Anatomy Of Emission

The ultrastructure of the flashing lantern was first seen in the 1960s, when the electron microscope revealed that a miniature and new type of structure, the tracheal end organ, occurred throughout the flashing lantern, and that each microunit was obviously involved in controlling the photocytes associated with it. The light-emitting layer of a flashing lantern is organized into a sheet of rosettes, each with a central channel (cylinder), through which air-supply tubes and nerve trunks pass, and surrounding photocytes, which abut the photocytes of neighboring rosettes (Fig. 1).

The flashing lantern of adult fireflies does not develop (ontogenetically) from the glowing lantern of juveniles. The difference in the light output of these two lantern types is remarkable. On the one hand, larval lanterns require perhaps a full second to reach their full but much lesser intensity, and in

FIGURE 1 Diagram of part of a single rosette ("unit") in the flashing lantern. The central channel (cylinder) is ringed by photocytes, which are differentiated into inner and outer regions. Within the cylinder are two tracheal trunks and two tracheal end organs, one cut longitudinally, one transversely. Note within the end organ the intimate contact of the air supply, nerve ending (arrows), tracheal end cell, and tracheolar cell (the last two indicated by lightly and densely stippled structures, respectively). Original "magnification" approximately 1800X. (Reproduced, with permission, from H. Ghiradella, 1983, Permeable sites in the firefly lantern tracheal system: Use of osmium tetroxide vapor as a tracer. J. Morphol. 177, 145-156. See Ghiradella 1998.)

FIGURE 1 Diagram of part of a single rosette ("unit") in the flashing lantern. The central channel (cylinder) is ringed by photocytes, which are differentiated into inner and outer regions. Within the cylinder are two tracheal trunks and two tracheal end organs, one cut longitudinally, one transversely. Note within the end organ the intimate contact of the air supply, nerve ending (arrows), tracheal end cell, and tracheolar cell (the last two indicated by lightly and densely stippled structures, respectively). Original "magnification" approximately 1800X. (Reproduced, with permission, from H. Ghiradella, 1983, Permeable sites in the firefly lantern tracheal system: Use of osmium tetroxide vapor as a tracer. J. Morphol. 177, 145-156. See Ghiradella 1998.)

an array of lantern types their behavior is little removed from the granules in subdermal fat cells or excretory tubules that glow continuously or in a simple circadian (daily) rhythm (Keroplatus, Orfelia), which is perhaps controlled by changes in hormone level. On the other hand, a flashing lantern is capable of photic finesse that can be appreciated only with electronic detector systems—the flashes of male fireflies of some species have very sharp on transients, and field recordings of flying males reveal that a flash can reach its bright peak in 20 ms (Figs. 2A and 2B), the flicker signal of a Florida Photuris species is modulated up to 45 Hz (Fig. 2C), and the four subliminal peaks of what appears to the eye to be a single flash of an Andean Mountain Photinus occur at 25 Hz (Fig. 2D).

The triggering of such light emission is currently thought to be connected with the release or gating of oxygen into the photocytes. This occurs in response to patterned volleys from the central nervous system, delivered by neurons that connect to or are closely associated with other key elements within the tracheal end organ (Fig. 1). A recent study suggests that nitric oxide gas plays a key role in the release of oxygen into the photocytes.

Bee Keeping

Bee Keeping

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