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Stefan K Hetz - One of the best experts on this subject based on the ideXlab platform.
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spiracle activity in moth pupae the role of oxygen and carbon dioxide revisited
Journal of Insect Physiology, 2010Co-Authors: Thomas D Forster, Stefan K HetzAbstract:Abstract After decades of intensive research, the actual mechanism behind discontinuous gas exchange in insects has not been fully understood. One open question concerns the actual way (closed, flutter, and open) of how Spiracles respond to tracheal gas concentrations. As the results of a classic paper [Burkett, B.N., Schneiderman, H.A., 1974. Roles of oxygen and carbon dioxide in the control of spiracular function in cecropia pupae. Biological Bulletin 147, 274–293] allow ambiguous interpretation, we thus reexamined the behavior of the Spiracles in response to fixed, controlled endotracheal gas concentrations. The tracheal system of diapausing pupae of Attacus atlas (Saturniidae, Lepidoptera) was flushed with gas mixtures varying in P O 2 and P C O 2 while the behavior of the Spiracles was monitored using changes in the pressure signal. This novel pressure based technique proved to be superior to classic visual observation of single Spiracles. A two-dimensional map of the spiracle behavior in response to endotracheal P O 2 and P C O 2 was established. Typically, it contained two distinct regions only, corresponding to “closed” and “open” Spiracles. A separate “flutter” region was missing. Because fluttering is commonly observed in moth pupae, we suggest that the intermittent spiracle opening during a flutter phase is an effect of non-steady-state conditions within the tracheal system. For low P C O 2 the minimum P O 2 resulting in open Spiracles was linearly dependent upon P C O 2 . Above a threshold of 1–1.5 kPa CO2 the Spiracles were open irrespective of P O 2 . We propose a hypothetical spiracular control model, which is simple and explains the time course of endotracheal partial pressures during all phases of discontinuous gas exchange.
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tradeoffs between metabolic rate and spiracular conductance in discontinuous gas exchange of samia cynthia lepidoptera saturniidae
Journal of Insect Physiology, 2010Co-Authors: Christian Moerbitz, Stefan K HetzAbstract:Abstract The insect tracheal system is a unique respiratory system, designed for maximum oxygen delivery at high metabolic demands, e.g. during activity and at high ambient temperatures. Therefore, large safety margins are required for tracheal and spiracular conductance. Spiracles are the entry to the tracheal system and play an important role in controlling discontinuous gas exchange (DGC) between tracheal system and atmosphere in moth pupae. We investigated the effect of modulated metabolic rate (by changing ambient temperature) and modulated spiracular conductance (by blocking all except one Spiracles) on gas exchange patterns in Samia pupae. Both, spiracle blocking and metabolic rates, affected respiratory behavior in Samia cynthia pupae. While animals showed discontinuous gas exchange cycles at lower temperatures with unblocked Spiracles, the respiratory patterns were cyclic at higher temperatures, with partly blocked Spiracles or a combination of these two factors. The threshold for the transition from a discontinuous (DGC) to a cyclic gas exchange ( cyc GE) was significantly higher in animals with unblocked Spiracles (18.7 nmol g −1 min −1 vs. 7.9 nmol g −1 min −1 ). These findings indicate an important influence of spiracle conductance on the DGC, which may occur mostly in insects showing high spiracular conductances and low metabolic rates.
