The role of ocelli in circadian singing rhythms of crickets

ABSTRACT. . There is a direct quantitative relationship between the free-running period (r) of the circadian stridulation rhythm of male Australian field crickets, Teleogryllus commodus (Walker), and the intensity of the constant light conditions. Both T. commodus and the house cricket, Acheta domesticus (L.), show free-running periods of the singing rhythm of c. 24 h when the light intensity is 0.00025 lux. In both species the severance of the three ocellar nerves significantly slows the circadian period which is indicative of a reduced perception of the available light intensity. To test whether this period reduction is a peripheral or a central effect, electro-retinograms (ERGs) were recorded from compound eyes of male T. commodus with the ocelli fully functional, then occluded, and then uncovered. The size of the compound eye ERG is reduced by 20% with ocellar occlusion and can subsequently be fully restored to the intact level, which indicates that the ocellar effect is a peripheral one. Intensified CoCl₂ fills reveal one neurone in A. domesticus and two in T. commodus which travel from the lateral ocellar nerve out into the ipsilateral optic lobe of the compound eye. These neurones all terminate in or distal to the lobular neuropile. The data are interpreted to indicate a role for ocelli in modulating the light intensity perception of the compound eye. The final effect of the ocellar afferents is at a peripheral level prior to the input of the visual information to the optic lobe circadian pacemaker. Hence ocelli play an indirect role in circadian rhythmicity, augmenting the sensitivity of the primary photoreceptors to better perceive photic entrainment signals.     

Diel rhythms of adipokinetic hormone, fat body response, and haemolymph lipid and sugar levels in the house cricket

Abstract. The adipokinetic hormone (Grb-AKH) content in the corpora car-diaca of the house cricket, Acheta domesticus , varied during a day with two peaks in the scotophase and one peak in the photophase. There were two distinct peaks of total lipid concentration in the blood, one early in the photophase and the other early in the scotophase. Fat body sensitivity to adipokinetic hormone also varied in close synchrony with the lipid rhythm. It was not possible to attribute the rhythm of blood lipid titre unequivocally to either the rhythm of adipokinetic hormone content in the corpora cardiaca or to the rhythm of sensitivity of the fat body to the hormone. In adult crickets the blood carbohydrate titre had two peaks in adult females, one towards the end of scotophase and another in the late photophase (c. 12h apart), but a single peak at the end of scotophase was apparent in last instar larvae. The blood carbohydrate rhythm persists in DD and is therefore endogenous. Carbohydrates were not mobilized by the Grb-AKH, therefore could not be involved in the blood carbohydrate rhythm. Exposure to various day lengths caused shifts in the patterns of the carbohydrate rhythms, but imposition of a cyclic temperature regime had no effect on the rhythm.     

Daily rhythms of locomotor and demand-feeding activities in Schizothorax pelzami (Kessler, 1870)

A study was carried out to investigate the daily rhythms of locomotor and feeding activity of Khajoo, Schizothorax pelzami, a candidate species for freshwater aquaculture. Using self-feeder juvenile Khajoo were exposed to a 12/12 LD cycle to determine the rhythms of locomotor and feeding activity. The effects of feeding on locomotor and feeding activity of fish were also examined. Finally, the endogenous rhythmicity under different lighting condition tested. Fish displayed a strictly diurnal feeding and locomotor activities with 98% and 84% of the total activity occurred in the photophase, respectively. In scheduled feeding, both the L-group (fed in light) and the D-group (fed in the dark) showed a diurnal locomotor activity pattern. However, the L-group had a peak of locomotor activity near the feeding time, but the D-group had a scarce locomotor activity in the scatophase with no significant change at the mealtime. Most of the individuals display free-running rhythms when exposed to different lighting condition including, constant darkness, ultradian 45:45 min LD cycle and reversed DL photo cycle. Taken together the results of this study showed that both locomotor and feeding activity have diurnal rhythms in Khajoo S. pelzami, even fish feeding had taken place at night. Additionally, the free-running locomotor activity of the fish in the absence of external light stimuli, suggests the existence of an endogenous timing mechanism in this fish species.     

Influence of social situation on food consumption and growth in nymphs of the house cricket, Acheta domesticus

ABSTRACT. Grouped nymphs of Acheta domesticus L. (Orth., Gryllidae), which mature faster than isolated ones (Chauvin, 1958), consumed more food per milligram of body weight and converted it to body tissue more efficiently than did isolated nymphs, during the fifth and sixth instars. Grouped nymphs; usually had fewer instars than isolated ones. Feeding and growth rates did not decline after isolation part-way through development. Previously isolated females, paired at 25 days, matured as rapidly as females paired throughout development, but isolated males paired at 25 days matured no faster than males which remained isolated. Nymphs paired with an older cricket gained weight as fast as nymphs in same-age pairs in early instars, but their rate of weight gain declined in later instars, and their maturation was slower. However, all females, and males paired with older males, were heavier at emergence as adults than were adults from same-age pairs. When grouped with both an older cricket and one of the same age, females developed at normal rates, but males still showed some retardation.     

