In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406, more
Also appears in:
De Blok, J.W.; Dorrestein, R.; Nienhuis, P.H.; Postma, H.; Weber, R.E. (Ed.) (1973). 7th European Symposium on Marine Biology, Texel, 11-16 September 1972. Netherlands Journal of Sea Research, 7. Netherlands Institute for Sea Research: Texel. 505 pp., more
The photic orientation of hatchling sea turtles during water finding behaviour was tested in a new type of experimental light field. The azimuthal vector diagram of this light field is sensitive to the detector's angle of acceptance. When this angle is small, for instance 1 degree, the diagram takes the form of a snail-shell. Moreover the major vector and the minor vector do not point in opposite directions as they do in the usual experimental light fields as produced by a lamp. The mean directions of hatchlings of Chelonia mydas and of Lepidochelys olivacea almost coincided with the major vector as measured with a detector with a horizontal angle of acceptance of 180 degrees. The conclusions are that the animals moved in the 'brightest direction' of the angular light distribution and not in the direction opposite to the 'darkest direction', and that they obtained information about the brightest direction by processing of photic stimuli impinging through an input cone with an impressively large horizontal angle of acceptance. Suggestions are given with respect to relevant taxis concepts.