Relative Importance of Sex,Pre-Starvation Body Mass and Structural Body Size in the Determination of Exceptional Starvation Resistance of Anchomenus dorsalis (Coleoptera: Carabidae)

In nature, almost all animals have to cope with periods of food shortage during their lifetimes. Starvation risks are especially high for carnivorous predatory species, which often experience long intervals between stochastic prey capturing events. A laboratory experiment using the common predatory carabid beetle Anchomenus dorsalis revealed an exceptional level of starvation resistance in this species: males survived up to 137 days and females up to 218 days without food at 20°C. Individual starvation resistance was strongly positively affected by pre-starvation body mass but only slightly by beetle structural body size per se. Females outperformed males even when the effect of gender was corrected for the effects of structural body size and pre-starvation body mass. The better performance of females compared to males and of beetles with higher relative pre-starvation body mass could be linked to higher fat content and lean dry mass before starvation, followed by a greater decrease in both during starvation. There was also a difference between the sexes in the extent of body mass changes both during ad libitum feeding and following starvation; the body masses of females fluctuated more compared to males. This study stresses the need to distinguish between body mass and structural body size when investigating the ecological and evolutionary consequences of body size. Investigation of the net effects of body size and sex is necessary to disentangle the causes of differences in individual performances in studies of species with significant sexual size dimorphism.     

Sexual dimorphism in desiccation responses of the sand scorpion Smeringurus mesaensis (Vaejovidae)

The osmoregulatory and respiratory responses of male and female Smeringurus mesaensis (Vaejovidae) to prolonged desiccation were measured. No significant effect of sex on mass-loss rates (MLRs) was found. Still, females maintained their haemolymph osmolality when desiccated to 10% mass loss, whereas that of males increased significantly after loss of as little as 5% of initial mass. Females had a 3-fold larger hepatopancreas, significantly higher hepatopancreas water content and higher metabolic rates when adjusted to hepatopancreas-free dry mass. Thus, females not only store more water in the hepatopancreas but also mobilise it to the haemolymph at a higher rate during desiccation, thus maintaining haemolymph osmolality. Gas exchange rates of both males and females decrease as desiccation progresses. An initial respiratory exchange ratio (RER) of approximately 0.9 is followed by a significant increase at mass loss levels of 7.5% and higher. RER values greater than 1.0 may result from partial shift to anaerobic catabolism, which allows closure of the book lung spiracles for longer duration, thus minimising respiratory water loss. The effects of gas exchange rates on rates of water mobilisation between body compartments and water loss to the environment suggest a trade-off between maintaining osmotic stability and conserving body water stores under stressful conditions.     

Humidity responses and water balance of riparian species of Bembidiini (Col., Carabidae)

Abstract. 1. The humidity responses of Asaphidion pallipes (Duftschmid) and Bembidion spp. were studied at various temperatures in choice chambers.
2. Several species initially showed a hygropositive or indifferent response. Other species had a hygronegative reaction which later changed to a hygropositive one. The duration of the hygronegative reaction varied with species, age, temperature and relative humidity. B.litorale (Olivier) and B.semipunctatum (Donovan) change response when they have lost 8–9% of their initial body weight as water.
3. The survival time of species of Bembidion under dry conditions was short compared with that reported for many other carabid beetles. Newly emerged adults of B.argenteolum Ahrens that had been kept away from sand for 3 weeks had lower transpiration rates than any other species. Young adult Bembidion had lower transpiration rates than those in the breeding phase, larvae and dead adults. Transpiration rate appeared to be inversely proportional to the relative humidity whereas there was a non-linear increase in weight loss with increasing temperature.
4. The species gain most water by drinking and/or from food.
5. There was no correlation between humidity response and transpiration rate or ability to tolerate dry conditions of the species. There was, however, a correlation between behaviour/habitat affinity and humidity response. Diurnal species, living in sandy or silty, half shady-exposed habitats had an initial hygronegative response, whereas those which hide among gravel/stones, leaves or vegetation were indifferent or hygropositive.     

