The comparative susceptibilities of Pieris brassicae and P. rapae to a granulosis virus from P. brassicae

A comparison was made of the dosage-mortality responses of larvae of Pieris brassicae and P. rapae to infection by P. brassicae granulosis virus (GV). Bioassays with first, second, third, and fourth-instar larvae of both species revealed a marked difference in susceptibility between instars and between species. Median lethal dosages (LD₅₀s) for P. rapae larvae ranged from five capsules for the first instar to 662 capsules for the fourth instar. With P. brassicae, this range extended from 66 capsules to 2.3 × 10⁷ capsules. The time-mortality responses of the two species were similar when fed virus dosages equivalent to an LD₉₀. Median lethal times (LT₅₀s) ranged from 5 days for first-instar larvae to 7–8 days for fourth-instar larvae. A comparison between a long-established laboratory stock of P. brassicae and a stock recently acquired from the field showed no significant difference in their susceptibility to GV. The implications of the pronounced species differences in susceptibility to GV infection are discussed in relation to the potential field control of P. rapae and P. brassicae.     

Supradian and infradian cycles in oxygen uptake of diapausing pupae of Pieris brassicae

The general characteristics of diapause respiration in P. brassicae are described, together with an examination of short-term (supradian) and long-term (infradian) variation in oxygen uptake. Supradian cycles occur approximately every 3 hr at 10°C and are shown by closed box analyses to be initiated by carbon dioxide bursts. Maximal rates of oxygen uptake occur shortly after the burst in carbon dioxide release, not at the start of the burst as recorded in other diapausing species. The frequency of supradian cycles is directly related to temperature and metabolism in accordance with the characteristics of discontinuous carbon dioxide release.Infradian cycles of between 3 and 7 days duration are recorded for both oxygen uptake and net exchange rates. Peaks in oxygen demand occur on average every 4 days at 10°C, and are related in frequency to the level of metabolism of individual pupae. Just before post-diapause development, oxygen demands fall to about half their normal levels; these changes are associated with appropriate changes in the frequency of supradian and infradian cycles.     

Circadian and circatidal rhythms of oxygen consumption in the sandy-beach isopod Tylos granulatus Krauss

The sandy-beach isopod Tylos granulatus Krauss burrows at the high tide mark, and has rhythms of nocturnal emergence coincident with the low tide period. Measurements of the respiration rate show that a low rate of oxygen consumption is maintained throughout the day but there is a circatidal rhythmic increase of between 300 and 700% during the nocturnal low tide. The height of this peak and the percentage of animals displaying a peak both increase from spring tide to neap tide suggesting a semi-lunar rhythm. The respiratory peaks have a 24.8 h periodicity, being later each night until low tide falls in the dawn, when there is a ‘switch-back’ so that peaks are then during the subsequent evening low tide. These respiratory rhythms are persistent under constant light and coincide with previously described activity rhythms. The respiratory rhythms considerably reduce metabolic energy losses, particularly as the activity rhythms ensure avoidance of high diurnal temperatures and activity during the cooler nocturnal period.     

Factors controlling in vitro hatching of Vairimorpha plodiae (Microspora) spores and their infectivity to Plodia interpunctella,Heliothis virescens, and Pieris brassicae

Factors which influence the hatching of spores and proliferation of stages of the microsporidium Vairimorpha plodiae in two susceptible insects, Plodia interpunctella and Heliothis virescens, and one nonsusceptible insect, Pieris brassicae, were investigated. Spores hatched in 0.1 and 1 m KCl solutions when subjected to a change in pH, from pH 11 to pH 8. K⁺ was essential for hatching; NaCl solutions were not effective. Ca²⁺ and Mg²⁺ inhibited hatching, and calcium and magnesium chelating agents enhanced it. All three insect species had alkaline midgut contents and smooth, fragile peritrophic membranes. Spores hatched inside the midguts of all three insect species (P. interpunctella: maximum rate, 92.5%; H. virescens, 91.5%; P. brassicae, 82%). Sporoplasms were observed in the midgut epithelial and associated tracheole cells of P. brassicae. Both H. virescens and P. brassicae became infected when injected intrahemocoelically with spores.     

