Castaneum Females Research Articles

Progression of phosphine resistance in susceptible Tribolium castaneum (Herbst) populations under different immigration regimes and selection pressures.

Insecticide resistance is an escalating global issue for a wide variety of agriculturally important pests. The genetic basis and biochemical mechanisms of resistance are well characterized in some systems, but little is known about the ecological aspects of insecticide resistance. We therefore designed a laboratory experiment to quantify the progression of phosphine resistance in Tribolium castaneum populations subject to different immigration regimes and selection pressures. Mated resistant females were added to originally susceptible populations under two distinct migration rates, and in addition, half of the populations in each migration treatment were exposed to selection pressures from phosphine fumigation. The progression of phosphine resistance was assessed by screening beetles for the resistance allele at rph2. Phosphine resistance increased slowly in the low migration treatment and in the absence of selection, as expected. But at the higher migration rate, the increase in frequency of the resistance allele was lower than predicted. These outcomes result from the high levels of polyandry known in T. castaneum females in the laboratory, because most of the Generation 1 offspring (86%) were heterozygous for the rph2 allele, probably because resistant immigrant females mated again on arrival. Phosphine resistance was not fixed by fumigation as predicted, perhaps because susceptible gametes and eggs survived fumigation within resistant females. In terms of phosphine resistance progression in populations exposed to selection, the effect of fumigation negated the difference in migration rates. These results demonstrate how species‐specific traits relating to the mating system may shape the progression of insecticide resistance within populations, and they have broad implications for the management of phosphine resistance in T. castaneum in the field. ​We specify and discuss how these mating system attributes need to be accounted for when developing guidelines for resistance management.

Transovarial Effect of Novaluron on Tribolium castaneum (Coleoptera: Tenebrionidae) After Termination of Direct Contact.

The insect growth regulator novaluron (Rimon 10 EC, Makhteshim-Agan Ltd, Israel) is used against many field pests on corn, vegetables, orchards, forests, and cotton plantations. Previously, we studied various effects of novaluron on stored grain pests. Termination in Tribolium castaneum (Herbst) eggs hatching after treating adults with novaluron and following restoration after adult transfer to untreated media was observed. The objective of this study was to investigate the restoration of T. castaneum egg hatch following transfer of adults from treated media to untreated favorable and unfavorable media. The time needed for hatching restoration of 50% of eggs laid by adults transferred from novaluron (1 ppm) treated flour to untreated flour (RT50) was 2.7 d. RT50 for those transferred to untreated wheat grain was 4.1 d. RT90 in flour was 3.6 d, in grain—6.1 d. Varieties of RTs in grain and in flour with nonoverlapping confidence intervals indicate that RTs were significantly different. Delay of eggs hatching restoration for adults transferred from treated flour to unfavorable media (Petri dishes with limited amount of flour, lying of eggs not detected) was observed. RT50 in flour was 2.1 d and RT90—3.1 d, while RT50 in the unfavorable media was 3.4 d and RT90 6.5 d. Delayed effect of egg hatching restoration after adult transfer to unfavorable media provides evidence of the significant role of insect physiological state in novaluron excretion and (or) degradation by T. castaneum females.

Potential of pyrethroid insecticides and plant extracts on fecundity and egg viability of Tribolium castaneum (Herbst)

Context: Sythetic pyrethroid and two botanical may reduce the fecundity and egg viability of red flour beetle, Tribolium castaneum (Herbst) and can be used in grain protection. Objective: To determine the effect of cypermethrin, fenitrothion, Murraya paniculata L. and Jatropha gossypifolia L. plant extracts on fecundity and egg viability of T castaneum. Materials and Methods: Newly hatched T. castaneum larvae were kept in a petridish containing 30 g either fresh or treated flour separately. After pupation the pupae were sieved and sexed by microscopic examination and kept separately for adult emergence. Twenty five pairs (1?: 1?) adults were paired from treated and one pair from untreated media and placed in a glass vial containing 2 g of food either treated or untreated for oviposition in an incubator at 30 ± 0.5°C. Eggs were collected and counted after every three days over a period of 45 days. The eggs laid by the first 15 pairs from each treatment were collected from the experimental vials and kept in separate petridish for hatching. Eggs were regularly observed with a microscope and hatched larvae were counted. Results: The females of all treated media laid less number of eggs than the untreated females. Both insecticides and botanicals affected oviposition significantly (P<0.001) at all doses levels. All the treatments of both the insecticides and botanicals significantly (P < 0.001) reduced the fertility of eggs laid by T. castaneum females in comparison to those of the control. Conclusion: The plant extracts of kamini and jamalgota can effectively reduced the fecundity and egg viability against stored product insect pests with low mamalian toxicity. DOI: http://dx.doi.org/10.3329/jbs.v19i0.13007 J. bio-sci. 19 95-97, 2011

