不同饥饿程度的拟小食螨瓢虫成虫摄食朱砂叶螨前后的运动格局变化

【目的】对比分析饥饿和未饥饿的拟小食螨瓢虫Stethorus parapauperculus成虫取食朱砂叶螨Tetranychus cinnabarinus前后的运动格局变化,为探明其搜索行为的生态学机制提供参考。【方法】基于Nakamuta装置原理,跟踪并绘制拟小食螨瓢虫成虫取食前后的运动轨迹,采用ArcGIS空间分析模块对运动轨迹进行处理,获取其统计参数,对比分析该瓢虫在两种状态下取食前后的搜索距离、搜索速度、搜索角度变化等特征,并阐述其搜索行为特性。【结果】饥饿24 h和未饥饿瓢虫取食单头朱砂叶螨所需时间分别为(5.99±0.91)min和(2.25±0.58)min。饥饿24 h的瓢虫在取食前多呈直线或锐角行走,运动轨迹主要分布于试验区域近边缘处,且各停点间曲线距离、搜索速度均大于取食后;取食后掉头次数频繁,活动角度转换增大,运动轨迹主要在猎物附近区域进行搜索,且在取食后60~75 s的搜索距离、搜索速度与取食前均存在显著差异。未饥饿状态瓢虫取食前后运动轨迹角度波动较大,无明显规律,且各停点间的曲线长度、搜索速度经t检验无显著差异。【结论】拟小食螨瓢虫成虫对猎物的搜索行为受其饥饿状态的影响。饥饿状态下,取食前为广域型搜索,取食后一段时间内为地域集中型搜索;未饥饿状态下的瓢虫取食前后的搜索行为则无明显规律,其搜索类型兼有广域和地域集中型搜索特征,具有一定随机性。     

Control of activity and regression of the silk glands in the last-larval instar of Galleria mellonella

The weight increase of silk glands in isolated larval abdomens is enhanced by brain implants which stimulate RNA and protein synthesis. It is proposed that, in intact last-instar larvae, a blood-borne factor from the brain promotes silk gland activity during the facultative feeding period. In the post-feeding larvae, some starving larvae and in isolated larval abdomens the silk glands regress. The regression is accelerated and the glands degenerate under the action of 20-hydroxyecdysone. This effect is not associated with an increase in protease and RN-ase activities. In the normal larvae, the protease activity increases gradually during the last instar to a maximum at the time of regression and drops in the degenerating glands. RN-ase activity is maintained at a high level in the fully active, regressing and degenerating glands The results indicate that regression and degeneration of the silk glands are caused by structural cell reorganization rather than by an appearance of cytolytic enzymes.     

Effects of feeding on medicinal leech swimming performance

The locomotor system of sanguivorous leeches is presented with a unique challenge: how to maintain mobility while coping with a >500% increase in body mass during feeding. A meal of this size is likely to disrupt the function of the muscular hydrostat during swimming, reducing speed and increasing predation risks. We quantified the effects of feeding to satiety on swimming kinematics, and the time course of recovery of swimming performance post-feeding in the medicinal leech Hirudo verbana . There was a 5.07 ± 0.04-fold increase in mass during feeding (mean ± sem , n =7). Despite this, leeches were able to swim immediately after feeding, reaching 27% of their pre-feeding speed. Reduced speed was a consequence of a reduction in both swimming cycle frequency and stride length to 69 and 42% of the pre-feeding values, respectively. Recovery of swimming ability was rapid, despite a prolonged increase in body mass. Fifty per cent restoration of swimming speed was achieved in c . 1 h while body mass was still 4.2-fold greater than before feeding. Rapid mass and volume reduction immediately post-feeding, and the properties of the obliquely striated swimming muscles appear to aid recovery of swimming performance. Such features that aid post-feeding recovery of mobility may have been important in the evolution of leech sanguivory.     