Water loss and metabolic water in starving Argas reflexus nymphs (Acari: Argasidae)

Basic components of the water balance were determined in A. reflexus unfed second instar nymphs kept at 30 degrees C and different relative humidities in darkness. At 2.5% and 32.5% RH, A. reflexus survived for 170+/-60 and 246+/-71 days, respectively. At 56%, 75.5% and 96.5% RH, the experiment was terminated after 168 days without any mortality. The initial water content of hydrated A. reflexus kept at 85% RH was 70.3+/-1.8% while the water content was close to 50% in ticks dehydrated at /=56% suggesting that A. reflexus increased its oxidative metabolism under dehydrating conditions and thus delayed lethal dehydration. Interestingly, the dry mass of dead ticks was almost identical irrespective of whether the ticks had previously been kept at 2.5% and 32.5% RH, i.e. irrespective of their different survival periods. This raises the question whether the ticks had died by dehydration or by exhaustion of energy reserves.     

Responses to starvation in a mantis,Paratenodera angustipennis (S.)

Summary Survival period, pattern of decrease in body weight and metabolic rate under starvation conditions were examined to clarify responses to starvation of a predatory insect, the mantis, Paratenodera angustipennis (S.). (i) The average survival period in starved condition was the shortest in the 1st instar larvae (5.4 days) and the longest in the adults (15.0 days for males, 26.7 days for females). (ii) The body weights of the 3rd and the 5th instar larvae decreased almost linearly during fasting period, whereas those of adults decreased greatly during the initial 5 days, and then exhibited little further decline until their death. (iii) The carbon dioxide production by the adult mantids in the dark condition at constant 26°C was measured by the improved Boysen-Jensen's method. There was a linear relationship between the body weight and the metabolic rate per individual on a double logarithmic scale, and the regression coefficient b was 0.806. (iv) The metabolic rate per individual was greatest at satiation, but the rate per unit weight was maximum on the 5th day after satiation when the food had been just digested completely, and both decreased with the progress of starvation. (v) Based on the above mentioned results, properties of P. angustipennis as a predator were discussed.     

Postembryonic development and food consumption of Dichroplus elongatus Giglio-Tos and Dichroplus maculipennis (Blanchard) (Orhtoptera: Acrididae: Melanoplinae) under laboratory conditions

Dichroplus maculipennis (Blanchard) and D. elongatus Giglio-Tos are two of the most important melanoplines in Argentina, both ecologically and economically. The postembryonic development and forage loss (consumption of Bromus brevis Ness + fallen material) caused by older nymphs (instars IV, V, VI) and adults of both species were studied under controlled conditions (30oC, 14L:10D, 40% RH). Five nymphal instars were recorded in D. elongatus, and six in D. maculipennis. Total nymphal development was similar in both species (D. elongatus: 32 ± 0.70 days; D. maculipennis: 34.5 ± 0.37 days). Daily consumption increased from nymphal instars to pre-reproductive adult stage. In both species, pre-reproductive females had higher consumption rates than other stages considered (D. elongatus: 30.6 ± 0.56 mg dry weight/day; D. maculipennis: 48.7 ± 0.74 mg dry weight/day). In the reproductive stage, consumption decreased significantly in both sexes. When feeding, D. maculipennis let some plant material to drop, increasing total loss. The percentage of fallen material was greater in reproductive adults, representing 3.9% and 2.9% of the total daily loss for males and females, respectively. Females and males of D. maculipennis were heavier than those of D. elongatus (P < 0.05), and daily consumption was significantly higher (P < 0.05). Regardless sex and reproductive status, adults of D. maculipennis consumed 29.1 ± 0.64 mg dry weight/day on average, while one of D. elongatus 20.0 ± 0.3 mg dry weight/ day.     

Intracellular Substrates for Endogenous Metabolism During Long-Term Starvation of Rod and Spherical Cells of Arthrobacter crystallopoietes

