swordfish, and other predator fish and groundfish. Parasites Bigfin reef squids serve as hosts to the copepod ectoparasite Doridicola similis and the worm-like dicyemid endoparasites Dicyema koshidai and Dicyema orientale. Biology and behaviour Bigfin reef squids are closely related to the Caribbean reef squid (Sepioteuthis sepioidea), a species noted for its complex social interactions. Like Caribbean reef squids, bigfin reef squids also exhibit elaborate mating displays. Bigfin reef squids also exhibit both schooling and shoaling behaviours. Very young bigfin reef squids will also stay close together (shoaling), but do not swim together parallel to each other (schooling). Unlike most other squid species, bigfin reef squids are rarely cannibalistic. Shoals can include animals of different sizes without the threat of larger members attacking and consuming the smaller members. Whether bigfin reef squids recognise each other individually still remains unknown. Phototaxis Bigfin reef squids exhibit strong positive phototactic behaviour (attraction to light) and will move readily within a certain distance of a light source. Studies have proposed that this might be an involuntary stimulus behaviour, as the squids immediately stop all other movements once a light source is switched on. The colour of the light does not matter, but it has been shown that they react more strongly to underwater lights between the intensities of 1.5 to 2.5 lx, with peak ranges of 2.5 to 10.0 lx. Hearing Bigfin reef squids and the common octopus (Octopus vulgaris) were studied to resolve a century-long debate over whether cephalopods can hear. Unlike fishes, cephalopods do not possess air-filled swim bladders, which might amplify sound waves travelling in water. The results were published in 2009. It showed that bigfin reef squids and octopuses utilise their statocysts for detecting vibrations, an organ primarily used for maintaining spatial orientation. The common octopus can hear sounds between 400 Hz and 1000 Hz. Bigfin reef squids have a slightly better hearing range of 400 Hz to 1500 Hz. Both hear best at a frequency of 600 Hz. Relatively, their hearing is comparable to prawns and some other invertebrates but is less sensitive than that of most fishes. The difference in the hearing ranges for octopus and bigfin reef squids may be explained by the difference in their habitats. The octopus is demersal (bottom-dwelling) with excellent camouflage capabilities. Bigfin reef squids, on the other hand, are usually in open water with limited hiding places. Hearing would thus be more important