Osmotic Concentration of Zebrafish (Danio rerio) Body Fluids is Lower in Larvae than in Adults

Research output: Contribution to journalArticle


We intended to perform optical and structural measurements on larval zebrafish eyes at 5 days post fertilization, that is, the earliest age at which zebrafish show visually guided behavior. However, excised larval crystalline lenses deteriorated quickly if immersed in a medium that gives good results with adult lenses from a variety of fish species. We suspected that the larvae have body fluids of lower osmolality and tested a medium with 240 mOsm, which is 75% of the established adult value of 320 mOsm. The optical quality of freshly excised and immersed lenses was used to judge the osmotic matches. In addition, we tested how well the shape of the eye is preserved in fixatives of different osmolalities. In both cases, 240 mOsm produced the best results. Immersed lenses performed better and the fixed eyes had a more natural shape. Our findings indicate that zebrafish body fluids have lower osmolality in larvae than in adults. This is probably due to an unfavorable body surface-to-volume ratio and incompletely developed regulatory mechanisms. Body fluid osmolality deviating from the adult value has to be taken into account in optical and histological work.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Zoology
  • Physiology


  • development, crystalline lens, fixation, fast Fourier transform, histology, osmolarity
Original languageEnglish
Pages (from-to)9 -14
Number of pages6
Issue number1
Early online date2017 Oct 23
Publication statusPublished - 2018 Feb 1
Publication categoryResearch

Related research output

Kozłowski, T. M., 2018 Jan, Lund: Lund University, Faculty of Science, Department of Biology. 110 p.

Research output: ThesisDoctoral Thesis (compilation)

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