Locomotory rhythms and burrowing habits of Penaeus semisulcatus (de Haan) and P. Monodon (Fabricius) (Crustacea: Penaeidae)

The locomotor activity of adult Penaeus semisulcatus (de Haan) and P. monodon (Fabricius) has been studied. The former was reared entirely, and the latter partly under artificial conditions. Both species display circadian activity rhythms in response to light entrainment. Light appears to be a major synchronizer, although the results indicate that feeding also has a certain synchronizing effect in starved prawns.The expression of endogenous activity rhythms in both species is affected by their substratum requirements and burrowing habits. Choice experiments show that both P. semisulcatus and P. monodon select a fine grade sand for burrowing, although the burrowing frequency of the latter species is always low. In a non-choice situation, P. semisulcatus will readily enter a coarse substratum whereas P. monodon will very seldom do so.The effects of various light regimes on the activity patterns of P. semisulcatus and P. monodon were examined and the results show that for both species an imposed long photoperiod regime (18:6 LD) induced 6-h periods of brief but intense activity, alternating with 18-h periods of almost complete inactivity. This activity pattern is discussed in relation to feeding and energy expenditure.     

Circadian oscillations outside the optic lobe in the cricket Gryllus bimaculatus

Although circadian rhythms are found in many peripheral tissues in insects, the control mechanism is still to be elucidated. To investigate the central and peripheral relationships in the circadian organization, circadian rhythms outside the optic lobes were examined in the cricket Gryllus bimaculatus by measuring mRNA levels of period (per) and timeless (tim) genes in the brain, terminal abdominal ganglion (TAG), anterior stomach, mid-gut, testis, and Malpighian tubules. Except for Malpighian tubules and testis, the tissues showed a daily rhythmic expression in either both per and tim or tim alone in LD. Under constant darkness, however, the tested tissues exhibited rhythmic expression of per and tim mRNAs, suggesting that they include a circadian oscillator. The amplitude and the levels of the mRNA rhythms varied among those rhythmic tissues. Removal of the optic lobe, the central clock tissue, differentially affected the rhythms: the anterior stomach lost the rhythm of both per and tim; in the mid-gut and TAG, tim expression became arrhythmic but per maintained rhythmic expression; a persistent rhythm with a shifted phase was observed for both per and tim mRNA rhythms in the brain. These data suggest that rhythms outside the optic lobe receive control from the optic lobe to different degrees, and that the oscillatory mechanism may be different from that of Drosophila.     

Le contrôle de l'émergence et des nages nocturnes chez les péracarides des plages de méditerranée. Eurydice affinis Hansen (Isopoda), Gastrosaccus mediterraneus Bacescu, Gastrosaccus spinifer (goës) (Mysidacea)

Along the Mediterranean sandy shores, Eurydice affinis Hansen, Gastrosaccus mediterraneus Bacescu and Gastrosaccus spinifer (Goës) are present during the day in the sand of the beaches, either near the limit of the wave wash or in the superficial fringe of the infralittoral. In the evening there is a general emergence and the animals rejoin the planktonic populations of the open sea.All the three species when kept in aktographs under constant conditions and continuous darkness exhibit a circadian rhythm of emergence and swimming activity of nocturnal frequency. The rhythm is clear and in the two Gastrosaccinae persists for ten days at least; it has been observed over about fifty days in G. spinifer. In E. affinis, the rhythm is only on some occasions clear; one frequently observes a permanent burying in the sediment, in which case the swimming rhythm can be brought to light by a mechanical disturbance or the withdrawal of the sediment.A study of the changes in the photokinetic reactions in a horizontal beam of white light, with intensities varying from 4000 to 10^?6 lux, allow the synchronization of the rhythms to be ascribed to a slight photonegative tendency of the animals at intensities > 1000 lux and a photopositive tendency, often marked, at lower intensities. The variations in the intensity of the reactions in the three species allows an explanation of the autonomous rhythms.A comparison between the photokinetic reactions of these species and those of the infralittoral Peracarida, which migrate in the nocturnal plankton, shows great differences with respect to light intensity. In the latter, the phototaxis is strongly negative and frequently accompanied by a strong photo-inhibition while in the former the phototaxis is still often positive and the kinesis is high. The photopositive reaction allows the animals to rejoin their daytime habitat soon after dawn when the swimming activity decreases.     

A recombinant immunosuppressive protein from Pimpla hypochondriaca (rVPr1) increases the susceptibility of Lacanobia oleracea and Mamestra brassicae larvae to Bacillus thuringiensis

The precise mechanisms underlying Bacillus thuringiensis-mediated killing of pest insects are not clear. In some cases, death may be due to septicaemia caused by Bt and/or gut bacteria gaining access to the insect haemocoel. Since insects protect themselves from microbes using an array of cellular and humoral immune defences, we aimed to determine if a recombinant immunosuppressive wasp venom protein (rVPr1) could increase the susceptibility of two pest Lepidoptera (Lacanobia oleracea and Mamestra brassicae) to Bt. Bio-assays indicated that injection of 6 μl of rVPr1 into the haemocoel of both larvae caused similar levels of mortality (less than 38%). On the other hand, the LD_30-40 of Bt for M. brassicae larvae was approximately 20 times higher than that for L. oleracea larvae. Furthermore, in bio-assays where larvae were injected with rVPr1, then fed Bt, a significant reduction in survival of larvae for both species occurred compared to each treatment on its own (P < 0.001); and for L. oleracea larvae, this effect was more than additive. The results are discussed within the context of insect immunity and protection against Bt.     