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the role of the Spiracles in gas exchange during development of samia cynthia lepidoptera saturniidae
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2007Co-Authors: Stefan K HetzAbstract:Spiracles and the tracheal system of insects allow effective delivery of respiratory gases. During development, holometabolous insects encounter large changes in the functional morphology of gas exchange structures. To investigate changes in respiratory patterns during development, CO2-release was measured in larvae, pre-pupae and pupae of Samia cynthia (Lepidoptera, Saturniidae). Gas exchange patterns showed great variability. Caterpillars had high metabolic rates and released carbon dioxide continuously. Pre-pupae and pupae showed typical discontinuous gas exchange cycles (DGC) at reduced metabolic rates. Changes in gas exchange patterns can partly be explained with low metabolic rates during pupation. Sequential blocking of Spiracles in pre-pupae and pupae reduced spiracle conductance with tracheal conductance remaining unaffected. Analysis of gas exchange patterns indicates that caterpillars and pre-pupae use more than 14 Spiracles simultaneously while pupae only use 8 to 10 Spiracles. Total conductance is not a simple multiple of single Spiracles, but may be gradually adaptable to gas exchange demands. Surprisingly, moth pupae showed a DGC if all except one spiracle were blocked. The huge conductance of single Spiracles is discussed as a pre-adaptation to high metabolic demands at the beginning and the end of the pupal as well as in the adult stage.
Kom Sukontason - One of the best experts on this subject based on the ideXlab platform.
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Chrysomya chani Kurahashi (Diptera: Calliphoridae), a blow fly species of forensic importance : morphological characters of the third larval instar and a case report from Thailand
2018Co-Authors: Tanin Bhoopat, Narin Sontigun, Anchalee Wannasan, ... ,sangob Sanit, Amendt Jens, ... ,chutharat Samerjai, Kom SukontasonAbstract:Blow flies are worldwide the most important insects from a forensic point of view. In Thailand, aside from the two most common species, Chrysomya megacephala (F.) and Chrysomya rufifacies (Macquart), Chrysomya chani Kurahashi was also found to be of forensic importance. We present a case of a human female cadaver in its bloated stage of decomposition, discovered at Pachangnoi Subdistrict, northern Thailand. Entomological sampling during the autopsy displayed an assemblage of numerous dipteran larvae. Macroscopic observations showed the coexistence of third instar larvae of the three blow flies C. megacephala, Chrysomya villeneuvi Patton, an unknown blow fly species and one muscid, Hydrotaea sp. The minimum post-mortem interval was estimated to be six days, based on the developmental rate of C. megacephala. The ID of the unknown larva, which is the focus of this report, was revealed later as C. chani by DNA sequencing, using a 1205 bp of cytochrome c oxidase subunit I (COI). The occurrence of C. chani on a human body revealed the need to analyse and describe the morphology of its immature stage, to enable forensic entomologists to identify this fly species in future cases. The morphological examination of the third instar was performed, revealing peculiar characteristics: protuberant tubercles encircling abdominal segments; 9–11 lobes on the anterior spiracle; six prominent pairs of tubercles along the peripheral rim of the eighth abdominal segment; a heavily sclerotized complete peritreme of the posterior Spiracles. A key to differentiate the third instar of blow flies of forensic importance in Thailand is provided
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identifying fly puparia by clearing technique application to forensic entomology
Parasitology Research, 2007Co-Authors: Radchadawan Ngernklun, Duanghatai Sripakdee, Kom SukontasonAbstract:In forensic investigations, immature stages of the fly (egg, larva, or puparia) can be used as entomological evidence at death scenes, not only to estimate the postmortem interval (PMI), analyze toxic substances, and to determine the manner of death but also to indicate the movement of a corpse in homicide cases. Of these immature stages, puparia represent the longest developmental time, which makes them of useful. However, in order for forensic entomologists to use puparia effectively, it is crucial that they are able to accurately identify the species of fly found in a corpse. Typically, these puparia are similar in general appearance, being coarctate and light brown to dark brown in color, which makes identification difficult. In this study, we report on the clearing technique used to pale the integument of fly puparia, thereby allowing observation of the anterior end (second to fourth segments) and the profile of the posterior spiracle, which are important clues for identification. We used puparia of the blowfly, Chrysomya megacephala (F.), as the model species in this experiment. With placement in a 20% potassium hydroxide solution daily and mounting on a clearing medium (Permount®, New Jersey), the profile of the posterior spiracle could be clearly examined under a light microscope beginning on the fifth day after pupation, and the number of papillae in the anterior spiracle could be counted easily starting from the ninth day. Comparison of morphological features of C. megacephala puparia with those of other blowflies (Chrysomya nigripes [Aubertin], Chrysomya rufifacies [Macquart], Chrysomya villeneuvi [Patton], Lucilia cuprina [Wiedemann], and Hemipyrellia ligurriens [Wiedemann]) and a housefly (Musca domestica L.) revealed that the anterior ends and the profiles of the posterior Spiracles had markedly distinguishing characteristics. Morphometric analysis of the length and width of puparia, along with the length of the gaps between the posterior Spiracles of seven fly species, displayed differences among them. This provides a key to identifying the puparia of these seven fly species.
