Loss of function of the yellow-e gene causes dehydration-induced mortality of adult Tribolium castaneum
Mi Young NohKarl J. KramerSubbaratnam MuthukrishnanRichard W. BeemanMichael R. KanostYasuyuki Arakane
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Cuticle (hair)
Ecdysis
Red flour beetle
In many if not most species of crabs (but not quite all) there is a limit to growth, when no more moulting or ecdysis is possible in normal circumstances. This condition of permanent anecdysis is known as the terminal anecdysis. In the spider crab Maia squinado , the last moult is the moult of puberty, when the animal finally attains sexual maturity, and this moult has different biometrical characteristics from the others. In Carcinus maenas , in contrast, the moult of puberty takes place when the animal is quite small and may be succeeded by about ten further moults before the terminal anecdysis begins. The immediate cause of the cessation of moulting in Maia squinado is shown to be the degeneration of the Y-organ, which secretes a moult-promoting hormone. In the absence of this gland and its secretion moulting can no longer continue. In Carcinus the Y-organ does not degenerate after the final ecdysis and the cause of the cessation of moulting is to be sought in the excessive production by the X-organ-sinus gland complex of the moultinhibiting hormone. This effectively prevents moulting from proceeding Removal of the X-organ-sinus gland complex in Carcinus allows ecdysis to continue, so that giant crabs can be produced in the laboratory by this means, and at the same time the life-span may be increased. The operation has no such effect on Maia. In either species injection of Y-organ extracts produces transiently the first signs of an approaching moult, in the form of a heightened blood-calcium level. In Carcinus repeated injection led to eventual ecdysis. The presence of the Y-organ is shown to be necessary for removal of the X-organ-sinus gland complex to stimulate moulting in Carcinus . Two separate methods of producing terminal anecdysis exist in crabs, both involving the hormones which normally regulate the moult cycle, but no reason is known for the existence of the phenomenon.
Ecdysis
Carcinus maenas
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Insect development occurs through moulting, where the individual generates a new cuticle and sheds the old one, allowing the insect to grow and develop. This process can be impacted by parasites. However, the way different parasites can impact insect moulting is unknown. We first review studies on insect infection and its effect on insect moulting by considering interactions between insects and: (i) protozoans; (ii) fungi; (iii) viruses; and (iv) parasitoids. We show that insect moulting is impacted by moulting delays, non-moult and defects after moulting, besides increasing insect mortality during moulting. However, while there is evidence that parasite- infected insects can experience increased mortality during moulting, this process is not well understood yet. We then documented this so as to raise hypotheses about the mechanisms, with a focus on behaviour, using as a model system the triatomine bug Rhodnius prolixus (Hemiptera: Reduviidae) and the protozoan parasite Trypanosoma rangeli. We quantified mortality and investigated alterations in ecdysis-related behaviour. We found that the high mortality of infected insects is related to increases in the time taken to finish ecdysis. We then investigated cuticular thickness and ecdysone levels as potential factors to explain this phenomenon. Mortality of infected insects was 6% higher than that of uninfected insects. Infected insects show a thinner cuticle over time and lower ecdysone levels compared to controls. We suggest this thin cuticle in infected insects is associated with the moulting delay. As moulting is delayed, we investigate glycogen content in the fat body and intestine morphology as possible factors. Infected insects have low glycogen content in the fat body and intestine morphology is not altered between infected and control insects, but intestine epithelium is apparently thicker in infected than the control. Our results allow us to understand better the effect of insect infections at behavioural, morphological and hormonal levels. This study is a starting point for further reasearch on the moulting physiology of insects infected by parasites in order to improve our understanding of insect-parasite interaction. Keywords: Cuticle. Development. Ecdysis. Ecdysone. Fungus. Moult. Parasitoid. Pathogen. Physiology. Virus.