Tissue-specific changes in polyamine levels of neural tissue and fat body in adult crickets

The three major polyamines—putrescine, spermidine, and spermine—were studied and changes of their levels were examined in extracts of cerebral ganglia and fat body from adult Acheta domesticus. In nervous tissue, only spermidine and spermine were present and spermine was two- to three-fold more abundant than spermidine. The polyamine levels were high up to day 3, decreased on day 4, and then remained relatively unchanged up to day 10. The spermidine/spermine ratios decreased during the imaginal life. Higher spermidine titres were observed in the neural tissue of egg-laying females compared to virgin females. In the fat body, putrescine was detected together with spermidine and spermine. Spermidine and spermine levels were two-fold higher than putrescine. Fat body of virgin females contained two times more polyamines than male fat body. Low at emergence, spermidine and spermine concentrations peaked on days 2–3 only in females, and egg-laying was characterized by an increase of putrescine and spermidine titres. Starvation did not change polyamine contents, implying homeostatic regulation of the intracellular polyamine metabolism. These data showing tissue specific changes in polyamine levels during the imaginal life of Acheta domesticus point to the physiological importance of polyamines as possible intracellular regulators during adult insect development. © 1993 Wiley-Liss, Inc.     

Diel feeding rhythms and daily food consumption of juvenile Atlantic salmon in the River Alta, northern Norway

Atlantic salmon fry (0+) sampled from the River Alta exhibited only minor differences in stomach content weights and feeding rates throughout diel periods, but feeding rates were generally lowest at night. In contrast, salmon parr (1+ to 3+) had large diel fluctuations in stomach content weight, with the largest weights usually being recorded during the night and early morning. Accordingly, their feeding rates were highest at night. This nocturnal feeding pattern was consistent throughout all sampling occasions, and appeared to reflect a persistent feeding periodicity in the salmon parr. The daily food consumption rates of both fry and parr were highest during midsummer and decreased towards autumn.     

The effect of incubation temperatuer on oxygen consumption and organ growth in domestic-fowl embryos

1. 1.|Oxygen consumption and organ growth were measured in domestic-fowl embryos incubated at different temperatures (36, 38 and 40°C).

2. 2.|Embryonic oxygen consumption was highest at an incubation temperature of 40°C and lowest at 36°C. These differences were ascribed largely to variations in embryo size at different incubation temperatures.

3. 3.|At incubation temperatuers of 40 and 38°C, there was a plateau in oxygen consumption late in incubation, but this was not apparent at 36°C.

4. 4.|At 36°C, some tissues (e.g. eyeballs) were “spared” the repression of growth that characterized the embryo as a whole, while other tissues (e.g. stomach) incurred a much greater growth reduction. Similarly, at 40°C, stomach growth exceeded that of the embryo as a whole, while the eyeballs were largely spared the enhanced growth.

5. 5.|A simple index of tissue age revealed that, in general, there were consensual changes in tissue maturity and growth at different temperatures but that there were some disparities between growth and maturity in individual organs.

The effects of starving versus fasting on blood composition in larval house crickets

Larval crickets (Acheta domesticus) starved for 2 days during the growth phase of the instar consumed twice as much water as larvae that ceased feeding of their own accord during the last 2 days of the last instar. The behaviour of drinking more water during starvation may compensate for dry weight loss and prevent the larvae from missing the critical weight required to initiate the next moult. During starvation the plasma volume increased while the tissue volume remained constant, which produced a shift in both organic and inorganic solutes from the tissues into the plasma. During fasting there was no change in tissue or plasma volume, therefore large osmotic adjustments were unnecessary, and the only change in plasma solutes noted was a decline in plasma proteins.The titres of proteins, lipids and amino acids remained constant during 2 days of starvation, though the amount of each increased because of the increased plasma volume. Although both the titre and the amount of plasma sugar sharply declined during starvation, there was no change in the sugar titre when the insects fasted. There was some evidence that prior to fasting the programmed gradual decline in food intake matched the decline in metabolic rate, which permitted a plasma sugar stability not evident in starved larvae. The decline in plasma proteins during the fasting phase appeared due to the removal of a larval specific protein and not a direct result of fasting.     