Cells of Arthrobacter crystallopoietes, harvested during growth as spheres and as rods, were starved by shaking at 30 C in phosphate buffer for 30 days, during which time they maintained 100% viability. Changes in cellular components and the activity of specific enzyme pathways were monitored. A glycogen-like polysaccharide comprised 40% of the dry weight of growing spherical cells and 10% of the dry weight of rod cells. This material was utilized at approximately the same rate, on a percentage basis, during starvation of both cell forms. The rods degraded intracellular protein at approximately twice the rate of the spheres. At the end of 30 days, the rods had degraded 40% and the spheres 20% of their initial content of protein. Ribonucleic acid (RNA) was degraded significantly more rapidly in the rods. After 30 days starvation, 85 and 32% of the initial RNA of rods and spheres, respectively, had been depleted. Magnesium ion followed this same general pattern; the rods lost 65% and the spheres 45% of their initial content during 28 days of starvation. Deoxyribonucleic acid increased by 20% during the first few hours of starvation of both cell forms and then remained constant. The ability of glucose-, succinate-, and 2-hydroxypyridine (2-HP)-grown cells to oxidize glucose remained constant during 14 days of starvation. The ability of succinate-grown cells to oxidize succinate decreased rapidly during the first few hours of starvation to a rate which remained constant for 14 days. Cells adapted to growth on 2-HP completely lost their ability to oxidize this substrate after 3 days starvation.     

Energy Provision,Tissue Utilization,and Weight Loss in Prolonged Starvation

Daily weight loss measurements in 76 fasting, obese patients (58 females, 18 males) have shown a characteristic pattern of rapid loss initially (up to day 14) followed by a slower but uniform reduction in weight. There were significant sex differences. Measurements of tissue breakdown showed that the initial rapid weight loss was due to the continuing utilization by the nervous system of glucose derived from lean tissue. This requirement fell noticeably from the second week of starvation. Irreversible fluid elimination also contributed to the initial phase of rapid weight loss. Fat remained the primary source of energy throughout starvation and in established fasting (more than 14 days) contributed 96% of that requirement.     

饥饿胁迫对麦长管蚜有翅成蚜能量物质含量的影响

【目的】分析饥饿胁迫下麦长管蚜Sitobion avenae(Fabricius)的能量物质含量变化,以期从生理生化角度为蚜虫饥饿胁迫下的能量适应机制提供依据。【方法】以取食小麦苗的麦长管蚜为对照,测定饥饿胁迫下麦长管蚜有翅成蚜的鲜重、干重、含水量、可溶性糖、糖原、总脂和可溶性蛋白质含量变化,通过这些不同生化物质含量之间的相关关系,分析饥饿胁迫下麦长管蚜的能量代谢特点。【结果】麦长管蚜饥饿组鲜重和干重均低于羽化后同一时间取食个体,前者范围分别为5.30~8.73和1.67~3.10 mg/20头,后者分别为7.93~8.73和2.53~3.10 mg/20头;饥饿组和取食组含水量范围分别为63.16%~71.76%和63.25%~67.32%,除羽化后1 d外,饥饿组含水量均高于羽化后同一时间取食个体;饥饿组可溶性糖、糖原、总脂和可溶性蛋白质的含量分别在6.60~11.21,0.35~10.81,18.28~30.42和12.77~33.44μg/mg鲜重之间,均低于羽化后同一时间取食个体(分别为7.53~11.21,3.66~10.81,27.53~33.63和21.54~34.43μg/mg鲜重)。饥饿3 d恢复取食后1 d,鲜重、干重、含水量和糖原含量均增加,而可溶性糖、总脂和可溶性蛋白质的含量均降低。相关分析表明,饥饿组可溶性糖与糖原、总脂或者可溶性蛋白质的含量以及可溶性蛋白质与糖原或者总脂的含量存在正相关关系。【结论】饥饿胁迫下麦长管蚜的代谢变化与其糖原、总脂和可溶性蛋白质含量降低有密切关系,通过能量物质的综合利用来适应短期饥饿胁迫。     

Elemental composition of Mysis mixta (Crustacea, Mysidacea) and energy costs of reproduction and embryogenesis under laboratory conditions

