Being able to find what it is you wish to feed on in a featureless landscape is a tall order for the inhabitants of the mesopelagic and bathypelagic zones (Björn & Ghiradella 2008). Predators apply bioluminescence in a number of different ways to aid in the search or to simply bring the prey to them. The most obvious of these is as a searchlight in the dark (Douglas & Partridge 1997). Pinpointing prey with large, focused bioluminescent organs on the animals head, sometimes after using other weaker sources to lure prey species closer in. A good example of this is the Lanternfish described in The Fishes.
Other predators mimic smaller organism’s bioluminescent strobes and pulses to fool organisms such as squid, who have excellent eyesight, into thinking they could be food. The aptly named Deep-sea anglers (Figure 8.1) flash bioluminescent baubles on the end of a bony rod protruding from the head (Mensinger & Case 1990). Any unwitting squid or fish that gets too close to the jaws while examining the bauble are snapped up.
Similarly cephalopods, such as the Vampire squid, have bioluminescent tentacle tips to lure fish into ambush range. This is doubly effective for these species as not only is it an effective way to catch prey it also minimises the energy expenditure in doing so, as very little movement is required from the predator (Robison et al. 2003). Until the moment they strike of course. The same lures used to hunt by Vampyroteuthis infernalis can also be used in defence (see next page).