Different circadian pacemakers control feeding and locomotor activity rhythms in European starlings

Summary In higher organisms, many physiological and behavioral functions exhibit daily variations, generated by endogenous circadian oscillators. It is not yet clear whether all the various rhythms that occur within an individual depend on one and the same pacemaker or whether different pacemakers are involved. To examine this question, the feeding and perch-hopping rhythms were measured in European starlings (Sturnus vulgaris) under light-dark cycles and continuous dim light. In dim light, the internal phase relationship between the feeding and perch-hopping rhythms changed systematically as a function of the circadian period, and the two rhythms could even dissociate and show different circadian periods in individuals with extremely long or extremely short circadian periods. Moreover, in some birds kept on lowamplitude light-dark cycles, the rhythm of feeding was synchronized 180° out of phase with the rhythm of locomotor activity. These results strongly suggest that in the European starling the feeding and locomotor activity rhythms are controlled by separate circadian pacemakers.     

Bite force,body size,and octopamine mediate mating interactions in the house cricket (Acheta domesticus)

Mating interactions are rife with conflict because the evolutionary interests of males and females seldom coincide. Intersexual conflict affects sexual selection, yet the proximate factors underlying male coercive ability and female resistance are poorly understood. Male combat outcomes are often influenced by bite force, with superior biters being more likely to achieve victory over poorer biters in a range of species, including crickets. If good performers also achieve mating success through sexual coercion, then bite force might play a role in intersexual conflict as well. We tested the capacity of bite force to influence mating interactions in house crickets both directly by measuring bite forces of males and females and by altering male bite capacity through neuropharmacological manipulation. In addition, the invertebrate neurotransmitter octopamine both mediates aggression and underlies motivation to bite in male house crickets. By blocking octopamine receptors through the application of an antagonist, epinastine, we tested the effects of reduced bite force on male mating success. Our results show that male bite capacity, in combination with body size, influences both the likelihood and the outcomes of mating interactions, whereas treatment of males with epinastine eliminates motivation to mate. Our results suggest a functional role for bite force in affecting both sexual conflict and sexual selection and expand our knowledge of the influence of biogenic amines on reproductive behaviour.     

Circadian entrainment by feeding cycles in house sparrows,Passer domesticus

Summary We studied the potential zeitgeber qualities of periodic food availability on the circadian rhythms of locomotor and feeding activity of house sparrows. The birds were initially held in a LD-cycle of 12:12 h, with food restricted to the light phase. After transfer to constant dim light, the birds remained entrained by the restricted feeding schedule. Following an exposure to food ad libitum conditions, the rhythms could be re-synchronized by the feeding cycle. Shortening of the zeitgeber period to 23.5 h resulted in the loss of entrainment in most birds, whereas a longer zeitgeber period of 25 h re-entrained the rhythms of most birds. Although these results prove that periodic food availability can act as a zeitgeber for the circadian rhythms of house sparrows, several features of our data indicate that restricted feeding is only a weak zeitgeber. The pattern of feeding activity prior to the daily time of food access shown under some experimental conditions suggests that anticipation is due to a positive phase-angle difference of the birds' normal circadian system rather than being caused by a separate pacemaker.     

Pharmacological effects of vinorelbine on body temperature and locomotor activity circadian rhythms in mice

The effects of vinorelbine (VRL) on the circadian rhythms in body temperature and locomotor activity were investigated in unrestrained B6D2F₁ mice implanted with radio-telemetry transmitters. A single intravenous VRL dose (24 or 12 mg/kg) was given at 7 h after light onset (HALO), a time of high VRL toxicity, and resulted in transient suppression of temperature and activity circadian rhythms in mice kept in light-dark (LD) 12h:12h. Such suppression was dose-dependent. It occurred within 1-5 d after VRL dosing. Recovery of both rhythms was partially complete within 5 d following the high dose and within 2 or 3 d after the low dose and was not influenced by suppression of photoperiodic synchronization by housing in continuous darkness. Moreover, VRL induced a dose-dependent relative decrease in amplitude and phase shift of the temperature circadian rhythm. The mesor and amplitude of the activity rhythm were markedly reduced following the VRL administration. The relevance of VRL dosing time was studied in mice housed in LD 12h:12h. Vinorelbine was injected weekly (20 mg/kg/injection) for 3 wk at 6 or 18 HALO. Vinorelbine treatment ablated the rest-activity and temperature rhythms 3-6 d after each dose, with fewer alterations after VRL dosing at 18 HALO compared to 6 HALO, especially for the body temperature rhythm. There was at least partial recovery 1 wk after dosing, suggesting the weekly schedule of drug treatment is acceptable for therapeutic purposes. Our findings demonstrate that VRL can transiently, yet profoundly, alter circadian clock function. Vinorelbine-induced circadian dysfunction may contribute to the toxicokinetics of this and possibly other anticancer drugs.     