Daily oxygen consumption rhythms of Senegalese sole solea senegalensis (Kaup, 1858) juveniles

Senegalese sole is known to be a species with pronounced nocturnal feeding behaviour. However, as for most fish species, there is a lack of knowledge concerning the influence of such biological rhythm on metabolic rate. The aim of this study was to determine whether individual variation in routine and fed metabolic rate was affected by daily light-dark rhythms in juveniles of Senegalese sole. The individual oxygen consumption measurements in Senegalese sole juveniles were determined by flow-through respirometry, at fasted conditions and after the fish were fed a single meal, the meal time started at 0930 h and fish fed ad libitum for 30 min. The measurements were made during 22 h, of which 8 h was in the light and 14 h in the dark, and started immediately after transfer to the respiratory chambers at 1100 h. The results suggest an influence of light-dark cycles in routine metabolism. It was observed that oxygen consumption increased during the dark phase in fasted fish (FAST) but was higher during the light phase in fed fish (FEED). However, when feed is provided during the light phase, juveniles are capable of shifting oxygen consumption rhythms to respond to the energetic demands of digestion and growth. These results suggest that routine metabolism varies according to the species natural habits as Senegalese sole is known to be nocturnal. The findings of this study underline the importance of understanding the biological rhythms of the species under study before metabolic data are interpreted.     

Endogenous rhythms of locomotion in the American horseshoe crab, Limulus polyphemus

American horseshoe crabs (Limulus polyphemus) exhibit clear circadian rhythms of visual sensitivity in the laboratory and in the field they exhibit seasonal patterns of mating behavior that are closely associated with the tides. Recent reports suggest that Limulus locomotor activity may be controlled by endogenous circadian and/or circatidal clocks and that light:dark (LD) cycles may affect the rhythmic output of both of these clocks. In this study, we examined locomotor behavior in the laboratory to determine the extent of this endogenous activity and to examine the influence of LD cycles on these rhythms. Thirty-three L. polyphemus were captured during the breeding season and their activity was monitored with activity boxes and “running wheels” in seawater kept at constant temperature and salinity. Activity patterns were analyzed using visual inspection of actograms and Chi-square and Lomb-Scargle periodograms. Overall, 36% of the animals was significantly more active during L, while only 12% was more active during D (52% showed no preference). Circatidal rhythms were observed in LD in 67% of the horseshoe crabs. Surprisingly, LD cycles appeared to synchronize these rhythms at times. In DD, the majority of animals tested (63%) exhibited circatidal rhythms that persisted for at least seven days. Overall, the results demonstrate that an endogenously controlled tidal rhythm of locomotion operates during, and significantly after, the breeding season in this species. In addition, the present results are consistent with the presence of circalunidian oscillators controlling these rhythms.     

The relationship of hunger to predatory behaviour in hawks (Falco sparverius and Buteo platypterus)

The relationship of hunger (as measured by food consumption) to predatory behaviour in two species of falconiform birds was investigated in the laboratory. The tendency to kill prey was correlated with hunger, and only hungry birds killed prey. I suggest that there is no predatory instinct or drive which operates independently of hunger and offer other rationales for the occasional excessive killing by some vertebrate predators. Falco sparverius exhibited a circadian rhythm of hunger and killing by some vertebrate predators. Falco sparverius exhibited a circadian rhythm of hunger and killing tendency, with a peak in the late afternoon. Buteo platypterus possibly showed a slight peak in the morning.     

Activation of latent virus infections in larvae of Adoxophyes orana (Lepidoptera: Tortricidae) and Barathra brassicae (Lepidoptera: Noctuidae) by foreign polyhedra

The number of larvae containing polyhedra increased when larvae of Adoxophyes orana and Barathra brassicae were fed on polyhedra of nuclear polyhedrosis virus (NPV) of the reciprocal species. Comparison of restriction endonuclease EcoRI cleavage patterns of DNA isolated from polyhedra used as inocula and from polyhedra obtained after cross-inoculation showed that cross infection did not occur. The observations indicate that latent viruses were activated in both insects. Activation of the A. orana latent NPV with polyhedra of a cytoplasmic polyhedrosis virus (CPV) of B. brassicae, and cross-inoculation with an extract prepared from healthy larvae indicated that an activating agent does not have to be a component of nuclear polyhedra.     