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morphology of the puparia of the housefly musca domestica diptera muscidae and blowfly chrysomya megacephala diptera calliphoridae
Parasitology Research, 2005Co-Authors: Sirisuda Siriwattanarungsee, Somsak Piangjai, Kom Sukontason, Budsabong Kuntalue, Jimmy K OlsonAbstract:Examination of the puparia of the housefly, Musca domestica L. and blowfly Chrysomya megacephala (F.), through scanning electron microscopy (SEM), revealed many differences in the profile of their morphology. Special attention was focused on puparial characteristics used to differentiate between the two fly species studied, and between other forensically important flies. Results of this study indicate that the housefly puparia are almost evenly rounded at both ends and the anterior spiracle bears six papillae. A pair of pupal respiratory horns is found laterally before the posterior boundary of the first abdominal segment, bearing numerous papillae that have a longitudinal opening along the oval convex base. The peritreme of each posterior spiracle forms a crude forward or reverse D-shape, encircling three sinuous slits. The blowfly pupariums anterior spiracle contains 8-12 papillae. The pupal respiratory horns protrude slightly and in some specimens a group of approximately 38 globules on the bubble-like membrane may be observed. Each of the posterior Spiracles is more or less an oval- shaped peritreme, encircling three straight spiracular slits. The anatomical features presented herein allow for the differentiation of puparia of the two fly species studied and could prove useful in future forensic entomological assessments.
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larval ultrastructure of parasarcophaga dux thomson diptera sarcophagidae
Micron, 2003Co-Authors: Kom Sukontason, Somsak Piangjai, Tarinee Chaiwong, Noppawan Boonchu, Hiromu Kurahashi, Roy C. VogtsbergerAbstract:Ultrastructure of all larval instars of Parasarcophaga dux (Thomson), a common flesh fly species in Thailand, is presented using scanning electron microscopy. Special attention is given to the structure of anterior and posterior Spiracles since these are important features used to differentiate between other sarcophagids. Each anterior spiracle in second and third instars has a single row of papillae varying in number from 14 to 17. The posterior spiracular discs have incomplete peritremes, with a prominent inner arc. Three long, narrow spiracular slits are oriented more or less vertically in each spiracular disc of third instar. Posterior spiracular hairs lack extensive branching and emanate approximately midway down the length of each slit. Microscopic morphology of the mouthhooks markedly differs between the first and second instars. The structure of these mouthhooks supports this fly species as being necrophagous or capable of producing myiasis.
Lutz T Wasserthal - One of the best experts on this subject based on the ideXlab platform.
