MOLTING AND CYCLIC ACTIVITY IN CHROMATOPHOROTROPINS OF THE CENTRAL NERVOUS SYSTEM OF THE BARNACLE, BALANUS EBURNEUS
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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.Keywords:
Ecdysis
Balanus
Muda
Balanus
Ecdysterone
Ecdysis
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ABSTRACT A series of experiments was conducted to elucidate the events immediately preceding and following moulting (ecdysis) in the blue crab, Callinectes sapidus Rathbun. The crabs gain weight (mostly water) to a level more than twice the premoult value excluding the shed carapace. The gain begins about 4 h before ecdysis, accelerates rapidly to a maximum rate at about the time of ecdysis, and is essentially complete by 2h after ecdysis. Both calcification and net H+ excretion remain at control (intermoult) levels until 1–2 h post-moult, whereupon a very rapid increase in both begins, with the same time course for both processes. The ratio of internal to external calcium concentration drops from 1·4:1 during intermoult to 0·85:1 by 2 days after the moult, reversing the electrochemical gradient during the post-moult period. Calcification is strongly inhibited by the protein synthesis inhibitors actinomycin D and cycloheximide. Isolated whole gills and gill slices do not show significant changes in rates of calcium uptake related to moult stage, indicating that the uptake of calcium across the gills may be largely passive. A low-affinity Ca2+-activated ATPase is present in both gills and epithelium, but only the epithelial activity shows a substantial (fivefold) increase in the hours after ecdysis. The control mechanisms for stimulation of the transport processes remain elusive. Eyestalkless crabs progress normally through moult and post-moult calcification. Peptide profiles from blood and from suspected neurohormone-producing tissues differ markedly with moult stage, but several different approaches to developing a bioassay using peptides from crab tissues and vertebrate sources have been unsuccessful. The physiological events in the hours surrounding ecdysis suggest a complex and precisely timed series of control signals.
Ecdysis
Callinectes
Muda
Rostrum
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After removal of the eyestalks in Uca pugilator, all of the animals moulted within 35 days after the operation, and a few of the animals moulted twice within 48 days. Only 29 per cent of the normal animals moulted within 48 days, and none moulted twice. Eyestalk removal not only accelerated moulting but shortened the time in which the first and second moults occurred. The time at which the same percentage of moulting occurred was somewhat greater for non-segregated than for segregated animals.Viability is related to moulting, and most of the deaths following eyestalk removal in this species are due in part to a mechanical difficulty and in part to some severe deficiency occurring during or aggravated by ecdysis. There is insufficient evidence to decide whether the eyestalks secrete a specific, life-sustaining hormone directly responsible for the continued life of the animal, or whether the viability effect is in some way dependent on the moult-inhibiting function of the eyestalk. We do not believe that the loss of the eyestalks per se is directly responsible for the total mortality seen in eyestalkless crabs because of the negligible percentage of deaths occurring from 1 to 5 weeks before moulting, and because operated animals live for 5 weeks without showing any external signs of serious debilities only to succumb after ecdysis. Seventy-five per cent of the total mortality can be related directly or indirectly to ecdysis, while 25 per cent (which includes the 10.5 per cent viable specimens) does not fall in this category and may be cited in support of a differentiation of the viability and moult-inhibiting functions of the eyestalk.Eyestalk removal also leads to increased size. Some of the eyestalkless specimens 48 days after the operation have attained gigantic proportions. Pigmentation also seems to be lost, an effect which is noticeable after the first moult. No effect of eyestalk removal has been noted on copulation and shedding of eggs.
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Eyestalk
Muda
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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.
Ecdysis
Cuticle (hair)
Muda
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Analysis of the natural diet of prawns over the moult cycle shows a preference for molluscan tissue at all stages, with an apparent greater preference in the stage immediately following the moult dropping in the intermoult stages and then increasing again before the next moult. A laboratory study was carried out to provide more information on feeding behaviour over the moult cycle. Adults of Penaeus esculentus (carapace length 25 to 30 mm, weight 15.5 to 25.2 g) held at 32 to 35 and 23 to 25°C did not feed on the night of ecdysis. On the following nights, feeding increased to peak at 2.7 g of penaeid tissue per day in moult Stage C. For the rest of the moult cycle, feeding was fairly steady at about 1.23 g of penaeid tissue per day but dropped sharply two nights before ecdysis. The prawns increased in weight by 0.7 to 6.1 g (mean 3.5 g) over a moult cycle. A stepwise linear-regression analysis showed that, within the range tested, the increase in weight was not a function of prawn weight, duration of moult cycle (range 14 to 34 days), or daily food consumption (0.95 to 2.33 g). They ate more crustacean tissue (Metapenaeus bennettae) than bivalve tissue (Perna canaliculatus) over the entire moult cycle, except for the night before and after ecdysis, when they ate bivalve tissue almost exclusively.
