Red Flour Beetle Tribolium Castaneum Research Articles

Light Sheet-based Fluorescence Microscopy of Living or Fixed and Stained Tribolium castaneum Embryos.

The red flour beetle Tribolium castaneum has become an important insect model organism in developmental genetics and evolutionary developmental biology. The observation of Tribolium embryos with light sheet-based fluorescence microscopy has multiple advantages over conventional widefield and confocal fluorescence microscopy. Due to the unique properties of a light sheet-based microscope, three dimensional images of living specimens can be recorded with high signal-to-noise ratios and significantly reduced photo-bleaching as well as photo-toxicity along multiple directions over periods that last several days. With more than four years of methodological development and a continuous increase of data, the time seems appropriate to establish standard operating procedures for the usage of light sheet technology in the Tribolium community as well as in the insect community at large. This protocol describes three mounting techniques suitable for different purposes, presents two novel custom-made transgenic Tribolium lines appropriate for long-term live imaging, suggests five fluorescent dyes to label intracellular structures of fixed embryos and provides information on data post-processing for the timely evaluation of the recorded data. Representative results concentrate on long-term live imaging, optical sectioning and the observation of the same embryo along multiple directions. The respective datasets are provided as a downloadable resource. Finally, the protocol discusses quality controls for live imaging assays, current limitations and the applicability of the outlined procedures to other insect species. This protocol is primarily intended for developmental biologists who seek imaging solutions that outperform standard laboratory equipment. It promotes the continuous attempt to close the gap between the technically orientated laboratories/communities, which develop and refine microscopy methodologically, and the life science laboratories/communities, which require 'plug-and-play' solutions to technical challenges. Furthermore, it supports an axiomatic approach that moves the biological questions into the center of attention.

Recognition of the Duration and Prediction of Insect Prevalence of Stored Rough Rice Infested by the Red Flour Beetle (Tribolium castaneum Herbst) Using an Electronic Nose.

The purpose of this research is to explore the feasibility of applying an electronic nose for the intelligent monitoring of injurious insects in a stored grain environment. In this study, we employed an electronic nose to sample rough rice that contained three degrees of red flour beetle (Tribolium castaneum Herbst) infestation for different durations—light degree (LD), middle degree (MD), and heavy degree (HD)—and manually investigated the insect situation at the same time. Manual insect situation investigation shows that, in all three rice treatments, the insect amounts gradually decreased after infestation. When the insect population of stored rough rice was under 13 insects per 60 g of rough rice, the natural speed of decrease of the insect population became very slow and reached the best artificial insect killing period. Linear discriminant analysis (LDA) provided good performance for MD and HD insect harm duration identification, but performed poorly for LD insect harm duration identification. Both k-means clustering analysis (K-means) and fuzzy c-means analysis (FCM) effectively identified the insect harm duration for stored rough rice. The results from the back-propagation artificial neural network (BPNN) insect prevalence prediction for the three degrees of rough rice infestation demonstrated that the electronic nose could effectively predict insect prevalence in stored grain (fitting coefficients were larger than 0.89). The predictive ability was best for LD, second best for MD, and least accurate for HD. This experiment demonstrates the feasibility of electronic noses for detecting both the duration and prevalence of an insect infestation in stored grain and provides a reference for the intelligent monitoring of an insect infestation in stored grains.

Thermal death kinetics of adult red flour beetle Tribolium castaneum (Herbst) in canola seeds during radio frequency heating

