428:. In most insects that demonstrate discontinuous gas exchange, spiracle movements and active ventilation are closely coordinated by the nervous system to generate unidirectional air flow within the tracheal system. This coordination leads to the highly regulated bursting pattern of CO
600:
is supported by studies that have demonstrated that respiratory water loss is substantially higher in insects forced to keep their spiracles open, than those of the same species who exhibit discontinuous gas exchange. In addition, laboratory selection experiments on
505:
discontinuous gas exchange cycles are known to cease entirely, as muscle function is lost and spiracles relax and open. The temperature at which muscular function is lost is known as the chill coma temperature.
553:
environment (the hygric hypothesis). However, recent studies question the hygric hypothesis, and several alternative hypotheses have been proposed. For discontinuous gas exchange cycles to be considered
150:
Discontinuous gas exchange cycles are characterized by a repeating pattern of three phases. These phases are named according to the behaviour of the spiracles and are most commonly identified by their
816:
was largely dismissed in the 1970s, but has recently gained additional attention. The strolling arthropods hypothesis is supported by evidence that tracheal parasites can substantially limit O
578:
was first proposed in 1953, making it the earliest posed hypothesis for the evolution of discontinuous gas exchange. The hygric hypothesis proposes that the discontinuous release of
388:
of discontinuous gas exchange cycles. During the open phase, spiracular muscles relax and the spiracles open completely. The open phase may initiate a single, rapid release of CO
1225:
Harrison JF, Camazine S, Marden JH, Kirkton SD, Rozo A, Yang X (1995). "Mite not make it home: tracheal mites reduce the safety margin for oxygen delivery of flying honeybees".
396:
with time as a result of the repeated opening and closing of the spiracles. During the open phase, a complete exchange of gases with the environment occurs entirely by
699:, water will be lost from the respiratory system to the environment. Discontinuous gas exchange cycles, therefore, may limit water loss while facilitating O
955:
Chown SL, Gibbs AG, Hetz SK, Klok CJ, Lighton JR, Marias E (2006). "Discontinuous gas exchange in insects: a clarification of hypotheses and approaches".
108:
patterns, ranging from largely diffusive continuous ventilation, to cyclic respiration, of which discontinuous gas exchange cycles are the most striking.
793:
for the evolution of discontinuous gas exchange cycles. It was postulated that discontinuous gas exchange cycles and spiracles which close off the
765:
over time. This would lead to the expectation of prolonged flutter periods in insects that may be particularly sensitive to high levels of O
424:
may occur through a single open spiracle, or the coordination of several spiracles. Spiracle function is controlled almost entirely by the
62:
to the external environment. Discontinuous gas exchange is traditionally defined in three phases, whose names reflect the behaviour of the
436:
levels during the flutter phase may either directly affect spiracular opening, affect the nervous system while being pumped through the
999:
902:
691:
gradients between an insect’s respiratory system and the environment in which it lives. Alternatively, insects could obtain enough O
189:
is close to that of the external environment, but closure of the spiracles drastically reduces the capacity for the exchange of
639:, there is no benefit to having a flutter phase. This has led to the belief that some other factor may have contributed to the
623:
loss during discontinuous gas exchange is only limited during the flutter phase if gas exchange during the flutter phase is
541:
of discontinuous gas exchange cycles are largely unknown. Discontinuous gas exchange cycles have long been thought to be an
794:
477:
in the external environment. Environmental stimuli may affect one or more aspects of discontinuous cycling, such as cycle
277:
of discontinuous gas exchange cycles, spiracles open slightly and close in rapid succession. As a result of the negative
1270:
683:
in enclosed spaces underground. Lighton and
Berrigan hypothesized that discontinuous gas exchange cycles may be an
632:
497:
animals, and changes in metabolic rate can create large differences in discontinuous gas exchange cycles. At a
194:
603:
711:
and consider it to support the hygric hypothesis. However, others emphasize the importance of maximizing
680:
452:
63:
663:. It was observed that many insects that demonstrate discontinuous gas exchange cycles are exposed to
1265:
1189:
829:
753:
reaches levels near that of the external environment. However, over time during the closed phase the
750:
616:
354:
346:
326:
258:
242:
230:
198:
127:
82:
1133:
Lighton JR, Berrigan D (1995). "Questioning paradigms: caste-specific ventiation in harvester ants,
301:
and its exportation through the tracheal system. As a result, during the flutter phase, additional O
695:
by opening their spiracles for extended periods of time. However, unless their environment is very
770:
656:
628:
590:
550:
286:
715:
gradients alone and consider the chthonic hypothesis to be distinct from the hygric hypothesis.
