Life cycle and behaviour of the aquatic firefly Luciola leii (Coleoptera: Lampyridae) from Mainland China

The aquatic larvae of the firefly Luciola leii Fu and Ballantyne occur on the substrate of rice fields and ditches in Hubei Province of central China. The behaviour and ecology of L. leii are described. We recorded L. leii larvae attacking four species of aquatic snails: Lymnaea stagnalis (L.) (Basommatophora: Lymnaeidae), Gyraulus convexiusculus (Hutton) (Basommatophora: Planorbidae), Radix auricularia (L.) (Lymnaeidae), and Bellamya purificata Heude (Mesogastropoda: Viviparidae). At dusk, flying males produced two types of advertising flashes. One type consisted of a train of 8 rapid, green flashes followed by 2–3 slow, prolonged flashes produced by patrolling males as a long-distance signal. The duration of flashes in the patrolling pattern was 530 ms and the interflash interval was 80 ms. The other type was a short-range signal consisting of a green glow, which was emitted by flying males that had located a female. Once a female had been located, the male landed and switched to a courting pattern. The male courtship pattern consisted of single flashes of about 400 ms duration, delivered every 1.8 s. Females produced single answering flashes of 910 ms duration, with a latency of approximately 630 ms after the male flash. Luciola leii was univoltine. Females oviposited 1 to 7 times (mean = 4.78). Females laid, on average, 187.19 eggs. The eggs hatched at 21.52 days. Eggs became luminescent 4 or 5 days before hatching. The larval stage had six instars. Mature larvae climbed onto land to construct pupal cells at the end of April of the next year. The pupal stage lasted, on average, 4.88 days. The imago lasted 10.13 days. No predators of larvae were observed. The spider Tetragnatha praedonia Koch (Araneae: Tetragnathidae) was frequently observed to capture adult male fireflies in its web.

Flash Activity in Two Synchronic Firefly Species (Coleoptera: Lampyridae)

Synchronic flashing in fireflies is a precisely timed behavior. This is a potentially useful tool to study sensory processing, the location and circuitry of the flash oscillator, and neuroeffector processing and coupling. Synchronic flashing, once thought to occur only in Southeast Asian fireflies, has recently been shown to be a prominent part of the behavior of a North American Photinus and Photuris species. To gain insights into the mechanisms of synchronic timing in fireflies, we compared spontaneous flashing and entrainment flashing in Photuris frontalis LeConte, a synchronic firefly found in Georgia's Coastal Plain, to analogous flashing in Pteroptyx malaccae Olivier, a synchronic firefly found in Malaysia. The timing of spontaneously produced flashes and entrainment flashes was recorded by photometry. Artificially produced, rhythmic stimulus flashes were used to induce a counterfeit synchrony (between subject fireflies and an LED), i.e., flash entrainment. We found that the spontaneously produced interflash intervals were repeated with a high degree of precision in P. frontalis and P. malaccae. However, the pattern of flashing was different during spontaneous flashing and flash entrainment. An isolated P. frontalis flashed intermittently during spontaneously flashing and entrainment flashing. Flash entrainment in P. frontalis started with an initial inhibition and then steady-state entrainment occurred with a fixed delay. In contrast, an isolated P. malaccae flashed continuously during spontaneous flashing and entrainment flashing. No initial inhibition occurred at the start of entrainment, and there was a gradual change in interflash interval until steady-state entrainment occurred at a fixed delay. We think that in-depth studies of the flash activities of different synchronic firefly species, including the locally available P. frontalis, could help our understanding of rhythmic temporal coordination of behavior by the nervous system.

Duration Illusions in a Train of Visual Stimuli

The first stimulus in a sequential train of identical flashes of light appears to last longer than those in the middle of the train. Four flashes (each 600 or 667 ms) were presented and the first was shortened until it appeared to have the same duration as that of the next. The duration of the first stimulus was found to be overestimated by about 50%. The illusion was unaffected by stimulus contrast, size, or interflash interval (between 100 and 600 ms). For some subjects, the last stimulus in the train also appeared to be about 50% longer than the penultimate flash. The results are discussed in terms of theories of how attention, arousal, and stimulus processing can affect duration perception. The mechanisms activated are peculiar to the visual system, since no similar illusion of duration was consistently experienced with a train of auditory tones.

Characteristics of membrane currents evoked by photoreleased inositol trisphosphate in Xenopus oocytes

Photorelease of inositol 1,4,5-trisphosphate (InsP3) from a caged precursor was used to study characteristics of Ca(2+)-activated Cl- currents activated in Xenopus oocytes by the InsP3-Ca2+ signaling pathway. Photolysis flashes shorter than a threshold duration evoked no response, but the current amplitude then grew about linearly as the flash duration was further lengthened. Currents directly evoked by photorelease of Ca2+ from a caged precursor grew linearly with increasing flash duration and showed a small threshold before they were activated. However, the major part of the threshold of InsP3-evoked responses appears to arise because a certain concentration of InsP3 (estimated to be approximately 60 nM) is required to evoke Ca2+ liberation. Subthreshold conditioning flashes potentiated responses to subsequent flashes, and the potentiation increased linearly with increasing conditioning flash duration before abruptly declining. The potentiation decayed exponentially with a time constant of approximately 17 s with increasing interflash interval. Currents evoked by photoreleased InsP3 began after a latency that shortened from 10 s or longer to 100 ms as the photolysis intensity was increased. This dose dependence of the latency could be quantitatively explained by the time required for the InsP3 concentration to rise above threshold. Intracellular injection of heparin (a competitive antagonist at the InsP3 receptor) increased the threshold for InsP3 action, as did increased temperature. We conclude that several characteristics of InsP3-evoked responses, including their dose dependence, latency, and facilitation with paired stimuli, arise because a distinct threshold level of InsP3 is required to evoke release of Ca2+ from intracellular stores.