High-Resolution Manometry in Clinical Practice

High-resolution manometry (HRM) is the primary method used to evaluate esophageal motor function. Displayed and interpreted by esophageal pressure topography (EPT), HRM/ EPT provides a detailed assessment of esophageal function that is useful in the evaluation of patients with nonobstructive dysphagia and before foregut surgery. Esophageal motility diagnoses are determined systematically by applying objective metrics of esophageal sphincter and peristaltic function to the Chicago Classification of esophageal motility disorders. This article discusses HRM study, EPT interpretation, and the translation of EPT findings into clinical practice. Examples are provided to illustrate several clinical challenges.

Flow time through esophagogastric junction derived during high-resolution impedance-manometry studies: a novel parameter for assessing esophageal bolus transit

This study aimed to develop and validate a method to measure bolus flow time (BFT) through the esophagogastric junction (EGJ) using a high-resolution impedance-manometry (HRIM) sleeve. Ten healthy subjects were studied with concurrent HRIM and videofluoroscopy; another 15 controls were studied with HRIM alone. HRIM studies were performed using a 4.2-mm-outer diameter assembly with 36 pressure sensors at 1-cm intervals and 18 impedance segments at 2-cm intervals (Given Imaging, Los Angeles, CA). HRIM and fluoroscopic data from four barium swallows, two in the supine and two in the upright position, were analyzed to create a customized MATLAB program to calculate BFT using a HRIM sleeve comprising three sensors positioned at the crural diaphragm. Bolus transit through the EGJ measured during blinded review of fluoroscopy was almost identical to BFT calculated with the HRIM sleeve, with the nadir impedance deflection point used as the signature of bolus presence. Good correlation existed between videofluoroscopy for measurement of upper sphincter relaxation to beginning of flow [R = 0.97, P < 0.001 (supine) and R = 0.77, P < 0.01 (upright)] and time to end of flow [R = 0.95, P < 0.001 (supine) and R = 0.82, P < 0.01 (upright)]. The medians and interquartile ranges (IQR) of flow time though the EGJ in 15 healthy subjects calculated using the virtual sleeve were 3.5 s (IQR 2.3-3.9 s) in the supine position and 3.2 s (IQR 2.3-3.6 s) in the upright position. BFT is a new metric that provides important information about bolus transit through the EGJ. An assessment of BFT will determine when the EGJ is open and will also provide a useful method to accurately assess trans-EGJ pressure gradients during flow.

Acid and nonacid reflux monitoring

Detection of acid and nonacid reflux using esophageal reflux monitoring, which includes conventional and wireless pH monitoring and pH impedance, can be a valuable diagnostic tool when used appropriately in the assessment of patients with gastroesophageal reflux disease. Reflux monitoring may be especially helpful if a management change is desired, such as when initial or empirical treatment is ineffective. However, each of these methods has its limitations, which need to be accounted for in their clinical use. Indications, test performance, interpretation, and clinical applications of esophageal reflux monitoring, as well as their limitations, are discussed in this review.

A material isolated from human hands that attracts female mosquitoes

The residue left on glass surfaces by human hands was found to be attractive to femaleAedes aegypti (L.) andAnopheles quadrimaculatus Say mosquitoes. The material lost half of its activity in 1 hr. A solvent wash technique was developed to recover and concentrate the residuum from handled glass beads. The residuum could be recovered effectively with absolute ethanol and less effectively with several other solvents. More mosquitoes were attracted to heated than to unheated residuum, an indication of its volatility. Also, attraction of the residuum decreased with decreasing concentration or dose. Concentrated residuum collections, stored under refrigeration and tested for longevity, showed no appreciable loss of attractiveness up to 60 days of storage.

