Temporary feeding inhibition caused by artificial abdominal distension in the bedbug, Cimex lectularius

Abdominal distension of haematophagous insects caused by ingested blood has been recognised as an important contributor to triggering meal termination, feeding inhibition and further susceptibility to host signals. Factors that regulate feeding behaviour of the common bedbug, Cimex lectularius, are poorly understood. By injecting air directly into the body cavity of virgin female C. lectularius we artificially induced abdominal distension without providing chemical cues of the blood meal and without applying gut distension. Body length increased to 138% after feeding and 147% after inflation. The early decline in body volume is similar in blood-fed bugs but after between 8 and 24h became faster in inflated than fed bedbugs. Artificially inflated individuals remained feeding-inhibited at lower abdominal distensions than those that terminate blood ingestion (to ca. 135% initial body length, or up to about 5h). Feeding activity resumed earlier in inflated than blood-fed bugs. These results suggest that artificial abdominal distension has an inhibitory effect on feeding but is not the sole mechanism in preventing further feeding.

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

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 microL 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.

Sperm numbers vary between inter- and intra-population matings of the grasshopper Chorthippus parallelus

Comparing the reproductive output of intra- and inter-population matings is the most common way to assess whether post-mating reproductive isolation is caused by genetic incompatibilities. Such genetic incompatibility can however, only assume that the quantity of the post-mating signals involved does not differ between intra- and inter-population matings. This assumption may not be true because sexual selection predicts reduced mating effort towards low-quality mates and in many circumstances, allopatric partners are low-quality mates. Post-mating efforts may, therefore, be reduced in inter- compared to intra-population matings. Here, I test this crucial assumption by studying variation in one post-mating trait, sperm number, in crosses of two parapatric grasshopper populations. In both populations, males transferred fewer sperm to allopatric than sympatric females. If such plasticity with respect to population is common in other post-mating traits, differences between inter- and intra-population crosses may be more frequently caused by differences in sperm number rather than gamete incompatibility. Additionally, I found that sperm numbers declined less rapidly in the female storage organ of allopatric than sympatric females but its rate differed markedly between populations. This is discussed with respect to female adaptations to male traits.

Biology of the bed bugs (Cimicidae)

The cimicids, or bed bugs, belong to a highly specialized hematophagous taxon that parasitizes primarily humans, birds, and bats. Their best-known member is the bed bug, Cimex lectularius. This group demonstrates some bizarre but evolutionarily important biology. All members of the family Cimicidae show traumatic insemination and a suite of female adaptations to this male trait. Cimicids therefore constitute an ideal model system for examining the extreme causes and consequences of sexual selection. Our dual goal in re-examining the extensive literature on this group is to identify issues relevant to pest control, such as dispersal ecology and the recent global spread, and to understand the selective forces that have shaped the unique aspects of this insect's biology.

[Combined simulation training: a new concept and workshop is useful for crisis management in gastrointestinal endoscopy]

INTRODUCTION

Crisis management as well as realistic emergency situations can be trained in the new developed simulation workshop "Gastrointestinal Endoscopy and Crisis Resource Management" by combining a full-scale simulator and the Erlanger Endoscopy Trainer. The aim of the current study was to evaluate the efficiency of the newly developed simulation workshop.

METHODS

Endoscopists with more than 12 months experience can train their endoscopic skills and crisis resource management with the help of different simulators. In addition, two different scenarios (GI bleeding with significant blood loss and sedation overdoses) embedded in a realistic surrounding (emergency room) have to be managed by the participants. Vital parameters, endoscopic skills, as well as personal interactions were recorded and graded.

RESULTS

100 participants took part in the newly developed workshop (between June and December 2003). The participants showed a significantly better endoscopic performance and a significantly better crisis management after the standardized training program.

CONCLUSIONS

Simulation training plays an essential role in aviation and minimizes the risk for human errors. In the current study it is clearly shown that simulation training is also useful in gastrointestinal endoscopy. The newly developed workshop may thus be of crucial importance to improve personal crisis management. Simulation also leads to an improvement of endoscopic and emergency skills. Accordingly, simulation training should be recommended or offered as an education option in gastrointestinal endoscopy.

An advantage for young sperm in the house cricket Acheta domesticus

We show that males of the house cricket Acheta domesticus regularly expel sperm packages (spermatophores) independently of copulation and at a rate that is not affected by the presence of females. We then show for the first time that the age of sperm affects their likelihood of being stored by females after copulation; younger sperm were overrepresented in the female sperm storage organ and therefore in the sperm population used for fertilization. Our results suggest that the reproductive success of males may increase if they deliver ejaculates with young sperm, and the results may explain why the males of several species are regularly observed to discard ejaculates. Our results also suggest that phenomena such as female multiple mating, paternity bias, and/or exaggerated ejaculate sizes may be related to the advantage both genders gain by using young sperm.

Reducing a cost of traumatic insemination: female bedbugs evolve a unique organ

The frequent wounding of female bedbugs (Cimex lectularius: Cimicidae) during copulation has been shown to decrease their fitness, but how females have responded to this cost in evolutionary terms is unclear. The evolution of a unique anatomical structure found in female bedbugs, the spermalege, into which the male's intromittent organ passes during traumatic insemination, is a possible counteradaptation to harmful male traits. Several functions have been proposed for this organ, and we test two hypotheses related to its role in sexual conflict. We examine the hypotheses that the spermalege functions to (i) defend against pathogens introduced during traumatic insemination; and (ii) reduce the costs of wound healing during traumatic insemination. Our results support the 'defence against pathogens' hypothesis, suggesting that the evolution of this unique cimicid organ resulted, at least partly, from selection to reduce the costs of mating-associated infection. We found no evidence that the spermalege reduces the costs of wound healing.

