Multiple flash activation of the water-photolysis system in intermittently illuminated wheat leaves

The chloroplasts from wheat leaves greened under intermittentillumination at long intervals (1-msec light$5-min dark) arecapable of photoreducing DPIP (2,6- dichlorophenolindophenol)with DPC (diphenylcarbazide) as the electron donor but incapableof photoreducing this Hill oxidant with water as the donor.Exposure of such leaves to flashes at short intervals of theorder of a second rapidly induced the water-photolysis activityto reduce DPIP. The activation by single flashes at uniformintervals greatly depended on the interval, and the activitywas maximal at an interval of a few seconds. A pair of two flashesgiven successively at an interval of a few seconds was strikinglymore effective than a pair of two flashes given simultaneously.This suggested that at least two sequential photoevents areinvolved in the activation of the latent water-photolysis system.Double, triple and multiple flashes at the short intervals gaveprogressively higher yields of activation per flash. The mechanismof activation is discussed based on these activity data obtainedwith multiple flashes at various dark intervals. ¹ On leave for thesis from Kitazato University of Hygienic Sciences,Sagamihara-shi, Kanagawa, Japan. (Received November 21, 1974; )     

Slow fluorescence fluctuations following high light to low light or dark transitions in Chlamydomonas reinhardi.

Slow fluorescence transients in Chlamydomonas reinhardi arise after transitions from high light intensities to low light or dark conditions. Characteristics of the newly described transient phenomena include: (a) A slow biphasic decrease in fluorescence yield occurs in the dark, followed by an even slower, hour long, increase in fluorescence. (b) A similar, but faster, fluorescence yield decrease and subsequent increase also occurs during low intensity illumination periods separating high light intervals, or after transitions from high intensity to low intensity light. (c) Short (several seconds) flashes of light given during a dark period have no effect on the dark fluorescence decay, regardless of the flash frequency. Such flash regimes accurately monitor the dark decline of the M2 level by tracing the parallel decay of flash-generated P2 (Kautsky) peaks. However, flashes during a low light illumination period do influence the decay kinetics. Frequent flashes allow decay similar to that occurring in dark, but less frequent flashes inhibit the decrease in fluorescence yield.     

Response entrainment of movement fibers in the optic tract of crayfish

The response properties of jittery movement fibers (JMF) in the crayfish optic tract reacting to a non-moving temporally patterned light were analyzed. The JMFs usually show no response during the regular flickering of stationary light with a flash duration of less than 50 msec when the stimulus frequency is between 4 and 20 per second; however they do respond when the flickering stops if a certain number of flashes have been given. The response appears about 50 msec after the first missing flash, i.e., the latency of the response after the last flash of the train changed from 100 to 300 msec. Thus, the “off” response at the end of the flicker is entrained to the stimulus repetition interval and locked onto the time of the first missing flash. The response of a sustaining fiber to an identical stimulus has quite different features as illustrated in Fig. 2. Some of the fibers show responses to the beginning part of the flicker but not necessarily to each flash, and habituate after several flashes. When a single flash longer than 250 msec is given, the fiber shows an “off” response with about 50 msec latency, as it does to sustained light. Some fibers show a double burst of “off” discharge to single flashes; the first at 50 msec is followed after 120 msec by the second one. However, when the flash duration is between 250 and 50 msec, a single flash elicits little or no response. The latency of the “off” response is as much as 300 msec for short single flashes less than 50 msec. An “on” response to flashes of light is observed when the inter-stimulus interval is more than 5 sec. The responses to the beginning part of flicker train are not simply locked to the just preceding flash except the “on” response to the very first one, but they can be the long latency responses to the flash before that. This response is modified in latency by the succeeding flashes in flicker trains and becomes entrained to the missing flash. Four types of entrainment are classified on the basis of the change in latency from the missing flash with regard to the number of flashes in a train. In most cases, 10 flashes are sufficient to entrain the response to the first missing flash. Non-resposiveness, i.e., habituation, during a regular flicker, may be due to an active inhibitory process, initiated by each succeeding light pulse. The response to the missing flash, therefore results from a disinhibited modified response to the last flash. Some JMFs continue to respond to the flicker even after a considerable number of flashes but only when the repetition interval is about 120 msec corresponding well to the interval of the double burst “off” discharge, thus the JMF has a resonant frequency of about 8 Hz. The JMFs appear to be acting as an irregularity detector in temporal sequence.     