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x ray computed tomography study of the flight adapted tracheal system in the blowfly calliphora vicina analysing the ventilation mechanism and flow directing valves
The Journal of Experimental Biology, 2018Co-Authors: R Fink, Peter Cloetens, Lutz T WasserthalAbstract:ABSTRACT Following the discovery of flight motor-driven unidirectional gas exchange with rising PO2 in the blowfly, X-ray computed tomography (CT) was used to visualize the organization of the tracheal system in the anterior body with emphasis on the arrangement of the pathways for airflow. The fly9s head is preferentially supplied by cephalic tracheae originating from the ventral orifice of the mesothoracic spiracle (Sp1). The respiratory airflow during flight is a by-product of cyclic deformations of the thoracic box by the flight muscles. The air sacs below the tergal integument (scutum and scutellum) facilitate the respiratory airflow: the shortening of the thorax turns the scutellum and the wings downward and the scutum upward with a volume increase in the scutal air sacs. The resulting negative pressure sucks air from Sp1 through special tracheae towards the scutal air sacs. The airflow is directed by two valves that open alternately: (1) the hinged filter flaps of the metathoracic Spiracles (Sp2) are passively pushed open during the upstroke by the increased tracheal pressure, thereby enabling expiration; (2) a newly described tracheal valve-like septum behind the regular spiracular valve lids of Sp1 opens passively and air is sucked in through Sp1 during the downstroke and prevents expiration by closing during the upstroke. This stabilizes the unidirectional airflow. The tracheal volume of the head, thorax and abdomen and their mass were determined. Despite the different anatomy of birds and flies, the unidirectional airflow reveals a comparable efficiency of the temporal throughput in flies and hummingbirds.
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structure of the thoracic spiracular valves and their contribution to unidirectional gas exchange in flying blowflies calliphora vicina
The Journal of Experimental Biology, 2017Co-Authors: Lutz T Wasserthal, Anja S FrohlichAbstract:The operation of the thoracic spiracular valves was analysed using anatomical and physiological techniques. Dense spiracular filter trichomes impede a diffusive gas exchange. However, the hinged posterior filter flap of the metathoracic spiracle (Sp2) opens passively during upstroke of the wings and closes by the suction of the sub-atmospheric tracheal pressure during the down stroke, which supports a unidirectional respiratory airflow. The action of the interior spiracular valve lids was recorded by photocell-sensors oriented above the enlarged Spiracles and projected onto the screen of a video camera. The thoracic Spiracles opened much quicker (approximately 0.1 s) than they closed (1 s) suggesting that the spiracular muscles are openers, confirmed by experimental induction of muscle contraction. Simultaneous photocell measurement revealed that the first and second thoracic Spiracles act concordantly. At rest the Spiracles were mostly closed or only slightly open (below 1%). During intermittent short flights, the valves opened wide at the start of the flight for a short time, and in many cases opened again after the flight ended. Often the opening was wider after the flight ended than during the preceding flight itself. During long spontaneous continuous flight phases (up to two hours) the valves were only slightly open (below 5%), widening shortly after transient increases of wing stroke intensity. It is an amazing paradox that the Spiracles were only slightly open most of the time during sustained flight. The advantage of generating sub-atmospheric pressure, supporting a unidirectional airflow with a P O2 increase above the resting level, is discussed.
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flight motor driven respiratory airflow increases tracheal oxygen to nearly atmospheric level in blowflies calliphora vicina
The Journal of Experimental Biology, 2015Co-Authors: Lutz T WasserthalAbstract:It is widely accepted that an efficient oxygen supply and removal of CO2 in small flying insects are sufficiently performed by diffusion with open Spiracles. This paper shows that in the tethered flying blowfly, gas exchange occurs by autoventilation and unidirectional airflow. The air is inspired through the mesothoracic Spiracles (Sp1) during the downstroke of the wings and is expired through the metathoracic Spiracles (Sp2) during the upstroke. This directed airflow through the thoracic tracheal system was documented by pre-atrial pressure measurements at the Sp1 and Sp2, revealing a sub-atmospheric mean pressure at the Sp1 and an over-atmospheric mean pressure at the Sp2. In the mesothoracic air sacs, the mean pressure is sub-atmospheric, conditioned by the only slightly open Spiracles. In a split flow-through chamber experiment, the CO2 released through the Sp2 confirmed this unidirectional respiratory gas flow, implicating an inner tracheal valve. In the thoracic tracheal system, the P O2 during flight exceeds the high resting P O2 by 1–2 kPa, reaching nearly atmospheric values. In the abdominal large air sacs, the P O2 drops during flight, probably due to the accumulation of CO2. Periodic heartbeat reversals continue during flight, with a higher period frequency than at rest, supporting the transport of CO2 via the haemolymph towards the metathoracic tracheae and abdominal air sacs.