Mysis mixta were reared under laboratory conditions (temperature: 9-10 degrees C; salinity: 7 per thousand, ad libitum food). Dry weight, ash, total carbon and nitrogen content of mysids (muscle tissue, eggs, and embryos of different developmental stages) have been analyzed. We found significant variations in ash content and elemental composition during growth and maturation for both sexes. The proportion of carbon in abdominal muscle decreased gradually from juveniles with body weight of 3-4 mg (42.9%) to males and gravid females ( approximately 40.0%). The nitrogen content was relatively constant (11.4% in average) with significant differences only between juveniles (11.3%) and mature females (11.6%). In embryos, carbon and nitrogen content were highest in early stages (58.6 and 14.3%, respectively). By the end of the marsupial development, carbon had decreased to 51.4% and nitrogen to 12.6%. The C:N ratio reflected the change in somatic carbon content, and the ratio decreased 6.2% from juveniles to gravid females, indicating lipids to be an energy source during maturation and reproduction. The weight-specific female investment in reproduction increases with body size. In gravid females, intersegmental growth during brooding period was observed, while males appear to store energy only for copulation and die after mating. Ontogenetic variation in body composition has implications for elemental budgets of M. mixta, its value as prey for fish and in modeling energy and nutrient cycling.     

黑水虻幼虫的耐饥力及饥饿幼虫复食后的生物学特性

【目的】旨在明确黑水虻Hermetia illucens幼虫的耐饥力及饥饿幼虫复食后的发育、生殖力等生物学特性,为评估饥饿对黑水虻后续发育的影响并指导生产实践提供依据。【方法】将不同日龄或不同体重黑水虻幼虫进行不同时长的饥饿处理,测定和分析其耐饥力与日龄、百头重的关系;对7日龄幼虫进行不同时长的饥饿处理后再复喂,测定不同饥饿时长对其预蛹出现时间、总预蛹率、预蛹重、成虫繁殖等的影响。【结果】黑水虻幼虫饥饿后的半数致死时间(LT₅₀)与日龄成指数关系,与体重呈线性相关。7日龄幼虫的耐饥力较强,LT₅₀超过了50 d,饥饿30 d时存活率仍然达到了95%。百头重小于0.5 g的个体,其LT₅₀小于30 d;百头重在2～2.5 g的个体,其LT₅₀在45～70 d。幼虫超过8日龄时或百头重超过4.5 g时,多数个体在饥饿5 d时就提前进入了后续发育阶段。7日龄幼虫饥饿40 d内复食,其预蛹率未受到影响,但预蛹重显著增加;短期饥饿(0～10 d)对其成虫产卵量无显著影响,长期饥饿(30～40 d)使其成虫产卵量显著下降;饥饿长达30 d以上时,卵孵化率也显著降低。【结论】本研究明确了不同体重或不同日龄的黑水虻幼虫都具有一定的耐饥力;饥饿幼虫复食后预蛹重显著增加。     

Population features of Microphrys bicornutus Latreille, 1825 (Brachyura, Majidae) from Isla Margarita, Venezuela

The aim of this study is to characterize the population biology (sex ratio, size structure, relative growth of reproductive characters and realised fecundity) of the crab Microphrys bicornutusfrom Isla Margarita, Venezuela. Nearly 100 crabs were collected and fixed monthly during 1998. In the laboratory, crabs were sexed and measured: maximum carapace length, chelae length, chelae and abdomen width for females and first pleopod length for males. Additionally, 96 ovigerous females were collected to determine fecundity. The following measurements were taken for each female: body wet weight (BWW), body dry weight (BDW), egg wet weight (EWW), egg dry weight (EDW) and number of eggs (NE). The following determinations were made: relative fecundity (RF) = NE/BDW and reproductive output (RO) = (EDW/ BDW) × 100. Relative size at the onset of maturity (RSOM) was calculated as minimum ovigerous female/female's maximum size. The results indicate that the sex ratio is nearly 1:1 during the entire year. Ovigerous females and moulted males and females were observed throughout the year. Size frequency distribution and size at the onset of sexual maturity, estimated by relative growth of the sexual secondary characters and RSOM value, differed from those estimated in studies done in Jamaica and Buchuaco, Venezuela.     

