The timing of larval wandering and puparium formation in the flesh-fly Sarcophaga argyrostoma

ABSTRACT. In mixed-age cultures of the flesh-fly, Sarcophaga argyrostoma (Robineau-Desvoidy), the initiation of larval wandering (exodus behaviour) occurs as a gated circadian rhythm. In light-dark (LD) cycles, most of this activity occurs in the dark, except in very short nights, or in certain phase relationships between the rhythm and light cycle. When transferred from series of LD cycles into continuous darkness (DD), cultures show a weakly persistent free-running rhythm with a period of about 21 h. However, after transfer of first instar larvae from continuous light (LL) to DD, no such rhythm is observed. In contrast to larval exodus, formation of the puparia occurs at any stage of the LD cycle. The physiological mechanisms underlying this gated exodus behaviour, and its possible selective advantages, are discussed.     

Manipulation of the length of the sensitive period,and the induction of pupal diapause in the flesh-fly,Sarcophaga argyrostoma

Larvae of the flesh-fly Sarcophaga argyrostoma were raised in short-day cycles (LD 12: 12) and at temperatures (18° and 20°C) in which short-day induction of pupal diapause was less than ‘saturated’. The cultures were then subjected to experimental treatments which modified the duration of larval development (the sensitive period). Overcrowding the larvae within a limited quantity of meat, premature extraction of the third instar larvae from their food, or exposure of the mature larvae to pure CO₂ for 24 h, were all found to accelerate puparium formation, thereby curtailing the sensitive period, and reducing the incidence of pupal diapause. Conversely, lengthening the sensitive period by allowing the mature larvae to wander in wet sawdust increased diapause incidence. The results are interpreted in terms of an interaction between the length of the sensitive period and the ‘required day number’, and also in the light of what is known about the endocrinological control of diapause and development in flesh flies.     

The selection for early and late pupariation in the flesh-fly, Sarcophaga argyrostoma, and its effect on the incidence of pupal diapause

ABSTRACT. Artificial selection from the first and last larvae of Sarcophaga argyrostoma (Robineau-Desvoidy) to form puparia gives rise to two strains, 'fast' (F) and 'slow' (S), 'fast' pupariating about 3 days earlier than 'slow' in continuous light, 25°C. The two strains differ only in the time from larval wandering to pupariation; other aspects of development are identical. In light-dark cycles (1°C) the distributions of pupariation times in 'fast' are unimodal and nearly normal, whereas those for 'slow' are multimodal and with a marked skew, especially in short daylengths. Pupariation times in 'fast'×'slow' hybrids, an F₂ generation, and a backcross [(F×S)×S] are intermediate between 'fast' and 'slow' but incline towards 'fast'. It is concluded that control of pupariation time is polygenic, and that 'slow' contain considerable residual variation. When compared with the unselected stock, 'fast' and 'slow' both produce a reduced incidence of pupal diapause in short daylengths, and 'fast' show a shorter critical daylength. These effects are interpreted in terms of a modified version of Gibbs' (1975) photoperiodic 'counter' hypothesis.     

Developmental cytology of the midgut in the flesh-fly, Sarcophaga bullata (Parker)

The cytological comparisons of the midgut in Sarcophaga bullata (Parker) between the second instar, the third instar larvae and the adult are made. The adult midgut differs from that of the larvae in the following ways: (1) the peritrophic membrane is thicker than in the larvae and has become multi-layered; (2) epithelial cells are smaller; (3) branched microvilli are present throughout the entire midgut instead of being present only in the posterior region as in the larval midgut; (4) nuclear pores are less frequent; (5) lysosome-type structures occur less frequently; (6) the basal membrane is thicker; (7) the z-bands in the surrounding muscle fibers are more distinct in adults. The possible function and the significance of these structures related to previous observations in Sarcophaga and other Diptera are discussed.     

Histogenesis of the cuticle of the adult flies,Sarcophaga bullata and S. argyrostoma

Sequential patterns of cuticle deposition and “melanization” in the imaginal cuticle of Sarcophaga argyrostoma in parts of the body darkening before or after emergence are examined on a histological basis. The patterns in the cuticles examined range from a simple absence of “melanization” to a complex of histological changes involving “melanization” and deposition. Ultrastructural changes in the post-emergent cuticle of Sarcophaga bullata during the hardening and darkening process and cuticle deposition are described.     

