| Summary: | There are four morphs of Arctic charr living in Thingvallvatn: two benthic Small and Large Benthivorous charr (SB and LB) and two limnetic Planctivorous (PL) and Piscivorous (PI). They differ extensively in morphology, behavior and life history characteristics. Families of PL, SB and LB as well as a domesticated aquaculture morph (AQ) from Holar aquaculture station, were created. The progeny of these morphs have been sampled at different points of development. In this study I stained 15 embryos per stage per morph using an acid-free double stain solution (Walker & Kimmel, et al. 2006). On a morphological level I found that tails start to ossify from the middle part and extent to the two sides gradually. Fin rays appear to ossify in a similar manner. In addition, heads appear to start ossifying earlier than tails for all studied morphs. From the comparison of the different morphs, I found differences in the SB shape compared to the other 3 morphs: SB tails have the two sides of the tail skin connected at the edges, but open in the middle. Furthermore at earlier stages of development SB tails have an L-shape, whereas this same bone is straighter in the other 3 morphs. Tails of AC start to ossify later than in the other morphs whereas LB fin rays develop the fastest. Subsequently I studied the gene expression of 14 genes found to be involved in bone development in other species. I tested the expression of these genes at 2 points of development in two morphs (PL and AC) using qPCR. I found 2 genes (col11a1, ihh) to be differentially expressed.
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