Enhancement and phototransduction in the ventral eye of limulus

Limulus ventral photoreceptors were voltage clamped to the resting (dark) potential and stimulated by a 20-ms test flash and a 1-s conditioning flash. At a constant level of adaptation, we measured the response to the test flash given in the dark (control) and the incremental response produced when the test flash occurred within the duration of the conditioning flash. The incremental response is defined as the response to the conditioning and test flashes minus the response to the conditioning flash given alone. When the test flash was presented within 100 ms after the onset of the conditioning flash we observed that: (a) for dim conditioning flashes the incremental response equaled the control response; (b) for intermediate intensity conditioning flashes the incremental response was greater than the control response (we refer to this as enhancement); (c) for high intensity conditioning flashes the incremental response nearly equaled the control response. Using 10-μm diam spots of illumnination, we stimulated two spatially separate regions of one photoreceptor. When the test flash and the conditioning flash were presented to the same region, enhancement was present; but when the flashes were applied to separate regions, enhancement was nearly absent. This result indicates that enhancement is localized to the region of illumination. We discuss mechanisms that may account for enhancement.     

Shifts to C675-670 and to C696-684 in etiolated leaves illuminated with series of brief flashes

Absorbance changes seen when etiolated primary bean leaves aregiven series of short, low-intensity flashes of light were recorded.Whatever its order in a series, each flash induced an initial,fast increase of the absorbance, producing an absorption bandbetween 660 and 700 nm with a peak at 680 nm. This occurredin less than 30 msec and was followed within seconds by eithera slow dark increase or a slow dark decrease of the leaf absorbance,depending on the order of the flash and the analytical wavelength.The dark absorbance changes were due to shifts of the initialabsorption band produced by the flash, either towards 685 or670 nm. The shift was always towards 670 nm after the firstflash. It appeared to move progressively towards 685 nm fromone flash to the next, this direction becoming predominant aftera certain number (n_inv) of flashes. The (n_inv) depended on thelight dose, but not on the flash frequency. Three proposalsare made to account for the results. (Received May 14, 1977; )     

Detection of red and green flashes: evidence for cancellation and facilitation.

Green and red flashes of light will differentially stimulate the middle- and long-wavelength sensitive cones. Interaction of cone signals was studied by measuring increment thresholds for combinations of green and red flashes on a yellow adapting field. When the yellow adapting field was at 10.000 trolands (td), green and red incremental flashes (1 degree, 200-msec duration) produced cancellation when presented simultaneously and facilitation when presented sequentially. A green incremental flash (1.15 degrees, 200 msec, 5000-td adaptation field) and red decremental flash, or vice versa, produced facilitation when presented simultaneously. The results can be explained by color-differencing, opponent-mechanisms. The cancellation effect for the simultaneous incremental flashes largely disappeared when the flashes were exposed briefly (10 msec) or reduced in size (0.04 degrees). It is unlikely that the stimuli were exclusively detected by achromatic, luminance channels, as suggested by previous work, since observers could partially distinguish the hue of threshold flashes of 570- and 590-nm light (0.04 degrees, 10 msec) on a bright yellow field.     

Control of misses in oxygen evolution by the oxido-reduction state of plastoquinone in Dunaliella tertiolecta

The way misses happen in oxygen evolution is subject to debate (Govindjee et al. 1985). We recently observed a linear lowering of the miss probability with the flash number (Meunier and Popovic 1989). Therefore, we investigated in Dunaliella tertiolecta the link between the average miss probability and the redox state of plastoquinone after n flashes. The effect of flashes was to oxidize the plastoquinone pool; we found that the oxidation of plastoquinone highly correlated (linear regression: R ²=0.996) with the lowering of the miss probability. The flash frequency was found to affect both the miss probability and the redox state of plastoquinone. When pre-flashes were given using a high flash frequency (10 Hz), the plastoquinone pool was oxidized and misses were low; however, if long dark intervals between flashes were used, the oxidizing effect of flashes was lost and the misses were high. We could not explain our results by assuming equal misses over all S-states; but unequal misses, caused by deactivations, were coherent with our results. We deduced that chlororespiration was responsible for the reduction of plastoquinone in the dark interval between flashes. We compared oxygen evolution with and without benzoquinone, using a low flash frequency (0.5 Hz) for maximum misses. Benzoquinone lowered the misses from 34% to 3%, and raised the amplitude of oxygen evolution by more than a factor of two (2). From this we deduced that the charge carrier C postulated to explain misses (Lavorel and Maison-Peteri 1983) did not account for more than 3% of miss probability in Dunaliella tertiolecta. These results indicate that the misses in oxygen evolution are controlled by the redox state of plastoquinone, through deactivations.     