Elevated temperature changes female costs and benefits of reproduction

Despite obvious benefits, reproduction also imposes severe costs on females. Such costs and benefits are highly sensitive to environmental factors. Rapidly changing conditions may thus disturb a finely poised balance between the two and pose a challenge to natural populations. A more complete understanding of reproduction and population fitness across different environments is, hence, crucial. In particular, sexual selection could either be beneficial or detrimental when conditions change abruptly. Here Tribolium castaneum females were subjected to mating treatments with or without sexual selection (virginity, monogamy, polyandry) replicated at standard versus elevated temperatures. We found a substantial survival cost of reproduction at the standard, but not at the elevated temperature. Reproductive success was similar across mating treatments at the standard temperature, but at elevated temperature we detected a significant benefit of polyandry compared to monogamy. These findings indicate that environmental heterogeneity can strongly influence the balance between costs and benefits when sexual selection is allowed to act. Furthermore, reproduction may be critically affected by changes in temperature with potentially profound consequences for population fitness.

An integrative view of sexual selection in Tribolium flour beetles

Sexual selection is a major force driving the evolution of diverse reproductive traits. This evolutionary process is based on individual reproductive advantages that arise either through intrasexual competition or through intersexual choice and conflict. While classical studies of sexual selection focused mainly on differences in male mating success, more recent work has focused on the differences in paternity share that may arise through sperm competition or cryptic female choice whenever females mate with multiple males. Thus, an integrative view of sexual selection needs to encompass processes that occur not only before copulation (pre-mating), but also during copulation (peri-mating), as well as after copulation (post-mating), all of which can generate differences in reproductive success. By encompassing mechanisms of sexual selection across all of these sequential reproductive stages this review takes an integrative approach to sexual selection in Tribolium flour beetles (Coleoptera: Tenebrionidae), a particularly well-studied and economically important model organism. Tribolium flour beetles colonize patchily distributed grain stores, and juvenile and adult stages share the same food resources. Adults are highly promiscuous and female reproduction is distributed across an adult lifespan lasting approximately 1 year. While Tribolium males produce an aggregation pheromone that attracts both sexes, there appears to be little pre-mating discrimination among potential mates by either sex. However, recent work has revealed several peri-mating and post-mating mechanisms that determine how offspring paternity is apportioned among a female's mates. During mating, Tribolium females reject spermatophore transfer and limit sperm numbers transferred by males with low phenotypic quality. Although there is some conflicting evidence, male copulatory leg-rubbing appears to be associated with overcoming female resistance to insemination and does not influence a male's subsequent paternity share. Evidence suggests that Tribolium beetles have several possible post-mating mechanisms that they may use to bias paternity. Male sperm precedence has been extensively studied in Tribolium spp. and the related Tenebrio molitor, and several factors influencing male paternity share among a female's progeny have been identified. These include oviposition time, inter-mating interval, male strain/genotype, the mating regimen of a male's mother, male starvation, and tapeworm infection. Females exert muscular control over sperm storage, although there is no evidence to date that females use this to differentiate among mates. Females could also influence offspring paternity by re-mating with additional males, and T. castaneum females more readily accept spermatophores when they are re-mating with more attractive males. Additional work is needed to examine the possible roles played by both male and female accessory gland products in determining male paternity share. Sexual selection during pre-mating episodes may be reinforced or counteracted by peri- and post-copulatory selection, and antagonistic coevolution between the sexes may be played out across reproductive stages. In Tribolium, males' olfactory attractiveness is positively correlated with both insemination success and paternity share, suggesting consistent selection across different reproductive stages. Similar studies across sequential reproductive stages are needed in other taxa to provide a more integrative view of sexual selection.

