Let there be Light
Fireflies use an illuminating system that is intrinsic in function where a number of organs within which the components of light production are synthesised -photocytes (Smith, 1963). The emission of light is thus produced by the combination of the components into an intracellular region (Smith, 1963). Fireflies therefore, do not use or require luminescent bacteria in the body – another illuminating system. It has been found that the luminous organs of the fireflies are so diverse that general inferences of the anatomy in which the fireflies have adopted can only be made (Buck, 1948). The light organ is located close to the body surface in conjunction with a translucent cuticle however; this varies between males, females and larvae (Buck, 1948). Size of the light organs vary dramatically from being the size similar to that of a grain of sand to being masses that occupy the entire ventral surface of several abdominal segments. Position of the light organ also varies significantly; as it can be located from the head to the tip of the abdomen, and on both the ventral or dorsal surfaces (Buck, 1948). The emission of light is produced by specialised cells known as photocytes, and the physiology and structure as stated above are varied widely. However, the general structure consists of localised masses of photocytes with specific tracheal and nervous supplies. Photocytes contain the principal components necessary for the chemical based light reaction to occur; these are the enzyme luciferase and the substrate luciferin. In addition these
cells are full of mitochondrial cells which provide ATP (adenosine triphosphate) as the energy source for the bioluminescent reaction (Buck, 1948).
cells are full of mitochondrial cells which provide ATP (adenosine triphosphate) as the energy source for the bioluminescent reaction (Buck, 1948).
Oxygen has been implicated in many studies as being the controlling agent in the photochemical reaction however; the discovery of hydrogen peroxide has since been suggested as being a possible controlling agent (Ghiradella & Schmidt, 2004). As a group fireflies are versatile: most of them being able to modulate their light to a greater or lesser extent; along with the ability to flash causing a sharp change in behaviour either being on or off (Ghiradella & Schmidt, 2004). This single event has caused the search for that switch; that final step that pushes the photochemical reaction to completion (Ghiradella & Schmidt, 2004). The paper by Ghiradella and Schmidt (2004) provides a possible model as to how hydrogen peroxide pushes the reaction to completion but has of yet not been fully accepted. Oxygen is still the accepted element responsible for completion (Ghiradella & Schmidt, 2004).