the brainy bunch A STUDYGUIDE B Y A NDREW FILDES www.metromagazine.com.au www.theeducationshop.com.au the brainy bunch Introduction squid, their close relatives and they are members of the cephalopod (head-footer) group of molluscs, Imagine a creature so alien that it has which also includes octopuses. The octopus is noted for its intelligence three hearts, no bones, blue blood, ten and generally believed to be the arms sticking out of its head, can fly smartest invertebrate, but are these little beasts just as bright? by jet propulsion and can make itself ‘When you come across your first cuttlefish, they’re the most invisible; or even change its own shape amazing creatures … they’re this sort of small, alien space ship and and colour. It sounds too bizarre for you couldn’t get a weirder looking animal underwater.’ (Dr Mark a Star Wars episode and yet it exists Norman, Museum Victoria) for real, right now and not far from This remarkable documentary explores the ecology, psychology you. In fact, the seas teem with them and biology of this amazing group of creatures. And there is plenty to – cuttlefish. study because it is hard to imagine another genus that has developed ou’ve seen the evidence such an extraordinary range of of their short lives on the physical characteristics and social beach, the light, white, behaviours. While it is of interest Y chalky shells (plates) that to middle and senior level biology budgies love to chew and yet few students, it is also of interest to of us have seen them in the wild. students of psychology interested Most of us would confuse them for in the application of conditioning theory to animals other than rats! SCREEN EDUCATION 2 Synopsis Cuttlefish can control the pigmentation in their skin so they are often difficult to see as they match (and blend in with) their background, but that ability also can be used to create outrageous the brainy bunch mating displays or strange pulsating cross dressers who can sneak past quickly that the molluscs are patterns that seem to hypnotize the posturing giants and quickly making some quite sophisticated their prey. They can even push mate, a triumph of brains over decisions. up ridges of skin and change their bravado. shape, becoming indistinguishable After this study the question has from clumps of seaweed or rough Marine biologist Dr Mark Norman to be asked – just how intelligent rock surfaces. But we begin in the also takes us to warmer waters is this beast? The normal crude shallow waters off the coast of than the southern Australian method of measuring intelligence South Australia where the largest shores to investigate two tropical level is to examine the ratio of of the cuttlefish, aptly named the species that have very special body weight to brain weight and Giant Cuttlefish, gather in their abilities or features. In Indonesia size. This is why we first suspected thousands for mating rituals. The we witness the astonishing display that dolphins are intelligent and usually shy animals forget their of the Broadclub Cuttlefish, which it is clear that the cuttlefish has chameleon style camouflage ability, radiates pulsating bands of colour the highest brain:body ratio of any throw caution to the currents and across its body in an attempt to invertebrate, even the octopus. the males fight, dance, display in hypnotize larger prey animals just By this measure, it has to be very attempts to intimidate their rivals. long enough to strike with its smart indeed. tentacles. Dr Norman engages in But some of the smaller males ‘Am I smart enough to find out a number of simple experiments now show their real cunning and how smart they are?’ (Dr Jean to find exactly what triggers this use their camouflage ability to Boal) masquerade as females, marine remarkable behaviour and realizes Two US scientists, a comparative psychologist and an animal behaviourist, develop a range of tasks to test their IQ and their ability to remember complex tasks over time, assessing the animals’ responses to a range of carefully designed conditioning experiments. The problem of finding ways of measuring the intelligence of a creature so different to ourselves is a challenge and helps us to understand the nature of intelligence itself. Finally, back in Indonesia, Dr Norman takes the opportunity to examine a tiny species of cuttlefish, the Flamboyant Cuttlefish. Despite its size and the fact that it walks Dr Mark Norman – Marine biologist SCREEN EDUCATION 3 the sea floor and hardly swims anymore, it chooses not to hide but responds to threats with a vivid, colourful display. In nature, this is normally the behaviour of poisonous species but no cuttlefish the brainy bunch is known to be poisonous – could this be an exception or is it just The other sub-Class, Nautiloidea, a