title: Relationship between frequency of upside-down posture and space size around upside-down catfish, Synodontis nigriventris.
abstract: The catfish Synodontis nigriventris shows a unique habit taking a stable upside-down posture in free water regardless of an above, one-sided illumination. This upside-down posture can be observed when the catfish is apart from objects because the catfish usually orients its ventral side towards the water bottom or objects due to a so-called ventral substrate response. Thus, it is not easy to study the mechanism of the upside-down posture. To resolve this problem, the frequency of the upside-down posture was measured by using various sizes of vessel in which the catfish was kept. Video analysis showed that the frequency of the upside-down posture depended on the space size around the catfish. The smaller the size became, the higher the frequency of the upside-down posture became. Furthermore, the frequency of the upside-down posture depended on the shape of the vessel bottom. Curved-bottom vessels induced the upside-down posture more frequently than flat bottom. These findings suggest that a small, curved-bottom vessel is ideal for researching the upside-down postural control mechanism.
authors.affiliation: Department of Physiology, Nara Medical University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ohnishi
authors.forename: A
authors.initials: A
authors.lastname: Takahashi
authors.forename: H
authors.initials: H
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Ohnishi
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002397:Catfishes / Q000502:physiology*; D005556:Form Perception / Q000502:physiology*; D006799:Housing, Animal; D009043:Motor Activity / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D013550:Swimming