ABSTRACTThermal mortalities of adult red flour beetles Tribolium castaneum (Herbst) infesting canola seeds at various moisture contents and volumes were determined after radio frequency (RF) heating (i.e. temperature between 30 and 80°C). The mortality of 92% was achieved at the end temperature of 343 K for small-volume (1.96 × 10−4 m3, 0.250 kg) seeds, and the mortality of 99% at 333 K for large-volume (1.77 × 10−3 m3, 2.26 kg) seeds. Regardless of sample volume, the thermal mortalities of the test insects increased significantly after the seed temperature reached 333 K (60°C). The kinetic parameters of the thermal death of the adult T. castaneum were estimated using inverse simulation. The ordinary differential equation-based kinetic model with the Arrhenius temperature-dependent reaction rate constant was solved using the fourth-order Runge–Kutta method. The kinetics followed first-order reaction with the activation energy of 100 kJ/mol. Good agreements were observed between the mortalities predicted using the kinetic model and the experiments (R2 = 0.972–0.987) except for the small-volume seeds at 11% MC (11 g/100 g raw materials) (R2 = 0.741). The predicted lethal times (s) to achieve 95 and 99% mortalities using the kinetic model agreed well with those determined from the experiments.

An analysis of trends, frequencies and factors influencing the development of resistance to phosphine in the red flour beetle Tribolium castaneum (Herbst) in Australia

Although resistance to phosphine, the key disinfestant used worldwide in the stored grain environment has been an ongoing industry issue, studies on its trend over large geographic region and over long period of time is very limited. In this study, we critically analysed 20 years' phosphine resistance diagnosis data for the red flour beetle Tribolium castaneum (Herbst) stored in the Australian Grain Insect Resistance Database. Resistance diagnosis on a staggering 6336 samples, along with information on storage types and treatment history was interrogated to establish trends and frequencies of resistance development in this species and factors that may have contributed towards these resistance occurences. Using descriptive statistics, linear and trend analysis and a well established Bayesian hurdle model, we determined that strong resistance in T. castaneum was significantly more prevalent in quarantine intereceptions than in central storages and on farms. The strong resistance incidences had been confined to eastern states of Queensland, New South Wales, Victoria and South Australia, whereas it is yet to be detected in the state of Western Australia. We could not establish any significant correlation between the strong resistance development and any commodity or treatments. After an initial increasing trend in incidences since the first detection of strong resistance in 1997 in this species, the frequency was stabilised during 2001–08; after which there had been an upward trend since 2009 till the last survey in 2013. The conclusions derived from this analyses highlighted the importance of a resistance monitoring program with relevant information being used in Australia as the basis for ongoing and future phosphine resistance management strategies. This research may also proved valuable towards devising similar strategies in overseas countries with phosphine resistance problems.

Status resistensi terhadap fosfin pada Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) dari gudang penyimpanan biji kakao di Makassar Sulawesi Selatan

Control of postharvest pest on cocoa beans during storage is generally conducted by fumigation with phosphine. Long-term exposure to phosphine and improper fumigation practices could stimulate the development of resistant strains against phosphine. The aims of this research were to know the resistance status of red flour beetle Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) against phosphine from cocoa bean storages in Makassar, South Sulawesi and to conduct the field efficacy test of phosphine against insects resistant strain to confirm their resistance status. The study was conducted by collecting T. castaneum from five different cocoa beans storages in Makassar. Resistance status was tested in the laboratory using the standard method recommended by FAO and by conducting field efficacy test on adult strains resistant to phosphine. The results showed the presence of insect resistance to phosphine. Adult, pupae, and larvae of T. castaneum were found to be resistant to phosphine with the resistance factors of 1.15–8.08, 1.58–13.63, 1.53–3.25, respectively. The results of field efficacy tests showed that dosage 2 tablets/m 3 was effective in controlling resistant strain of adult, pupae, and larvae of T. castaneum .

Upshot of Food Add-Ons on the Life History and Development ofTribolium castaneum(Herbst) (Coleoptera: Tenebrionidae)

Growth and development of insects in the laboratory cultures can be significantly enhanced by improving the nutrient quality of their culturing medium. One way to achieve this is by including add-ons in the food medium. This approach is commonly followed in culturing red flour beetle Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) which is used as a model insect for a variety of laboratory studies. Commonly yeast is used as a food admixture for escalating beetle production and promoting oviposition. In this study, we aim to evaluate some alternates for yeast, i.e. agar-agar and folic acid at three levels (3.33 %, 6.66%and 10 %) for enhancing laboratory culturing of T. castaneum. The results demonstrated that highest adult production was achieved by adding yeast at the rate of 6.66%(279±23.24) to the food medium while agar-agar and folic acid produced more adults albeit with prolonged larval duration of about 5 days as compared to yeast when ad-mixed at rates of 10%(196.6±21.52) and 3.33%(164.8±3....

