Exposure to continuous light disrupts retinal innervation of the preoptic nucleus during parr-smolt transformation in Atlantic salmon

Research output: Chapter in Book/Report/Conference proceedingPaper in conference proceeding


High quality salmon smolts are essential for aquaculture, enhancement programs and wild populations. However, intensification of aquaculture smolt production and changes in natural habitats can cause sub-optimal environmental conditions, which may result in poor smolt quality. The salmon brain, as the integrator of environmental information, plays a focal role in relaying this information through the light-brain-pituitary axis, which includes retinal and pineal innervation of the hypothalamus. Here we investigated the effect of rearing juvenile Atlantic salmon, Salmo salar, under constant light (LL) on optic nerve fiber growth into the hypothalamus. This was compared with the normal increased fiber growth in fish reared under a simulated-natural photoperiod (LDN). Parr were sampled from the LDN group in February and from the LDN and LL groups in May (peak smolt status for the LDN group). Retinohypothalamic projections to the preoptic area were traced using 1, 1'-dioctadecyl-3,3, 3,3-tetramethylindocarbocyanine perchlorate (DiI) and confocal laser scanning microscopy. Data showed that parr exposed to LL did not develop the same extensive retinal innervation to the preoptic nucleus (NPO) observed in control salmon smolts raised under LDN. Since the cells in NPO are central pituitary regulatory neurones, the increased retinohypothalamic innervation during normal smoltification may be responsible for the increased endocrine response to photoperiod information. The deprivation of photoperiod information, during continuous light exposure, may inhibit the natural developmental program to proceed during the parr-smolt transformation. (C) 2007 Elsevier B.V. All rights reserved.


  • Lars O. E. Ebbesson
  • Sven O. E. Ebbesson
  • Tom O. Nilsen
  • Sigurd O. Stefansson
  • Bo Holmqvist
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Cancer and Oncology
Original languageEnglish
Title of host publicationAquaculture
Publication statusPublished - 2007
Publication categoryResearch
Event7th International Workshop on Salmonid Smoltification - Tono, Japan
Duration: 0001 Jan 2 → …

Publication series

ISSN (Print)1873-5622
ISSN (Electronic)0044-8486


Conference7th International Workshop on Salmonid Smoltification
Period0001/01/02 → …

Bibliographic note

The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Pathology, (Lund) (013030000)