The fine structure of the larval firefly light organ

Abstract

AbstractLight organs of larval photurid fireflies, which emit their light in a steady glow, differ from those of adults, which have a precisely controlled flash pattern, in having no specialized tracheal end organs and no morphologically distinct cortical region of the photocytes. However, like the adult organs, larval lanterns are abundantly supplied with both tracheoles and nerve fibers. Each of the two abdominal light organs of the larva consists of a dorsal (“reflector”) layer and a conical ventral photogenic layer. The dorsal layer is a single layer of columnar cells containing “urate” granules, mitochondria and a rich supply of glycogen. The photogenic layer is a compact mass of photocytes, containing photocyte granules similar to those of the adult organ, many elongated mitochondria, and a vesiculated reticulum. Numerous tracheoles run between the interlocking membranes of the photocytes. A large nerve traverses the dorsal layer and enters the photogenic layer, where its fibers diverge between the photocytes. Many structures having the appearance of neurosecretory nerve endings are found among the folds of the photocyte membranes. However, no tight junctions (synapses?) were found.