Multiple resistance to pirimiphos-methyl and bifenthrin in Tribolium castaneum involves the activity of lipases, esterases, and laccase2

Several recent studies have elucidated the molecular mechanisms that confer insecticide resistance on insect pests. However, little is known about multiple resistance in red flour beetle (Tribolium castaneum) at molecular level. The multiple resistance is characterized as resistance to different classes of insecticides that have different target sites, and is mediated by several enzymatic systems. In this study, we investigated the biochemical and molecular mechanisms involved in multiple resistance of T. castaneum to bifenthrin (pyrethroid [Pyr]) and pirimiphos-methyl (organophosphate [Org]). We used artificial selection, biochemical and in silico approaches including structural computational biology. After five generations of artificial selection in the presence of bifenthrin (F5Pyr) or pirimiphos-methyl (F5Org), we found high levels of multiple resistance. The hierarchical enzymatic cluster revealed a pool of esterases (E), lipases (LIPs) and laccase2 (LAC2) potentially contributing to the resistance in different ways throughout development, after one or more generations in the presence of insecticides. The enzyme-insecticide interaction network indicated that E2, E3, LIP3, and LAC2 are enzymes potentially required for multiple resistance phenotype. Kinetic analysis of esterases from F5Pyr and F5Org showed that pirimiphos-methyl and specially bifenthrin promote enzyme inhibition, indicating that esterases mediate resistance by sequestering bifenthrin and pirimiphos-methyl. Our computational data were in accordance with kinetic results, indicating that bifenthrin has higher affinity at the active site of esterase than pirimiphos-methyl. We also report the capability of these insecticides to modify the development in T. castaneum. Our study provide insights into the biochemical mechanisms employed by T. castaneum to acquire multiple resistance.

Do males pay for sex? Sex-specific selection coefficients suggest not.

Selection acting on males can reduce mutation load of sexual relative to asexual populations, thus mitigating the twofold cost of sex, provided that it seeks and destroys the same mutations as selection acting on females, but with higher efficiency. This could happen due to sexual selection-a potent evolutionary force that in most systems predominantly affects males. We used replicate populations of red flour beetles (Tribolium castaneum) to study sex-specific selection against deleterious mutations introduced with ionizing radiation. We found no evidence for selection being stronger in males than in females; in fact, we observed a nonsignificant trend in the opposite direction. This suggests that selection on males does not reduce mutation load below the level expected under the (hypothetical) scenario of asexual reproduction. Additionally, we employed a novel approach, based on a simple model, to quantify the relative contributions of sexual and offspring viability selection to the overall selection observed in males. We found them to be similar in magnitude; however, only the offspring viability component was statistically significant. In summary, we found no support for the hypothesis that selection on males in general, and sexual selection in particular, contributes to the evolutionary maintenance of sex.

A key role for foxQ2 in anterior head and central brain patterning in insects.

ABSTRACTAnterior patterning of animals is based on a set of highly conserved transcription factors but the interactions within the protostome anterior gene regulatory network (aGRN) remain enigmatic. Here, we identify the red flour beetle Tribolium castaneum ortholog of foxQ2 (Tc-foxQ2) as a novel upstream component of the aGRN. It is required for the development of the labrum and higher order brain structures, namely the central complex and the mushroom bodies. We reveal Tc-foxQ2 interactions by RNAi and heat shock-mediated misexpression. Surprisingly, Tc-foxQ2 and Tc-six3 mutually activate each other, forming a novel regulatory module at the top of the aGRN. Comparisons of our results with those of sea urchins and cnidarians suggest that foxQ2 has acquired more upstream functions in the aGRN during protostome evolution. Our findings expand the knowledge on foxQ2 gene function to include essential roles in epidermal development and central brain patterning.