416:
respiratory cycles can largely be explained by differences in spiracle function, body size and
1242:
1207:
1158:
1112:
1069:
995:
972:
898:
664:
563:
1234:
1197:
1150:
1104:
1061:
1031:
964:
754:
746:
712:
688:
636:
460:
250:
210:
178:
74:
177:
contract, causing the spiracles to shut tight. At the initiation of the closed phase, the
559:
338:
222:
1193:
1017:"A temperature-induced switch from diffusive to convective ventilation in the honeybee"
836:
739:
579:
490:
471:
425:
417:
378:
362:
306:
262:
218:
151:
97:
47:
1065:
1016:
1259:
847:
840:
821:
608:
444:
on both spiracles and the nervous system do not appear to be related to changes in
421:
158:
105:
31:
769:
within the body. Strangely however, termites that carry a highly oxygen-sensitive
451:
Variability in discontinuous gas exchange cycles is also dependent upon external
672:
502:
494:
486:
456:
123:
58:
follow a cyclical pattern characterized by periods of little to no release of CO
281:
within the tracheal system, created during the closed phase, a small amount of
1202:
1177:
813:
801:
790:
728:
684:
624:
612:
597:
586:
555:
542:
518:
437:
342:
298:
226:
135:
119:
86:
798:
774:
640:
538:
522:
478:
397:
393:
139:
28:
1246:
1211:
1073:
976:
707:
removal in such environments. Many researchers describe this theory as the
1238:
1162:
1154:
1116:
1108:
1035:
825:
696:
318:
290:
278:
246:
517:, and these differences have been used in the past to support or refute
325:
may be assisted in some insects by active ventilatory movements such as
644:
593:
526:
514:
510:
498:
401:
330:
131:
115:
101:
85:
through the spiracles, and diffused through the tracheal system to the
35:
1178:"Respiratory Biology: why insects evolved discontinuous gas exchange"
843:
732:
464:
413:
366:
358:
202:
174:
112:
90:
70:
55:
39:
968:
289:
each time the spiracles are opened. However, the negative internal
620:
546:
190:
537:
Despite being well described, the mechanisms responsible for the
404:, but may be assisted by active ventilatory movements in others.
249:
inside the system relative to the external environment. Once the
111:
Discontinuous gas exchange cycles have been described in over 50
832:
809:
805:
317:
is released. The flutter phase may continue even after tracheal
193:
with the external environment. Independent of cycles of insect
659:
in 1995, doctors John
Lighton and David Berrigan proposed the
509:
Discontinuous gas exchange cycles vary widely among different
282:
78:
321:
is equal to that of the environment, and the acquisition of O
445:
66:: the closed phase, the flutter phase, and the open phase.
596:
to limit respiratory water loss to the environment. This
213:
decreases within the tracheal system. In contrast, as CO
1095:: the effect of selection for desiccation resistance".
369:
and they are opened widely, initiating the open phase.
1052:
Chown SL (2002). "Respiratory water loss in insects".
727:
states that discontinuous gas exchange cycles are an
38:; they occur when the insect is at rest. During DGC,
761:
drops, limiting the overall exposure of tissues to O
173:of discontinuous gas exchange cycles, the spiracle
1128:
1126:
408:Variability in discontinuous gas exchange cycles
558:, the origin and subsequent persistence of the
138:, but the mechanisms and significance of their
134:, discontinuous gas exchange cycles are likely
533:Evolution of discontinuous gas exchange cycles
631:). From a water conservation perspective, if
8:
1087:Williams AE, Rose MR, Bradley TJ (1997). "CO
950:
948:
946:
944:
942:
940:
938:
936:
934:
635:during the flutter phase occurs entirely by
305:from the environment is acquired to satisfy
265:causes the initiation of the flutter phase.
