In the Beginning was Information
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ments with <strong>the</strong> black firefly (Photinus pyralis) it <strong>was</strong> found that <strong>the</strong> flyingmale emitted 0.06 second flashes at intervals of 5.7 seconds, and <strong>the</strong> femaleon <strong>the</strong> ground replied after exactly 2.1 seconds with <strong>the</strong> same rhythm.These flashing signals are obviously understood by <strong>the</strong> prospective mate.There also are insects that have lamps which emit different colours, like <strong>the</strong>Brazilian train worm (Phrixothrix). This beetle larva (Driliden) which liveson snails, normally carries two orange-red lights in front. At <strong>the</strong> approachof danger two sets of 11 greenish lanterns are switched on, one on eachside. This resembles a train, and <strong>the</strong> name “train worm” is quite apt.During a visit to Israel in 1985 we went to <strong>the</strong> underwater observatory inEilath and could watch <strong>the</strong> lantern fish (Photoblepharon palpebratussteinitzi) living in <strong>the</strong> Red sea. This fish does not produce its own light,but obtains it from symbiotic luminescent bacteria. These bacteria are sosmall that <strong>the</strong> light of a single one is invisible, but <strong>the</strong> light of an entirecolony can be observed. They congregate on an oval light organ situatedbelow <strong>the</strong> eyes of <strong>the</strong> fish and are fed and provided with oxygen through adensely branching network of capillary blood vessels. They continuouslygenerate light, but <strong>the</strong> fish can deliberately switch <strong>the</strong> light on and off. Itdoes this by pulling a black skin flap over <strong>the</strong> luminescent organ like aneyelid, and is thus able to transmit different flashing signals. These signalsattract <strong>the</strong> prey it requires for subsistence.Bacterial emission of light is fundamentally different from that of o<strong>the</strong>rluminescent organisms. O<strong>the</strong>r marine organisms only emit light when<strong>the</strong>y are disturbed or stimulated (e. g. by <strong>the</strong> passage of a ship or of amackerel school, or <strong>the</strong> breaking of waves). But bacteria continuouslyemit light of a constant intensity.The bioluminescence of abyssal creatures, like glowing fishes, crabs,arrow worms, and jellyfishes, is quite impressive. Many kinds of fish havelamps along <strong>the</strong>ir sides, while o<strong>the</strong>rs have several rows of lamps. Theluminous organs can be arranged in curves, in oscillatory patterns, or quiteirregularly. The five striped star constellation fish (Bathysidus pentagrammus)has five beautiful shining lines on both sides of its body, each ofwhich consists of a row of large pale yellow lights, surrounded by serratedbright purple “jewels”.Luminous shrimps (Sergestes prehensilis) have more than 150 light points,all of which can be quickly switched on and off. For one or two secondsyellow-green lights flash sequentially and quickly from head to tail justlike neon advertisements in cities. Many kinds of fish employ luminescentbacteria to generate light flashes, but o<strong>the</strong>rs have highly specialisedorgans which produce <strong>the</strong>ir own luminous substances. Some fishes have239