Vapormate® as a fumigant for the control of mealybugs in pineapple and pests of stored rice and maize

Experiments were carried out at the National Plant Quarantine Service at Katunayake and at the Food Research Unit at Gannoruwa, Peradeniya, Sri Lanka to evaluate the efficacy of Vapormate® (Ethyl formate 16.3% w/w in liquid carbon dioxide 83.7% w/w), against mealybugs in pineapples [Ananas comosus (L.) Merr.] and stored grain pests of rice (Oryza sativa L.) and maize (Zea mays L.). Vapormate® is an eco-friendly safer alternative for Methyl Bromide, and accepted worldwide for quarantine and non-quarantine treatment of food items, packaged and stored foods and processing equipment. Fumigation standards recommended by the manufacturer for pineapples (4h exposure of 360g Vapormate®/m3) resulted 100% mortality in mealybugs, (Dysmicoccus brevipes), without deteriorating the organoleptic and physicochemical properties of the fruits. The recommended fumigation stand-ards by the manufacturer for stored grains (24h exposure of 420 g Vapormate®/m3) found to be highly effective in controlling both larvae and adults of stored grain pests of rice and maize namely, maize weevil (Sitophilus zeamais), rice weevil (Sitophilus oryzae), red flour beetle (Tribolium castaneum), confused flour beetle (Tribolium confusum) and rice moth (Corcyra cephalonica). Therefore, Vapormate® can be recommended for pre-shipment fumigation of pineapples and for pre-entry and non-quarantine treatment of stored rice and maize in Sri Lanka as recommended by the manufacturer.

Gene Ages, Nomenclatures, and Functional Diversification of the Methuselah/Methuselah-Like GPCR Family in Drosophila and Tribolium.

Affecting lifespan regulation and oxidative stress resistance, the G-protein coupled receptor (GPCR) gene methuselah (mth) plays important roles in the life history of Drosophila melanogaster. Substantial progress has been made in elucidating the molecular pathways by which mth affects these traits, yet conflicting ideas exist as to how old these genetic interactions are as well as how old the mth gene itself is. Root to these issues is the complex gene family history of the Mth/Mthl GPCR family, which experienced independent expansions in a variety of animal clades, leading to at least six subfamilies in insects. Within insects, drosophilid flies stand out by possessing up to three times more Mth/Mthl receptors due to the expansion of a single subfamily, the mth superclade subfamily, which contains an even younger subfamily introduced here as the melanogaster subgroup subfamily. As a result, most of the 16 Mth/Mthl receptors of D. melanogaster are characterized by n:1 orthology relationships to singleton mth superclade homologs in nondrosophilid species. This challenge is exacerbated by the inconsistent naming of Mth/Mthl orthologs across species. To consolidate this situation, we review established ortholog relationships among insect Mth/Mthl receptors, clarify the gene nomenclatures in two important satellite model species, the fruit fly relative D. virilis and the red flour beetle Tribolium castaneum, and discuss the genetic and functional evolution of the D. melanogaster Mth GPCR.

Insecticidal activity and composition of essential oils from Pistacia atlantica subsp. kurdica against the model and stored product pest beetle Tribolium castaneum

This study is the first report to compare the compositions of the gum, fruit and leaves essential oils of Pistacia atlantica subsp. kurdica and the fumigant toxicity against the model and important stored product pest insect, the red flour beetle Tribolium castaneum (Herbst) (Col.: Tenebrionidae). The essential oils of the three parts showed qualitative differences in their chemical compositions, but the major common compounds were α-pinene, spathulenol, β-myrcene and D-limonene. The fumigant tests against Tribolium beetles confirmed insecticide activity and the gum essential oil was the most toxic; the concentration to kill 50 % of treated insects (LC50) was 29 μl/l air. Our data confirm the usefulness of natural plant products as essential oils from Pistacia trees to be used as a botanic fumigant insecticide against important pest insects.