Contact sex pheromone in the tsetse flyGlossina pallidipes (Austen) Identification and Synthesis

Adult maleG. pallidipes attempted to copulate with decoys treated with a branched paraffin obtained from laboratory-reared female flies. The compound causing maximal response was isolated and identified as 13,23-dimethylpentatriacontane. The synthesized compound elicited increasing responses with increasing doses. This sex- and species-specific compound was always present in physiological amounts in females, as it increased from 2 μg at emergence to 10 μg per female at 14 days. It was present in wild-caught females from a wide geographical range.

High-resolution manometry and esophageal pressure topography: filling the gaps of convention manometry

Although conventional manometry set the basis for the diagnosis of esophageal motility disorders, the large axial spacing between recording sites leaves large portions of the esophagus unevaluated and vulnerable to movement artifact. However, continuous spatiotemporal representations of pressure through the esophagus recorded with high-resolution manometry offers greater detail and improved accuracy for many of the most important measurements of esophageal motor function. This review describes how the new classification schemes for esophageal pressure topography have evolved from conventional criteria and focuses on how esophageal pressure topography has improved the ability to subcategorize conventional manometric diagnoses into new functional phenotypes.

Influence of exogenous gonadotropin-releasing hormone on seasonal reproductive behavior of the coyote (Canis latrans)

Wild Canis species such as the coyote (C. latrans) express a suite of reproductive traits unusual among mammals, including perennial pair-bonds and paternal care of the young. Coyotes also are monestrous, and both sexes are fertile only in winter; thus, they depend upon social and physiologic synchrony for successful reproduction. To investigate the mutability of seasonal reproduction in coyotes, we attempted to evoke an out-of-season estrus in October using one of two short-acting gonadotropin-releasing hormone (GnRH) agents: (1) a GnRH analogue, deslorelin (6-d-tryptophan-9-(N-ethyl-l-prolinamide)-10-deglycinamide), 2.1 mg pellet sc; or (2) gonadorelin, a GnRH (5-oxoPro-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-GlyNH₂) porcine hypothalamic extract, 2.0 μg/kg im once daily for 3 consecutive days. A transient increase in serum concentrations of estradiol and progesterone (1 and 2 wk, respectively) was detected after treatment with deslorelin but not gonadorelin. Also, socio-sexual behaviors reminiscent of winter mating (including courtship, mate-guarding, precoital mounts, and copulatory ties) were observed among the deslorelin group. During the subsequent breeding season (January and February), however, preovulatory courtship behavior and olfactory sampling appeared suppressed; emergence of mounts and copulations were delayed in both deslorelin and gonadorelin treatment groups. Furthermore, whereas 8 of 12 females treated in October ovulated and produced healthy litters in the spring, 4 naïve coyotes failed to copulate or become pregnant. Thus, perturbation of hormones prior to ovulation in species with complex mating behaviors may disrupt critical intrapair relationships, even if fertility is not impaired physiologically.

Determination by HPLC fluorescence analysis of the natural enantiomers of sex pheromones in the New World screwworm fly, Cochliomyia hominivorax

Bioassays of six racemic synthesized candidate sex pheromone compounds against male New World screwworm Cochliomyia hominivorax (Coquerel) flies showed that the most potent bioactivity was found with 6-acetoxy-19-methylnonacosane and 7-acetoxy-15-methylnonacosane compared with four other isomeric acetoxy nonacosanes and a larger aliphatic ketone. As all these methyl-branched compounds have two asymmetric carbons and four possible enantiomers, characterization of the natural enantiomers was essential. All four enantiomers for the two most bioactive isomers of the natural sex pheromone were synthesized for bioassay. Hydrolysis and derivatization of these enantiomers with different fluorescent reagents was followed by column-switched high-performance liquid chromatography. The use of two linked, reversed-phase columns of different polarity held at sub-ambient temperatures allowed good separation of each enantiomer. This analysis applied to natural material was successful, as (6R,19R)-6-acetoxy-19-methylnonanocosane, and (7R,15R)- and (7R,15S)-7-acetoxy-15-methylnonanocosane were detected in extracts of recently colonized female flies.