The circadian eclosion rhythm in Sarcophaga argyrostoma: delineation of the responsive period for entrainment

ABSTRACT. The circadian rhythm of pupal eclosion in Sarcophaga argyrostoma shows a declining responsiveness to the phase-shifting effects of single light pulses as development proceeds, the intrapuparial stages becoming largely 'insensitive'. Maximum responses occur in the intra-uterine embryos and first-instar larvae. Pharate adults, however, are responsive to single high temperature pulses. Pupae, pharate adults, and females carrying ovarian eggs, also respond to single stepwise transfers from light to dark, or vice versa, but the peaks of eclosion show a phase angle to the light which differs from that produced by transfers of embryos or larvae. The results are consistent with the view that separate 'larval' and 'adult' clocks occur at different stages of development.     

Circadian nature of the photoperiodic clock in Japanese quail

Summary The photoperiodic clock in quail (Coturnix colurnix japonica) is based upon a rhythm of photoinducibility (Øi) but the extent to which this rhythm is circadian remains unclear. Two types of experiment investigated this situation. In the first, gonadectomized quail were adapted to live in periods of darkness by training them on a schedule containing one short day and 3 days of darkness (SD/DD/DD/DD). They were then exposed to a single pulse of 6 or 10 h of light at different times across 3 days of darkness. The photoperiodic response, measured by the increase in LH secretion, showed clear rhythmicity, demonstrating unequivocally the circadian nature of Øi. The second set of experiments employed Nanda-Hamner cycles and varied the length of the photoperiod from 6 to 11 h. Responsiveness in a 36 h or a 60 h cycle was highly dependent upon the length of the photoperiod, something not predicted from theory. For instance, LD 6:30 was not photoperiodically inductive but LD 10:26 was clearly inductive. Close analysis of patterns of LH secretion indicated an unexpected delay before induction occurred and then a rapid rise to a stable level of induction. When LH was measured in every pulse under LD 10:26 there was no evidence that LH levels alternately increased and decreased. This is not consistent with the simplest interpretation of Nanda-Hamner experiments where alternate pulses of light are thought to entrain the rhythm or induce a photoperiodic response by coinciding with Øi. It is concluded that the quail's photoinducible rhythm is indeed based on a circadian rhythm but one that is only weakly self-sustaining. Possibly as a consequence of this, the rhythm's behaviour under abnormal photoperiodic cycles may be rather different from that found in other species and from other circadian rhythms in quail.Abbreviations Øi photoinducible phase - LH luteinizing hormone     

Photoperiodic sensitivity and diapause induction during ovarian,embryonic and larval development of the flesh fly,Sarcophaga argyrostoma

Sensitivity to the daily photoperiod, particularly with respect to pupal diapause induction, was studied during ovarian, embryonic, and larval development of the flesh flySarcophaga argyrostoma. Large flies were shown to have a greater number of primary follicles in their ovaries and to be capable of limited ovarian maturation in the absence of exogenous protein (autogeny). Such ovarian development occurred independently of photoperiod. However, long days experienced during embryogenesis caused more rapid development, and earlier larviposition, than short days. Short days during embryonic and subsequent larval development also induced pupal diapause, whereas long days led to continuous or non-diapause development of the pupae. Pupal diapause could not be induced by photoperiods during the vitellogenic phase of ovarian development. InSarcophaga argyrostoma, a maternal effect preventing pupal diapause among the progeny of files with a diapause history was not observed.     

Some effects of constant temperature and photoperiod on the diapause response of the flesh fly, Sarcophaga argyrostoma

ABSTRACT. The sensitive period for the induction of pupal diapause in Sarcophaga argyrostoma (R.-D.) (Diptera, Sarcophagidae) extends from the intra-uterine embryos to puparium formation, although the degree of 'sensitivity' declines during that period. Embryos and larvae 'add up' both long and short nights to a threshold. The incidence of diapause may also be influenced by the photoperiodic manipulation of female flies containing ovarian eggs. High temperatures eliminate or override the diapause response, whilst lower temperatures enhance it. Still lower temperatures (10–12°C) bring about a high larval and pupal mortality and a failure to pupate which is more marked in long than in short nights. The results are discussed in terms of the external coincidence model and the concept of the 'photoperiodic counter'.     