Geographic differences in flash intervals and pre-mating isolation between populations of the Genji firefly, Luciola cruciata

Abstract.  1. Two types of Genji firefly, Luciola cruciata , have been recognised on the basis of the inter-flash interval.
2. The fast-flash and slow-flash type fireflies, distributed in the western and eastern parts of Japan, exhibit a 2- and 4-s interval of bioluminescence flash, respectively. In addition, an intermediate-flash type is found on the boundary between these two regions.
3. The differences in the responses of the males of four field populations to different intervals of artificial flashes were examined.
4. The results revealed that in the Aomori and Sendai populations (slow-flash type), a significantly larger number of males approached the 4- and 5-s flash intervals than approached the 2- and 3-s intervals of artificial flashes. On the other hand, in the Ohtsu population (fast-flash type), a significantly larger number of males approached the 2- and 3-s flash intervals than the 4- and 5-s intervals of artificial flashes. The Inuyama population (intermediate-flash type) did not show any particular preferences to flash intervals.
5. This study shows that in firefly populations, geographic variation in flash pattern can cause some degree of pre-mating isolation between populations.     

Oxygen Evolution from Algae Illuminated by Short and Long Flashes of Light

The oxygen produced by illuminating Ankistrodesmus braunii withsingle light flashes has been determined using the Hersch galvanicoxygen cell. Measurements were made with the cells suspendedin alkaline solution equilibrated with nitrogen containing oxygenat a partial pressure of 10^–4 mm. Hg.

1. A single light flash, if very brief (less than 5 millisec.)results in no measurable oxygen production; a longer flash (35millisec.) gave a yield of approximately 1 mole O₂/800 moleschlorophyll.
2. A pair of flashes suitably spaced gave a greateryield thanthe sum of the yields when given individually, althoughonewas so brief that by itself it produced no measurable oxygen.The yield of a long flash preceded by a short flash was twiceas great as that of the long flash given alone; when the flashorder was reversed the combined yield was smaller but stillgreater than for the long flash alone.
3. The combined yieldof a pair of flashes varies with the intervalseparating theflashes, rapidly rising to a maximum and thendecaying moreslowly. With a long and short flash the optimalinterval was0.7 sec. but some enhancement of yield was observedwhen theflashes were separated by as long as 10 or 15 sec.
4. When theflashes were superimposed on background illuminationthe yieldswere increased and were measurable even for the shortflashes.Measured with background illumination the optimal yieldfora pair of short flashes was obtained with flashes separatedby about 0.05 sec.

     

Linear Superposition of Retinal Action Potentials to Predict Electrical Flicker Responses from the Eye of the Wolf Spider, Lycosa baltimoriana (Keyserling)

Retinal action potentials were elicited from light-adapted posterior median ocelli of the wolf spider Lycosa baltimoriana (Keyserling) by rectangular shaped photic stimuli representing 8 per cent increments or decrements of the background illumination. Responses to trains of recurrent incremental or decremental flashes were successfully predicted by graphical linear superposition of a single flash response, which was repeatedly drawn and added to itself at intervals equal to the period of the intermittent stimulus. Incremental stimuli inverted to form decremental stimuli elicited responses which were also inverted. Responses to single incremental flashes were successfully predicted by linear superposition of the response to one incremental step stimulus, which was inverted and added to itself at an interval equal to the duration of the flash.     

Reactions between primary and secondary acceptors of photosystem II in Chlorella pyrenoidosa under anaerobic conditions as studied by chlorophyll fluorescence.

