Estimating the mean abundance and feeding rate of a temporal ectoparasite in the wild: Afrocimex constrictus (Heteroptera: Cimicidae)

Abstract The feeding frequency of blood-feeding invertebrates in the wild is largely unknown but is an important predictor for the potential of disease transmission and for estimating the effects blood feeding may have on the host population. We present a method to estimate the mean feeding frequency per individual parasite from the frequency distribution of fed and unfed individuals in the wild. We used three populations of the cimicid species, Afrocimex constrictus, that parasitises the fruit bat Rousettus aegyptiacus. We found that the area occupied by a bug refugium was a good predictor of the number of bugs in that refugia. The estimated parasite population sizes ranged from ca. 25,000 to 3 million bugs. Their mean abundance was 1-15 bugs per host individual. Preventing feeding by bugs in their natural habitat showed that bugs took approximately 20 days to return to an unfed stage. A formula is presented by which the distribution of digestion stages in the samples was used to calculate that A. constrictus feeds approximately every 7-10 days. The dry weight of a full blood meal was approximated as 13.3 mg. Therefore A. constrictus is estimated to draw an average of 1-28 lL blood per host per day. We suggest that any of our methods can be adjusted to be used in other haematophagous insects to estimate host and parasite population size, mean parasite abundance and blood meal size as well as mean feeding frequency in the wild, including the bed bug species that parasitise humans.

Male Mating Rate Is Constrained by Seminal Fluid Availability in Bedbugs, Cimex lectularius

Sexual selection, differences in reproductive success between individuals, continues beyond acquiring a mating partner and affects ejaculate size and composition (sperm competition). Sperm and seminal fluid have very different roles in sperm competition but both components encompass production costs for the male. Theoretical models predict that males should spend ejaculate components prudently and differently for sperm and seminal fluid but empirical evidence for independent variation of sperm number and seminal fluid volume is scarce. It is also largely unknown how sperm and seminal fluid variation affect future mating rate. In bedbugs we developed a protocol to examine the role of seminal fluids in ejaculate allocation and its effect on future male mating rate. Using age-related changes in sperm and seminal fluid volume we estimated the lowest capacity at which mating activity started. We then showed that sexually active males allocate 12% of their sperm and 19% of their seminal fluid volume per mating and predicted that males would be depleted of seminal fluid but not of sperm. We tested (and confirmed) this prediction empirically. Finally, the slightly faster replenishment of seminal fluid compared to sperm did not outweigh the faster decrease during mating. Our results suggest that male mating rate can be constrained by the availability of seminal fluids. Our protocol might be applicable to a range of other organisms. We discuss the idea that economic considerations in sexual conflict research might benefit from distinguishing between costs and benefits that are ejaculate dose-dependent and those that are frequency-dependent on the mating rate per se

A standardised protocol for measuring phenoloxidase and prophenoloxidase in the honey bee,

The prophenoloxidase activating system (ProPO-AS) is an integral part of the constitutive innate immune response in insects, the products of which are commonly assayed to assess an individual’s ability to respond to immune challenges. However, there is considerable variation in the methodologies associated with these assays, and as such, it is not always clear how to interpret results. We have optimised assays for measuring phenoloxidase in its active (PO) and zymogen (ProPO) forms in the honey bee, Apis mellifera. Contrary to results for other insects, we found that the activator α-chymotrypsin, when used at a low concentration (0.5 mg mL−1), combined with a minimal activation time (5 min), provided optimal conditions for assaying ProPO. In addition, a saturated L-dopa solution was required for assaying both PO and ProPO. The results highlight the importance of defining the working parameters of each assay to be species-specific

Traumatic insemination in terrestrial arthropods

Traumatic insemination is a bizarre form of mating practiced by some invertebrates in which males use hypodermic genitalia to penetrate their partner's body wall during copulation, frequently bypassing the female genital tract and ejaculating into their blood system. The requirements for traumatic insemination to evolve are stringent, yet surprisingly it has arisen multiple times within invertebrates. In terrestrial arthropods traumatic insemination is most prevalent in the true bug infraorder Cimicomorpha, where it has evolved independently at least three times. Traumatic insemination is thought to occur in the Strepsiptera and has recently been recorded in fruit fly and spider lineages. We review the putative selective pressures that may have led to the evolution of traumatic insemination across these lineages, as well as the pressures that continue to drive divergence in male and female reproductive morphology and behavior. Traumatic insemination mechanisms and attributes are compared across independent lineages.17 page(s

Adaptive innate immunity? Responsive-mode prophylaxis in the mealworm beetle, Tenebrio molitor.

A primary infection by a parasite may indicate a higher risk of being reinfected in the near future (since infection may indicate that enemies are becoming more abundant). Acquired immunity does not exist in invertebrates despite the fact that they also face increased risks of reinfection following primary exposure. However, when subjected to immune insult, insects can produce immune responses that persist for long enough to provide prophylaxis. Because these immune responses are costly, persistence must be maintained through a selective advantage. We tested for the possibility that these long-lasting immune responses provided increased resistance to later infections by experimentally mimicking a primary immune insult (pre-challenge) in larvae of the mealworm beetle, Tenebrio molitor, with lipopolysaccharides (LPS) prior to early or late exposure to spores of the entomopathogenic fungus Metarhizium anisopliae. We found that pre-challenged larvae produced a long-lasting antimicrobial response, which provided a survival benefit when the larvae were exposed to fungal infection. These results suggest that the observed response is functionally "adaptive"

Antimicrobial defense and persistent infection in insects.

3 pagesInternational audienceDuring 400 million years of existence, insects have rarely succumbed to the evolution of microbial resistance against their potent antimicrobial immune defenses. We found that microbial clearance after infection is extremely fast and that induced antimicrobial activity starts to increase only when most of the bacteria (99.5%) have been removed. Our experiments showed that those bacteria that survived exposure to the insect's constitutive immune response were subsequently more resistant to it. These results imply that induced antimicrobial compounds function primarily to protect the insect against the bacteria that persist within their body, rather than to clear microbial infections. These findings suggest that understanding of the management of antimicrobial peptides in natural systems might inform medical treatment strategies that avoid the risk of drug resistance

Age-related reproductive parameters of the common bedbug <i>Cimex lectularius</i>.

<p>Mating rate (a), size of sperm vesicles (b), sperm density (c), and the volume of sperm (V_S) (d) and seminal fluid (V_F) (e) increases with male age in the common bedbug. V_S (d) is a composite measure of sperm vesicle size and sperm density. Circles represent means, error bars = 1 standard error. Sample sizes are given near the mean values for each age group. Samples sizes in c–e are identical. Equations in graphs represent regression parameters from curve fitting procedures.</p

Ejaculate allocation over successive matings in the common bedbug, <i>Cimex lectularius</i>.

<p>The data points show cross sections of males after a number of matings in a) the size of sperm vesicles and sperm density, b) sperm volume (V_S) and c) seminal fluid volume (V_F). Black circles show sexually isolated males after a number of prescribed matings. The solid lines show linear least-square curve fittings. White circles show males drawn at random from a population that were examined after they stopped mating. Stippled lines show the value of the respective parameter at eclosion, i.e. a value below which mating is impossible. Grey circles show the replenishment of V_S and V_F of ejaculate depleted males in relation to time since sexual isolation. Circles represent means, error bars 1 standard error. Sample sizes are stated near the mean values. Sample size in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022082#pone-0022082-g003" target="_blank">Figure 3a and b</a> are identical.</p