Flybrella: a device to attract and kill house flies

Flybrella is a lightweight inexpensive trap that can be suspended like an upside-down umbrella in prominent locations where house flies, Musca domestica L., rest. It consists of a solid, cylindrical backbone to which is attached a perforated transparent tube, or baffle, with a commercial sugar/toxicant strip affixed inside. Centered directly beneath the tube and also attached to the backbone is a 10-cm-diameter inverted opaque plastic cone. House flies readily enter the tube, feed on the fast-acting toxicant, and then fall directly down the tube where they are collected in and concealed by the cone. The cone may be emptied easily through a capped opening in the bottom. In paired indoor tests, the efficacy of the commercial sugar/toxicant strip was increased significantly by the individual addition of several other attractant materials. Variants of the original design were tested, including a more efficient design featuring two concentric tubes with offset perforations. The toxicant strip may be easily removed and/or replaced when desired.

Candidate sex pheromones of the New World screwworm Cochliomyia hominivorax

Five novel homologous acetate derivatives of long-chain secondary alcohols and a related ketone were tested for their efficacy as contact mating stimulants for Cochliomyia hominivorax Coquerel (Diptera: Calliphoridae). Full copulatory behaviour at a high percentage was found in tests with racemic 6-acetoxy-19-methylnonacosane at 2.5-20 microg using fertile males from three strains. Males of two strains responded nearly as well to 7-acetoxy-15-methylnonacosane, but an older strain first colonized in 1992 did not respond to this compound. Few or no copulatory responses were obtained to the other secondary alcohol acetates and a related ketone. These two acetate derivatives are the first sex pheromones identified in a calliphorid fly. The threshold of response was also tested, but could not be pinpointed.

Tsetse and other biting fly responses to Nzi traps baited with octenol, phenols and acetone

Octenol (1-octen-3-ol), acetone, 4-methylphenol, 3-n-propylphenol, and other potential attractants (human urine, stable fly faeces), as well as guiacol, creosol (potential repellents), were tested as baits for biting flies in North America using standard phthalogen blue IF3GM cotton Nzi traps, or similar commercial polyester traps. Baits were tested during the summers of 2001-04 at a residence in Canada and during January-August 2001 at a dairy in the U.S.A. Behaviour in the presence of octenol was also studied by intercepting flies approaching a trap through the use of transparent adhesive film. Analogous bait and/or trap comparisons were conducted in natural settings in June 1996 in Kenya and in September-December 1997 in Ethiopia. In Canada, catches of five of six common tabanids (Tabanus similis Macquart, Tabanus quinquevittatus Wiedemann, Hybomitra lasiophthalma [Macquart], Chrysops univittatus Macquart, Chrysops aberrans Philip) and the stable fly Stomoxys calcitrans L. were increased significantly by 1.2-2.1 times with octenol (1.5 mg/h). Catches of T. quinquevittatus and S. calcitrans were 3.5-3.6 times higher on a sticky enclosure surrounding a trap baited with octenol. No other baits or bait combinations had an effect on trap catches in North America. In Ethiopia, standard Nzi traps baited with a combination of acetone, octenol and cattle urine caught 1.8-9.9 times as many Stomoxys as similarly baited epsilon, pyramidal, NG2G, S3, biconical and canopy traps, in order of decreasing catch. When baits were compared, catches in Nzi traps of six stable fly species, including S. calcitrans, were not affected by octenol (released at approximately 1 mg/h), or cattle urine (140 mg/h), used alone or in combination with acetone (890 mg/h). Acetone alone, however, significantly increased the catches of common Stomoxys such as Stomoxys niger niger Macquart, Stomoxys taeniatus Bigot, and S. calcitrans by 2.4, 1.6 and 1.9 times, respectively. Catches of Glossina pallidipes Austen were increased significantly in traps baited with acetone, urine or octenol, or any combination, relative to those in unbaited traps (1.4-3.6x). Catches of Glossina morsitans submorsitans Newstead were increased significantly by 1.5-1.7 times, but only when baits were used individually. Unlike other studies with East African tsetse, catches of both tsetse species with the complete bait combination (acetone, urine and octenol) did not differ from those in unbaited traps. Experiments with an incomplete ring of electric nets surrounding a Nzi trap, and a new approach using a sticky enclosure made from transparent adhesive film, revealed diverse responses to artificial objects and baits among biting flies. In Kenya, daily trap efficiency estimates for traps baited with either carbon dioxide (6 L/min) or a combination of acetone, cattle urine and octenol were 21-27% for G. pallidipes, 7-36% for Glossina longipennis Corti, 27-33% for S. n. niger, and 19-33% for Stomoxys niger bilineatus Grünberg, assuming 100% electrocution efficiency. Actual trap efficiencies may have been lower, given observed outside : inside electric net catch ratios of 0.6 : 1.6. Observed ratios averaged 54% of expected values, with 10 of 15 possible ratios less than the minimum possible value of 1.0.