Electroantennographic responses of red flour beetle Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) to volatile organic compounds

AbstractThe red flour beetle Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is the most encountered and destructive stored product insect pest of cereal grains and seeds. Although this beetle has been used as a model organism for many decades, there is no systematic knowledge about antennal detection of host and non‐host volatiles. Electroantennogram responses to 94 selected volatile organic compounds including alkanes, alkenes, alcohols, aldehydes, ketones, carboxylic acids, esters, terpenoids and aromatic compounds were recorded from both sexes of T. castaneum. Overall, female and male T. castaneum exhibited similar electroantennography (EAG) responses. Compounds eliciting the strongest EAG responses within compound groups of chemical similarity were undecane, 1‐hexen‐3‐ol, octanal, 2‐heptanone, hexanoic acid and ethyl hexanoate. Comparison of vapour pressure and EAG amplitudes within homologous series of compounds revealed responses to undecane, octadecane, octanal, nonanal, 2‐heptanone, hexanoic acid and octanoic acid as outstanding. Given that systematic EAG screenings have not been conducted before, these are the best candidates for evaluation in future behavioural studies to unravel their potential for application in integrated pest management strategies of T. castaneum.

Morphological and Transcriptomic Analysis of a Beetle Chemosensory System Reveals a Gnathal Olfactory Center.

BackgroundThe red flour beetle Tribolium castaneum is an emerging insect model organism representing the largest insect order, Coleoptera, which encompasses several serious agricultural and forest pests. Despite the ecological and economic importance of beetles, most insect olfaction studies have so far focused on dipteran, lepidopteran, or hymenopteran systems.ResultsHere, we present the first detailed morphological description of a coleopteran olfactory pathway in combination with genome-wide expression analysis of the relevant gene families involved in chemoreception. Our study revealed that besides the antennae, also the mouthparts are highly involved in olfaction and that their respective contribution is processed separately. In this beetle, olfactory sensory neurons from the mouthparts project to the lobus glomerulatus, a structure so far only characterized in hemimetabolous insects, as well as to a so far non-described unpaired glomerularly organized olfactory neuropil in the gnathal ganglion, which we term the gnathal olfactory center. The high number of functional odorant receptor genes expressed in the mouthparts also supports the importance of the maxillary and labial palps in olfaction of this beetle. Moreover, gustatory perception seems equally distributed between antenna and mouthparts, since the number of expressed gustatory receptors is similar for both organs.ConclusionsOur analysis of the T. castaneum chemosensory system confirms that olfactory and gustatory perception are not organotopically separated to the antennae and mouthparts, respectively. The identification of additional olfactory processing centers, the lobus glomerulatus and the gnathal olfactory center, is in contrast to the current picture that in holometabolous insects all olfactory inputs allegedly converge in the antennal lobe. These findings indicate that Holometabola have evolved a wider variety of solutions to chemoreception than previously assumed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-016-0304-z) contains supplementary material, which is available to authorized users.

Functional traits in red flour beetles: the dispersal phenotype is associated with leg length but not body size nor metabolic rate

