due to local adaptation to different strata) and that both preferences tend to relax over time.

Overall, this study provides important information for improving the use of Trichogramma species as biological agents. For example, it may help to establish breeding lines adapted to the microhabitat and/or growing parts of plants on which agricultural pests lay eggs most. Similarly, it suggests that the use of multiple strains with different microhabitat selection preferences could lead to better coverage of host plants, as well as a reduction in intraspecific competition in the preferred parts. Finally, this study provides a new methodology to efficiently and automatically study oviposition preferences in Trichogramma, which could be used in other insects with a particularly small size.

References

Bianchi, F. J. J. A., Schellhorn, N. A. and Cunningham, S. A. (2013). Habitat functionality for the ecosystem service of pest control: reproduction and feeding sites of pests and natural enemies. Agricultural and Forest Entomology, 15, 12–23. https://doi.org/10.1111/j.1461-9563.2012.00586.x

Burte V., Perez G., Ayed F., Groussier G., Mailleret L, van Oudenhove L. and Calcagno V. (2021). Up and to the light: intra- and interspecific variability of photo-and geo-tactic oviposition preferences in genus Trichogramma. bioRxiv, 2021.03.30.437671, ver. 4 peer-reviewed and recommended by PCI Zoology. https://doi.org/10.1101/2021.03.30.437671

Brower, J. H. and Cline, L. D. (1984). Response of Trichogramma pretiosum and T. evanescens to Whitelight, Blacklight or NoLight Suction Traps. The Florida Entomologist, 67, 262–268. https://doi.org/10.2307/3493947

Flanders, S. E. (1930). Mass production of egg parasites of the genus Trichogramma. Hilgardia, 4, 465–501. https://doi.org/10.3733/hilg.v04n16p465

Flatt, T. and Heyland, A. (2011). Mechanisms of life history evolution: the genetics and physiology of life history traits and trade-offs. Oxford University Press. https://doi.org/10.1093/acprof:oso/9780199568765.001.0001

Gäde, G. and Goldsworthy, G. J. (2003). Insect peptide hormones: a selective review of their physiology and potential application for pest control. Pest Management Science, 59, 1063–1075. https://doi.org/10.1002/ps.755

Hassan, S. A. (1993). The mass rearing and utilization of Trichogramma to control lepidopterous pests: Achievements and outlook. Pesticide Science, 37, 387–391. https://doi.org/10.1002/ps.2780370412

Smith, S. M. (1996). Biological Control with Trichogramma : Advances, Successes, and Potential of Their Use. Annual Review of Entomology, 41, 375–406. https://doi.org/10.1146/annurev.en.41.010196.002111

van Atta, K. J., Potter, K. A. and Woods, H. A. (2015). Effects of UV-B on Environmental Preference and Egg Parasitization by Trichogramma Wasps (Hymenoptera: Trichogrammatidae). Journal of Entomological Science, 50, 318–325. https://doi.org/10.18474/JES15-09.1

Wilby, A. and Thomas, M. B. (2002). Natural enemy diversity and pest control: patterns of pest emergence with agricultural intensification. Ecology Letters, 5, 353–360. https://doi.org/10.1046/j.1461-0248.2002.00331.x

Up and to the light: intra- and interspecific variability of photo- and geo-tactic oviposition preferences in genus TrichogrammaBurte, V., Perez, G., Ayed, F. , Groussier, G., Mailleret, L., van Oudenhove, L. and Calcagno, V.<p>Trichogramma are parasitic microwasps much used as biological control agents. The genus is known to harbor tremendous diversity, at both inter- and intra-specific levels. The successful selection of Trichogramma strains for biocontrol depends o...Behavior, Biocontrol, Biodiversity, Ecology, Insecta, Parasitology, Pest management, Systematics, TerrestrialJoël Meunier Kévin Tougeron, Eveline C. Verhulst2021-04-02 16:10:28 View
14 Dec 2023
article picture

Transcriptomic responses of sponge holobionts to in situ, seasonal anoxia and hypoxia

Future oceanic conditions could leave sponge holobionts breathless – but they won’t let that stop them

Recommended by ORCID_LOGO based on reviews by Maria Lopez Acosta and 2 anonymous reviewers

It is now widely accepted that anthropogenic climate change is a severe threat to biodiversity, ecosystem function and associated ecosystem services. Assessing the vulnerability of species and predicting their response to future changes has become a priority for environmental biology (Williams et al. 2020).

Over the last few decades, oxygen concentrations in both the open ocean and coastal waters have been declining steadily as the result of multiple anthropogenic activities. This global trends towards hypoxia is expected to continue in the future, causing a host of negative effects on marine ecosystems. Oxygen is indeed crucial to many biological processes in the ocean, and its decrease could have strong impacts on biogeochemical cycles, and therefore on marine productivity and biodiversity (Breitburg et al. 2018).

Whenever facing such drastic environmental changes, all organisms are expected to have some intrinsic ability to adapt. At shorter than evolutionary timescales, ecological plasticity and the eco-physiological processes that sustain it could constitute important adaptive mechanisms (Williams et al. 2020)

Marine sponges seem particularly well-adapted to oxygen deficiency, as some species can survive seasonal anoxia for several months. This paper by Strehlow et al. (2023) examines the mechanisms allowing this exceptional tolerance. Focusing on two species of sponges, they used transcriptomics to assess how gene expression by sponges, by their mitochondria, or by their unique and species-specific microbiome could facilitate this trait. Their results suggest that sponge holobionts maintain metabolic activity under anoxic conditions while displaying shock response, therefore not supporting the hypothesis of sponge dormancy. Furthermore, hypoxia and anoxia seemed to influence gene expression in different ways, highlighting the complexity of sponge response to deoxygenation. As often, their exciting results raise as many questions as they provide answers and pave the way for more research regarding how anoxia tolerance in marine sponges could give them an advantage in future oceanic environmental conditions.

References

Breitburg et al. (2018): Declining oxygen in the global ocean and coastal waters. Science 359, eaam7240. https://doi.org/10.1126/science.aam7240 

Strehlow et al. (2023): Transcriptomic responses of sponge holobionts to in situ, seasonal anoxia and hypoxia. bioRxiv, 2023.02.27.530229, ver. 4 peer-reviewed and recommended by Peer Community in Zoology.  https://doi.org/10.1101/2023.02.27.530229 

Williams et al. (2008) Towards an Integrated Framework for Assessing the Vulnerability of Species to Climate Change. PLOS Biology 6(12): e325. https://doi.org/10.1371/journal.pbio.0060325 

Williams et al. (2020):  Research priorities for natural ecosystems in a changing global climate. Global Change Biology 26: 410–416. https://doi.org/10.1111/gcb.14856 

Transcriptomic responses of sponge holobionts to in situ, seasonal anoxia and hypoxiaBrian W Strehlow, Astrid Schuster, Warren R Francis, Lisa Eckford-Soper, Beate Kraft, Rob McAllen, Ronni Nielsen, Susanne Mandrup, Donald E Canfield<p>Deoxygenation can be fatal for many marine animals; however, some sponge species are tolerant of hypoxia and anoxia. Indeed, two sponge species, <em>Eurypon </em>sp. 2 and <em>Hymeraphia stellifera</em>, survive seasonal anoxia for months at a ...Biology, Ecology, Genetics/Genomics, Invertebrates, Marine, SymbiosisLoïc N. Michel Maria Lopez Acosta2023-05-12 16:22:47 View