Performance of the Nzi and other traps for biting flies in North America

The performance of Nzi traps for tabanids (Tabanus similis Macquart, T. quinquevittatus Wiedemann, Chrysops aberrans Philip, C. univittatus Macquart, C. cincticornis Walker, Hybomitra lasiophthalma (Macquart)), stable flies (Stomoxys calcitrans Linnaeus) (Diptera: Muscidae) and mosquitoes (Aedes) (Diptera: Culicidae) was investigated at various sites in Canada (Ontario, Alberta) and USA (Iowa, Florida, Louisiana). Traps made from selected fabrics, insect nettings and hand-dyed blue cotton were compared to the African design to provide practical recommendations for temperate environments. Comparisons of substituted materials showed that trap performance was optimal only when traps were made from appropriate fabrics in the colours produced by either copper phthalocyanine (phthalogen blue), or its sulphonated forms (turquoise). Fabrics dyed with other blue chromophores were not as effective (anthraquinone, disazo, formazan, indanthrone, triphenodioxazine). An appropriate texture as well as an appropriate colour was critical for optimal performance. Smooth, shiny synthetic fabrics (polyester, nylon) and polyester blends reduced catches. Low catches occurred even for nominal phthalogen blue, but slightly-shiny, polyester fabrics in widespread use for tsetse. The most suitable retail fabric in place of phthalogen blue cotton was Sunbrella Pacific Blue acrylic awning/marine fabric. It was both attractive and durable, and had a matching colour-fast black. Nzi traps caught grossly similar numbers of biting flies as canopy, Vavoua, and Alsynite cylinder traps, but with differences in relative performance among species or locations.

Sex pheromone of the tsetse species, Glossina austeni: isolation and identification of natural hydrocarbons, and bioassay of synthesized compounds

Copulatory responses of male Glossina austeni (Newstead) (Diptera: Glossinidae), that were elicited after contact with frozen female tsetse, were not observed after solvent washing of cuticular lipids. Chromatographic analysis of extracts from laboratory-reared and field-collected G. austeni females yielded natural hydrocarbons that were highly stimulatory to males. Most of this activity was produced by compounds in the alkene fraction. Gas chromatograms (GC) contained five natural alkenes; these were separated by preparative GC for bioassays conducted in Tanzania. The two major alkenes were identified using gas chromatography-mass spectrometry (GC-MS) to be 13,17-dimethyltritriacont-1-ene and 13,17-dimethylpentatriacont-1-ene, after the samples had undergone derivatization using dimethyl disulphide and saturation with deuterium. These alkenes and natural alkanes were quantified from G. austeni of both sexes from laboratory and field samples to confirm that their presence was consistent in this species. Trials of synthetic samples resulted in the order of biological activity for the stereoisomers of 13,17-dimethyltritriacont-1-ene as follows: S,R-33:1 > R,S- 33:1 > S,S-33:1 > R,R-33:1. Dose-response data showed an ED(50) at 5 microg per treated, solvent-washed male decoy. Of the four stereoisomers of 13,17-dimethylpentatriacont-1-ene, R,R-35:1 showed the most activity. This is the first report of alkene-induced sexual activity in males of the genus Glossina.