Female mate choice across mating stages and between sequential mates in flour beetles

Few studies have examined how female premating choice correlates with the outcome of copulatory and post-copulatory processes. It has been shown that polyandrous Tribolium castaneum females discriminate among males before mating based on olfactory cues, and also exert cryptic choice during mating through several mechanisms. This study tested whether a male's relative attractiveness predicted his insemination success during copulation. Bioassays with male olfactory cues were used to rank two males as more and less attractive to females; each female was then mated to either her more attractive male followed by less attractive male, or vice versa. Dissections immediately after second copulations revealed a significantly higher percent of successful inseminations for females that remated with more attractive males compared with those that remated with less attractive males. These results indicate that cryptic female choice during copulation reinforces precopulatory female choice in T. castaneum, and suggest that females could use cryptic choice to trade up to more attractive males, possibly gaining better phenotypic or genetic quality of sires.

Proximal traits and mechanisms for biasing paternity in the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae)

A comprehensive understanding of sexual selection requires knowledge of the traits and mechanisms responsible for increasing a male’s paternity share (proportion of progeny sired) relative to that of other males mating with the same female. In this study we manipulated by starvation the expression of traits that might influence male paternity share in Tribolium castaneum. We then conducted experiments to examine how male starvation affects male performance during sequential episodes of sexual selection from mating to progeny production, and investigated female control over specific stages by using live vs dead females. Comparison of starved vs fed males revealed that T. castaneum females have control over spermatophore transfer during mating, as live females rejected inseminations by starved (“low quality”) males. None of the measured male copulatory behaviors (leg-rubbing frequency, asymmetry, and percent of time spent rubbing) affected the probability of successful insemination, but the last two were positively associated with male paternity share. Spermatophore positioning within the female reproductive tract was not affected by male treatment (starved/fed), by female treatment (live/dead), or by male copulatory behaviors. Starvation, however, had a dramatic effect on male reproductive physiology, decreasing both accessory gland size and total number of sperms transferred (but not sperm viability in seminal vesicles). In addition, females who mated to starved males stored fewer sperms in their spermathecae, which, together with decreased ejaculate size, may explain the reduced paternity share of starved males compared to fed males. This study elucidates some cryptic mechanisms influencing male reproductive success and aids our understanding of trait evolution through sexual selection.

Sperm stratification and paternity success in red flour beetles

Abstract. When females are inseminated by multiple males, male paternity success (sperm precedence) is determined by the underlying processes of sperm storage and sperm utilization. Although informative for many questions, two‐male sperm competition experiments may offer limited insight into natural mating scenarios when females are likely to mate with several males. In this study, genetic markers in Tribolium castaneum are used to trace paternity for multiple sires, and to determine whether displacement of stored sperm that occurs after a third mating equally affects both previous mates, or if fertilizations are disproportionately lost by the female's most recent mate. For 20 days after triple‐matings, first males retain significantly higher paternity success (relative to first male paternity in double‐matings) compared with second males. These results demonstrate that when females remate before sperm mixing occurs, sperm stratification results in differential loss of sperm from the most recent mate. This study provides insight into the mechanisms underlying sperm precedence in a promiscuous mating system, and suggests that T. castaneum females could limit paternity success of particular mates by remating with more highly preferred males.

Sperm precedence and sperm storage in multiply mated red flour beetles

In insects, the last male to mate with a female often gains access to a disproportionate number of subsequent fertilizations. This study examined last-male sperm precedence patterns in doubly and triply mated Tribolium castaneum females. Sperm storage processes were investigated by measuring the quantity of sperm stored within the female spermatheca following single, double, and triple matings. Both doubly mated and triply mated females exhibited high last-male sperm precedence for progeny produced during the first 48 h following the last mating, with females in both groups exhibiting parallel declines in sperm precedence 1 and 2 weeks later. The number of sperm stored by females increased by 33% between singly mated and doubly mated females, indicating that the spermatheca is filled to only two-thirds capacity following insemination by the first male. Based on the proportion of stored sperm from first and second matings, we tested predictions about sperm precedence values based on models of random sperm mixing. High initial last-male sperm precedence strongly supports stratification of last-male sperm. By 1–2 weeks after double matings, sperm precedence declined to levels indistinguishable from values expected under random mixing. These results provide insight into mechanisms of sperm storage and utilization in this species.

