title: I know my neighbour: individual recognition in Octopus vulgaris.
abstract: BACKGROUND
  Little is known about individual recognition (IR) in octopuses, although they have been abundantly studied for their sophisticated behaviour and learning capacities. Indeed, the ability of octopuses to recognise conspecifics is suggested by a number of clues emerging from both laboratory studies (where they appear to form and maintain dominance hierarchies) and field observations (octopuses of neighbouring dens display little agonism between each other). To fill this gap in knowledge, we investigated the behaviour of 24 size-matched pairs of Octopus vulgaris in laboratory conditions.
  
  
  RESULTS
  The experimental design was composed of 3 phases: Phase 1 (acclimatization): 12 "sight-allowed" (and 12 "isolated") pairs were maintained for 3 days in contiguous tanks separated by a transparent (and opaque) partition to allow (and block) the vision of the conspecific; Phase 2 (cohabitation): members of each pair (both sight-allowed and isolated) were transferred into an experimental tank and were allowed to interact for 15 min every day for 3 consecutive days; Phase 3 (test): each pair (both sight-allowed and isolated) was subject to a switch of an octopus to form pairs composed of either familiar ("sham switches") or unfamiliar conspecifics ("real switches"). Longer latencies (i.e. the time elapsed from the first interaction) and fewer physical contacts in the familiar pairs as opposed to the unfamiliar pairs were used as proxies for recognition.
  
  
  CONCLUSIONS
  Octopuses appear able to recognise conspecifics and to remember the individual previously met for at least one day. To the best of our knowledge, this is the first experimental study showing the occurrence of a form of IR in cephalopods. Future studies should clarify whether this is a "true" IR.
authors.affiliation: Dipartimento di Biologia Evoluzionistica Leo Pardi, Università degli Studi di Firenze, Firenze, Italy. elena.tricarico@unifi.it
authors.forename: Elena
authors.initials: E
authors.lastname: Tricarico
authors.forename: Luciana
authors.initials: L
authors.lastname: Borrelli
authors.forename: Francesca
authors.initials: F
authors.lastname: Gherardi
authors.forename: Graziano
authors.initials: G
authors.lastname: Fiorito
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D005260:Female; D008297:Male; D049831:Octopodiformes / Q000502:physiology*