Flying through the air on a summer's evening or sparkling in the ocean you may see magical flashes of light that signal some of nature's most enchanting creatures, those that are bioluminescent.

Underwater environments are dominated by blue light. Ironically, whales and seals cannot see blue, because they have independently lost their short-wavelength opsins.

One of the most surprising convergences amongst animals is that seen between a small fish that lives in coral sands, known as the sandlance, and the lizards known as chameleons.

Bats show a fascinating array of convergences, from echolocation to flight to nectar feeding. Vampire bats can even detect infrared radiation, while others might be able to see into the ultraviolet end of the spectrum.

On each of the four club-like extensions (rhopalia) near the base of the cubozoan jellyfish bell there are two camera-eyes, one pointing upwards and the other downwards.

Who has not enjoyed the splash of colour in a market: gorgeous red peppers, the green of basil and what on earth are these purple vegetables over there? All thanks to trichromatic vision, another story of convergence.

Warnowiids propel themselves through the water, but unlike other dinoflagellates which are photosynthetic, they are hunters and the chloroplast is employed to make the lower part of the eye.

One of the more obvious eye adaptations in whales is the extraordinary capacity of the pupil to change the size of its opening, from very small when in surface sunlit water to very large when exploring the abyssal gloom.

Some of the silica spicules of glass sponges are very long, and extraordinarily have a striking similarity to the optical fibres employed in the telecommunications industry.

Nocturnal colour vision is clearly convergent, and found in groups as disparate as the hawkmoths (insects), geckos (reptiles) and aye-aye (mammals).

Warm-blooded rodents watch out! There are heat-sensing predators on the prowl...

Spectral tuning of the eye generally depends on key substitutions of amino acid sites in opsin proteins.

In some of the flatworms (platyhelminthes) the lens is formed from mitochondria, and it is intriguing to speculate whether a mitochondrial enzyme has been co-opted to provide a crystallin.

Anti-reflection coating? Not only on mobile phone displays, but also on insect eyes...

Among brittlestars and sea urchins we find visual systems that in some ways rival the arthropods in the form of compound eye-like structures.

Light sensitivity based on opsins is well documented, notably in the cyanobacterium Anabaena where it is involved with photosynthesis and in particular the production of key pigments.

It is clear that amongst the arthropods as a whole the compound eye has evolved at least twice, and possibly even more times.

Compound eyes have evolved convergently in the annelids, notably amongst the sabellids, where they evidently serve as an optical alarm system.

There is a striking example in the group known as the alciopids, which are pelagic polychaetes. The similarity of their camera eye to the vertebrate eye has attracted considerable comment.

The pinhole eye has evolved not only in the Pearly Nautilus, but also in another group of molluscs, the bivalves and specifically the giant clams (Tridacna).

Read on if you want to know more about bivalves with burglar alarms…

The fast-moving cephalopod molluscs are famous for their camera eyes, but why on earth have gastropod snails, which are not exactly known for their speed, evolved this superb visual organ at least four times?

Some sea snails have a linear retina. What a hopeless arrangement, to see the world through just a narrow slit! Not quite, because they have come up with a rather intriguing trick to extend their visual field - and it's a trick too good to use only once.

Pursued by the paparazzi? Watch out for those animals equipped with telephoto lenses...

Arthropods are famous for their compound eyes, but some groups have had a fair crack at evolving the optically superior camera eye…

Strepsipteran females spend their whole life inside a wasp. The males are rather more exciting, particularly in terms of convergence…

The beetles are probably the most diverse animal group on earth, so it is not at all surprising that they provide many fascinating insights into convergence.

Whilst predominantly marine, quite a number of crustaceans have invaded freshwater habitats and even more interestingly a few demonstrate terrestrialization, effectively freeing themselves from their aquatic ancestry.

Snail shells typically form a helical spiral, but within this geometry there is a considerable degree of convergence.

Whereas typically technology demands furnaces, so that the glass for a lens is produced at hundreds of degrees Celsius and then requires most careful grinding, so nature calls upon proteins known as crystallins.

Read on if you want to know about the numerous animal equivalents to the invisible man...

The Japanese firefly squid (Watasenia scintillans), which inhabits the deep ocean, has three visual pigments located in different parts of the retina that are likely to allow colour discrimination as they each have distinct spectral sensitivities.

In vertebrates the sensitivity of the retina changes during the growth of the animal. In invertebrates this only occurs in the cephalopods, or at least cuttlefish, where this sensitivity has been acquired convergently.

In bees detection of polarized light from different quadrants of the sky is an important component in their navigation.

Notable instances of convergence involving annelids include luminescence, moulting and the independent evolution of both compound eyes (e.g. in sabellids) and camera eyes (in alciopids).

In a number of cases one eye is used in preference to another. This convergent phenomenon is found in octopus (cephalopods), dolphins, birds, and other animals.

Normally one thinks of an eye as a structure that allows light to pour into the body, but in at least some squid (cephalopods) the opposite has been achieved.

The majority of complex eyes not surprisingly do possess a lens and they are an excellent example of convergent evolution, especially in terms of camera-eyes and compound eyes, as well as employment of crystallins.

The remarkable similarity between the camera eyes of cephalopods and vertebrates is one of the best-known examples of evolutionary convergence.

In some vertebrates (fish, mammals) and cephalopods we find an interesting convergence whereby some of the incoming ultraviolet is screened out.

What could be more different from us than the alien-like octopus? Hold on. Look it in the eye and think again.

Camera eyes are superb optical devices, so it is not surprising that they have evolved several times. But why, of all animals, in the brainless jellyfish? Or for that matter in a slow-moving snail?