Mechanisms of Sperm Transfer and Storage in the Red Flour Beetle (Coleoptera: Tenebrionidae)

This study examines mechanisms of sperm transfer during copulation in Tribolium castaneum (Herbst), red flour beetles, and describes the dynamics of sperm movement within the female reproductive tract. During copulations that range in duration from 30 s to 32 min, T. castaneum males transfer sperm to females in a spermatophore consisting of a membranous sperm sac attached to a gelatinous posterior rod. The spermatophore is deposited in the female bursa copulatrix; shortly afterward, the sperm sac membrane ruptures and sperm are released. Sperm begin to appear in the complex, tubular spermatheca of the female within 10 min after mating. Between 0 and 60 min after mating, the number of sperm stored in the spermatheca exhibits an 8.5-fold increase, and sperm quantity in the bursa declines. Both bursal and spermathecal sperm numbers remain nearly constant between 60 and 120 min after mating. Only ≈4% of the total sperm transferred by mating males are translocated to the female's spermatheca for long-term storage. T. castaneum females continue to use sperm stored in the female spermatheca to fertilize their eggs for up to 140 d following a single mating. Neither male body size nor copulation duration appear to influence the number of sperm transferred during copulation or the number of sperm stored within the female spermatheca.

Postcopulatory, prezygotic isolation: intraspecific and interspecific sperm precedence in Tribolium spp., flour beetles.

We investigated intraspecific and interspecific patterns of paternity in Tribolium castaneum, the flour beetle, by mating females either to pairs of conspecific males or to one conspecific and one heterospecific male of the closely related species, T. freemani. Females of both species store sperm in the spermatheca after copulation and postcopulatory, prezygotic reproductive isolation has been reported between this pair of species. When conspecific males of contrasting genotype are mated simultaneously to T. castaneum females, we observed extremely high levels of variation among females in the pattern of sperm precedence as shown by the offspring genotypes. In contrast, T. castaneum females mated simultaneously to a conspecific and a heterospecific male produced over 99 per cent conspecific progeny. When conspecific males were mated sequentially to T. castaneum females, within 3-7 days, all offspring were sired by the second male. In contrast, when a conspecific male was replaced with a T. freemani male, most females continued to produce only first-male, conspecific offspring for the next 10 days. When a heterospecific male was replaced with a conspecific male, T. castaneum females changed from producing hybrid to conspecific offspring within 3 days. We discuss the evolutionary implications of these findings.

SEQUENTIAL INTERSPECIFIC AND INTRASPECIFIC MATINGS BETWEEN TRIBOLIUM CASTANEUM AND T. CONFUSUM (COLEOPTERA: TENEBRIONIDAE): EFFECTS ON FECUNDITY, EGG FERTILITY, AND NUMBER OF PROGENY

AbstractWhen female Tribolium castaneum (Herbst) were sequentially paired with male T. castaneum and then with male T. confusum Jacquelin duVal, 93% of the eggs hatched after the first confinement but only 58.9% hatched after the second confinement. The reciprocal order of pairing produced 0% hatch after the first week of confinement and 55.2% hatch after the second week of confinement. However, the numbers of progeny produced as a result of both sequences were proportional to the percentage hatch. Thus, T. castaneum females appeared to have mated with, and utilized sperm from, males of both species for egg fertilization.When T. confusum females were sequentially paired in the same way, reductions in egg hatch and production of progeny did not occur. The females either did not mate with T. castaneum males, or if they did mate, they did not utilize T. castaneum sperm for egg fertilization. Moreover the percentage of egg hatch and the numbers of progeny produced were not affected by the sequential order of males as long as one of them was T. confusum.

Oöcyte Maturation in Tribolium castaneum1 after Repetitive Sublethal Carbon Dioxide Exposures3

Flaherty et al. (1973) found that sublethal CO2 exposures reduced egg production and egg hatchability in Plodia interpunctella (Hubner). AliNiazee and Lindgren (1970) observed that eggs of Tribolium castaneum (Herbst) did not hatch in atmospheres with CO2 concentrations of 25% or more, even though O2 concentrations were as high as 15.5%. Dick (1937) noted that females of T. confusum Jacquelin duVal are not sexually mature until the 4th or 5th day after emergence. This observation was confirmed by Erdman (1962) who showed that T. confusum females produced no progeny before 5 days of adult life at 30°C and 60–70% RH. Erdman (1964) also showed that T. castaneum females were not sexually mature at emergence.