Summary Individuals vary in their ability to disperse. Much of this variation can be described by covarying phenotypic traits that are related to dispersal (constituting the ‘dispersal phenotype’ or ‘dispersal syndrome’), but the nature of the associations among these traits is not well understood. Unravelling the associations among traits that potentially constitute the dispersal phenotype provides a foundation for understanding evolutionary trade‐offs due to variation in dispersal. Here, we tested five predictions pertaining to the relationships among physiological, morphological and movement traits that are associated with dispersal, using a species with a long history as a laboratory model for studying ecological phenomena, red flour beetles (Tribolium castaneum). We identified a dominant axis of movement ability that describes variation in dispersal‐related movement traits. Individuals that scored positively on this axis moved at higher speed, travelled longer distances, had lower movement intermittency and dispersed quicker to a specified area. Relative leg length, but not body size nor routine metabolic rate related positively with movement ability, indicating a likely mechanistic relationship between increased stride length and movement ability. Our data suggest that the dispersal phenotype may be more strongly linked to morphological traits than physiological ones. We demonstrate that associations among many functional traits do not necessarily conform to a priori expectations, and predict that the substantial intraspecific variation in trait values may be important for selection. Movement is a complex behavioural trait, but it has a mechanistic basis in locomotor morphology that warrants further exploration. A lay summary is available for this article.

Repellency of three plant essential oils against red flour beetle Tribolium castaneum (Herbst, 1797) (Coleoptera: Tenebrionidae)

Tribolium castaneum (Herbst, 1797) depolanmis urunlerde bulunan zararli bir bocek turudur. Bu zararliyi kontrol etmek icin, tehlikeli fumigantlar yerine guvenli alternatiflerin gelistirilmesi gerekmektedir. Bu arastirma laboratuvar kosullarinda T. castaneum erginlerine karsi uc farkli bitki, Hypericum hemsleyanum, Mentha haplocalyx ve Stemona japonica esansiyel yaglarin kacirici etkilerini belirlemek amaciyla yapilmistir. Ucucu yaglarin kacirici ozelligi, alan tercihi yontemi ile 31.5 µg/cm 2 'lik bir konsantrasyonda belirlenmistir. Filtre kagidi diskleri petri kabina yerlestirilmis ve bir yarisi ucucu yag ile muamele edilmis, diger yarisi ise kontrol olarak kullanilmistir. Yirmi adet T. castaneum ergini her bir kagit diskin ortasina yerlestirilmistir. Boceklerin sayimi, kontrol ve uygulama alaninda bocek salinmasindan 12, 24, 48 ve 72 saat sonra yapilmistir. Hypericum hemsleyanum ve M. haplocalyx , tum degerlendirme zamanlarinda en guclu kacirici etkiyi gostermis; 12, 24, 48 ve 72 saat sonra sirasiyla %94, 71, 69, 70 ve %91, 65, 73, 83 degerleri elde edilmis olup; ve S. japonica bunlari takip etmistir. Bu arastirma, bu yaglarin guclu kaciricilar oldugunu ve depolanmis urunlerde T. castaneum ’u uzaklastirmak icin potansiyel olarak kullanilabilir oldugunu gostermistir.

Divergent immune priming responses across flour beetle life stages and populations.

Growing evidence shows that low doses of pathogens may prime the immune response in many insects, conferring subsequent protection against infection in the same developmental stage (within‐life stage priming), across life stages (ontogenic priming), or to offspring (transgenerational priming). Recent work also suggests that immune priming is a costly response. Thus, depending on host and pathogen ecology and evolutionary history, tradeoffs with other fitness components may constrain the evolution of priming. However, the relative impacts of priming at different life stages and across natural populations remain unknown. We quantified immune priming responses of 10 natural populations of the red flour beetle Tribolium castaneum, primed and infected with the natural insect pathogen Bacillus thuringiensis. We found that priming responses were highly variable both across life stages and populations, ranging from no detectable response to a 13‐fold survival benefit. Comparing across stages, we found that ontogenic immune priming at the larval stage conferred maximum protection against infection. Finally, we found that various forms of priming showed sex‐specific associations that may represent tradeoffs or shared mechanisms. These results indicate the importance of sex‐, life stage‐, and population‐specific selective pressures that can cause substantial divergence in priming responses even within a species. Our work highlights the necessity of further work to understand the mechanistic basis of this variability.

Radio frequency (RF) control of red flour beetle (Tribolium castaneum) in stored rapeseeds (Brassica napus L.)