Distinctive hydrocarbons of the black dump fly, Hydrotaea aenescens (Diptera: Muscidae)

Hydrotaea aenescens (Wiedemann), the black dump fly, is a potential biological control agent originally from the western hemisphere, now found in many parts of the Palearctic region except for the United Kingdom, where it cannot be imported for any reason. A complication of classical biological control is the problem of strain identification, as one must be able to somehow mark or follow a particular strain that has been introduced into the field or is contemplated for release. Gas chromatographic analysis of the surface hydrocarbons of pooled and individual dump fly adults resulted in reproducible hydrocarbon patterns that differentiated widely distributed strains of H. aenescens and showed similarities between strains that were related. Sexual dimorphism was observed in the surface hydrocarbons. Conspecific similarities included identities of the hydrocarbons found in colony material collected worldwide, with differences being found in the quantities of compounds present.

Mechanical barrier for preventing climbing by lesser mealworm (Coleoptera: Tenebrionidae) and hide beetle (Coleoptera: Dermestidae) larvae in poultry houses

Mechanical barriers consisting of bands of polyethylene terepthalate resin attached to wooden posts by latex caulk adhesive and staples were 100% effective in preventing passage of dispersing lesser mealworm, Alphitobius diaperinus (Panzer), larvae in the laboratory. Barriers continued to be 100% effective after beinig held in a caged layer poultry house for 3 mo. Polyethylene terepthalate barriers installed on support posts in a pullet house in Brooker, FL, were >92% effective against natural populations of lesser mealworm larvae 6 mo after installation. The barriers also were >94% effective against natural populations of larvae of the hide beetle, Dermestes maculatus DeGeer, when fly populations were low. Fecal spot depositions by house flies in excess of 31 cumulative fly spots per square centimeter on spot cards reduced the effectiveness of the barriers to 79-90%, and barrier efficacy was reduced to 40-56% when fly spots covered >80% of the surface of the plastic. Washing the barriers with water to remove fly spots restored their effectiveness against hide beetle larvae to >99%.

Behavioral response of Stomoxys calcitrans (Diptera: Muscidae) to conspecific feces and feces extracts

The attraction response of Stomoxys calcitrans (L.) to its own feces was evaluated in a triple cage olfactometer. Both time- and concentration-response relationships were obtained for female S. calcitrans exposed to cellulose sponges impregnated with fresh fly feces or filter papers treated with chloroform:methanol extracts of fresh fly feces in 6-min tests. Attraction to feces collected on cellulose sponges decreased as the air flow increased. Feces collected on cellulose sponges and held for 28-31 retained attractive activity. More female flies were attracted than males to feces on sponges or to polar solvent extracts of feces-contaminated cages. The activity of feces extract on filter paper decreased rapidly. Chemical identification of the active compounds present could lead to useful baits for traps.

Open tongue-type calcaneus fracture with a partial posteromedial subtalar dislocation

Calcaneus fractures with a subtalar dislocation are extremely rare. A case of a tongue-type calcaneus fracture with a posteromedial dislocation of the calcaneal posterior facet and tuberosity is presented. Treatment included lag screw fixation to maintain the reduction without further soft-tissue trauma.

