The main use for bioluminescence amongst vertebrates is to act as a lure to attract its prey to it. Some vertebrates, like species in the order Lophiiformes (Anglerfish), cannot produce luciferin and luciferase (mentioned in Invertebrates above), but instead have developed a symbiotic relationship with bacteria, who produce the light for them (Douglas 1994). Some have light organs which extend from parts of their gut, but others contain and culture these bacteria in a specific organ (Herring 2007), separated from their main body, which in the Lophiiformes species tends to be a lure close to the region of the mouth. This is so that they are able to attract prey to them, meaning they have to spend little energy actively seeking them; however the exact use of these lures remains in question as few have ever observed them in their natural habitat and only a handful have ever been captured alive (Byatt et al. 2001).

Figure 5. An example of a Whip-nosed Anglerfish, Family Gigantactinidae (Whipnose angler)

There are a variety of lures used by Lophiiformes to attract prey. The whip-nosed anglers, family Gigantactinidae (Figure 5), have lures which can measure many times their own body length, but it is difficult to understand how this can be used to feed. However, they have been observed swimming upside down near the sea floor (Moore 2002) which suggests they try to ensnare benthic organisms. Anglerfish of the genus Thaumatichthys (Figure 6) have lures attached to the roof of their mouth enticing the quarry directly into their trap (Bertelsen and Struhsaker 1977).

Figure 6. Showing Thaumatichthys binghami with its lure clearly shown (Kreaturen der Tiefe)

The fish here are mainly dark colours, blacks, browns and reds, causing them to become practically invisible to other predators and prey (Richard et al. 2007), as there is no far-red light this deep. Some have disproportionally large eyes to pick up bioluminescence but most are lacking sight.

Loose-jawed dragonfish of the genera Malacosteus, Aristostomias and Pachystomias are the only known fish which can produce red bioluminescence (Douglas et al. 2000), which can only be seen by the fish itself, meaning it is able to locate prey without being seen (Byatt et al. 2001). Aristostomias and Pachystomias (Figure 7) are able to see this red light due to them having three visual pigments which are orientated to detect far-red light (Douglas et al. 2000). Malacosteus however only has two of these pigments but it able to enhance its sight through the use of a chlorophyll photosensitizer which it is thought to obtain from its diet of copepods (Douglas et al. 2000).

Figure 7. Pachystomias microdon, a species of dragonfish able to create and see red light (Deep sea pelagic species)

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