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Muda
Penaeus
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Abstract This study aims to elucidate the physical evidence of the moulting stages and the characteristics of ecdysteroid levels in the moulting cycle of Neocaridina denticulata sinensis . From hatching to the first complete pleopod development, N. denticulata sinensis moults 14 times at 25°C in the laboratory. The whole process was divided into four stages based on the moulting characteristics during the various intervals. Using the structural changes of the telson and Drach’s classification system, four moulting periods (postmoult, intermoult, premoult, and ecdysis) were recognized. In addition, based on the changes of the setal lumen, internal cone, and the epidermis, the premoult period was further divided into five substages (D 0 , D 1 , D 2 , D 3 , and D 4 ). Despite similar fluctuation patterns in mature males and females, significant differences of haemolymph ecdysteroid titers were revealed in postmoult, intermoult, and premoult. These works will provide an important additional reference for the exploration of the moulting mechanism in crustaceans.
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Ecdysteroid
Muda
Hemolymph
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1. A transitional series of color changes which occurs during the premolt period of normal animals is described. These changes have been arbitrarily assigned to five stages and the duration of each stage measured. The last four of these are associated with hypodermal activity anticipating ecdysis.2. The inorganic constituents of normal and destalked animals are compared for the premolt and postmolt condition.3. Certain physical aspects of ecdysis are treated in a quantitative manner. These include the absorption of water and dimensional changes.4. The results suggest that the sinus gland-X organ complex plays a role in the regulation of water metabolism and in the metabolism of inorganic constituents.5. Evidence is presented for a diurnal rhythm of water-uptake under the control of the sinus gland-X organ complex.6. The possibility that molt and dimensional increase are separate factors under certain conditions is discussed.
Ecdysis
Muda
Fiddler crab
Sinus (botany)
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Balanus
Muda
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Balanus
Muda
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The currently accepted reproductive cycle of Alaskan female Dungeness crab (Cancer magister) is that females molt and mate during summer and fall, extrude eggs in the fall, and incubate eggs through the winter until larval hatching in May and June. In this cycle, molting and mating are coincident with ovarian maturation. In this study, we quantified circulating concentrations of hemolymph ecdysteroids (molting hormones) in laboratory and field sampled crabs using an enzyme-linked immunosorbent assay (ELISA), for molt status assessment of individuals. Captive female crabs from southeastern Alaska (mean |${\rm{CW = 134}}{\rm{.8\, mm}}$|; |${\rm{n = 48}}$|) had a typical crustacean molt cycle profile of circulating ecdysteroids. Concentrations of ecdysteroids were low during intermolt (|${\rm{20}}{\rm{.3 }} \pm {\rm{ 0}}{\rm{.7 ng/ml}}$|), maximal during premolt (|${\rm{1886}}{\rm{.5 }} \pm {\rm{ 186}}{\rm{.2 ng/ml}}$|) 15 days before ecdysis and precipitously declined to low levels |$\left( { \lt {\text{ 9}}0{\text{ ng}}/{\text{ml}}} \right)$| 5 days prior to ecdysis. The duration of premolt was 150 days. Crabs held in captivity either molted (67%), extruded eggs (7%), or demonstrated no reproductive or molting activity (26%). Peak molting occurred in November for crabs held in the laboratory. Most (98%) of the female crabs sampled (|${\rm{n = 579}}$|) in Port Frederick, Alaska during the expected premolt period (May-July), had intermolt ecdysteroid concentrations. The capability to predict ecdysis 150 days prior to ecdysis by measuring ecdysteroid concentrations provides a useful tool to assess the molt status and timing of ecdysis in Alaskan Dungeness crab populations.
Ecdysis
Muda
Hemolymph
Ecdysteroid
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