Tracheal compression in pupae of the beetleZophobas morio

Abstract

Insects that are small or exhibit low metabolic rates are considered to not require active ventilation to augment diffusive gas exchange. Some pupae with low metabolic rates exhibit abdominal pumping, a behaviour that is known to drive tracheal ventilation in the adults of many species. However, previous work on pupae suggests that abdominal pumping may serve a non-respiratory role. To study the role of abdominal pumping in pupa of the beetle Zophobas morio, we visualized tracheal dynamics with X-rays while simultaneously measuring haemolymph pressure, abdominal movement, and CO 2 emission. Pupae exhibited frequent tracheal compressions that were coincident with both abdominal pumping and pulsation of pressure in the haemolymph. However, more than 63% of abdominal pumping events occurred without any tracheal collapse and hence ventilation, suggesting that the major function of the abdominal pump is not respiratory. In addition, this study shows that the kinematics of abdominal pumping can be used to infer the status of the spiracles and internal behaviour of the tracheal system.

Comparison of the tracheal systems ofAnopheles sinensisandAedes togoilarvae using synchrotron X-ray microscopic computed tomography (respiratory system of mosquito larvae using SR-μCT)

“…The tracheal system DLTs of two different mosquito larvae were compared using SR‐μCT. Synchrotron X‐ray imaging technique has been employed to investigate insect breathing (Greenlee et al, ; Pendar, Kenny, & Socha, ). In this study, we found that the thorax and abdominal segments differed remarkably between the two mosquito larvae.…”

“…The rhythmic tracheal movement during respiration might be induced by combined effects of the macroscale geometry, microscale organization, and mesoscale heterogeneity (Webster, Socha, Teresi, Nardinocchi, & De Vita, 2015). The emission rate of CO 2 is affected by the intratracheal CO 2 level and the opening area of spiracles (Pendar et al, 2015). The dynamic behavior of spiracles could be affected by concentrations of O 2 and CO 2 (Burkett & Schneiderman, 1974).…”

“…The abdominal pumping has certain roles such as activation of ventilation, facilitation of hemolymph circulation, and internal gas mixing (Groenewald, Hetz, Chown, & Terblanche, 2012;Ichikawa, 2008;Pendar et al, 2015). The rhythmic abdominal pumping movement was reported to having about 20 mmHg hemolymph pressure pulses in giant mealworm beetle Zophobas atratus (Ichikawa, 2008).…”

Functional compartmentalization in the hemocoel of insects

“…The abdominal pump has most often been implicated as a mechanism of active respiration, but abdominal pumping does not always result in respiratory airflow. For example, in a study of Zophobas morio beetle larvae 7 , more than half (63.7%) of the observed abdominal pumping events occurred while the spiracles were closed, resulting in no tracheal compressions producing advection and no external gas exchange. Similar results were found in studies of adult Schistocerca gregaria grasshoppers 8 and Bombus terrestris bumblebees 9 , in which individuals exhibited periods of abdominal pumping with no CO 2 emission ranging in duration from 2 to 30 minutes.…”

Evaluation of contrasting techniques for X‐ray imaging of velvet worms (Onychophora)

“…Non‐invasive X‐ray computed tomography (=CT) methods have recently become popular for studying animal morphology and development (e.g. Hammel et al ., ; Friedrich et al ., ; Handschuh et al ., ; Blanke et al ., ; Pendar et al ., ; Weihmann et al ., ). This is because, in contrast to other imaging techniques, CT has the advantage of simultaneously accessing internal and external anatomical details of virtually any organism.…”