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periodic heartbeat reversals cause cardiogenic inspiration and expiration with coupled spiracle leakage in resting blowflies calliphora vicina
The Journal of Experimental Biology, 2014Co-Authors: Lutz T WasserthalAbstract:Respiration in insects is thought to be independent of the circulatory system because insects typically lack respiratory pigments and because oxygen transport occurs in the gaseous phase through a ramified tracheal system by diffusion and convection directly to the tissues. In the blowfly, as in other insects with periodic heartbeat reversal, the haemolymph is periodically shifted between the anterior body and abdomen, exerting alternating pressure changes on the compliant tracheae in the thorax and in the abdomen. Simultaneous pressure and O 2 optode measurements show that, during negative pressure periods, the tracheal partial pressure of oxygen ( P O 2 ) increases by 0.5 kPa. In the quiescent fly, tracheal P O 2 is rather high (17.5–18.9 kPa), although the thoracic Spiracles remain constricted. Microscopic video recordings and reflectance measurements revealed that the dorsal soft edges of the valve lips of the second spiracle leave a very small leak, which is passively widened during backward pulses of the heart. Thus, negative pressure, combined with increased leakage of the spiracle Sp2 valve enable inspiration in the thorax. The positive pressure periods are correlated with a new type of convective CO 2 micro-bursts as shown in flow-through measurements. The bulk of the CO 2 is, however, released after longer interbursts in macro-bursts with actively opening valves reminiscent of the open phase in a cyclic gas exchange. When the valves open, the P O 2 in the thoracic air sacs unexpectedly drops by a mean of 2.75±1.09 kPa, suggesting a displacement of O 2 by the transient accumulation of CO 2 in the tracheal system before its release.
Marcus J. Byrne - One of the best experts on this subject based on the ideXlab platform.
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The role of the mesothoracic Spiracles in respiration in flighted and flightless dung beetles.
The Journal of Experimental Biology, 2005Co-Authors: Frances D. Duncan, Marcus J. ByrneAbstract:The relative role of the mesothoracic and abdominal Spiracles in respiration was examined using flow-through respirometry in four dung beetle species from different habitats. Two species of flightless beetles, Scarabaeus ( Pachysoma ) gariepinus and Scarabaeus ( Pachysoma ) striatum , from the arid western region of southern Africa and a large flighted species, Pachylomerus femoralis , from a more mesic habitat were compared with Circellium bacchus , a flightless beetle from a low rainfall eastern area. All species showed a form of the discontinuous gas exchange pattern at rest. The mesic flighted species used a closed, flutter, open, cycle (CFO) while those species from more arid habitats used a closed, ventilation, cycle (CV) or a closed, burst cycle (CB). The relative importance of the mesothoracic Spiracles in CO2 emission varied between the species, even between those from the same genus and habitat. C. bacchus and P. femoralis represent extremes of CO2 emission from the mesothoracic Spiracles; from almost total to almost none, respectively. Overall, mesothoracic CO2 emission and convection were more pronounced in the dry habitat species, supporting the hypothesis that both strategies aid in the reduction of water loss.
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The role of the subelytral Spiracles in respiration in the flightless dung beetle Circellium bacchus.