Absolute and relative mortalities of red flour beetle (Tribolium castaneum) infesting the rapeseeds of a small (196.3 cm3) and a large (1766 cm3) volumes during radio frequency (RF) heating (1.5 kW, 27.12 MHz) were determined at different end temperatures (30–80 °C) and initial seed moisture contents (5%, 7%, 9%, and 11% wet basis). 100% absolute and relative mortalities of the adult insects were achieved at 80 °C for the small volume of the seeds at all moisture contents (MCs) and at 60 °C and 9% and 11% MCs, and 70 °C and 5% and 7% MCs for the large volume. Over 80% and 96% of the absolute and the relative mortalities of the adult insects were achieved at over 60 °C for both volumes of the seeds. 100% mortalities of larvae infesting the small and the large volume seeds were achieved at 55 °C at all MCs. Germination, major and minor axes, roundness, colour of the seeds and qualities of the rapeseed oil were not affected significantly by RF treatment temperature at entire MCs. Therefore, a complete mortality of the red flour beetle infesting the rapeseeds with acceptable thermal degradation to qualities of the seeds could be achieved at under 60 °C by the RF treatment with a proper design of RF disinfestation.

Superoxide dismutase 2 knockdown leads to defects in locomotor activity, sensitivity to paraquat, and increased cuticle pigmentation in Tribolium castaneum.

Insects can rapidly adapt to environmental changes through physiological responses. The red flour beetle Tribolium castaneum is widely used as a model insect species. However, the stress–response system of this species remains unclear. Superoxide dismutase 2 (SOD2) is a crucial antioxidative enzyme that is found in mitochondria. T. castaneum SOD2 (TcSOD2) is composed of 215 amino acids, and has an iron/manganese superoxide dismutase domain. qRT-PCR experiments revealed that TcSOD2 was present through all developmental stages. To evaluate TcSOD2 function in T. castaneum, we performed RNAi and also assessed the phenotype and antioxidative tolerance of the knockdown of TcSOD2 by exposing larvae to paraquat. The administration of paraquat resulted in significantly higher 24-h mortality in TcSOD2 knockdown larval groups than in the control groups. The TcSOD2 knockdown adults moved significantly more slowly, had lower ATP content, and exhibited a different body color from the control groups. We found that TcSOD2 dsRNA treatment in larvae resulted in increased expression of tyrosinase and laccase2 mRNA after 10 days. This is the first report showing that TcSOD2 has an antioxidative function and demonstrates that T. castaneum may use an alternative antioxidative system when the SOD2-based system fails.

Male Aggregation Pheromones Inhibit Ideal Free Habitat Selection in Red Flour Beetles (Tribolium castaneum)

The ideal free distribution (IFD) predicts that individuals should be distributed between habitats in proportion to habitat suitability such that mean fitness is equal in each habitat. The IFD is useful in studies examining habitat selection, yet its key assumptions are often violated and the expected IFDs are not consistently detected. While the use of aggregation pheromones by insects is expected to evolve in systems that experience positive density dependence (Allee effect), through a series of experiments we test the hypothesis that aggregation pheromones may limit the ability of individuals to achieve an IFD. Using red flour beetles (Tribolium castaneum), we specifically test the prediction that beetles in groups with an equal sex ratio or in the presence of an artificial aggregation pheromone will deviate from an IFD, whereas female-only groups will achieve an IFD. We also test the hypothesis that aggregation pheromones evolved to promote Allee effects by testing the prediction that beetle fitness will show positive density dependence at low densities. Consistent with our first hypothesis, female groups achieved an IFD, while mixed sex groups and females in the presence of an aggregation pheromone in the low food habitat under-matched the IFD. We found no evidence of Allee effects at low density, but we did find evidence of strong negative density dependence. We demonstrate that the use of aggregation pheromones may negatively impact a population’s ability to achieve an IFD and cast doubt on the hypothesis that male aggregation pheromones evolve to promote Allee effects.