Biphasic perimicrovillar membrane production following feeding by previously starved Dysdercus peruvianus (Hemiptera: Pyrrhocoridae)

The development of perimicrovillar membranes (PMM) from midgut cells of starved and fed Dysdercus peruvianus was studied by using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and assays for specific enzymatic markers of the perimicrovillar membranes (alpha-glucosidase), perimicrovillar space (aminopeptidase) and microvillar membranes (beta-glucosidase). High activities of these enzymes were observed 6h post-feeding and significant production of membranes was observed at 30 h post-feeding. In the gut cells of starved insects, the rough endoplasmic reticulum was organized in concentric bundles, with a greater number of mitochondria in the cellular apex. The presence of electron dense double-membrane vesicles and the production of PMM were not observed in this condition. Thirty hours post-feeding, a disorganization of the rough endoplasmic reticulum was observed, and it was possible to see double-membrane vesicles close to the cell apex. The membrane system formation was evident with a significant development of PMM in the midgut lumen. The luminal surface of the midgut during starvation and up to 48 h post-feeding was monitored using SEM. It was demonstrated that in the starved condition, the PMM was virtually absent from gut cells, except at the base of the microvilli. At 6h post-feeding, the microvilli were already completely covered with PMM, but with a maximum of PMM formation seen at 30 h post-feeding. Signals of PMM degradation were observed 48 h after pulse feeding.     

Postprandial increases in nitrogenous excretion and urea synthesis in the Chinese soft-shelled turtle, <Emphasis Type="Italic">Pelodiscus sinensis</Emphasis>

The objective of this study was to determine the effects of feeding on the excretory nitrogen (N) metabolism of the aquatic Chinese soft-shelled turtle, Pelodiscus sinensis, with a special emphasis on the role of urea synthesis in ammonia detoxification. P. sinensis is ureogenic and possesses a full complement of ornithine-urea cycle enzymes in its liver. It is primarily ureotelic in water, and the estimated rate of urea synthesis in unfed animals was equivalent to only 1.5% of the maximal capacity of carbamoyl phosphate synthetase I (CPS I) in its liver. Approximately 72 h was required for P. sinensis to completely digest a meal of prawn meat. During this period, there were significant increases in ammonia contents in the stomach at hour 24 and in the intestine between hours 12 and 36, which could be a result of bacterial activities in the intestinal tract. However, ammonia contents in the liver, muscle, brain and plasma remained unchanged throughout the 72-h post-feeding. In contrast, at hour 24, urea contents in the stomach, intestine, liver, muscle, brain and plasma increased significantly by 2.9−, 3.5−, 2.6−, 2.9−, 3.4 and 3.0-fold, respectively. In addition, there was a 3.3- to 8.0−fold increase in the urea excretion rate between hours 0 and 36 post-feeding, which preceded the increase in ammonia excretion between hours 12 and 48. By hour 48, 68% of the assimilated N from the feed was excreted, 54% of which was excreted as urea-N. The rate of urea synthesis apparently increased sevenfold during the initial 24 h after feeding, which demanded only 10% of the maximal CPS I capacity in P. sinensis. The postprandial detoxification of ammonia to urea in P. sinensis effectively prevented postprandial surges in ammonia contents in the plasma and other tissues, as observed in other animals, during the 72-h period post-feeding. In addition, postprandial ammonia toxicity was ameliorated by increased transamination and synthesis of certain amino acids in the liver and muscle of P. sinensis. After feeding, a slight but significant increase in the glutamine content occurred in the brain at hour 24, indicating that the brain might experience a transient increase in ammonia and ammonia was detoxified to glutamine.     

Distribution and activity of a Dippu DH31-like peptide in the large milkweed bug Oncopeltus fasciatus

The milkweed bug, Oncopeltus fasciatus, is a plant feeding hemipteran. While there has been much research done on the neurohormonal control of the post-feeding diuresis in the blood-feeding hemipteran, Rhodnius prolixus, little is known about the control of the post-feeding diuresis in O. fasciatus. One of the neurohormones that may play a role in this rapid diuresis belongs to the calcitonin-like diuretic hormone (DH31) family of insect peptides. In this study we demonstrate the presence of DH31-like immunoreactivity in the central nervous system (CNS) and gut of O. fasciatus 5th instars. As well, DH31-like material was quantified and partially purified from the CNS of 5th instar O. fasciatus using reversed-phase liquid chromatography (RPLC) and monitored with an enzyme-linked immunosorbent assay (ELISA). When tested on O. fasciatus 5th instar Malpighian tubules, DH31-like peptides significantly increased the rate of secretion over saline controls. The results suggest that there is a DH31-like peptide(s) present in the CNS of O. fasciatus and that this peptide may play a role in the control of Malpighian tubule secretion.     