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Rhodnius
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Abstract This study describes the behavioral and histological changes that take place during ecdysis in the Formosan subterranean termite. The molting process was described in four distinct phases, starting with the peristaltic contraction of the abdomen to the complete shedding of the exuvium. Although individual termites still managed to go through the molting process when isolated from their nestmates, it required more time for the molting individual to complete the process than when aided by its nestmates. Histological observations were made on termites during the intermolt period, the premolting or fasting period, the pre-ecdysis and the ecdysis periods, and on newly molted individuals. Symbiotic protozoans were voided at the beginning of the premolting/fasting period. The detachment and reattachment of the muscles of the abdominal segments occurred during pre-ecdysis, and the leg muscle detachment and reattachment occurred during ecdysis. During pre-ecdysis, the abdominal cuticle had a wrinkled texture and two layers of cuticles were observed, one of which was the newly formed cuticle underneath the old one. Finally, the old tracheae were shed from the tracheal system and were pulled out from the spiracular openings of the mesothorax with the help of the nestmates. We concluded that, as social insects, the presence of nestmates during the molting of individual termites reduced the time necessary to complete the ecdysis, and the histological description of the molting process provides a template for further studies on the effect of chitin synthesis inhibitors on ecdysis in termites.
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Muda
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1. The central nervous system of the barnacle, Balanus eburneus, was removed at known intervals following ecdysis, extracted in sea water, and assayed by injecting into eyestalkless U ca pugilator to determine if the barnacle chromatophorotropins exhibited a cyclic activity associated with molting.2. A cyclic pattern of activity was observed within one intermolt period. The changes in activity of the U ca black-pigment-dispersing substance, highly significant at the 95% level, were the low concentrations immediately following molting and 48 hours after ecdysis and the high concentration which occurred at 24 hours after molting. In barnacles which did not molt again within the usual 72-96-hour period following the first molt, the level of activity of the central nervous system extracts remained low. Body weight and the activity of the central nervous system extracts were found to be independent.3. The hypothesis is presented that in the absence of a storage organ comparable to the sinus gland of Brachyura, neurosecretory products originating from the central nervous system are released directly into the blood. The release of these products following the period of greatest concentration, 24 hours after molting, stimulates the physiological processes and cellular changes which culminate in ecdysis.
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Balanus
Muda
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Ecdysis
Cuticle (hair)
Hemolymph
Epidermis (zoology)
Arthropod cuticle
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Ecdysis
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Ecdysis
Cuticle (hair)
Hemolymph
Epidermis (zoology)
Arthropod cuticle
Appendage
Annelid
Muda
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With millions of extant species, ecdysozoans (Scalidophora, Nematoida and Panarthropoda) constitute a major portion of present-day biodiversity. All ecdysozoans secrete an exoskeletal cuticle which must be moulted periodically and replaced by a larger one. Although moulting (ecdysis) has been recognized in early Palaeozoic panarthropods such as trilobites and basal groups such as anomalocaridids and lobopodians, the fossil record lacks clear evidence of ecdysis in early scalidophorans, largely because of difficulties in recognizing true exuviae. Here, we describe two types of exuviae in microscopic scalidophoran worms from the lowermost Cambrian Kuanchuanpu Formation ( ca 535 Ma) of China and reconstruct their moulting process. These basal scalidophorans moulted in a manner similar to that of extant priapulid worms, extricating themselves smoothly from their old tubular cuticle or turning their exuviae inside out like the finger of a glove. This is the oldest record of moulting in ecdysozoans. We also discuss the origin of ecdysis in the light of recent molecular analyses and the significance of moulting in the early evolution of animals.
Ecdysis
Basal (medicine)
Cuticle (hair)
Muda
Fossil Record
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Ecdysis
Cuticle (hair)
Arthropod cuticle
Epidermis (zoology)
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With millions of extant species, ecdysozoans (Scalidophora, Nematoida and Panarthropoda) constitute a major portion of present-day biodiversity. All ecdysozoans secrete an exoskeletal cuticle which must be moulted periodically and replaced by a larger one. Although moulting (ecdysis) has been recognized in early Paleozoic panarthropods such as trilobites and basal groups such as anomalocaridids and lobopodians, the fossil record lacks clear evidence of ecdysis in early scalidophorans, largely because of difficulties in recognizing true exuviae. Here, we describe two types of exuviae in microscopic scalidophoran worms from the lowermost Cambrian Kuanchuanpu Formation (ca 535 Ma) of China and reconstruct their moulting process. These basal scalidophorans moulted in a manner similar to that of extant priapulid worms, extricating themselves smoothly from their old tubular cuticle or turning their exuviae inside out like the finger of a glove. This is the oldest record of moulting in ecdysozoans. We also discuss the origin of ecdysis in the light of recent molecular analyses and the significance of moulting in the early evolution of animals.
Ecdysis
Cuticle (hair)
Basal (medicine)
Fossil Record
Muda
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