Facultative sperm storage in response to nutritional status in a female insect

We investigated sperm storage by females of a predatory bug, Nabis rugosus, before and after hibernation and with regard to nutritional status. In the field, females had more sperm available before than after hibernation. Food-deprived females maintained fewer sperm than fed females before but not after hibernation. However, after hibernation food-deprived females suppressed egg production rather than decreasing sperm-storage efficiency. Because mated females did not exhibit increased overwinter survival relative to virgin females there is a low likelihood of direct benefits in the form of ejaculate-derived nutrients. If nutrition-dependent sperm storage by females is widespread in the animal kingdom, our findings may have important implications for the understanding of postcopulatory sexual selection and the evolution of food gifts.

Ejaculate size variation in the migratory locust, Locusta migratoria

Abstract

Sperm competition models suggest that ejaculate size (ES) is adjusted in relation to female fecundity and the risk of sperm competition, depending on the information males have about that risk. We tested these ideas in the migratory locust, Locusta migratoria, a species in which ES may be an important male fitness parameter. Copulation duration was positively correlated with ES. Males did not increase copulation duration but sperm transfer in the presence of competitors during mating. They did so only when they were reared in conditions that allowed female perception prior to mating. Males that prior to mating were kept with other males only did not show ES variation with regard to different sex ratios at mating. Increased female availability did not affect ES. A male size and condition related parameter was not significantly correlated to ES but older males delivered smaller ejaculates. Females of larger size were inseminated larger amounts of sperm. There was a positive correlation between female size and ES only for males of lower condition and lower relative testis weight but not for males of good condition or higher relative testis weight.

Linear models for assessing mechanisms of sperm competition: the trouble with transformations

Although sperm competition is a pervasive selective force shaping the reproductive tactics of males, the mechanisms underlying different patterns of sperm precedence remain obscure. Parker et al. (1990) developed a series of linear models designed to identify two of the more basic mechanisms: sperm lotteries and sperm displacement; the models can be tested experimentally by manipulating the relative numbers of sperm transferred by rival males and determining the paternity of offspring. Here we show that tests of the model derived for sperm lotteries can result in misleading inferences about the underlying mechanism of sperm precedence because the required inverse transformations may lead to a violation of fundamental assumptions of linear regression. We show that this problem can be remedied by reformulating the model using the actual numbers of offspring sired by each male, and log-transforming both sides of the resultant equation. Reassessment of data from a previous study (Sakaluk and Eggert 1996) using the corrected version of the model revealed that we should not have excluded a simple sperm lottery as a possible mechanism of sperm competition in decorated crickets, Gryllodes sigillatus.

Prevalence of errors in a pediatric hospital medication system: implications for error proofing

The purpose of this study was to determine the prevalence of errors in the medication system of a pediatric teaching hospital. Error was defined broadly to capture all deviations in the process from medication order through administration of the dose. The long-term goal was to provide direction to efforts to error-proof the system. The sample was 3,312 medication orders written during 669 patient-days for which a total of 11,978 doses were passed. Errors were categorized as intercepted errors (intercepted through the normal processes of the medication system) or administration errors (errors that involve the patient with or without adverse sequelae). Errors were also categorized as errors in primary activities (e.g., prescribing or preparing the medication for administration) or supporting activity (e.g., transferring the order to another record). A total of 784 errors were identified; 98% were intercepted and 2% were administration errors. More errors (71%) occurred in supporting activities than in primary activities. Medication systems are complex processes. Errors are imbedded in the medication system and are typically intercepted before patients are involved. Intercepting errors involves additional work that adds to an already cumbersome process. Error proofing will be different for errors in primary activities and for supporting activities.

An update on "special stain" histochemistry with emphasis on automation

For nearly 100 years, pathologists have utilized "special histochemical stains" to assist in tissue-based diagnosis. As illustrated in Figures 1 and 2, histochemical stains have been used to identify infectious microorganisms (e.g., Mycobacterium tuberculosis with acid-fast bacillus (AFB) stain), to detail inflammatory stromal or structural alterations (e.g., fibrosis in liver cirrhosis with Masson trichrome), to identify microanatomic sites of disease (e.g., basement membrane in glomerulonephritis with Jones methenamine silver), to identify abnormal chemical deposits (e.g., iron in hemochromatosis with Prussian blue stain), or abnormal immune deposits (e.g., amyloid via Congo red stain). The current surgical pathology laboratory may employ a repertoire of 20 to 25 "special stains" to ensure the full diagnostic complement. While the diagnostic repertoire and the biochemical recipes for the stains are now a well-established, codified part of surgical pathology, there is an ever-moving, leading edge of new developments including new reagents, applications, and methods. This review seeks to update the reader on some of the new applications including both new reagents and methods. Particular emphasis will be placed on the recent technologic advance of automating special stains in kinetic-mode (1-4). The authors consider in turn: 1. In brief, the "news" (recent literature review) of new staining applications; 2. In greater detail, two new applications for detection of Microsporidia and Helicobacer pylori; 3. The new technologic advancement of kinetic mode automation of special stains.