The effect of dietary cholesterol on the development of Hylemya brassicae

The influence of different concentrations of cholesterol upon the larval and postlarval development of Hylemya brassicae has been investigated using an artificial diet and axenic culture conditions.In contrast with other insects studied, H. brassicae larvae are extremely sensitive to cholesterol, even in minute concentrations, until after their second ecdysis. Concentrations of 0.1 to 0.$\text{4}$g/100 ml disturb the second moulting process in a typical way that could indicate an endocrine unbalance and result in a very high mortality during this process. When cholesterol at a concentration of 0.4g/100 ml is administered to the larvae after the second ecdysis, there is no longer an adverse effect on the further larval and postlarval development.The unusual sensitivity of young cabbage root fly larvae for cholesterol seems to point out some significant differences in the sterol requirements and metabolism of the species in comparison with other insects studied.     

Alanine aminotransferase in the three last larval instars of Barathra brassicae infected by Nosema plodiae

During three last larval instars of Barathra brassicae the alanine aminotransferase activity pattern exhibits two maxima which do not correspond with the maxima of activity of phosphatases and proteases. In the larvae infected by Nosema plodiae a different course of activity can be seen from the 5th day of infection. The activity pattern in the diseased larvae rises above that of a normal larva by 90% shortly before the last molt and reaches a maximum at the end of normal larval development. Alanine aminotransferase in the gut and in the fat body exhibits two main pH optima of activity, 8.0 and 9.5, respectively, and a low activity peak at pH 4.5. This last activity is not present in diseased animals. The temperature and pH inactivation are also described.     

Locomotory and stridulatory circadian rhythms in the cricket, Teleogryllus commodus

Male crickets of the species Teleogryllus commodus express circadian rhythms in both their stridulatory and locomotory behaviours. Both forms of activity show the same free-running period (τ) in either DD (23·4 hr) or LL (25·1 hr). Although some overlap is seen between periods of locomotion and stridulation, the majority of each activity is found in different phases of the circadian cycle: locomotion occurs mainly in the subjective day and stridulation in the subjective night. Entraining LD cycles with photoperiods of 12 hr produce exogenous effects that can obscure endogenous components of the rhythms. Red light (λ>600 nm) causes the period to lengthen and RD cycles can entrain both rhythms. Single white light pulses of 2 or 6 hr did not produce significant phase shifts, but did cause τ to shorten when given in the subjective night. The significance of these observations is discussed. Given the results obtained to date, it is not likely that each rhythm is under the control of a separate circadian pacemaker.     

Lactate dehydrogenase isoenzymes in the larvae of Barathra brassicae and Galleria mellonella during microsporidan infection

Changes in the activities of lactate dehydrogenase isoenzymes in the gut and fat body of Galleria mellonella and Barathra brassicae larvac infected by the microsporidans Nosema plodiae and Pleistophora schubergi were studied by means of dise electrophoresis. In the normal last instar G. mellonella gut and fat body three isoenzymes, LDH-1, LDH-2-3, and LDH-4, and in B. brassicae two isoenzymes, LDH-1 and LDH-2-3, were present. In the fat body of both the animals infected by N. plodiae, the isoenzyme LDH-2-3 increased in activity substantially by the fifth day of infection. The gut LDH isoenzymes were not affected by the microsporidan. The same LDH-2-3 effect could be provoked by some enzymes toxic for G. mellonella larvae such as phospholipase-C and protease preparations.     

Development and relationships of locomotor, feeding, and oxygen consumption rhythms in house crickets

ABSTRACT. Locomotor, feeding, drinking, and oxygen consumption rhythms in adult virgin Acheta domesticus L. all appear to peak in the first half of the scotophase, be entrained cophasically by a LD 14:10 h cycle, have a lights-off Zeitgeber and persist in LL with a π c. 25 h for the locomotor rhythm and c. 23 h for the oxygen consumption rhythm. There is no evidence of these rhythms in last instar larvae. The onset of the locomotor rhythm requires 3 days at 30°C but 5–7 days at 25–28°C after the final ecdysis in virgins, indicating a temperature related development of the locomotor rhythm. Oxygen consumption rhythms are lacking in 2-day-old virgins but present in 8-day-old virgins. Feeding rhythms can be recorded in virgins as young as 2 days (before locomotor rhythm developed). Both oxygen consumption and locomotor rhythms persist during starvation. The results suggest that a central brain oscillator drives both feeding and locomotor rhythms independently, but that the oxygen consumption rhythm is derived from the metabolic demands associated with the other rhythms.     