The kinetics of the fluorescence yield phi of chlorophyll a in Chlorella pyrenoidosa were studied under anaerobic conditions in the time range from 50 mus to several minutes after short (t 1/2 = 30 ns or 5 mus) saturating flashes. The fluorescence yield "in the dark" increased from phi = 1 at the beginning to phi approximately 5 in about 3 h when single flashes separated by dark intervals of about 3 min were given. After one saturating flash, phi increased to a maximum value (4-5) at 50 mus, then phi decreased to about 3 with a half time of about 10 ms and to the initial value with a half time of about 2 s. When two flashes separated by 0.2 s were given, the first phase of the decrease after the second flash occurred within 2 ms. After one flash given at high initial fluorescence yield, the 10-ms decay was followed by a 10 s increase to the initial value. After the two flashes 0.2 s apart, the rapid decay was not followed by a slow increase. These and other experiments provided additional evidence for and extend an earlier hypothesis concerning the acceptor complex of Photosystem II (Bouges-Bocquet, B. (1973) Biochim. Biophys. Acta 314, 250-256; Velthuys, B. R. and Amesz. J. (1974) Biochim. Biophys. Acta 333, 85-94): reaction center 2 contains an acceptor complex QR consisting of an electron-transferring primary acceptor molecule Q, and a secondary electron acceptor R, which can accept two electrons in succession, but transfers two electrons simultaneously to a molecule of the tertiary acceptor pool, containing plastoquinone (A). Furthermore, the kinetics indicate that 2 reactions centers of System I, excited by a short flash, cooperate directly or indirectly in oxidizing a plastohydroquinone molecule (A2-). If initially all components between photoreaction 1 and 2 are in the reduced state the following sequence of reactions occurs after a flash has oxidised A2- via System I: Q-R2- + A leads to Q-R + A2- leads to QR- + A2-. During anaerobiosis two slow reactions manifest themselves: the reduction of R (and A) within 1 s, presumably by an endogenous electron donor D1, and the reduction of Q in about 10 s when R is in the state R- and A in the state A2-. An endogenous electron donor, D2, and Q- complete in reducing the photooxidized donor complex of System II in reactions with half times of the order of 1 s.     

Effects of light flashes on the dark closure of Albizzia julibrissin pinnules

An electronic flash unit is used to deliver, at the beginning of a 10 min dark period and within a few ms, large doses of light to Albizzia julibrissin pinnules, to ascertain their effects on the rate of pinnule closing. In a series of alternating light flashes at 710 and 550 nm, the first 710 nm light flash significantly retards closing. A following light flash at 550 nm negates the far-red induced delay. The second 710 nm light flash delays closing less effectively than the first when given within 4 s after the green flash, but is just as effective when given after 30 s. The delay brought about by the second 710 nm light flash is again abolished by a light flash at 550 nm. A light flash at 660 nm has no effect on pinnule closing by itself and is also ineffective in reversing the far-red induced delay. A series of ten 710 nm light flashes becomes most effective in delaying closure when there is a dark interval of one min between flashes. The closing delay induced by a 710 nm light flash escapes reversal by a 550 nm light flash when the dark interval between the two flashes exceeds 2–3 min. A 750 nm light flash has no retarding effect on pinnule closing, but it becomes effective when preceded by a 660 nm or 550 nm light flash. The results obtained are suggested to be due to light absorbed by phytochrome and an unknown photoreceptor with green, far-red photoreversal property.     

Pigeons' memory for sequences of light flashes: reliance on temporal properties and evidence for delay interval/gap confusion

In Experiment 1, pigeons were trained to discriminate between sequences of two and four light flashes (illumination of the feeder). Retention functions obtained with dark delays exhibited a choose-many bias at a 1-s delay and a choose-few bias at delays of 4 and 8s. Retention functions obtained with illuminated delays only displayed a slight choose-few bias. In Experiment 2, additional birds were trained with the same sample sequences. However, the intertrial interval was illuminated by the houselight for Group Light, and it was dark for Group Dark. The acquisition data suggested that multiple temporal features of the light flash sequences controlled choice responding. For both groups, the retention functions were similar to those obtained in Experiment 1. In Experiment 3, baseline training with a 1-s dark delay eliminated the choose-many bias, but a significant choose-few bias at extended dark delays was still observed. Pigeons discriminate light flash sequences by relying on temporal properties of the sequence rather than using an event switch to count flashes. The biased-forgetting effects obtained in these studies appear to be primarily due to confusion between the delay interval and the gap between light flashes.     