932:
930:
928:
926:
924:
922:
920:
918:
916:
914:
812:from entering the respiratory system. This
679:levels) by spending at least part of their
261:drops below a lower limit, activity in the
157:output, primarily observed using open flow
738:delivered to tissues under periods of low
619:for tolerance to dry conditions. However,
1201:
1054:Comparative Biochemistry and Physiology A
118:, most of which are large beetles (order
205:level continues at a constant rate. As O
1047:
1045:
858:
651:Chthonic and chthonic-hygric hypotheses
562:must be demonstrated to be a result of
34:that have been documented primarily in
17:Discontinuous gas-exchange cycles (DGC)
888:
886:
884:
882:
828:. As a result of large populations of
333:. The flutter phase continues until CO
957:Physiological and Biochemical Zoology
897:. New York: Oxford University Press.
880:
878:
876:
874:
872:
870:
868:
866:
864:
862:
797:, may in part do so to prevent small
440:, or both. However, the effects of CO
384:to the environment characterizes the
7:
893:Chown, S.L.; S.W. Nicholson (2004).
27:, follow one of several patterns of
992:Insect Physiology and Biochemistry
345:and begins to build up within the
293:also prevents the liberation of CO
229:rather than being exported to the
73:was believed to occur entirely by
14:
1015:Lighton JR, Lovegrove BG (1990).
643:of discontinuous gas exchange in
392:, or several spikes declining in
357:has both a direct (acting on the
122:) or butterflies or moths (order
835:, honeybees are unable to reach
489:can have massive effects on the
285:from the environment enters the
25:discontinuous ventilatory cycles
1227:Journal of Experimental Biology
1143:Journal of Experimental Biology
1097:Journal of Experimental Biology
1024:Journal of Experimental Biology
808:and particulate matter such as
787:strolling arthropods hypothesis
781:Strolling arthropods hypothesis
607:have shown that more variable
1:
1066:10.1016/s1095-6433(02)00200-3
313:demand, while little to no CO
1141:(Hymenoptera: Formicidae)".
994:. Boca Raton: C.R.C. Press.
895:Insect Physiological Ecology
361:) and indirect (through the
197:which may be discontinuous,
142:are currently under debate.
725:oxidative damage hypothesis
719:Oxidative damage hypothesis
1287:
742:. During the open phase, O
709:chthonic-hygric hypothesis
525:of respiratory cycling in
233:. This mismatch between O
1203:10.1016/j.cub.2007.06.007
365:) impact on the spiracle
337:production surpasses the
100:. However, even at rest,
21:discontinuous ventilation
773:demonstrate continuous,
731:to reduce the amount of
485:released at each burst.
1093:Drosophila melanogaster
611:patterns can emerge in
604:Drosophila melanogaster
412:The great variation in
104:show a wide variety of
77:. It was believed that
54:release from the whole
481:and the quantity of CO
241:production within the
128:evolved more than once
126:). As the cycles have
1239:10.1242/jeb.204.4.805
1155:10.1242/jeb.198.2.521
1109:10.1242/jeb.200.3.615
1036:10.1242/jeb.154.1.509
990:Nation, J.L. (2002).
617:artificially selected
96:was delivered to the
1176:Lighton JRB (2007).
1091:release patterns in
850:, and are grounded.
629:muscular contraction
432:release. Building CO
245:leads to a negative
199:cellular respiration
1194:2007CBio...17.R645L
661:chthonic hypothesis
377:A rapid release of
217:is produced by the
795:respiratory system
771:symbiotic bacteria
703:consumption and CO
655:Following work on
339:buffering capacity
287:respiratory system
237:consumption and CO
71:insect respiration
48:carbon dioxide (CO
1271:Insect physiology
1149:(Pt 2): 521–530.
1103:(Pt 3): 615–624.
789:was a very early
576:hygric hypothesis
570:Hygric hypothesis
564:natural selection
549:when living in a
209:is consumed, its
1278:
1251:
1250:
1233:(Pt 4): 805–13.
1222:
1216:
1215:
1205:
1188:(16): R645–647.