Interspecific comparison of Cd bioaccumulation in European Pectinidae (Chlamys varia and Pecten maximus)

The uptake and loss kinetics of Cd were determined in two species of scallops from the European coasts, the variegated scallop Chlamys varia and the king scallop Pecten maximus, following exposures via seawater, phytoplankton and sediment using highly sensitive radiotracer techniques (¹⁰⁹Cd). Results indicate that, for seawater and dietary pathways, C. varia displays higher bioaccumulation capacities in terms of uptake rate from water and fraction absorbed from ingested food (assimilation efficiency) than Pecten maximus. Regarding sediment exposure, P. maximus displayed low steady-state Cd transfer factor (TF_SS < 1); however, once incorporated, a very large part of Cd transferred from sediment (92%) was strongly retained within P. maximus tissues.Both species showed a high retention capacity for Cd (biological half-life, T_b1/2 > 4 months), suggesting efficient mechanisms of detoxification and storage in both species. The digestive gland was found to be the main storage organ of Cd in the two scallops regardless of the exposure pathway. However, Cd was stored differently within this organ according to the species considered: 40% of the total Cd was found in the soluble cellular fraction in C. varia whereas this soluble fraction reached 80% for P. maximus. This suggests that the two species displayed different Cd detoxification/storage mechanisms.Finally, the present study has determined the relative contribution of the different exposure pathways to global Cd bioaccumulation for the two scallop species. Results clearly show that for both species, food constitutes the major accumulation pathway, contributing for > 99% and 84% of the global Cd bioaccumulation in C. varia and P. maximus, respectively. This work confirms the previous assumption, derived from a bibliographic overview, that dietary pathway plays a prevalent role in metal bioaccumulation in Pectinidae.     

Performance of Anisantha (Bromus) tectorum and Rumex acetosella in sandy calcareous soil

Many plants are adapted to an eroded landscape with a large proportion of virgin soil. Open and disturbed soils are today almost only restricted to agricultural fields with high loads of fertilizers. We conducted a pot experiment in order to investigate growth and nutritional constraints of one calcicole species, Anisantha (syn. Bromus) tectorum, and one calcifuge species, Rumex acetosella, in decalcified topsoil and recently exposed calcareous subsoil from a field experiment in sandy grassland. In the pot experiment we implemented one treatment where we limed topsoil with CaCO₃ to the same amount as in subsoil.The subsoil had approximately 10% CaCO₃ and both species grew less in this soil compared to the topsoil, which had less than 1% CaCO₃. Germination rate of A. tectorum was higher in subsoil than in topsoil or limed topsoil. P fertilization of the limed topsoil counteracted the negative liming effect for A. tectorum, but only partly so for R. acetosella. P fertilization of subsoil increased the shoot biomass of A. tectorum, but not of R. acetosella. P concentration in plants was not reduced when growing on subsoil or limed topsoil compared to topsoil. The results show that lime addition may reduce the P availability also to calcicole species such as A. tectorum and we found indications for that Ca toxicity may be a causing factor for the calcifuge behavior of R. acetosella. The significance of the results for conservation management practices in sandy grasslands is discussed.     

A possible storage form of tyrosine in the haemolymph of Pieris brassicae L. and four other lepidoptera

A ninhydrin-positive compound, called peptide I (PI), has been found in the haemolymph of Pieris brassicae. The substance has been partially purified and is presumed to be a peptide of low molecular weight and rich in tyrosine, or a derivative of tyrosine. Its phenolic nature is evident.PI is not present in fourth instar larvae but is first found in fifth instar larvae a few hours after ecdysis. Its concentration rises almost linearly and is 25 times higher at the end of feeding. The concentration falls to one-third of the peak value shortly after pupation. Some PI is still found in pharate adults and young emerged adults. Both sexes contain about equal amounts of PI.The content of tyrosine in the haemolymph was about 4 μmole/ml during the period studied (ecdysis was not examined). The content of tyrosine increases towards the end of the feeding period during both the fourth and fifth instars. This occurs also after pupation, when the concentration of PI decreases. PI is distributed in the ratio of 1 : 5 between tissues and haemolymph at the end of the fifth instar.PI is not of dietary origin. Its occurrence during development suggests a rôle in pupation. It is possible that PI is a reserve of tyrosine, owing to its greater solubility in comparison to that of tyrosine.A substance identical or very similar to the PI of P. brassicae was also found in four other randomly chosen species, Smerinthus ocellatus L., Pergesa elpenor L., Celerio galii L., and, possibly, Dicranula vinula, L. This would suggest that such a compound occurs rather commonly in Lepidoptera.