Department of Zoology, University of Gothenburg, Department of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Göteborg, Sweden. kristiansson@zool.gu.se|Department of Zoology, University of Gothenburg, Department of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Göteborg, Sweden. kristiansson@zool.gu.se|Department of Zoology, University of Gothenburg, Department of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, Göteborg, Sweden. kristiansson@zool.gu.se