1173:
1167:
1166:
1135:Messor pergandei
1130:
1121:
1120:
1084:
1078:
1077:
1049:
1040:
1039:
1021:
1012:
1006:
1005:
987:
981:
980:
952:
909:
908:
890:
820:delivery to the
755:partial pressure
747:partial pressure
713:partial pressure
689:partial pressure
637:simple diffusion
627:(or assisted by
461:partial pressure
251:partial pressure
211:partial pressure
179:partial pressure
75:simple diffusion
69:Until recently,
1286:
1285:
1281:
1280:
1279:
1277:
1276:
1275:
1256:
1255:
1254:
1224:
1223:
1219:
1182:Current Biology
1175:
1174:
1170:
1132:
1131:
1124:
1090:
1086:
1085:
1081:
1051:
1050:
1043:
1019:
1014:
1013:
1009:
1002:
989:
988:
984:
954:
953:
912:
905:
892:
891:
860:
856:
837:metabolic rates
819:
783:
768:
764:
760:
751:tracheal system
745:
736:
721:
706:
702:
694:
678:
670:
653:
583:
572:
535:
484:
475:
468:
443:
435:
431:
410:
391:
382:
375:
355:tracheal system
352:
347:tracheal system
336:
324:
316:
312:
304:
296:
271:
259:tracheal system
256:
243:tracheal system
240:
236:
231:tracheal system
216:
208:
188:
184:
167:
155:
148:
94:
61:
51:
43:
12:
11:
5:
1284:
1282:
1274:
1273:
1268:
1258:
1257:
1253:
1252:
1217:
1168:
1122:
1088:
1079:
1060:(3): 791–804.
1041:
1007:
1000:
982:
969:10.1086/499992
963:(2): 333–343.
910:
903:
857:
855:
852:
846:necessary for
822:flight muscles
817:
782:
779:
766:
762:
758:
743:
740:metabolic rate
734:
720:
717:
704:
700:
692:
676:
668:
657:harvester ants
652:
649:
581:
571:
568:
534:
531:
501:-specific low
491:metabolic rate
482:
473:
466:
441:
433:
429:
426:nervous system
418:metabolic rate
409:
406:
389:
380:
374:
371:
363:nervous system
350:
334:
322:
314:
310:
302:
294:
270:
267:
263:nervous system
254:
238:
234:
214:
206:
186:
182:
166:
163:
153:
147:
144:
92:
59:
49:
41:
19:, also called
13:
10:
9:
6:
4:
3:
2:
1283:
1272:
1269:
1267:
1264:
1263:
1261:
1248:
1244:
1240:
1236:
1232:
1228:
1221:
1218:
1213:
1209:
1204:
1199:
1195:
1191:
1187:
1183:
1179:
1172:
1169:
1164:
1160:
1156:
1152:
1148:
1144:
1140:
1136:
1129:
1127:
1123:
1118:
1114:
1110:
1106:
1102:
1098:
1094:
1083:
1080:
1075:
1071:
1067:
1063:
1059:
1055:
1048:
1046:
1042:
1037:
1033:
1029:
1025:
1018:
1011:
1008:
1003:
1001:0-8493-1181-0
997:
993:
986:
983:
978:
974:
970:
966:
962:
958:
951:
949:
947:
945:
943:
941:
939:
937:
935:
933:
931:
929:
927:
925:
923:
921:
919:
917:
915:
911:
906:
904:0-19-851549-9
900:
896:
889:
887:
885:
883:
881:
879:
877:
875:
873:
871:
869:
867:
865:
863:
859:
853:
851:
849:
845:
842:
838:
834:
831:
827:
823:
815:
811:
807:
803:
800:
796:
792:
788:
780:
778:
777:ventilation.
776:
772:
756:
752:
748:
741:
737:
730:
726:
718:
716:
714:
710:
698:
690:
686:
682:
674:
666:
662:
658:
650:
648:
646:
642:
638:
634:
630:
626:
622:
618:
614:
610:
606:
605:
599:
595:
592:
588:
584:
577:
569:
567:
565:
561:
557:
552:
548:
544:
540:
532:
530:
528:
524:
520:
516:
512:
507:
504:
500:
496:
492:
488:
480:
476:
469:
462:
458:
454:
449:
447:
439:
427:
423:
419:
415:
407:
405:
403:
399:
395:
387:
383:
372:
370:
368:
364:
360:
359:muscle tissue
356:
348:
344:
340:
332:
328:
320:
308:
300:
292:
288:
284:
280:
276:
275:flutter phase
269:Flutter phase
268:
266:
264:
260:
252:
248:
244:
232:
228:
224:
220:
212:
204:
200:
196:
192:
180:
176:
172:
164:
162:
160:
156:
145:
143:
141:
137:
133:
129:
125:
121:
117:
114:
109:
107:
103:
99:
95:
88:
84:
80:
76:
72:
67:
65:
57:
53:
45:
37:
33:
30:
26:
22:
18:
1230:
1226:
1220:
1185:
1181:
1171:
1146:
1142:
1138:
1134:
1100:
1096:
1092:
1082:
1057:
1053:
1027:
1023:
1010:
991:
985:
960:
956:
894:
786:
784:
724:
722:
708:
687:to maximize
671:levels) and
660:
654:
609:gas exchange
602:
589:that allows
575:
573:
545:to conserve
536:
508:
450:
422:Gas exchange
411:
385:
376:
274:
272:
171:closed phase
170:
168:
165:Closed phase
159:respirometry
149:
110:
106:gas exchange
89:, whereupon
81:entered the
68:
32:gas exchange
24:
20:
16:
15:
1266:Respiration
1139:M. julianus
1030:: 509–516.