Excretion of proteolytic enzymes by Aedes aegypti after a blood meal.

Excretion of active proteolytic enzymes during the period of blood digestion in a mosquito has been demonstrated for the first time. The rate of excretion has been determined for both proteases and uric acid; each appears in a distinct peak. During the first half of the digestion period, when protease activity in the midgut is increasing, uric acid excretion predominates. During the second half of the digestion period, after the protease has reached its maximum in the midgut, there is considerable excretion of active protease, mainly trypsin.By sealing the anus after feeding (blood enema), it has been demonstrated that secretion of the proteolytic enzymes in the midgut actually stops when maximum activity is reached. Sealing the anus did not interfere with egg development.A model for protease secretion is suggested in which the proteolytic enzymes are induced by their substrate (globular proteins), and secretion stops when 80 per cent of the protein is digested, or the inducer is removed.     

Habitat choice in shoals of roach as a function of water temperature and feeding rate

Temperature and food availability are two important factors which affect fish growth and therefore are expected to influence habitat choice in fish. In this study, shoals of 16 juvenile roach, Rutilus rutilus , were given a choice between two chambers that differed in temperature by 1·5°C or 3°C whereas food availability was the same in both chambers (ratio 1 : 1) or higher in the colder one (ratio 4 : 1). The number of fish in each chamber was recorded for 10 min each during a pre-feeding, feeding and post-feeding period. Roach generally preferred the warmer over the colder chamber during the pre-feeding periods. Temperature had a significant effect on the distribution of fish during all three time periods whereas food availability was a significant factor only during the feeding period. The important role of temperature was emphasized further by the fact that a relatively small difference in the temperature gradient of 1·5°C had a stronger effect on fish distribution than a four times higher feeding rate during the feeding period. The implications for growth rates of such short-term decision-making of roach are discussed.     

Post-feed buzzing in the tsetse, Glossina morsitans morsitans, is an endothermic mechanism

ABSTRACT. Post-feed buzzing in Glossina morsitans morsitans Westw. causes a rise in thoracic temperature relative to the length of the buzz. As lift is proportional to the square of wing-beat frequency, which increases with temperature up to 32°C, buzzing results in an increase in the lift which the fly can produce. Heat generated by buzzing, in combination with the heat received from the host at the time of feeding, may well allow the fly to maximize lift generated in the immediate post-feeding period. Buzzing flies excrete excess water from the meal more rapidly than non-buzzing flies. It is argued that this is due to a rise in abdominal temperature. Maximized lift in the immediate post-feeding period and the rapid elimination of water from the very large blood meals taken by these flies may be expected to have strong selective advantages for the flies.     

Secretion and formation of perimicrovillar membrane in the digestive system of the Sunn pest, Eurygaster integriceps (Hemiptera: Scutelleridae) in response to feeding

In this study, development of perimicrovillar membrane (PMM) from midgut cells of starved and fed Eurygaster integriceps (Hemiptera: Scutelleridae) was studied. Three different approaches, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), marker enzymes of the PMMs (α-glucosidase), perimicrovillar space (aminopeptidase), and microvillar membranes (β-glucosidase) were used. Activities of these enzymes were remarkably low in the starved insects. Moreover, microscopic observations revealed that PMM is not present in the starved insect. Activities of enzymatic markers increased at 5 h postfeeding, and TEM and SEM observations showed the formation of PMM as well as migration of double-membrane vesicles from center of the columnar cell to the cell apex. The highest PMM was observed at 20 h postfeeding which at this time marker enzyme activity, such as α-glucosidase activity, was high, too. Thus, at 20 h postfeeding, PMM system was evident and epithelial cells were completely covered by PMM system. After 20 h postfeeding, presence of the fine holes in PMM started to be seen and at 40 h post-feeding, observation showed degradation of PMM system. Thus, it could be concluded that PMM in E. integriceps is secreted by epithelial cell membrane when needed and its secretion and formation is regulated by feeding. This system was not present in the starved insects as its development takes place at 5 h postfeeding.     