The Journal of Experimental Biology, 2003Co-Authors: Marcus J. Byrne, Frances D. DuncanAbstract:SUMMARY The role of the subelytral cavity in flightless beetle species as an adaptation to water saving in arid habitats is still in dispute. We found that relatively little CO 2 was released from the subelytral cavity of a large apterous beetle Circellium bacchus during simultaneous measurements of CO 2 emission from the anterior mesothoracic Spiracles and posterior body, which included the subelytral Spiracles. However, when we sampled air directly from inside the subelytral cavity, we discovered that this pattern was reversed. A discontinuous gas exchange cycle (DGC) was recorded from the posterior body half, revealing a flutter phase that had been absent from the anterior mesothoracic DGC. The anterior mesothoracic and posterior subelytral Spiracles act in synchrony to maintain high CO 2 and water vapour levels inside the subelytral cavity. In addition, the O 2 concentration of the air within the subelytral cavity is lower than the air around the elytral case, irrespective of the time of sampling. These findings lead us to conclude that the subelytral Spiracles work in a coordinated fashion with the anterior Spiracles to create a DGC, which allows us to extend the hypothesis of the function of the subelytral cavity as a respiratory water-saving device.
Roy C. Vogtsberger - One of the best experts on this subject based on the ideXlab platform.
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Ultrastructure of Spiracles of Musca domestica and Hydrotaea chalcogaster (Diptera: Muscidae)
Parasitology Research, 2006Co-Authors: Rungkanta Methanitikorn, Worachote Boonsriwong, Somsak Piangjai, Hiromu Kurahashi, Roy C. VogtsbergerAbstract:Spiracles are major respiratory openings in the exoskeleton of insects. Oxygen, a necessary gas for cell activity, must pass through the spiracle to enter the respiratory system. In this study, we investigated the fine structure of Spiracles of adult females of Musca domestica L. and Hydrotaea chalcogaster (Wiedemann), both medically important fly species in many parts of the world, by utilizing scanning electron microscopy. The mesothoracic spiracle of M. domestica is large and elongate-oval in shape, with its anterior end being gradually tapered. The outer surface is densely covered with slender setae of variable distribution and orientation. The metathoracic spiracle is semicircular or D-shaped, with its rim possessing long, fine, inwardly curved setae. A net-like valve or sieve plate, which has a smooth rim with swollen surface, is located within the atrium of this species. The abdominal Spiracles are circular with a symmetrically swollen peritreme surrounding the opening. The inner filtering apparatus is composed of many spiral tubes, each possessing many small spines. As for H. chalcogaster , the tapering mesothoracic spiracle is covered with long setae arranged consistently inward from the peritreme, giving it a “combed” appearance. The metathoracic spiracle is similarly arranged but triangularly rounded in shape, with the anterior and posterior rims possessing long fine setae. The net-like valve within the atrium has a smooth, swollen rim, whereas the inner edge of the atrium bears short, slender setae where it meets with the peritreme of the spiracle. The abdominal Spiracles of this species look similar to that of M. domestica , with the exception of the filtering apparatus that bears only a few small spines. The function of these Spiracles is discussed.
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larval ultrastructure of parasarcophaga dux thomson diptera sarcophagidae
Micron, 2003Co-Authors: Kom Sukontason, Somsak Piangjai, Tarinee Chaiwong, Noppawan Boonchu, Hiromu Kurahashi, Roy C. VogtsbergerAbstract:Ultrastructure of all larval instars of Parasarcophaga dux (Thomson), a common flesh fly species in Thailand, is presented using scanning electron microscopy. Special attention is given to the structure of anterior and posterior Spiracles since these are important features used to differentiate between other sarcophagids. Each anterior spiracle in second and third instars has a single row of papillae varying in number from 14 to 17. The posterior spiracular discs have incomplete peritremes, with a prominent inner arc. Three long, narrow spiracular slits are oriented more or less vertically in each spiracular disc of third instar. Posterior spiracular hairs lack extensive branching and emanate approximately midway down the length of each slit. Microscopic morphology of the mouthhooks markedly differs between the first and second instars. The structure of these mouthhooks supports this fly species as being necrophagous or capable of producing myiasis.