Die Dauer der Dunkeladaptation beim Fliegenauge nach Belichtung mit heterochromatischen Blitzen

Zusammenfassung Versuche mit heterochromatischen Lichtblitzen von 2 msec Dauer zeigen, daß die Dauer der Dunkeladaptation beim Calliphora-ERG von der Reihenfolge der Farbblitze abhängt. Versuche mit 2 diskreten Blitzabständen von 40 msec und 2 sec ergaben unterschiedliche Wirkungsspektren. Bei 40 msec Blitzabstand wirkt UV-Strahlung verlängernd auf die Adaptationszeit, bei 2 sec Abstand verkürzend. Die aufgenommenen Wirkungsspektren sprechen für das Auftreten eines kurzlebigen, bei 490 nm absorbierenden Intermediärfarbstoffes während der Potentialbildung und für das Auftreten eines stark im UV-Bereich absorbierenden Folgefarbstoffes sofort nach der Potentialbildung.

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Dark-adaptation after heterochromatic flash-illumination in the compound eye of the blow-fly

Summary The time course of dark adaptation (increase in amplitude of the electroretinogram) in the fly Calliphora was tested by light flashes (2 msec) of various wavelengths. The results showed that the time course depends on the wavelength of the test flashes, and on the interval between them. Using white test light the time for completion of dark adaptation increases with the interval between flashes, up to an interval of 20 sec. With longer intervals dark adaptation proceeds slightly faster. In contrast, using ultra-violet (UV) test light, a short (40 msec) interval increases the duration of the dark adaptation, and a longer (2 sec) interval reduces the duration. The results suggest that an intermediate photopigment is formed during the generation of the receptor potential. The pigment, which absorbs maximally at 490 nm, exists for a short period only. Immediately after the receptor potential is set up, an UV absorbing secondary pigment is formed.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft, SFB Bionach.     

The Effect of Visual Apparent Motion on Audiovisual Simultaneity

Visual motion information from dynamic environments is important in multisensory temporal perception. However, it is unclear how visual motion information influences the integration of multisensory temporal perceptions. We investigated whether visual apparent motion affects audiovisual temporal perception. Visual apparent motion is a phenomenon in which two flashes presented in sequence in different positions are perceived as continuous motion. Across three experiments, participants performed temporal order judgment (TOJ) tasks. Experiment 1 was a TOJ task conducted in order to assess audiovisual simultaneity during perception of apparent motion. The results showed that the point of subjective simultaneity (PSS) was shifted toward a sound-lead stimulus, and the just noticeable difference (JND) was reduced compared with a normal TOJ task with a single flash. This indicates that visual apparent motion affects audiovisual simultaneity and improves temporal discrimination in audiovisual processing. Experiment 2 was a TOJ task conducted in order to remove the influence of the amount of flash stimulation from Experiment 1. The PSS and JND during perception of apparent motion were almost identical to those in Experiment 1, but differed from those for successive perception when long temporal intervals were included between two flashes without motion. This showed that the result obtained under the apparent motion condition was unaffected by the amount of flash stimulation. Because apparent motion was produced by a constant interval between two flashes, the results may be accounted for by specific prediction. In Experiment 3, we eliminated the influence of prediction by randomizing the intervals between the two flashes. However, the PSS and JND did not differ from those in Experiment 1. It became clear that the results obtained for the perception of visual apparent motion were not attributable to prediction. Our findings suggest that visual apparent motion changes temporal simultaneity perception and improves temporal discrimination in audiovisual processing.     

Short-term reactions of phytochrome in Mougeotia?

Summary Phytochrome controlled chloroplast movement in Mougeotia is induced by flashes of polarized red light. Two subsequent flashes, separated by a dark interval of a few seconds, are much more effective than two simultaneous flashes; a maximal cumulative effect is reached if the duration of the dark interval is 30 ms or longer. We propose two light reactions in series, separated by a very fast dark reaction. Preliminary evidence is given that the energy requirement for these light reactions is different. It is suggested that the two reactions are related in some way to free and bound phytochrome.Dedicated to Prof. Dr. E. Bünning on the occasion of his seventieth birthday.     