Decrease in respiratory rate in a wolf spider,Pardosa astrigera (L. Koch), under starvation

Effects of starvation on the suryival period and the respiratory rate in adults of a wolf spider, Pardosa astrigera (L. Koch ), were investigated. The spiders used were divided into four groups: well-fed, starved and two limited food groups; in the latter two, each spider was supplied with one leafhopper every second or third day. Adult males and females of P. astrigera could survive for a long time; 28.8±2.7 days and 54.4±18.9 days, respectively, without any food. The longevities shown here were 73.8% for males and 78.6% for females of those of well-fed spiders, indicating that P. astrigera adults have a strong tolerance to starvation. The respiratory rate of well-fed adults showed no tendency to increase or decrease with their aging; the mean respiratory rates were 4.86×10⁻⁴ mg CO₂/mg f.w. (fresh body weight)/hr for males and 3.80×10⁻⁴ mg CO₂/mg f.w./hr for females. The respiratory rates of starved spiders increased during the first two days of starvation but decreased markedly from the third to the twelfth day, and thereafter retained an almost constant level for each sex. The mean respiratory rates after the twelfth day of starvation were 2.49×10⁻⁴ mg CO₂/mg f.w./hr for males and 2.76×10⁻⁴ mg CO₂/mg f.w./hr for females; these values were respectively 48.4% and 63.0% of those prior to starvation. The fresh body weight of starved spiders decreased linearly with time but the rate was small. The respiratory rates of the limited food groups tended to decline with time and thereby their weight losses were minimized. The decrease in the respiratory rate under starvation was considered not to be due to spider exhaustion or senescence but due to an intrinsic change in behaviour and/or metabolism, because when the spiders were supplied with ample food for five days after starvation, the respiratory rate and the body weight rapidly recovered to near the levels prior to starvation. It is suggested that starved spiders use a higher ratio of fat as catabolic substrate than normally fed or satiated ones. Feeding strategies of poikilo-therm predators are discussed.     

Humidity‐controlled cold storage of Neoseiulus californicus (Acari: Phytoseiidae): effects on male survival and reproductive ability

Humidification can suppress water loss from an organism and has great potential for improving the cold storage of short‐lived arthropods, such as predatory mites. The effectiveness of humidity‐controlled cold storage was recently verified for Neoseiulus californicus (McGregor) females but was not examined for males. Combining both males and females in one storage protocol might increase the predator population because it would enhance the opportunity for multiple mating, which is necessary for females to maximize their egg production. Newly emerged adult males were stored at an air temperature of 5°C and relative humidity (RH) of 100% or 80%. The median survival time (LT₅₀) was 32 days at 100% RH and 14 days at 80% RH; the survival curves differed significantly. Males stored at 100% RH for 0, 10, 20 and 30 days were introduced to virgin females for mating at 25°C to evaluate their reproductive ability. The pre‐oviposition period was significantly prolonged in the females mated with males stored for ≥20 days. No negative effects of storage were observed on the oviposition period, total number of eggs or net reproduction rate (R₀) in the females mated with males stored for ≤20 days or on the mean generation time (T) for those stored for 30 days. A slight decrease in the intrinsic rate of increase (r_m) was observed in the females mated with males stored for ≥20 days. Our storage method can preserve N. californicus males for 20 days with only a minor reduction in their survival and reproductive ability.     

Feeding behaviour, digestive physiology and lipid content in macropterous females of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae)

Abstract. Macropterous females of Pyrrhocoris apterus (L.) reared under short-day conditions (LD 12:12 h) were analysed for temporal patterns of feeding and drinking behaviour, activities of digestive enzymes in the gut, and lipid and glycogen content in the haemolymph and fat body. Peaks of drinking activity were recorded at days 3, 7 and 10 during the first 14 days after imaginal ecdysis. Feeding activity peaked on the third day, ceasing completely after the fourth day of adult life. Esterase, protease, amylase and aminopeptidase activities exhibited the highest overall activity in the first days after imaginal emergence; then enzyme activities decreased. In the fat body, the content of lipids was highest on day 5, then a decrease of about 40% was observed at day 14; the amount of glycogen was highest on day 1 at 11 μg of glucose equivalents/mg of fat body, then decreased to 2 μg at day 14 after the imaginal moult. In the haemolymph, the lipid content rose until day 8 when it reached almost 0.3 μmol/μl; at day 14 the value was slightly lower. The association of fasting with reproductive arrest in macropterous females of P. apterus, accompanied by a decrease in digestive enzyme activities and a mobilization of lipid reserves from the fat body, was demonstrated.     