thin ‘stiffening’ structure. The faking it? Samples are taken back to contains only the Nautilus, cuttlebone is calcium carbonate the laboratory where it becomes cephalopods which grow a shell. and grows with the animal. It is clear that this little cephalopod is highly porous and the cuttlefish can Cuttlefish, squid and octopuses indeed poisonous – eating it would control its buoyancy by adjusting evolved from the nautilus and be a very bad idea indeed. It is as the gas to liquid ratio in the gradually lost and/or modified their poisonous as its deadly cousin, the cuttlebone, in a similar way to a fish outer shell to an inner shell. Blue-Ringed Octopus. inflating its internal air sac. Cuttlebone Tentacles CuttleFacts The cuttlefish ‘bones’ that litter The animal is a decapod – ten- Cuttlefish belong to the Class our beaches are not true bones armed. The eight main ‘arms’ of the Cephalopoda, sub-Class at all but an internal shell. It is cuttlefish are shorter than its two Coleoidea, which also includes a remarkable adaptation that specialized ‘feeding tentacles’ and squid and octopuses. distinguishes the cuttlefish from tend to droop down, giving the squid, which have no more than SCREEN EDUCATION 4 cuttlefish it’s characteristic ‘nosey’ appearance. The two long tentacles are adapted as high speed strike weapons which lash out and grip prey species which can then be drawn in and controlled with the the brainy bunch stronger short arms to a sharp, parrot-like beak in the centre. Blood Chemistry Skin Pigment Eyes The blood is an unusual blue- All of the cuttlefish can change They have large eyes and highly green colour because instead of skin colour and adjust skin shape developed eyesight with a using the red iron based protein as well. The colour changes can characteristic W shaped pupil. The haemoglobin like those of us with be made very rapidly, in a split eye structure is quite different to spines, they use the copper based second, far faster than that of that of vertebrates like fish, reptiles protein haemocyanin instead, like the chameleon lizards, which and mammals and appears to most molluscs. This is around four are the by-word for this ability. represent a different evolutionary times less efficient because copper The mechanism uses up to 200 process. They cannot see colour can bind and carry less oxygen than chromatophores per square but can see polarized light which iron so a much higher blood flow is millimetre, each a sac of red, improves their perception of required. To achieve this, they have yellow, brown and black pigment contrast (but asks why they have three hearts – one branchial heart controlled by tiny muscles. These such colourful courtship displays!) for each of the gills and one for the are combined with iridophores, They have two foveae, the focus rest of the body. However because plates which reflect blue and green areas on the retina which are rich haemocyanin has the ability to light as well as causing the silvery in photoreceptors – one optimized form large clusters, it does not and gold colours sometimes visible. for forward vision and one for rear. need blood cells to carry it and Contracting the tiny skin muscles There is no adjustable lens in the circulates in the body as large produces a full range of colours eye as the whole eye is distorted protein molecules resembling long very quickly, including rapidly to move the lenses and achieve cylinders. moving patterns of spots and bands focus on one fovea or the other. in normal or polarized light (which SCREEN EDUCATION 5 their eyes can see). The ability to change skin colour is used for camouflage and concealment, courtship displays, communication and mimicry. Movement the brainy bunch Fast movement is by so-called jet ink was once used to produce breeding areas and the Giant propulsion. Water is taken into the the brown dye, Sepia. They are Cuttlefish numbers in South body cavity and passes over the widely exploited as a food species Australia were reduced drastically gills, inside the mantle, which is although they are less popular by overfishing. Now their mating the body tube. If rapid movement than squid. Mediterranean cookery grounds have been protected to is necessary, the mantle can be has many recipes, particularly allow numbers to recover. dishes that involve the ink as a contracted quickly and water The nervous system of sauce or a colouring for pasta. forced quickly out through the cephalopods is the most complex Like squid, they are abundant, fast hypernome or funnel, a muscular of the invertebrates. The giant breeding and short lived which tube beneath the tentacles, which nerve fibres of the cephalopod makes them a popular target can be contracted and directed. mantle have been a favourite for fishing around the world.