Evaluation of Stomoxys calcitrans (Diptera: Muscidae) behavioral response to human and related odors in a triple cage olfactometer with insect traps

A triple cage olfactometer provided with insect traps was used for evaluating behavioral responses of Stomoxys calcitrans (L.) females to human skin and breath, CO2, and L-lactic acid analogs. After demonstrating there were no significant differences caused by cage location or time of day, 3 sets of 3 olfactometer tests were performed in a day, every 2 h beginning at 0900 hours. When a human hand was used as attractant, the attraction (expressed as percentage of trapped flies) increased as a function of the time; an inverted U-shaped relationship between attractancy and air speed was observed; and variation in fly density in the range 25-75 per cage did not affect the attraction response. When human breath was used as attractant the attraction increased linearly as a function of time and it was exhalation frequency dependent; when air flow was absent the highest response was observed; and 24- to 38-h-old flies were more attracted than younger and older. When CO2 was tested, activation and orientation and probing behavior were concentration dependent with flows ranging between 0.0001 and 0.038 liter s(-1), but attraction was not. No attraction was observed with 10, 100, or 1,000 microg of compounds related to L-lactic acid and several synthetic human odors and related compounds, although orientation was often observed.

Safe placement of S1 and S2 iliosacral screws: the "vestibule" concept

OBJECTIVES

To determine the optimal starting points for placement of S1 and S2 iliosacral screws as well as the pertinent anatomy surrounding the S1 and S2 vertebral bodies.

DESIGN

Normal subject study evaluating helical CT scans of thirty normal posterior pelvic rings.

SETTING

Methodist Hospital, Indianapolis, Indiana, Level I trauma center.

PARTICIPANTS

Consenting adults for limited pelvis CT.

MAIN OUTCOME MEASUREMENTS

The three-dimensional anatomy of the posterior pelvic ring pertinent to S1 and S2 iliosacral screw placement. Safety of simulated S1 iliosacral screw placement using different lateral ilium starting points.

RESULTS

The transversely placed (horizontal) iliosacral screw was the least safe of the screws tested. The safest lateral ilium starting point for our entire population was at the posterior sacral body sagittally and at the inferior S1 foramen coronally. S2 iliosacral screws had less cross-sectional area for placement than S1 screws. Placement of the S2 screw slightly to the S1 foraminal side of the S2 vertebral body increased the safety of placement.

CONCLUSION

The iliosacral screw starting point at the posterior sacral body and inferior S1 foramen was the safest when considering the entire population. Careful attention to the size and orientation of the S2 vertebral body should be taken if S2 iliosacral screws are placed.

QSPR correlation and predictions of GC retention indexes for methyl-branched hydrocarbons produced by insects

A successful interpretation of the complex manner by which the GC retention indexes of methylalkanes produced by insects are related to chemical structure was achieved using the quantitative structure-property relationship (QSPR) method. A general QSPR model including mainly topological descriptors was obtained for 178 data points. The error of the model is similar to the experimental error. The model was supported by (i) leave-one-out cross validation and (ii) division into three sets and prediction of each set from the other two. As a further test of the utility of the model, retention indexes were successfully predicted for an external set of 30 methyl-branched hydrocarbons not involved in the deduction of the correction equation from the main data set. General trends of the structural variation of compounds in any given range of retention index are discussed. The average error was 4.6 overall and 4.3 for the 165 compounds remaining after leaving out small monomethyl alkanes.

Detection of cryptic species in the Tabanus nigrovittatus (Diptera: Tabanidae) complex in Massachusetts by morphometric and cuticular hydrocarbon analysis

Greenhead flies of the Tabanus nigrovittatus complex from Massachusetts salt marshes were identified as T. nigrovittatus Macquart and T. conterminus Walker using the morphometric model developed by Sofield et al. Four body measurements from a total of 5,983 female flies collected over 2 consecutive years yielded canonical scores producing a unimodal rather than the expected bimodal distribution. The lack of bimodality indicated that both species were not present at the study site. This was substantiated by cuticular hydrocarbon (CHC) analysis of a subsample of these specimens. Fifteen, female flies of the Tabanus nigrovittatus complex from the same site were identified to species using the Sofield et al. morphometric model and validated using CHC analysis. Two individuals of the T. nigrovittatus complex were identified incorrectly as T. conterminus by the morphometric model. The tendency of this model to incorrectly classify some individuals of T. nigrovittatus as T. conterminus brings into question the identity of the Walker syntypes of T. conterminus. Based on CHC analysis, our study shows that both species coexist within our study area.