Physiological changes during colony establishment in the termite Hodotermes mossambicus (Hagen): Water balance and energy content

The changes in dry mass, wet mass and energy content were determined during the establishment of the incipient colony. The winged reproductives of H. mossambicus are weak fliers. It is postulated that the alates compensate for the large quantity of reserve material by reducing their body water. The wet mass of both males and females increased significantly (twice original mass) from emergence until the first larvae appeared which tends support to this view. Furthermore, although the termites maintained in groups imbibed water, it is also clear that the reproductives, as long as they remain social, maintain the same low body-water content. This desiccated physiological condition appears to be and adaptation which assists flight and dispersal. In contrast with sterile eggs, fertile eggs absorbed water during development. The paired females (normal and homosexual) maintained the same energy/unit wet mass from egg production until the first workers appeared. Thus the possibility exists that the hydrophobic reserves (e.g. triglycerides) were converted to the hydrophilic reserves (e.g. carbohydrates). The same applied to the eggs and offspring.The changes in dry mass, wet mass, body water and energy content of females per unit of eggs (specific mass) produced were 0.005, 8.696, 21,276 and 12.820 respectively. The small specific dry mass value can probably be ascribed to the use of small amounts of glycerides and the increase in dry mass by the conversion from relatively light and “compact” glycerides to relatively heavy and “bulky” glycogen.Females utilised far more dry mass and energy in comparison to males to survive until the first workers appeared. Wet mass, body water and energy used in rearing of the offspring shows clearly that males made a larger contribution to the water and energy requirements of the offspring.     

Coping with resource variation: Effect of constant and variable intervals between feeding on reproductive performance at first spawning of female three-spined sticklebacks

Female three-spined sticklebacks Gasterosteus aculeatus exposed to spring conditions (14) C and a photoperiod of 16L: 8D), and fed 6% of initial body weight per day of enchytraeid worms (controls) over 56 days, or either at regular 3-day or variable 1–5-day intervals between feeds, did not differ significantly in the proportion spawning (72%), in time to first spawning (24·5 days), in fecundity at first spawning (34) or in egg diameter (1·4 mm) at first spawning. There was no significant effect of feeding regime on lipid concentration of females immediately after first spawning (18·8% dry weight), but the experimental females had a slightly lower dry matter content and lower fresh and dry liver weight than controls. Eggs of females on the variable-interval regime had a higher lipid content than eggs from other groups. Days to spawning was correlated inversely and fecundity positively with initial length. Females adjusted their food intake to compensate for short periods of food deprivation, allowing them to maintain their reproductive performance at first spawning.     

Ripe pollen carbohydrate changes in Trachycarpus fortunei: the effect of relative humidity

Pollen of the palm Trachycarpus fortunei was kept at 25°C and relative humidities (RH) of 20, 55 and 98%. Changes in viability, water content and carbohydrates were measured over 2–17 days. Water content remained almost constant at 20 and 50% RH and increased dramatically at 98%. Pollen viability and germination rate remained almost constant over 14 days at 20% RH and decreased to about 2% after 7–9 days at 55% and to even less at 98% RH. Although the three experimental conditions were constant, qualitative and quantitative variations in pollen carbohydrates were recorded, even after pollen had lost its viability. The quantities of mono-, di- and polysaccharides varied with the period of pollen storage at the various RH. The greatest changes in glucose, fructose and sucrose content were recorded at 55 and 98% RH. At these relative humidities, maximum glucose and fructose content and minimum sucrose content occurred at maximum water content. Starch was not present in mature pollen but appeared and peaked after 7–9 days of pollen storage at 55 and 98%. Appearance of starch coincided with an increase in pectin content. PAS-positive cytoplasmic polysaccharides showed an increasing trend at 20% RH. A relation was found between pollen viability, water content and monosaccharide content. Pollen viability and germination capacity remained high at 20% RH for 14 days. At this relative humidity, pollen water, glucose and fructose contents remained almost constant, while sucrose reached its maximum value. The fluctuations of more complex carbohydrates (starch, pectins and PAS-positive cytoplasmic polysaccharides) were less easy to interpret. Changes observed under experimental conditions could simulate processes occurring in nature during pollen presentation and dispersal.     