Effect of the 33-kDa protein on the S-state transitions in photosynthetic oxygen evolution

The effect of the extrinsic 33-kDa protein on the photosynthetic oxygen evolution was studied by comparing spinach Photosystem II particles depleted of the 33-kDa protein with those reconstituted with the protein. The light-intensity dependence of the oxygen-evolution activity under continuous illumination suggests that a dark step, but not a light step, in the oxygen-evolving reaction is accelerated by the 33-kDa protein. Consistently, the pattern of oxygen yield with a series of short saturating flashes, which showed a maximum on the third flash and a damped oscillation with a period of 4, was not much affected by the removal and rebinding of the 33-kDa protein, when the dark interval between the flashes was long enough, i.e., longer than 0.5 s. The millisecond kinetics of oxygen release after the third flash was retarded by the removal of the 33-kDa protein and stimulated by its rebinding, suggesting that the transition from S₃ to S₀ is accelerated by the 33-kDa protein. The stability of the S₂ and S₃ states in darkness was higher in the absence of the 33-kDa protein than its presence.     

Mechanisms of synchrony in the North American fireflyPhotinus carolinus (Coleoptera: Lampyridae)

Photometric recordings combined with computer stimulation, acquisition and analysis were used to study synchrony in the North American fireflyPhotinus carolinus. A computer-generated burst of simulatedP. carolinus flashes was used to trigger a firefly flash burst. We found that the first triggered firefly flashes occurred after the second or third flashes in the stimulus burst, that there were fewer flashes in a triggered burst than a spontaneous burst, and that extending the stimulus flashes into the firefly's interburst interval inhibited firefly flashing. When the stimulus flash interval (389–560 ms) was changed, no change was seen in the interflash interval. When the stimulus flash interval was changed, the average time between stimulus flash and firefly flash (flash delay) changed as if the firefly interflash interval was constant. Thus, interflash interval inP. carolinus does not change its length, making it similar to the Southeast Asian synchronizerPteroptyx cribellata and different fromPteroptyx malaccae, which can change its interval. We suspect that the time between bursts is functionally analogous to the time between flashes in Southeast Asian synchronizers.     

Female preference for male courtship flashes in Photinus ignitus fireflies

In Photinus fireflies, males produce spontaneous bioluminescentcourtship flashes. Females preferentially respond to particularmale flashes with flashes of their own. This study exploredvariation in female flash responsiveness as a function of maleflash duration, female condition, lantern size, and lanterndistance, as well as the relationship between male characteristicsand spermatophore mass in Photinus ignitus fireflies. We determinedfemale preference by scoring female flash response to simulatedmale flashes and determined variation in overall female flashresponsiveness for laboratory-mated, laboratory-fed, and controlP. ignitus females. Flash duration, lantern size, and body masswere recorded for field-collected males. Males were then matedto determine spermatophore mass. Females exhibited greater preferencefor artificial flashes representing the upper range of conspecificmale flash duration and lantern size as well as flashes producedat a closer distance. Both laboratory-mated and laboratory-fedP. ignitus females showed lower overall responsiveness acrossall flash durations relative to control females that did notmate or feed in the laboratory. Male flash duration predicteda significant proportion of the variation in spermatophore massfor early-season males. These results suggest that female Photinusignitus may prefer long flashes in order to obtain the directbenefit of larger spermatophores and may adjust their overallflash responsiveness as the relative importance of this benefitvarieswith changing female condition.     

Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, Taningia danae

Our newly developed underwater high definition video camera system took the first live images of adults of the mesopelagic large squid, Taningia danae, between 240 and 940 m deep off Ogasawara Islands, western North Pacific. The resulting footage includes attacking and bioluminescence behaviours, and reveals that T. danae is far from the sluggish neutrally buoyant deep-sea squid previously suspected. It can actively swim both forward and backward freely by flapping its large muscular triangular fins and changes direction quickly through bending its flexible body. It can attain speeds of 2-2.5 ms(-1) (7.2-9 km h(-1)) when attacking bait rigs. They emitted short bright light flashes from their large arm-tip photophores before final assault, which might act as a blinding flash for prey as well as a means of measuring target distance in a dark deep-sea environment. They also emitted long and short glows separated by intervals while wandering around the double torch lights attached to the bait rig, suggestive of potential courtship behaviours during mating.