Heritable variation in the timing of spermatophore removal, a mechanism of post-copulatory female choice in crickets

Female crickets can exert post-copulatory mating preferences by prematurely removing a male's spermatophore after copulation, which terminates sperm transfer. Although most models of sexual selection assume that female mating preferences are heritable, there has been little work addressing genetic variation underlying post-copulatory mate choice. We used a paternal half-sib design, in which different males were randomly assigned as mates to several females to create half-sib families, to determine the heritability of spermatophore retention time in female house crickets, Acheta domesticus. There was significant additive genetic variance in the timing of spermatophore removal by females [h(2) = 0.50 +/- 0.19 (+/- SE)], suggesting that the timing of spermatophore removal is determined, in part, by the female's own genotype independent of the quality of her mate. The relatively high heritability of spermatophore retention time may be reflective of the absence of strong selection on this trait, consistent with previous work showing no difference in the fitness of females permitted to freely remove the spermatophore of their mates and those forced to accept complete ejaculates.     

Emergence rhythms and protandry in relation to daily patterns of locomotor activity inTrichogramma species

Summary In insect parasitoids, the mating structure of the population depends on the emergence pattern of adults and on their behaviour after emergence. In order to study some aspects of these characteristics in four species of egg parasitoid of the genusTrichogramma, laboratory experiments using automatic video analysis are performed. Adult emergence is concentrated in the morning, with an earlier time for males. The variability of the time of emergence is under genetic control. The relationships between the emergence pattern and the locomotor activity are considered by measuring individually: first, the delay between the emergence and the first locomotion which is significantly greater in females than in males and, second, the activity of newly emerged males, which is maximum at the time of the emergence of females. The locomotor activity is influenced by mating; mated females are much more active than virgin ones, mated males are less active than virgin ones. The adaptive values of the rhythmicity of emergence and of protandry are discussed together with their relationship with the patterns of locomotor activity. The results are also considered with respect to mating strategies in insect parasitoids; they actually support the hypothesis of mating occurring principally among individuals native to the same host patch inTrichogramma species.     

Circadian rhythms of melatonin in European starlings exposed to different lighting conditions: relationship with locomotor and feeding rhythms

In passerine birds, the periodic secretion of melatonin by the pineal organ represents an important component of the pacemaker that controls overt circadian functions. The daily phase of low melatonin secretion generally coincides with the phase of intense activity, but the precise relationship between the melatonin and the behavioral rhythms has not been studied. Therefore, we investigated in European starlings (Sturnus vulgaris) (1) the temporal relationship between the circadian plasma melatonin rhythm and the rhythms in locomotor activity and feeding; (2) the persistence of the melatonin rhythm in constant conditions; and (3) the effects of light intensity on synchronized and free-running melatonin and behavioral rhythms. There was a marked rhythm in plasma melatonin with high levels at night and/or the inactive phase of the behavioral cycles in almost all birds. Like the behavioral rhythms, the melatonin rhythm persisted for at least 50 days in constant dim light. In the synchronized state, higher daytime light intensity resulted in more tightly synchronized rhythms and a delayed melatonin peak. While all three rhythms usually assumed a rather constant phase relationship to each other, in one bird the two behavioral rhythms dissociated from each other. In this case, the melatonin rhythm retained the appropriate phase relationship with the feeding rhythm. Accepted: 10 December 1999     

Inconsistency in the expression of locomotor and ERG circadian rhythms in the German cockroach, Blattella germanica (L.).

ERG recordings from German cockroaches showed that the amplitude of light-evoked responses have a circadian rhythmicity in adult males that coincided with the locomotor circadian rhythm. The peak of the response occurred during the subjective night, and the circadian period was less than 24 h under DD condition. In contrast, although the locomotor circadian rhythm was masked by the development of ovaries and pregnancy in females, their visual responses displayed circadian rhythmicity. This inconsistency in expression of locomotor and visual sensitivity circadian rhythms in females implied separate pacemakers for these two overt rhythms. After severing the optic nerves, changes in ERG amplitude of the operated cockroaches still displayed a circadian rhythm under DD condition, demonstrating that the visual sensitive pacemaker was located in the eye and independent from the locomotor pacemaker.     

日本三角涡虫的耗氧率和窒息点

应用静水呼吸室法,测定10℃、14℃、18℃、22℃、26℃和32℃温度下日本三角涡虫（Dugesiaj aponica）的耗氧率和窒息点,并测定涡虫耗氧率是否与温度和昼夜节律有关。结果表明,10℃和14℃涡虫耗氧率很低;18℃、26℃和32℃耗氧率较高;22℃涡虫耗氧率低于18℃、26℃和32℃条件下的耗氧率（P〈0,05）高于10℃和14℃条件下的耗氧率（P〈0．05）。18℃时窒息点最高,22℃窒息点最低。10℃、14℃、18℃、22℃、26℃和32℃温度下涡虫的窒息时间分别为125h,120h,55h,42h,37．5h和18．5h。18℃、22℃和26℃3个温度下涡虫耗氧率都呈昼夜节律性变化,白天耗氧率低,晚上耗氧率高（P〉0．05）。同一时间段比较,22℃耗氧率也最低。