The most remarkable luciferin in terms of its distribution is known as coelenterazine. This nitrogen-ring based molecule is found in nine separate groups, ranging from radiolarians to fish.

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.

Some cavefish are completely blind, so how do they manage to navigate through their environment with astonishing ease?

Dicyemids and chromidinids are tiny, worm-like or 'vermiform' creatures that typically live inside the kidneys ('renal organs') of cephalopod molluscs such as octopus, squid and cuttlefish.

A series of striking convergences can be found in the sea-hares (Aplysia), a group of gastropods and only remotely related to the cephalopods.  Not only do they emit ink clouds (the colour is derived from ingested red algae), but they also employ chemical cues that assist in defense.

In the reptiles, different forms of skin membrane (called ‘patagia’) and in some extinct species, primitive feathers, have evolved convergently as adaptations for gliding.

There is a striking convergence between the aorta of the cephalopod and vertebrate heart, notably in its structure and the employment of elastic proteins.

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).

Suffering from insomnia? Fruit flies do as well...

The degree of similarity between the active sites in arthropod and molluscan haemocyanin has been called “remarkable” and “startling”, but actually suggests that wherever in the universe life employs copper for aerobic respiration it will call upon haemocyanin.

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

Social play is the hall-mark of the most intelligent of this planet’s species, and there is a particularly striking convergence between birds and mammals.

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 effect, two of octopus' arms are applied sucker-side down to the sea-floor and unfurl along their length to provide a rolling locomotion that kinematically can be classified as walking.

An almost universal, but convergent, method to detect changes in orientation is for small grains (statoliths) to be attached to fine hairs, whose movement triggers nervous impulses.

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.

Burrowing owls place pieces of collected dung. These attract insects such as beetles that are then eaten by the owls.

Personality in the vertebrates might, therefore, be deeply embedded in their phylogeny, although this does not rule out the convergent appearance of more complex personality traits in more advanced vertebrates, notably birds and mammals.

Complex interactions between males and females prior to mating have evolved independently many times. Amongst the most familiar examples are leks.

Swim bladders have evolved independently in fish and in Ocythoe octopus females.

If you want to see a truly remarkable example of convergence, then present an octopus with a piece of food and have a high-speed camera ready…

Defensive mimicry is usually Batesian, where an innocuous species adopts the colouration of a toxic species, but Mullerian mimicry is also known whereby one species, already toxic, converges on the colouration of a more common toxic species.

A very important component of complex brains is an effective barrier between the blood vascular system and the brain, both to regulate electrolyte balance (e.g. potassium) and exclude potentially harmful substances.

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.

The most familiar examples of colour change in cephalopods are related to camouflage, but there are also striking examples of sexual and defensive (Batesian) mimicry.

Sexual mimicry is widespread, and the most famous example is probably the male-like genitalia in the females of the hyaena.

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.

Convergence in learning (and by implication memory) is important not only because it will give us clues as to the nature of consciousness, but it will also have a bearing on the reality (or otherwise) of pain and suffering in “primitive” animals.

Cephalopod brains show some striking convergences with those of vertebrates, including optic lobes and a cerebellum-like region.

Ammonoids, perhaps most familiar from the Mesozoic ammonites, are abundant as fossils and typically occur as planispiral forms. They show extensive homeomorphy, that is the same shapes repeatedly evolve.

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

Other cephalopods achieve reflectivity by employing collagen fibrils, of which the deep-sea Vampyroteuthis is perhaps the most striking example.

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?