Effect of starvation and desiccation on the water balance and humidity response of adult Oryzaephilus surinamensis (Coleoptera: Cucujidae)

The water content, dry matter content, and humidity response of adult Oryzaephilus surinamensis were determined after the beetles had been starved at 30 ± 1° and <5% RH for 0, 12, 24, 36, 48, or 72 hr. Humidity response was determined in alternative chambers in which the beetles were presented a choice between 2 relative humidities.Beetles which had been starved for 48 hr showed a hygropositive response to all the humidity pairs presented (0–40, 10–50, 30–70, 60–100% RH). The response was stronger in males than in females but did not vary in intensity with the position of the alternative on the RH scale.The response to alternatives of 60 and 100% RH, which gradually changed from hygronegative to hygropositive as the beetles were starved and desiccated, was correlated both with water loss and with loss of dry matter. Providing water to beetles that had been starved and desiccated for 48 hr caused a reversal of their response from hygropositive back to hygronegative.

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Zusammenfassung Wassergehalt, Trockenmasse und Verhalten zur Feuchtigkeit erwachsener Oryzaephilus surinamensis wurden bestimmt, nachdem die Käfer 0, 12, 24, 36, 48 oder 72 Std lang bei 30 ± 1° und <5% rel.LF gehungert hatten. Die Feuchtereaktion wurde in Alternativ-Wahlkammern geprüft, in denen den Käfern die Wahl zwischen zwei rel.LF geboten wurde.Der Gewichtsverlust während Hunger und Austrocknung resultierte aus dem Verlust sowohl von Wasser wie von Trockensubstanz, doch bleibt das Verhältnis von Wasser zu Trockensubstanz im wesentlichen konstant.Die Feuchtereaktion nicht ausgetrockneter Käfer variierte in Richtung und Intensität mit dem Geschlecht und mit der Lage der alternativ gebotenen LF-Stufen. Nach 48stündigem Hungern und Wasserentzug zeigten Männchen wie Weibchen eine hygropositive Reaktion gegenüber allen zur Wahl gestellten LF-Paaren (0–40, 10–50, 30–70, 60–100% rel.LF). Die Reaktion war bei den Männchen stärker als bei den Weibchen, ihre Intensität änderte sich aber mit der Lage der Wahlpaare auf der LF-Skala nicht.Die Reaktion gegen die Alternative von 60 und 100% rel.LF, welche sich allmählich von hygronegativ zu hygropositiv verschob, wenn die Käfer Hunger und Trockenheit ausgesetzt wurden, war sowohl mit Wasserverlust als auch mit Trockensubstanzverlust korreliert. Die Reaktion der Männchen änderte sich bei Gewichtsverlust (Wasser und Trockensubstanz) etwas rascher als die der Weibchen und in beiden Geschlechtern veränderte sich die Reaktion während der frühen Stadien des Hungerns rascher als in späteren. Wurden Käfern, die 48 Std lang Hunger und Trockenheit ausgesetzt waren, wieder Wasser geboten, so schlug ihre Reaktion von hygropositiv wieder zu hygronegativ um.Die Korrelation der Feuchtereaktion mit dem Gesamtgewichtsverlust während Hunger und Austrocknung ist für Insekten-Arten von hohem Anpassungswert, die normalerweise hygronegativ reagieren. Wenn ihre Wasserreserven und die Quellen ihres Stoffwechselwassers (die Nahrungsreserven) erschöpft sind, kehrt sich ihre Feuchtereaktion um und sie suchen feuchte Gebiete auf.

     

A sexually dimorphic response in supercooling temperature, enhanced by starvation, in the lesser mealworm Alphitobius diaperinus (Coleoptera: Tenebrionidae)

The effect of starvation on supercooling temperature (SCP) distribution was investigated in adults and larvae of Alphitobius diaperinus (Coleoptera: Tenebrionidae).

The mean values for SCPs of adults fed at 20°C were −14.5±2.4°C (31 males) and −10.3±1.3°C (29 females). The distribution of the SCPs of these control adults was unimodal. No significant differences were observed in either mean wet weight or mean dry weight between males and females.

The mean values for SCPs of adults starved for 1 month at 20°C were found to be bimodal due to sexual dimorphism. The mean SCPs for males was lower (−17±2.6°C; 28) than that for females (−11.2±1.8°C; 26). No significant differences were observed in either mean dry weight or wet weight between males and females.

The SCPs of both fed and starved larvae, kept for 1 month at 20°C were −12.3±2.4°C (fed) and −18.0±2.6°C (starved).