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The movement of an organism or a cell toward or away from a source of light.

pho′to·tac′tic (-tăk′tĭk) adj.
pho′to·tac′ti·cal·ly adv.


(ˌfəʊtəʊˈtæksɪs) or


(Biology) the movement of an entire organism in response to light
phototactic adj


(ˌfoʊ təˈtæk sɪs)

also pho′to•tax′y,

movement of an organism toward or away from a source of light.
pho`to•tac′tic (-ˈtæk tɪk) adj.
pho`to•tac′ti•cal•ly, adv.

phototaxis, phototaxy

the movement of an organism away from or toward a source of light. — phototactic, adj.
See also: Light
the movement of an organism away from or toward a source of light. — phototactic, adj.
See also: Motion
References in periodicals archive ?
Ontogenetic shift of spectral sensitivity in the larval phototaxis of two sympatric caridean shrimp, Lysmata wurdemanni and L.
It has also been suggested that Echinometra species and the purple sea urchin, Strongylocentrotus purpuratus, have a form of low-resolution vision (Blevins and Johnsen, 2004; Yerramilli and Johnsen, 2010), based on sea urchin phototaxis in the presence of dark shapes of varying angular width.
The aggregation of adult whiteflies on the eastern side of the cage is consistent with a previous study that showed a strong flight phototaxis, especially right after dawn, on the eastern side of the cages (Taravati et al.
Ontogeny of phototaxis and meta-morphic competence in larvae of the nudibranch Pheslilla sibogae Bergh (Gastropoda: Opisthobranchia).
In previously determining that these animals prefer to swim away from the light (negative phototaxis) and preferably be touching the sides of the tanks (positive thigmotaxis), they first set about asking whether these preferences could be altered by the size and shape of their testing tanks.
A method described by Behrendt and Krocker [55] is based on two well-known effects; first, the positive phototaxis of zooplankton individuals; and, secondly, the phenomenon that these individuals migrate to the bottom of closed vessels.
Beetles were attracted to the light from the hole where the Falcon tube was attached, as a result of positive phototaxis. Box seams were sealed with standard gray duct tape to prevent beetles from escaping.
Exposure to ammonia-based cleaner impacts Dictyostelium discoideum phototaxis and fruiting body production.
formosa) was positively phototactic in the absence of any chemical influence of its host mussel, Anodonta (now Pyganodon) cataracta, but exhibited negative phototaxis when tested in water containing extract of host gill tissue or in water from the mantle cavity of the host.
The role of gaseous metabolites in phototaxis by Dictyosteliumdiscoideum slugs.