Universal Trap Timer Design to Examine Temporal Activity of Wildlife

Abstract: We designed a reliable and inexpensive universal trap timer that records the time from the moment a single-live-capture trap is triggered by an animal to when the observer checks the trap. Combined with trapping information, the diel activity pattern of a given species or demographic group can then be described or compared between imposed treatments. The universal trap timer is adaptable to operate reliably with most single-capture trap designs, requires no permanent modification of traps, and is easy to construct.     

A transgenerational interval timer inhibits unseasonal sexual morph production in damson-hop aphid, Phorodon humuli

Abstract.  The induction of sexual and parthenogenetic morphs of the damson-hop aphid, Phorodon humuli , on hops is controlled by daylength. The ability of P. humuli , to produce winged pre-sexual females (gynoparae) in the short-day conditions of spring is inhibited by an interval timer present in generations immediately after hatching of the overwintering egg. The inhibition expires after three generations when nymphs are born and reared in short days (LD 12 : 12 h), irrespective of whether their parents are reared in short or long days (LD 18 : 6 h). No gynoparae are produced by aphids maintained for 13 generations in long days. Two wingless aphids from 35 survive transfer from Prunus spinosa to hops. No winged females are produced during nine generations among their progeny maintained in long days on hops, but gynoparae, followed by males, are produced one generation after these aphids are transferred to short days.     

Interactions between TIME and PIN could play a role in the system that controls the duration of diapause development and synchronization with seasonal cycles in the silkworm Bombyx mori*

The significance of winter cold in the termination of diapause was investigated with regards to TIME and PIN in eggs of the silkworm Bombyx mori. TIME (time interval measuring enzyme) is an ATPase that can measure time intervals by exhibiting a transitory burst of activation of the enzyme in accordance with diapause development, which requires cold for resumption of embryonic development in the silkworm. The possible timer function of TIME comprises a built‐in mechanism in the protein structure. TIME is a metallo‐glycoprotein consisting of 156 amino acid residues with a unique sequence in the N‐terminal region to which a sugar chain is attached. PIN (peptidyl inhibitory needle) inhibits the ATPase activity of TIME. PIN is not a simple enzyme inhibitor, but holds the timer by forming a time‐regulatory complex with TIME. The carbohydrate moiety of TIME is essential for the assembly of a high‐affinity PIN‐binding site within the timer motif of the TIME structure. The binding interaction between TIME and PIN was much tighter (nearly 1000 times) at 25°C than that at 4°C, as measured by fluorescence polarization. Because the logEC₅₀ at 4°C was approximately 7 nmol/L, PIN must dissociate from TIME at the physiological concentration of TIME in eggs in the winter cold. Based on the results of our study, we propose that the dissociation of the TIME–PIN complex in the winter cold cues a series of conformational changes of TIME, ultimately reaching the active form of ATPase which in turn causes the completion of diapause development and initiates new developmental programs.     

Recording of elapsed time and temporal information about biological events using Cas9

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Clock genes period and timeless are rhythmically expressed in brains of newly hatched, photosensitive larvae of the fly, Sarcophaga crassipalpis

While roles of the clock genes period (per) and timeless (tim) are relatively well understood in relation to circadian clocks, their potential roles in insect photoperiodism remain enigmatic. In this study, the expression of per and tim genes under two contrasting photoperiods is described in the central nervous system of photoperiodically sensitive, newly hatched first instar larvae of the flesh fly, Sarcophaga crassipalpis. Using qPCR, diel oscillations were observed in the mRNA levels of both genes under long-day (15 h light:9 h dark, promotes direct development) and short-day conditions (11 h light:13 h dark, induces pupal diapause). Peak per and tim mRNA oscillations were closely associated with the light/dark transition. The conspicuous difference between the two photoperiodic conditions was that the sharp increase in per and tim mRNA abundance occurred during the light phase under long days but during the dark phase under short days. The diel oscillations were, at least in part, driven by an endogenous component, as demonstrated by transferring larvae to continuous darkness. The cells displaying Tim- and Per-like immunoreactivities (Tim- and Per-LIRs) were localized using anti-Drosophila-Per and anti-Chymomyza-Tim antibodies. Per-LIR and Tim-LIR co-localized in three groups of cells in each brain hemisphere. Two other groups, one in the brain hemispheres and the other in the fused ventral nerve ganglion, expressed only the Per-LIR.     