Increasing sodium bicarbonate level in high-concentrate diets for heifers. II. Effects on chewing and feeding behaviors

Four Holstein heifers (264 ± 12 kg initial BW) were used in a 4 × 4 Latin square design with 21-day experimental periods to determine the effect of increasing levels of sodium bicarbonate (BICARB) (0%, 1.25%, 2.5% and 5%, of concentrate dry matter (DM) basis) on chewing and feed intake behavior when fed high-concentrate diets. Concentrate (13.41% CP, 13.35% NDF) and barley straw were fed once a day at 0830 h ad libitum. Feed bunks placed on scales and video recording were used to measure 24-h feed intake and chewing behavior, respectively. The patterns of feeding behavior (feed intake, meal size and length) and chewing behavior (eating, ruminating and total chewing) were studied by dividing the day into 12 intervals of 2-h each, beginning at feeding (interval 1 through 12). Number of meals per day and eating rate decreased linearly with increasing buffer level, but meal length increased linearly. No treatment effects were observed in sum of daily meal lengths or average meal size. The treatment × interval interaction was significant on meal size, length and feed intake. The size and length of those meals occurring during the 4 h post-feeding increased linearly. However, meal size tended to decrease in the evening between 8 and 12 h, whereas feed intake decreased linearly from 6 to 10 h and from 12 to 14 h post-feeding. Buffer concentration did not affect the percentage of time spent ruminating, eating or drinking per day but the buffer level × interval interaction was significant. Time spent eating expressed as min per kg of DM or organic matter (OM) intake increased linearly with buffer levels. Proportion of time spent eating increased linearly during the intervals between 0 and 4 h post-feeding. Time spent ruminating decreased linearly during the 2 h post-feeding, and also in the evening from 12 to 14 h, and at night from 18 to 22 h post-feeding, but the effect was quadratic between 8 and 10 h when intermediate buffer levels showed the greatest ruminating time. Time spent drinking decreased linearly from 6 to 8 h but increased during the 2 h following feeding and from 10 to 12 h post-feeding. Daily eating rate and meal frequency decreased linearly as the buffer level increased, but average meal size and daily chewing times were not affected. However, significant time of the day × buffer level interactions were observed for feed intake, meal size and length and chewing behavior.     

EFFECTS OF FASTING AND FEEDING ON SERUM UREA AND SERUM CREATININE LEVELS IN POLAR BEARS

Polar bears were held in captivity and fasted for an average of 38 d prior to being fed for three days. Blood samples were collected prior to feeding and then at one and three days post-feeding in 1984 and at one, four, and seven days post-feeding in 1985. The ratio of serum urea to serum creatinine varied significantly in 1984, rising from a pre-feeding mean of 11.0 (SE = 2.6) to 32.0 (SE = 3.2) on the first day post-feeding and then dropped to 22.8 (SE =3.2) in the last sample. In 1985, the ratio of serum urea to serum creatinine increased from a pre-feeding mean of 15.8 (SE = 2.3) to 61.2 (SE = 10.6) after three days of feeding and dropped to a mean of 29.2 (SE = 5.1) seven days after feeding ended. Serum urea levels varied over the study period in both years. No significant variation in serum creatinine levels was found in 1984, but in 1985, serum creatinine levels demonstrated significant variation, declining from the pre-feeding mean of 1.83 mg/dl (SE = 0.29) to 0.96 mg/dl (SE = 0.12) in the last sample.
The findings suggest that polar bears can have a low serum urea to serum creatinine ratio, similar to that found in hibernating black bears, or higher ratios after feeding. Polar bears can rapidly return to a fasting serum urea to creatinine ratio after food is withheld. Polar bears may demonstrate urea conservation, similar to that found in black bears, and may be able to move between a fasting and a feeding metabolism based on food availability throughout the year, an adaptation to life on the labile sea ice.     