Sugar meal composition of five north central Florida mosquito species (Diptera: Culicidae) as determined by gas chromatography

Gas chromatography was used to analyze sugars found in individual crops fed on by wild caught adult Anopheles quadrimaculatus s.l. (Say), Coquillettidia perturbans (Walker), Culex nigripalpus Theobald, Culiseta melanura (Coquillett), and Psorophora ferox (von Humboldt) from several north central Florida locations. A wide range of sugars was found, including fructose, glucose, sucrose, maltose, turanose, melezitose, trehalose, raffinose, erlose, and traces of arabinose, rhamnose, and several unknowns. The frequency of individuals testing positive for crop sugars ranged from 9-10% in An. quadrimaculatus and Ps. ferox to 46% in Cq. perturbans. Based on the presence of melezitose or erlose in the crop, honeydew feeding was shown to be an important dietary component in An. quadrimaculatus (57%), Cs. melanura (31%), Cx. nigripalpus (15%), Cq. perturbans (10%), and Ps. ferox (7%). Gas chromatography of crude crop contents is a rapid one-step process that can address important questions such as the source and occurrence of sugar feeding in Diptera. Unique sugar feeding field observations were recorded for several mosquito species.

Analysis of composition of sugar meals of wild mosquitoes by gas chromatography

Gas chromatography (GC) was successfully used for the first time to determine the components of natural sugar meals in individual mosquitoes and to determine whether carbohydrases are present in the crops of these insects. Crops of wild mosquitoes collected from a 2-ha cypress swamp north of Gainesville, FL, contained fructose, glucose, sucrose, maltose, turanose, melibiose, erlose, melezitose, raffinose, and a few unidentified carbohydrates. Time course studies with male and female Aedes albopictus showed rapid hydrolysis (> 90%) of sucrose occurring within 2 h of ingestion, whereas melezitose remained relatively unchanged even 8 h after ingestion. The crop extraction/GC analysis technique is an improvement over the cold anthrone test traditionally used for sugar analysis. This procedure is a rapid one-step process used to determine natural sugar sources, hydrolysis, occurrence, and preferences for individual wild sugar-feeding Diptera.

Gas chromatography/mass spectrometry analysis of the cuticular hydrocarbons from parasitic wasps of the genus Muscidifurax

Parasitic Hymenoptera can be difficult to identify by conventional taxonomic techniques. Examination of the cuticular hydrocarbons (CHCs) provides a basis for chemotaxonomic differentiation, which may lead to the discovery of pheromones, and can be a means of examining colonies for species cross-contamination. The parasitic wasps examined were Muscidifurax raptor, M. zaraptor, M. uniraptor, and the gregarious form of M. raptorellus. Species within the genus Muscidifurax, as well as the sex, can clearly be differentiated by examining the gas chromatograms of the CHCs. Identification of the alkanes by mass spectrometry shows uncommon dimethylalkanes and trimethylalkanes for members of the genus. The methyl branched cuticular hydrocarbons of these insects are rare compared to those found on insects reported in the literature, but are present in significant amounts on these insects. Additionally, sexual dimorphism is observed in long chain alkanes (C21-C39) present on male and female cuticular surfaces for these species. Females tend to have cuticular hydrocarbons with methyl branches located externally on the carbon backbone chain for dimethyl-, trimethyl-, and tetramethylalkanes, whereas males tend to have dimethyl- and trimethylalkanes located internally on the hydrocarbon backbone chains. Mass spectra of novel and rare methyl branched compounds identified on these parasitoids are presented.