Kinetic timing: a novel mechanism that improves the accuracy of GTPase timers in endosome fusion and other biological processes

The GTPase superfamily contains a large number of proteins that function as molecular switches by binding and hydrolyzing GTP molecules. They are localized at various intracellular organelles and control diverse cellular processes. For many GTPases, the lifetime of the activated, GTP-bound state is believed to serve as a timer in determining the activation time of a biological event such as membrane fusion and signal transduction. However, such a timer is intrinsically stochastic due to thermal noise at the level of single GTPase molecules. Here, we describe a mathematical model that shows how a directional GTPase cycle, in a nonequilibrium steady-state driven by GTP hydrolysis, can significantly reduce the variance in the lifetime of an activated GTPase molecule and thereby increase the accuracy and efficiency of the timer. This mechanism, termed kinetic timing, articulates a clear function for the energy consumption in GTPase-controlled biological processes. It provides a rationale for why biological timers utilize a GTP hydrolysis cycle rather than a simple GTP binding–dissociation equilibrium, and why the GTP-bound state is a better timer than the GDP-bound state. It also explains the necessity for the existence of multiple GTP-bound intermediates identified by fluorescence spectroscopy and nuclear magnetic resonance studies.     

Internalization of seasonal time

Orientation of physiology and behavior in time is a major adaptation common to many organisms and represents a significant challenge. In the face of predictable seasonal changes in climatic factors, and as a result of natural selection, many mammals now restrict their reproductive efforts to the fraction of the year when conditions of temperature, food, and water are most favorable for successful weaning of offspring. Changes in day length figure prominently in the synchronization of mammalian seasonal reproductive cycles. In summer breeders (e.g., several hamster, vole, and mouse species), decreasing summer day lengths induce reproductive involution. During this interval, neuroendocrine mechanisms analogous to a simple reference memory permit discrimination of stimulatory from inhibitory photoperiods. The non-reproductive phenotype is sustained for several months thereafter by the inhibitory short days of late summer, autumn, and early winter. Mid-winter reactivation of the reproductive system is triggered after 20-25 weeks of exposure to decreasing or short days by an interval timer that renders the reproductive neuroendocrine system refractory to short days. Recent work that has explored formal and physiological properties of this photorefractoriness interval timer has identified sex differences, neural substrates, and changes in hypothalamic gene expression that may participate in the measurement of seasonal time.     

Diapause induction and photoperiodic clock in Chilo suppressalis (Walker) (Lepidoptera: Crambidae)

The mature larvae of the rice stem borer, Chilo suppressalis Walker (Lepidoptera: Crambidae) enters facultative diapause in response to short‐day conditions in the autumn (August–September). Diapause induction and photoperiodic clock mechanism were investigated in C. suppressalis larvae reared on an artificial diet in the present study. The critical night length for diapause induction was about 9 h 53 min to 10 h 39 min at 22 to 28°C. The third‐instar larvae were found to be relatively sensitive to diapause induction. Photoperiodic response under non‐24‐h light–dark cycles showed that scotophase length played an essential role in the induction of larval diapause in C. suppressalis, and consecutive exposure to long‐night cycles was necessary for a high diapause incidence. In the Nanda–Hamner experiment, diapause incidence peaked at scotophase of 12 h and dropped rapidly at scotophases > 24 h. In the Bünsow experiment, diapause incidence was clearly suppressed, especially at the light pulse located 8 h in the scotophase. Both the Nanda–Hamner and Bünsow experiments showed no rhythmic fluctuations with a period of about 24 h; thus the photoperiodic clock in C. suppressalis is a non‐oscillatory hourglass timer or a rapidly damping circadian oscillator.