The effect of delayed feeding on the post-feeding behaviour of sows

Previous research into oral persistence in pigs has shown that the relationship between motivation and performance of stereotypy is not a simple one, and that non-specific motivational factors such as arousal may be important. For chronically food-restricted sows the time before food arrives is characterised by increasing excitement and arousal which may be carried over into the post-feeding period facilitating the performance of persistent oral behaviour. To investigate this possibility, arousal was manipulated by delaying feeding. Five and 15 min delays were used and sows experienced delayed feeding 1 day in every 4. Principal components analysis (PCA) was used to group the behaviour data into two factors, ACTIVITY/CHEW and NOSE/ROOT/PEN and these scores were then analysed using ANOVA as well as the appropriate individual behaviours. The delay of feeding increased the rate of eating, presumably reflecting increased arousal (P<0.05). ACTIVITY/CHEW scores were highest in 5 min delay sets, and an interaction between day of set and delay length indicated that ACTIVITY/CHEW scores peaked on different days within a set (P<0.05). Time spent chewing was highest on the day of delay (P<0.05), while standing was highest in days 1 and 2 post-delay (P<0.05). The NOSE/ROOT/PEN scores were lower on the day of delay than on other days (P<0.05), and were lowest in the first delay set than in sets later in the trial (P<0.01). It appeared that increasing arousal in the pre-feeding period does affect activity and oral behaviours in the post-feeding period. However, some of the effects appeared in a more extended and diffuse manner, perhaps due to the general disturbance created by the experimental regime and the sows' experience of long-term food restriction.     

Post-feeding bubbling behaviour in fluid-feeding Diptera: concentration of crop contents by oral evaporation of excess water

Abstract During long post-feeding periods, adult tephritid flies (and apparently other non-blood feeding Diptera and even Hymenoptera) engage in behaviour consisting of oral extrusion and aeration of liquid droplets of varying size (‘bubbling’), proboscis pumping, and occasional deposition of regurgitate on the substrate that is followed by subsequent re-ingestion. Unlike evaporative cooling, which occurs in some insects when heat-stressed, these regurgitation behaviours take place regularly at moderate temperatures. To our knowledge, the significance of these behaviours has not been studied. We suggest that through bubbling behaviour, fully gorged Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) flies eliminate excess water by evaporation to concentrate nutrients suspended in dilute solution, and release crop volume to allow resumption of fluid feeding or minimize the water load while foraging for other resources. Fly weights were measured continuously during pre- and post-feeding periods and in relation to occurrence of regurgitation behaviours. Fly weight losses during pre-feeding were an order of magnitude lower than post-feeding weight losses when flies exposed regurgitated liquid crop contents to air. During a bout of droplet extrusions, lasting on average 23 min, weight loss averaged 66% of the weight of liquid ingested by a fly in the preceding meal. Fly weight loss while bubbling was significantly correlated with duration of bubbling, temperature and relative humidity during post-feeding, and initial fly weight (adj. R² = 0.95). Fly age, volume of liquid ingested and rate of pre-feeding weight loss did not significantly improve predicted weight loss through bubbling. Findings are discussed in relation to other behaviours adopted by fluid-feeding insects to eliminate excess water.     

The role of the frontal ganglion and corpora cardiaca/corpora allata complex in post-feeding weight loss in adult Heliothis zea

Abstract A post-feeding diuretic response has been observed in adult Heliothis zea (Boddie) (Lepidoptera: Noctuidae). 2-day-old starved adults which were allowed to feed to repletion on a 10% (w/v) sucrose solution lost 49.1% (females) and 85.8% (males) of the weight of the ingested meal during the first hour following feeding. Ligation between head and thorax or frontal ganglionectomy, when performed immediately following feeding, each resulted in a significant and permanent reduction in this normal weight-loss. Injection of homogenates of the corpora cardiaca/corpora allata (CC/CA) complex into non-ligated insects immediately after feeding also reduced significantly the post-feeding weight-loss, but this inhibition was transient and disappeared after 1 h. Dissection and weighing of the crop from either ligated, frontal ganglionectomized, or CC/CA-injected insects confirmed the crop as the predominant site of fluid retention in each case. We suggest that a soluble antidiuretic factor from the CC/CA acts in conjunction with the frontal ganglion to control the rate of crop emptying and subsequent diuresis by regulating the volume of ingested fluid that is passed into the haemolymph from the crop/midgut.     