Ingestion of sugar diets correlates with spike activity in labellar chemosensilla of the flesh-fly, Neobellieria (= Sarcophaga ) bullata

Abstract .Female 2-day-old Neobellieria (= Sarcophaga ) bullata (Parker) (Diptera: Sarcophagidae) were exposed to different concentrations of sucrose, glucose and fructose in a single-choice potometer, and the volume ingested in the first hour was measured. Nerve spike activity in response to the same sugars was recorded from medium labellar taste hairs of similar flies by tip-recording. Two classes of chemosensory cells responded to sucrose, glucose and fructose. Cell 1 showed an increasing spike activity with sugar concentration, whereas cell 2 did not; cell 1 was identified as the 'sugar cell'.
For both spike activity in cell 1 and feeding, sucrose was the most stimulatory sugar. The dose–response curves for glucose and fructose crossed over at about 200 m m . At higher concentrations, glucose was more stimulatory for both cell 1 and for feeding, and at lower concentrations, fructose. The pattern of spike activity supports a separate location on the sensory cells of receptors for pyranose and fructose forms of sugar. The strong correlation between volume ingested and spike activity indicates that sugar feeding is controlled by sensory input from the 'sugar' cells of labellar chemosensilla. Moreover, the results suggest that the flies do not distinguish between these sugars except by apparent 'sweetness'.     

Sexual difference in the photoperiodic induction of pupal diapause in the flesh fly Sarcophaga similis

The flesh fly Sarcophaga similis enters pupal diapause in response to short days, but averts diapause under long days. This species shows a sexual difference in the photoperiodic induction of diapause, with females having shorter critical daylength than males. Here, we proposed two hypotheses to explain this sexual difference. First, we proposed a sexual difference in the qualitative evaluation of photoperiods. This hypothesis assumes under the external coincidence model that although the photoinducible phase of both sexes locates at late scotophase, in males, it locates at a slightly earlier phase. However, the results of night interruption experiments clearly ruled out this hypothesis. Because we verified that S. similis evaluated photoperiods quantitatively, we next proposed a sexual difference in the quantitative evaluation of photoperiods. This hypothesis incorporates concepts of a hypothetical substance accumulation that shows a diapause‐inducing effect and an internal threshold that serves as a reference to determine the diapause/nondiapause developmental program. In long‐day exposure experiments and night interruption experiments, females consistently showed a lower incidence of diapause than males. Thus, the present study data satisfactorily meet the second hypothesis, that is a sexual difference in the quantitative evaluation of photoperiods exists in S. similis.     

Metabolic correlates in the working of an insect putative photoperiodic clock

Summary Analysis of the formal properties of photoperiodic systems has emphasized the importance of two discrete phases of nocturnal light sensitivity (the so-called points A and B) in a variety of taxa. This has been exemplified in the lepidopteran, Pieris brassicae, among other species, since the illumination of either of these phases in an otherwise short-day cycle (diapause inducing) gives rise to a long-day effect (development without diapause). In this species, the photoreceptor of diel cycles and the clock-counter system are very likely brain located. Using cytochrome oxidase activity as a marker of energy metabolism, a neuroanatomical base in the brain involved in long-day responses elicited by light at points A and B was investigated.Present results reveal that (i) the level of energy metabolism in the optic centres is connected with the photoperiodic process, and (ii) the two points A and B can be discriminated at a functional level. Referring to the formal models, the possible function of the optic centres, either as a photoreceptor or as a (part of the) clock, is discussed.Abbreviations CO cytochrome oxidase - OD optical density - PTM photoperiodic time measurement     

Influence of temperature on the survival and infectivity of Trichinella spiralis larvae in Sarcophaga argyrostoma (Diptera, Sarcophagidae) maggots

To investigate the role of fleshfly maggots as a paratenic host for Trichinella spiralis larvae, maggots of Sarcophaga argyrostoma (Muscidae, Sarcophagidae) kept at different temperatures (26, 22, 20, 16, 12, 8, and 4 C) were allowed to feed on T. spiralis-infected mouse meat. Trichinella larvae found in maggots kept at 8-26 C were able to cause infection when inoculated in mice. Infective larvae survived in maggots up to 5 days postinfection at 8 C and for shorter periods of time at higher temperatures. The survival time in maggots was negatively related to the temperature of maggot breeding. The results suggest that the role of S. argyrostoma in the dissemination of Trichinella larvae in nature is limited in comparison to the role played by mammals with scavenger and cannibalistic behavior.     