673:hypercapnia
633:ventilation
615:of insects
613:populations
591:terrestrial
551:terrestrial
503:temperature
495:ectothermic
487:Temperature
457:temperature
353:within the
327:contraction
273:During the
201:on a whole
195:ventilation
169:During the
130:within the
124:Lepidoptera
46:uptake and
1260:Categories
854:References
824:of active
814:hypothesis
791:hypothesis
729:adaptation
685:adaptation
681:life cycle
625:convective
598:hypothesis
587:adaptation
543:adaptation
519:hypotheses
438:haemolymph
386:open phase
373:Open phase
343:haemolymph
299:haemolymph
227:haemolymph
120:Coleoptera
87:tracheoles
826:honeybees
802:parasites
799:arthropod
775:diffusive
641:evolution
539:evolution
523:evolution
479:frequency
398:diffusion
394:amplitude
297:from the
181:of both O
140:evolution
64:spiracles
40:oxygen (O
29:arthropod
1247:11171363
1212:17714655
1074:12443935
977:16555192
830:tracheal
804:such as
675:(high CO
556:adaptive
459:and the
455:such as
400:in some
319:pressure
307:cellular
291:pressure
279:pressure
247:pressure
223:buffered
221:, it is
136:adaptive
83:tracheae
1190:Bibcode
1163:9318205
1117:9057311
749:in the
667:(low O
665:hypoxia
645:insects
594:insects
527:insects
521:of the
515:insects
511:species
499:species
453:stimuli
402:species
367:muscles
341:of the
331:abdomen
329:of the
257:in the
225:in the
185:and CO
175:muscles
132:insects
116:species
102:insects
36:insects
1245:
1210:
1161:
1115:
1072:
998:
975:
901:
848:flight
844:muscle
841:flight
585:is an
414:insect
203:animal
146:Phases
113:insect
56:insect
1020:(PDF)
833:mites
806:mites
697:humid
621:water
560:trait
547:water
219:cells
191:gases
98:cells
1243:PMID
1208:PMID
1159:PMID
1137:and
1113:PMID
1070:PMID
996:ISBN
973:PMID
899:ISBN
810:dust
785:The
757:of O
723:The
574:The
470:and
349:. CO
253:of O
1235:doi
1231:204
1198:doi
1151:doi
1147:198
1105:doi
1101:200
1062:doi
1058:133
1032:doi
1028:154
965:doi
839:in
513:of
493:of
463:of
283:air
79:air
23:or
1262::
1241:.
1229:.
1206:.
1196:.
1186:17
1184:.
1180:.
1157:.
1145:.
1125:^
1111:.
1099:.
1068:.
1056:.
1044:^
1026:.
1022:.
971:.
961:79
959:.
913:^
861:^
647:.
580:CO
566:.
529:.
472:CO
448:.
446:pH
420:.
379:CO
161:.
152:CO
1249:.
1237::
1214:.
1200::
1192::
1165:.
1153::
1119:.
1107::
1089:2
1076:.
1064::
1038:.
1034::
1004:.
979:.
967::
907:.
818:2
767:2
763:2
759:2
744:2
735:2
733:O
705:2
701:2
693:2
677:2
669:2
582:2
483:2
474:2
467:2
465:O
442:2
434:2
430:2
390:2
381:2
351:2
335:2
323:2
315:2
311:2
309:O
303:2
295:2
255:2
239:2
235:2
215:2
207:2
187:2
183:2
154:2
93:2
91:O
60:2
52:)
50:2
44:)
42:2
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