Evidence for CRF-like and kinin-like peptides as neurohormones in the blood-feeding bug,Rhodnius prolixus

In Rhodnius prolixus, the rapid post-feeding diuresis is under neurohormonal control. While serotonin has been demonstrated to be a diuretic neurohormone [J Exp Biol 156 (1991) 557], a peptide is also known to be involved. Previously, we have demonstrated the presence of corticotropin releasing factor (CRF)-like and kinin-like peptides in the central nervous system (CNS) of 5th instar Rhodnius [J Exp Biol 202 (1999) 2017; Peptides 22 (2001) 161]. These peptides are present in neurohemal sites of the corpus cardiacum and are co-localized in neurohemal sites on abdominal nerves. While various CRF-like peptides have been demonstrated to increase Rhodnius Malpighian tubule secretion the kinin-like peptides do not [Peptides 23 (2002) 671]. The kinin-like peptides do however, increase hindgut contraction which may contribute to the rapid post feeding diuresis by the mixing of hemolymph and/or hindgut contents and the removal of wastes. The presence of these peptides in neurohemal sites suggests that they could be released into the hemolymph and act as neurohormones.We have used immunohistochemical techniques and radioimmunoassay (RIA) to demonstrate qualitative and quantitative changes of CRF-like and kinin-like peptides in the CNS associated with feeding. As well we have examined Malpighian tubule secretion in response to assays of hemolymph from unfed and fed insects. Hemolymph was also partially purified by Sep-Pak and HPLC and the fractions assayed for kinin-like immunoreactivity and the ability to stimulate Malpighian tubule secretion. The results suggest that both kinin-like and CRF-like peptides are neurohormones in Rhodnius, released in response to feeding.     

The rapid adjustment of renal sodium excretion to changes in dietary sodium intake in sheep

The rapidity with which the kidney alters sodium excretion (ENa) in response to changes in dietary Na was studied in Merino sheep by analyzing hourly ENa for three control days, and then for three days after a change in Na intake. On a control diet of 117 mmol Na, sheep had a pre-feeding ENa of 3.5 mmol/hr., a striking post-feeding natriuresis that began 2 hours after feeding (less than 0.01), peaked at 4 hrs. and then declined to pre-feeding levels 7 hrs. after feeding. When in balance on a high Na diet the feeding of a low Na meal resulted in marked depression of ENa within 4 hours after feeding. On a low Na diet, a 100 mmol Na meal resulted in an increase in ENa within 4 hours but a 50 mmol Na meal did not. Thus, the sensitivity of post-feeding natriuresis is between 50 and 100 mmols Na. As post feeding natriuresis is a naturally occurring physiological event it should provide a useful paradigm for the investigation of mechanisms controlling Na balance.     

The relationship between time of feeding and aggression in a group of captive hamadryas baboons

The relationship between time of feeding and aggression in a one-male unit of captive hamadryas baboons was studied to determine if feeding once a day, at a designated time and in measured amounts leads to a high level of aggressive behavior. The performance of maintenance behaviors did not differ between pre-feeding and post-feeding periods, however, aggressive behavior significantly decreased after feeding.     

Changes in plasma volume and haematocrit in intact and splenectomized sheep during feeding.

Changes in jugular haematocrit during daily 2-h feeding periods in trained sheep with and without spleens were compared with changes in the concentration of the plasma tracer radio-iodinated human serum albumin. Jugular haematocrit was increased by 16% in intact sheep and 9% in splenectomized sheep 20 min after they started to eat dry rations. The dilution of tracer in plasma, studied after mixing in the vascular system had been completed, showed four phases. Phase 1 was the rate of removal of tracer in the period before eating began. Phase 2 was the sudden increase in plasma radioactivity that occurred in the first 20 min of eating, indicating a loss of plasma from the circulation. Phase 3 was the decrease in tracer concentration during the remaining feeding period and phase 4 was a post-feeding phase, characterized by a slower rate of decrease of tracer than during phase 3, implying that there was significant recycling of tracer during this phase. The sudden increase in plasma radioactivity, initiated by the onset of feeding, represented a reduction in plasma volume of 10-12%. Minimum plasma volume coincided with peak haematocrit values. The reduced plasma volume accounted for the increased haematocrit in splenectomized sheep, but only accounted for about half of the increase in intact sheep. The residual increase in haematocrit in intact sheep was most likely the result of splenic contraction.