A circadian clock measures photoperiodic time in the male lizard Anolis carolinensis

Summary Photoperiod plays an important role in controlling the annual reproductive cycle of the male lizard Anolis carolinensis. The nature of photoperiodic time measurement in Anolis was investigated by exposing anoles to 3 different kinds of lighting paradigms (resonance, T cycles, and night breaks) to determine if photoperiodic time measurement involves the circadian system. Both the reproductive response and the patterns of entrainment of the activity rhythm were assessed. The results show that the circadian system is involved in photoperiodic time measurement in this species and that a discrete photoinducible phase resides in the latter half of the animals' subjective night. Significantly, the ability of the circadian system to execute photoperiodic time measurement is crucially dependent on the length of the photoperiod. Resonance, T cycle and night break cycles utilizing a photoperiod 10–11 h in duration reveal circadian involvement whereas these same cycles utilizing 6 or 8 h photoperiods do not.Abbreviation CRPP circadian rhythm of photoperiodic sensitivity     

Some effects of low temperature on the photoperiodic clock in Drosophila triauraria

Abstract. Prior studies revealed that the photoperiodic clock in Drosophila triauraria operates during the scotophase and the processes measuring scotophase are composed of two phases: the A phase which lasts 6–7 h from the onset of the scotophase and the B phase which follows the A phase. In this study the photoperiodic clock in this species was analysed by low-temperature pulses. Low temperature (5C) or a low-temperature (2C) pulse of 3 or 4 h decreased the induction of diapause when applied during the scotophase, but not when applied within the photophase. The low-temperature pulse showed two maxima of the effect, 0–4 h and 8–10 h after the onset of the scotophase, approximately corresponding to the A and B phases, respectively. It is considered that low temperature retards the time measurement processes operating during these phases. In the period which was rather insensitive to the diapause-preventing action of low temperature, i.e. 5-7h after the onset of the scotophase, substances or stimuli accumulated during the A phase may be converted to information required for operation of the machinery in the B phase. Experiments using a combination of low-temperature and light pulses suggested that low-temperature decreases the sensitivity to light, especially in the B phase.     

Purification and characterization of an antibacterial protein from haemolymph of Sarcophaga peregrina (flesh-fly) larvae.

Three antibacterial proteins were induced when the body wall of Sarcophaga peregrina (flesh-fly) larvae was injured with a hypodermic needle. These proteins were separated and one was purified to homogeneity. The molecular weight of the purified protein was 5000 and its amino acid composition was similar to that of cecropins, which are antibacterial proteins in Hyalophora cecropia (cecropia moth) pupae. This protein was found to have bactericidal activity and to be effective at a concentration of 0.1 micrograms/ml against certain Gram-negative and Gram-positive bacteria.     

Circadian clock regulates photoperiodic responses governed by distinct output pathways in the bean bug,Riptortus pedestris

Effects of RNA interference (RNAi) targeted against circadian clock genes on two distinct types of photoperiodic responses – ovarian development and lipid accumulation – were investigated in a bean bug Riptortus pedestris, to explore which physiological process in the photoperiodic response involved the circadian clock. Ovarian development and lipid accumulation are known to be regulated by distinct output pathways. Control insects showed clear photoperiodic responses; i.e. induction of ovarian development and suppression of lipid accumulation under long-day conditions, whereas opposite characteristics under short-day conditions. We found that RNAi directed against period, a negative element of the circadian clock, produced a long-day effect for both the ovarian development and lipid accumulation, while RNAi directed against Clock, a positive element of the circadian clock, produced a short-day effect for both, irrespective of photoperiod. These results indicate that the circadian clock comprised of these genes regulates a process governing both distinct photoperiodic responses.