Artificial Flashes Research Articles

Effectiveness of artificial floods for benthic community recovery after sediment flushing from a dam.

The number of dams is predicted to increase worldwide under the current global change scenario. A major environmental problem associated with dams is the release of large quantities of fine sediment downstream. Therefore, future studies in river conservation will largely be focused on the management of sediments trapped by reservoirs. The aim of this study was to investigate the downstream ecological impacts of sediment flushing from a dam and the effectiveness of artificial flash floods as a recovery strategy. Artificial flash floods have often been employed to remove large amounts of sediment from riverbeds, but their importance in improving the biological quality of lotic environments is almost unknown. We carried out a series of quantitative macroinvertebrate samplings over a 2-year period that started before sediment release and included the artificial flushing events. We characterized the macroinvertebrate community in its structural and functional aspects and tested the performance of two biomonitoring indexes, comparing their diagnostic ability. Our results demonstrated that sediment flushing significantly altered the structure and composition of benthic communities for more than 1year. Flash floods exacerbated the overall biological quality, but we believe that this treatment was useful because, by removing large amounts of sediment, the biological recovery process was accelerated. Finally, regarding the water quality assessment, we found that the biomonitoring index for siltation, composed of a selection of taxonomical and functional metrics, was more reliable than the generic one.

Experimental study of the interaction between building clusters and flash floods

In recent years, flash flood disasters have occurred frequently in southwest China due to the increased frequency of extreme climate events. To solve this problem, great efforts have been made in studying the process of flash flood. However, little attention was paid on bearing body of hazard, the clusters of buildings. Thus the real disaster mechanism of flash flood remains unclear.Accordingly, based on the experiments of artificial flash floods in a conceptual solid model, this paper focuses on the flood-impacted inundation characteristics of the building clusters at different locations of the gully model, in order to obtain a better understanding of the disaster process and the interaction between the flash floods and building clusters. The results showed that, in a typical smallscale flash flood gully with hot and dry climate, 1)clusters of buildings on an alluvial fan could reduce about 35% of the flooding area by blocking the diffusion of the flood to the depression areas, and could also promote the deposition in lower reaches of the river channel by blocking the overbank flow from going back into the channel, making the width-depth ratio of the channel larger. 2) The flash flood rates of disaster and hazard on the alluvial fan are generally higher than that of the inner gully. For the inner gully,buildings located on the beaches along the lower river and the transitional areas of the straight channel and channel bends can easily be affected because of their lower elevations. For the alluvial fan, buildings nearby the meanders suffer the greatest impacts because of bank collapsing and flooding. 3) The safe vertical distance from a building to the river channel is 13 m for the buildings in the inner gully under extreme floods. Below this threshold, the smaller the vertical distance is, the greater the risk exposure is. For the buildings on the alluvial fan, especially for the buildings near the concave bank of the top rush point,the horizontal distance is more important, and the safe value is 80 m under extreme floods.

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.

Female preference for male courtship flashes in Photinus ignitus fireflies

In Photinus fireflies, males produce spontaneous bioluminescent courtship flashes. Females preferentially respond to particular male flashes with flashes of their own. This study explored variation in female flash responsiveness as a function of male flash duration, female condition, lantern size, and lantern distance, as well as the relationship between male characteristics and spermatophore mass in Photinus ignitus fireflies. We determined female preference by scoring female flash response to simulated male flashes and determined variation in overall female flash responsiveness for laboratory-mated, laboratory-fed, and control P. ignitus females. Flash duration, lantern size, and body mass were recorded for field-collected males. Males were then mated to determine spermatophore mass. Females exhibited greater preference for artificial flashes representing the upper range of conspecific male flash duration and lantern size as well as flashes produced at a closer distance. Both laboratory-mated and laboratory-fed P. ignitus females showed lower overall responsiveness across all flash durations relative to control females that did not mate or feed in the laboratory. Male flash duration predicted a significant proportion of the variation in spermatophore mass for early-season males. These results suggest that female Photinus ignitus may prefer long flashes in order to obtain the direct benefit of larger spermatophores and may adjust their overall flash responsiveness as the relative importance of this benefit varieswith changing female condition. Copyright 2003.

Brain windows in firefly communication

A quantitative model has been developed that explains numerous communication patterns in Photuris versicolor female fireflies. The model is based upon the concept of brain windows. Upon receiving the flash stimulus, the firefly brain generates a sequence of time windows of different width. Receiving and sending windows are interleaved in the sequence. Each receive window recognizes a particular subgroup of flash intervals. These flash intervals may represent courtship flashes of the female's conspecific male or courtship flashes of heterospecific males. Each sending window determines the latency of the response flash from the female. The windows are arrayed in priorities and controlled by the fireflies' memory. Memory stores the past history of flash stimulation. The brain windows are generated through a mutual coupling of the primary oscillator, answer oscillator and window generator. Hence, the brain windows are directly related to the inherent biological oscillators and to the memory. The brain window model has been programmed into the computer. Computer simulated response patterns are in excellent agreement with hundreds of experimental response patterns produced by Photuris versicolor female fireflies when tested with artificial flashes. A single model explains all the communication-behavior patterns observed in the female firefly. Brain windows could explain the communication and behavior in other species as well.

Response patterns of female Photinus macdermotti firefly to artificial flashes

The responses of female Photinus macdermotti fireflies to artificial flashes were investigated. Female response patterns change in characteristic fashion as the interval between simulated male flash pairs is varied. The effects of extra flashes inserted within the flash pair and flash duration on female response probability were examined. Female response latency to the second flash of the male flash pair is constant. Female response probability can be conditioned by previous flashes. The response characteristics of females are analysed in terms of flash interval and flash number.